NRM Coastal Values Mapping Project: Geomorphology Interpretation Report

NATURAL RESOURCE MANAGEMENT COASTAL VALUES MAPPING PROJECT: GEOMORPHOLOGY INTERPRETATION REPORT AND MANUAL NRM NORTH AND CRADLE COAST

November 2008

Prepared by Hydro-Electric Corporation ARBN: 072 377 158 ABN 48 072 377 158 4 Elizabeth Street, Hobart Tasmania, Australia

Coastal Values Mapping – NRM North and Cradle Coast

Hydro Tasmania Consulting

Revision No: 2

Document information Title

Coastal Values Mapping

Client organisation

North Barker Ecosystem Services

Client contact

Philip Barker

Document ID number

E202976.REP1

Project manager

Raymond Brereton

Project reference

P202976

Current document approval Prepared by

Reviewed by

Approved for submission

Dax Noble and Chris Sharples

Sign

[SRE; External Consultant]

Date

Raymond Brereton

Sign

[SRE]

Date

Scott Lobdale

Sign

[SRE]

Date

06/11/08

06/11/08

06/11/08

Current document distribution list Organisation North Barker Ecosystem Services

Date 06/11/08

Issued to Philip Barker

Document history and status Revision 2

Prepared by Dax Noble, Chris Sharples

Reviewed by Raymond Brereton

Approved by Scott Lobdale

Date approved 06/11/08

Revision type Final

The concepts and information contained in this document are the property of Hydro Tasmania Consulting. This document may only be used for the purposes for which, and upon the conditions, the report is supplied. Use or copying of this document in whole or in part for any other purpose without the written permission of Hydro Tasmania Consulting constitutes an infringement of copyright.

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Coastal Values Mapping – NRM North and Cradle Coast

Hydro Tasmania Consulting

Revision No: 2

Executive summary This report documents the coastal geomorphic values of western and northern Tasmania from Macquarie Heads through to Weymouth. This work was funded by the Natural Resource Management (NRM) group for the period 2007-2008. The overall purpose of the project was to enhance and add to data on natural coastal values (geomorphology, flora and fauna) of the NRM North and Cradle Coast region of Tasmania, and to provide management tools along with the data in order to assist State and Local Government and Cradle Coast NRM Committee planners in making appropriate decisions on the sustainable use and development of the coastline.

The project was broadly comprised of three parts: 1.

Collection of Coastal Geomorphic Data This was the largest part of the project which involved field mapping and air photo interpretation to enhance and add to existing mapped information on the distribution and characteristics of the variety of coastal rock types, soft sediment bodies and landforms that comprise the NRM North and Cradle Coast coastline. This is key base data for informed management of coastal values and vulnerabilities.

2.

Application of Decision Support Tools to the Data Information from the geomorphic mapping has been abstracted to create a number of indicative map layers, which provide planners with an indication of management issues that may be pertinent to particular coastal locations. These are referred to here as Decision Support Tools, and comprise: • • •

Geoconservation Priority ratings (for each distinctive coastline segment) Sensitivity ratings (sensitivity of landforms and landform processes to human disturbances) Condition ratings (degree of disturbance or otherwise of landforms and landform processes by human activities).

Section 5 of this report is a brief manual describing how these Decision Support Tools can be used, together with the more detailed underlying geomorphic base data, to inform coastal land management decision making processes which have landform and landform process conservation (Geoconservation) as an objective.

Other sections of this report provide background information to assist in displaying, interpreting and applying the Decision Support Tools and geomorphic mapping data to land management decisions 3.

Dissemination of and Training in Use of the Data and Decision Support Tools The use of the Decision Support Tools and underlying geomorphic base data compiled in the course of this project will be explained in a training course for State & Local Government planners and managers to be held at the end of this work, and through distribution of this manual and associated digital mapping. It is also intended that the map layers discussed and used in this manual will be available to planners via the LIST website.

Since the Decision Support Tools created through this project have not previously been applied to Land Management planning and zoning, there is no existing evaluation of the usefulness of these tools. It is expected that there will be scope for feedback from users, based on practical experience in applying these tools, to provide the basis for improving the usefulness of these tools in future.

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Coastal Values Mapping – NRM North and Cradle Coast

Hydro Tasmania Consulting

Revision No: 2

Contents PREFACE 1.0 INTRODUCTION 1.1 The Coastal Values Project 1.2 How to use this report 1.3 Glossary of Terms 2.0 COASTAL GEOMORPHOLOGY OF THE NRM NORTH AND CRADLE COAST NRM REGION 2.1 Introduction 2.2 Geological and Geomorphic History of the NRM North and Cradle Coast Region 2.3 Coastal Landform Types and Geomorphic Processes in the NRM North and Cradle Coast Region 3.0 KEY GEOMORPHIC MANAGEMENT ISSUES FOR THE NRM NORTH AND CRADLE COAST REGION COAST 3.1 Introduction – Coastal Landform Management Philosophies and Strategies 3.2 Geoconservation Values 3.3 Coastal Dune Mangement Issues 3.4 Coastal Slumping, Erosion & Shoreline Recession 3.5 Coastal Flooding (Storm Surge Inundation) 4.0 COASTAL GEOMORPHIC DATASETS AND DECISION SUPPORT TOOLS 4.1 Introduction 4.2 Coastal Geomorphology – Descriptive Line Map 4.3 Coastal Geomorphology – Descriptive Polygon Map 4.4 Coastal Photography 4.5 Coastal Geoconservation Values Mapping 4.6 Coastal Geomorphic Sensitivity and Condition Mapping 4.7 Coastal Geomorphic Hazard (Vulnerability) Mapping 4.8 Geoconservation Priority ("Indicative GeoValues") Map 5.0 PUTTING IT ALL TOGETHER – USING THE COASTAL MANAGEMENT DECISION SUPPORT TOOLS 5.1 The Purpose of the Coastal Geomorphic Values Decision Support Tools 5.2 The Decision Support Tools 5.3 Using the Decision Support tools 5.4 Example of Decision Support Tool Use BIBLIOGRAPHY APPENDIX ONE: DATA DICTIONARY FOR DIGITAL GEOMORPHIC MAPPING A1.1 Introduction A1.2 Data Models A1.2.1 Shoreline Geomorphic Types, Sensitivity and Condition line map A1.2.2 Quaternary Coastal Sediment Polygon Map A1.2.3 Coastal Geoheritage Maps Significant Features Map (areas) Significant Features Map (points) A1.2.4 Coastal Photography Photo Log (points) A1.3 Attribute Tables A1.3.1 Shoreline Geomorphic Types Line Map Descriptors Degree of Ground Truthing (Confidence) Upper Intertidal Zone Landform Type (Upperint) Lower Intertidal Zone Landform Type (Lowerint) Backshore Landform Type (Backshore) Intertidal Zone Slope (Slope) Shoreline Segment Exposure (Exposure) Sediment Budget (Sedbudg) November 2008

6 7 7 11 12 14 14 14 20 30 30 31 33 34 36 37 37 38 40 43 44 45 48 49 51 51 51 52 58 64 67 67 67 67 71 74 74 75 76 76 77 77 77 78 81 82 83 84 86 iv

Coastal Values Mapping – NRM North and Cradle Coast

Hydro Tasmania Consulting

Revision No: 2

Relevant Time Period (Time) 88 Shoreline Bedrock Type (Bedrock) 88 Hinterland Topography Class (Profile) 90 Wave Energy Zone (Wavenzn) 91 Geomorphic Process (Process) 93 Total Cliff Height (Cliffht) 93 Intertidal Zone Slope (Slopedeg) 93 A1.3.2 Quaternary Coastal Sediment Polygon Map Descriptors 94 Geological Age of Sediment Bodies and Soft Sediment Landforms 94 Sediment & Landform Types 94 Larger Scale Coastal Landforms or Landform Assemblages 96 Dune Mobility Status 97 Current Dune Mobility Status 97 Historic Dune Mobility Status 98 Rate of Sediment Supply to Estuaries 98 Mapping Data Sources 99 A1.3.3 Coastal Geoheritage Map Descriptors 99 Type of geoconservation value 99 Significance category 100 Significance level 100 Sensitivity category 100 Degree of degradation of geo-conservation values 102 Source 102 A1.3.4 Coastal Geomorphic Sensitivity, Condition and Geoconservation Priority Map Descriptors 103 Sensitivity of Coastal Geomorphic and Geological Features (Sens) 103 Geomorphic Condition Classification (Cond) 105 Geoconservation Priority ("Indicative Geovalues") of Coastal Segments (Geovalues) 107 APPENDIX TWO: COASTAL PHOTOGRAPHY – NRM North and Cradle Coast REGION109

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Introduction

PREFACE History and Future Development of Tasmanian Coastal Geomorphic Map Datasets This report documents the results of the third in a series of projects aimed at mapping and documenting the geomorphology and geoconservation values of Tasmania’s coastal regions (see further details in the Introduction below). The previous two projects documented these values for the southern and northern NRM region coasts (DTAE 2007a, b). For consistency, the same mapping formats and classifications have been used in this project as in the previous ones. The map datasets on which these projects have been based comprise a line-format geomorphic map (tascoastgeo_v5) and a polygon-format coastal Quaternary/landforms map (tascoastsed_v5), both of which originated in earlier projects prior to the current series of coastal NRM projects, and both of which have been considerably improved and upgraded during the NRM coastal values projects. The original version of the line format map was prepared in 1999-2000 for the Australian Maritime Safety Authority’s Oil Spill Response Atlas (Sharples 2000), whereas the polygon map originated as coarse (100K) polygon Quaternary sediment and landform mapping for a West North West Coastal Management Plan project (Sharples 1998).

The original line map (Sharples 2000) was complete for the entire Tasmanian coast, but was largely based on air photo interpretation; hence subsequent projects including the NRM North and Cradle Coast project have added considerable information to this map as a result of ground-truthing. In contrast, the polygon map originally compiled coarse landform mapping for only the west-north-west Tasmanian coasts (Sharples 1998); subsequently more polygon mapping was added for southeast Tasmania during the South East Tasmanian Integrated Coastal Management Strategy Project (Sharples 2001), and further polygon data was again added during the southern and northern NRM coastal values projects (DTAE 2007a, b). The present NRM North and Cradle Coastproject has added still further polygon map data for the project region (including some polygon mapping for the ArthurPieman coast by Sharples 2007), however some gaps in the polygon mapping remain for parts of the southwest Tasmanian coast.

It is important to be aware that the previous versions of both the line and polygon geomorphic maps (tascoastgeo_v4 and tascoastsed_v4) are currently being incorporated into national coastal geomorphic maps as part of a major National coastal vulnerability assessment project being carried out

by Geoscience Australia for the Commonwealth Department of Climate Change (currently still in progress). These new national maps contain all the detail that was recorded in the precursor Tasmanian maps, but use a new nationally-consistent geomorphic classification and attribute field system. As explained in the Introduction (below), for practical reasons it was not possible to apply these new classifications to the NRM North and Cradle Coastcoastal values mapping project. However, it is envisaged that the new mapping compiled during the NRM North and Cradle CoastProject (resulting in the new line and polygon maps tascoastgeo_v5 and tascoastsed_v5) should be reclassified to the new nationally-consistent classification and incorporated into the next version of the national coastal geomorphic line and polygon maps. The new nationally consistent coastal geomorphic line and polygon maps will be available on the Geoscience Australia “OzCoasts” website, and are expected to provide a national framework for compiling ongoing coastal mapping and data upgrades by a suitable data custodian agency in each state (likely DPIW for Tasmania).

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Introduction

1.0

INTRODUCTION

1.1 THE COASTAL VALUES PROJECT This report documents the geomorphic components of a project entitled Coastal Values Mapping, which was funded by the NRM North and Cradle CoastNatural Resource Management (NRM) and delivered by Hydro Tasmania Consulting during 2007 – 2008. This project ran in conjunction with a collection and integration of coastal vegetation and fauna habitat data assessment completed by North Barker Ecosystem Services. The overall purpose of the project was to enhance and add to data on natural coastal values (geomorphology, flora and fauna) of the NRM North and Cradle Coast region of Tasmania. The information will also provide management tools that can be used in conjunction with the data in order to assist State and Local Government and NRM North and Cradle Coast committee planners in making appropriate decisions on the sustainable use and development of the coastline.

The project constitutes an extension and further development of work previously undertaken in 20052006 for the Southern and Northern Tasmania Regional Coastal Management Committees of NRM and the Coast and Marine Branch of the Tasmanian Department of Primary Industries and Water (DPIW). The outputs of the earlier work were the Vegetation, Fauna Habitat and Geomorphology Coastal Values Information for the Southern and Northern Tasmania NRM Regions – Interpretation Manuals delivered in 2006 and published by Department of Tourism, Arts and the Environment in 2007 (DTAE 2007a, b).

The field validation and reporting for the NRM North and Cradle Coastwork was completed during 2008. The NRM North and Cradle Coast region project area extended from Macquarie Heads located west of Strahan to Weymouth. Areas excluded from the project included National Parks, some other reserves, and the coastline between Sandy Cape and Arthur River, the geomorphic mapping for which had been previously upgraded by C. Sharples during a separate mapping exercise for the Tasmanian Parks & Wildlife Service (DPIW 2007, Sharples 2007). Following the exclusion of these areas of coastline, the project area comprised 720 km of coastline measured at 1:25,000 scale.

The project undertaken broadly comprised three parts, which are outlined below: 1.

Collection of Coastal Geomorphic Data This largest part of the project involved field mapping and air photo interpretation to enhance and add to existing mapped information on the distribution and characteristics of the variety of coastal rock types, soft sediment bodies and landforms that comprise the NRM North and Cradle Coast coastline.

Prior to the current project, comprehensive mapping of the coastal landform types of the NRM North and Cradle Coast region existed in the form of a nominally 1:25,000 scale coastal digital line map encoding information on geology and landforms (the Tasmanian Shoreline Geomorphic Types map tascoastgeo_v4: Sharples, 2006b), however much of this mapping was based on a combination of existing geological mapping combined with air photo interpretation, with only limited ground truthing data (see also Section 4.2). In addition, whilst the line map identifies the presence of coastal dunes and soft-sediment bodies along the coast, it does not map their lateral extent. Partly in order to remedy the latter problem, a polygon (area) map of coastal soft sediment bodies and landforms was created during the 1999 for the West North West Councils from 100K maps interpreted from 250K and 50K geological mapping by Sharples (1998). This map has subsequently been extended and upgraded at better scales for the Southern & Northern NRM region coasts to produce version 4 of the Tasmanian Coastal Quaternary sediments polygon map tascoastsed_v4 (Sharples 2006c), however the Cradle Coast portion of the map remained at coarse 100K scale until additional polygon mapping of the Arthur-Pieman Conservation Area (APCA) coastal landforms was under-taken by C. Sharples during 2007 (Sharples 2007) The aim of the coastal geomorphic mapping undertaken during this 2007-2008 NRM North and Cradle Coast project was to enhance the accuracy and detail of the coastal geomorphic line map by means of ground-truthing, and to improve the coastal geomorphic polygon map for the NRM North and Cradle November 2008

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Introduction

Coastregion beyond the APCA by mapping coastal soft sediment bodies and landforms at greater levels of detail (much of the original 100K mapping provided by Sharples (1998) was based on preexisting 1:250,000 geological mapping, which was known to provide only a coarse representation of coastal Quaternary sediment types and areas). The resulting enhanced and extended digital maps are tascoastgeo_v5 and tascoastsed_v5 (see Appendix One for detailed descriptions of the data encoded in these maps).

In the case of both maps, the limited funding and time available for mapping resulted in the mapping work being prioritised to focus on key coastal landform types and attributes considered most important from the perspective of managing coastal geomorphic values and land degradation issues: Dax Noble, Brad Smith and Cliff Massey from Hydro Tasmania Consulting undertook ground – truthing of the line map, focussing in particular on coastal landform types most likely to be prone to slumping and/or to relatively rapid progressive erosion of non-sandy shoreline types (e.g., Tertiary-age clayey-gravely sediment shorelines, Quaternary talus (colluvium) shores including basalt landslide deposits, etc) and more cryptic coastlines comprising a mix of sensitivity (hard and soft coastlines).

Sandy shores are readily evident on air photos due to their high albedo (reflectance); hence, it was considered that the pre-existing air-photo interpreted line map indicated the location of these highly erodible shoreline types to a good level of confidence. However, the landwards extent of the sandy coastal sediment bodies required mapping, and the mobility (or degree of vegetation cover) of dunes forming parts of the coastal sand bodies was also considered important information for coastal planning purposes. Dax Noble completed digital Air Photo Interpretation (API) mapping of soft sediment coastal bodies, landforms, and their extent of mobility now to an accuracy of 10:000 scale or better such that it was possible to map individual clumps of vegetation and trees. The work was completed primarily through API with some fieldwork that mapped the landward extent of the sediment bodies (see also Section 4.3). This information was used to extend the coastal sediment polygon map (tascoastsed_v5) for the NRM North and Cradle Coast region. This now completes most of the mapping of sediment bodies at good scale for Tasmania’s coastline apart from the far south and south-west coast.

Concurrently with the Cradle Coast NRM mapping project, the classifications (attribute tables) previously used to identify differing sediment types and landforms in the prior (2006) version of the Tasmanian Shoreline Geomorphic Types line map (Sharples 2006b) have been undergoing significant revision as part of a national coastal geomorphic “Smartline” mapping project. This work is being undertaken by Chris Sharples and co-workers at the University of Tasmania, for Geoscience Australia and the Commonwealth Department of Climate Change (still in progress). Ideally, the Cradle Coast mapping now produced as tascoastgeo_v5 should be reclassified to reflect the new National coastal geomorphic line map classification. However, it was considered that it would create confusion to attempt this during the course of the NRM North and Cradle Coastproject, since the new national classification scheme was (and at the time of writing is) undergoing further development and changes.

It is intended that the NRM North and Cradle Coastgeomorphic line mapping will be reclassified as part of a subsequent incorporation of that data into the future second version of the national coastal geomorphic line map (Tasmanian tile auscstgeo_tas). However, for the reason noted above it was agreed to be more appropriate that the existing geomorphic classification and categories previously used for the Tasmanian Shoreline Geomorphic Types Map (Sharples 2006b) continue to be used for the Cradle Coast mapping project. Information collected in the new classification system breaks the intertidal and the backshore zones up into a dominant and subordinate category; knowing this, Hydro Tasmania Consulting staff verified data using the existing attributes table and maintained consistent notes on dominant and subordinate processes throughout all validated areas.

The mapping undertaken nominally covered a strip between the Low Water Mark (LWM) and 100 metres inland, however in practice coastal sediment bodies and their associated landforms were mapped to their full extent inland.

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Introduction

During the course of field mapping, photographs of the coastal landform types being mapped were taken for reference and desk based validation (for the helicopter validated segments), purposes (see Section 4.4 and Appendix Two).

Figure 1 The NRM North and Cradle Coast region, indicating the coastal sections subject to mapping during the present project, and major areas excluded from mapping during the present project.

2.

Application of Decision Support Tools to the Data The coastal geomorphic mapping described above is a relatively detailed dataset that provides a basis for coastal decision-making processes; however, it is recognised that in its "raw" form, the implications of the geomorphic mapping for management decision making will not necessarily be immediately obvious to planners. Consequently, information from the geomorphic mapping has been abstracted to create a number of indicative map layers that provide planners with an indication of management issues that may be pertinent to particular coastal locations. These are referred to herein as Decision Support Tools, and comprise the following: Sensitivity and Condition Coastal landforms have been classified in terms of their relative sensitivity to degradation resulting from human disturbances, and the extent of degradation that has actually occurred (condition) which has altered the landform(s) from the natural condition. A ranking scale of 1 to 4 has been attributed to describe the range in these classifications – from largely natural landforms with little or no degradation November 2008

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Introduction

(rank 1), to highly modified coastlines with little or no natural geomorphic character (rank 4). See Section (4.6).

Geoconservation Priority A Geoconservation Priority (Geovalues) layer was created to summarise the sensitivity and condition layers into a single high-level indicator of coastal areas in which management of geomorphic issues should be a priority, either by reason of landform sensitivity to disturbance or by reason of the existence of more natural (less-disturbed) sections of coast, whose conservation values warrant management attention for that reason. See Section (4.8).

However, whilst the Geoconservation Priorities layer provides a generalised indicator of potential coastal geoconservation management priorities for the whole NRM North and Cradle Coast region, it does not identify specific sites having specific geoconservation management issues. No systematic comprehensive assessment of coastal geoconservation sites has yet been undertaken for the Tasmanian coast, however a number of particular significant sites have been recognised and these are identified by the Tasmanian Geoconservation Database: Geoheritage All coastal geological, landform and soil sites listed on the Tasmanian Geoconservation Database (TGD) as significant geoheritage within the NRM North and Cradle Coast region were extracted from the TGD and are supplied as a separate map layer (see Section 4.5). Whilst the compilation of the TGD is an ongoing process and it is highly likely that new coastal sites will be recognised in future, the Geoconservation Values map layer highlights particular coastal sites that have been recognised to date as having special conservation values for geological or geomorphological reasons.

Coastal Vulnerability Indicative mapping of coastal vulnerability 1 to erosion and flooding, particularly with respect to likely increase in these hazards due to sea level rise, is additional information pertinent to coastal management planning in the Cradle Coast NRM region. This information has been provided by Sharples (2006a) and is accessible on the LIST website (http://www.coastalvulnerability.info or (http://www.thelist.tas.gov.au), hence it has not been reproduced in the dataset provided with this report. However, the relevance of this mapping as a key coastal management tool is outlined in Section (4.7) of this report.

3.

Dissemination of and Training in Use of the Data and Decision Support Tools The use of the Decision Support Tools and underlying geomorphic base data compiled in the course of this project will be explained in a training course for State & Local Government planners and managers to be held at the end of this work, and through distribution of this manual and associated digital mapping. It is also intended that the map layers discussed and used in this manual will be available to planners via the LIST website.

Since the Decision Support Tools created through this project have not been applied to Land Management planning and zoning prior to the recent series of NRM coastal values projects, there is no existing evaluation of the usefulness of these tools. Rather, this project represents an early stage in the application and testing of these tools. It is therefore expected, that there will be scope for feedback from users, based on practical experience in applying these tools, to provide a basis for improving the usefulness of these tools in the future.

1

The terms ‘geomorphic susceptibility’ or ‘sensitivity’ would be more correct here, since ‘vulnerability’ properly includes socio-economic factors and adaptive capacity, however the term ‘vulnerability’ is used here in accordance with its use by Sharples (2006a).

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Introduction

1.2 HOW TO USE THIS REPORT This manual and the accompanying digital mapping are intended to provide planners and land managers with an integrated set of tools to better support the process of arriving at the most informed possible decisions on sustainable coastal development and conservation management. The tools described by this report relate to geomorphic (landform) issues in coastal management and complement a set of maps and management tools relating to coastal flora and fauna that are described separately.

Section 5: Manual: Section 5 of this report functions as a succinct manual that briefly describes a practical method of using both the data and the decision support tools. The remaining sections of this report are reference materials that identify the most commonly encountered geomorphic management issues pertaining to coastal areas. These sections provide a descriptive background and technical support information that is summarised below.

The Manual (Section 5) is the key section of this report. The other sections should be referred to for explanatory information, as follows: Section 2: Geomorphic Description of the NRM North and Cradle Coast Region: An introduction to the geomorphic (landform) history and character of the region’s coast. A basic understanding of the physical nature of the coast will assist planners in understanding the management issues associated with the coast.

Section 3: Key Coastal Geomorphic Management Issues: A brief outline that highlights the key geomorphic management issues relevant to the NRM North and Cradle Coast region (more detailed information is available from references cited in this section). The issues briefly discussed in this section are not exhaustive, however they are probably the most widely relevant geomorphic management issues encountered in planning for the NRM North and Cradle Coast region coast. The data and management tools provided with this report have been prepared with their relevance to these issues in mind.

Section 4: Coastal Geomorphic Datasets and Decision Support Tools: This section provides general information on the history, purpose and characteristics of each map, dataset and planning tool referred to in this report. This information will enable planners to better understand the maps and tools provided, which in turn will allow them to extract valuable information.

Appendix One: Data Dictionary: This appendix provides a more technical description of each digital map dataset provided with this report. Planners may generally not need to delve into this appendix; however, the information provided here is essential for GIS workers needing to set up the GIS mapping accompanying this report in a format that will best facilitate their use by planners.

Appendix Two: Coastal Photography: A list and description of coastal landform photos are provided with this report. This photography is intended to provide users with a broad understanding of the coastal landform types described in this report, and their associated management issues. The collection of photos captured within this project is relatively comprehensive and represent most of the key coastal landform types within the NRM North and Cradle Coast region. The photos provide examples of the different types of coastal landforms encountered during the fieldwork. It is intended that future planning, management or development work that is likely to involve coastal areas, will be able to utilise this collection of photos in order to gain an understanding of the range of landforms types within their region and how to manage these areas. This will include an understanding of the status of sensitivity and condition for differing examples of the key coastal landform types.

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Introduction

1.3

GLOSSARY OF TERMS

APCA

Arthur Pieman Conservation Area

API

Air Photo Interpretation

Colluvium

Slope deposits. Deposits of boulders, cobbles and finer material that have accumulated on slopes as a result of erosion and movement of material from higher levels. Many colluvial deposits in Tasmania formed under the more sparsely-vegetated conditions of the last glacial climatic phase.

DPIW

Department of Primary Industries & Water, Tasmania.

DPIWE

The former Department of Primary Industries, Water & Environment, Tasmania. Now the Department of Primary Industries & Water (DPIW).

DTAE

Department of Tourism, Arts and the Environment, Tasmania

Flood – Tide Delta

A sediment deposit (usually sand) that has accumulated in a coastal lagoon or re-entrant, at the landwards end of a tidal channel or reentrant mouth through which tidal currents transport sand.

Geomorphology

The study of landforms, their forms, genesis, development and processes.

Geomorphic

Pertaining to geomorphology.

Glacial Phase

A relatively cool period of Earth history during which significant expansion of glaciers and ice caps occurs, and sea level drops significantly. Multiple glacial phases have occurred during the last few million years. The Last Glaciation peaked about 22,000 to 17,000 years ago, and ended about 10,000 years ago.

Holocene

The stage of geological time between the end of the Last Glaciation (about 10,000 years ago) and the present. The Holocene effectively equates to the present interglacial climatic phase.

Interglacial Phase

A relatively warm period of Earth history, between glacial phases, when glaciers and ice caps retreat and sea level rises significantly.

The Earth is currently in an interglacial phase, and the last (previous) interglacial phase occurred around 125,000 years ago.

IPCC

Intergovernmental Panel on Climate Change. An international organisation established in 1988 by the World Meteorological Organisation and the United Nations Environment Programme, for the purpose of reviewing and reporting on the current state of scientific understanding of and research into global climate change and its effects, including sea-level rise (see IPCC, 2001).

LIST

Land Information System Tasmania. Centralised Tasmanian Government land information (e.g., topographic mapping) data system, operated by DPIW.

Lithification

The geological processes whereby soft sediment becomes a hard, tough rock over a period of time. Lithification processes include compaction of the sediment and the precipitation of chemical cementing agents from groundwater.

Littoral Drift

Movement of sediment (e.g., sand) along a shore in the near-shore zone, usually resulting from along-shore currents generated by

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Introduction

wave action.

Pleistocene

The stage of geological time spanning most of the last 2 million years up until the end of the Last Glaciation 10,000 years ago. The Pleistocene has been marked by a succession of glacial and interglacial climatic phases, which have caused sea level to repeatedly rise and fall over a vertical range of about 130 metres, and to exert a strong influence on coastal landform development globally.

Post-glacial Marine Transgression

In this report, the period of relatively rapid and continuous global sea-level rise following the maximum intensity of the last glacial climatic phase (circa 22,000 to 17,000 years ago), when sea level rose by about 130 metres before stabilising close to its present level about 6,500 years ago.

Progradation

Seawards growth and accretion of a shoreline by addition of sediment, usually where the sediment budget involves a predominance of sediment supply and accretion over erosion.

Quaternary

The period of geological time spanning most of the last 2 million years up to and including the present. The Quaternary period is subdivided into the Pleistocene (older) and Holocene (recent) stages.

Semi-lithified

Refers to sediments which are coherent and partly "turned to rock" (lithified) by processes of compaction and the precipitation of chemical cementing agents from groundwater, yet remain softer and more erodible than a fully lithified rock.

Talus

A variety of colluvium (slope deposits) typically comprising loose boulders and cobbles that have fallen, rolled or slid from an escarpment and accumulated below.

Tasmanian Geoconservation Database (TGD)

A database of particular geological, geomorphic and soil features that have been recognised as having special geoconservation ("Geoheritage") values. The TGD is maintained by the Department of Primary Industries & Water (DPIW), and custodianship is vested in the Senior Earth Scientist (Earth Science Section, Nature Conservation Branch), or equivalent officer.

Transgression

In relation to the sea, a phase during which the sea rises or "transgresses" over land formerly dry.

Unconsolidated/Unlithified

Refers to sediments that remain more-or-less loose or friable, not formed into hard rock by geological processes such as compaction and precipitation of cements from groundwater.

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Key Coastal Geomorphic Management Issues

2.0 COASTAL GEOMORPHOLOGY OF THE NRM NORTH AND CRADLE COAST NRM REGION 2.1

INTRODUCTION

This section provides a brief description of the coastal geomorphology (landforms and land-forming processes) in the North and Western NRM region. This description is broad in outline, though specific examples have been provided of the different shoreline types. The intent is to provide a framework for users of the manual to discern the management issues relevant to the geomorphology of the Southern NRM coast. Readers interested in learning more about the coastal geomorphology of the Western and Northern NRM region, and Tasmanian coastal geomorphology generally, might usefully begin by reading the introductory descriptions provided by Fish & Yaxley (1966), Scanlon et al. (1990), Bird (2008), the more comprehensive description of Tasmanian coastal landforms provided by Kiernan (1997) and subsequently by exploring the extensive literature of papers and articles on Tasmanian coastal geomorphology, some of which are cited below.

2.2

GEOLOGICAL AND GEOMORPHIC HISTORY OF THE NRM NORTH AND CRADLE COAST REGION

Coastal Bedrock Types Much of the coast of the NRM North and Cradle Coast region (West and North-west Tasmania) is formed of or underlain by extensively folded sedimentary rocks (pyritic siltstone and mudstone from the Rocky Cape Group, quartzose sandstone, basalt and pyroclastic associations of the far Northwest and Devonian alkali-feldspar granite). Much of the west coast is exposed to high energy wave action including storm surges and physical weathering from high seas depositing larger than average sediment along the coastline. The exposure of the western coastline has meant that the coastline

has been more extensively weathered than the northern coastline, which is comprised of more sheltered bays, estuaries and low energy coastlines.

Tectonic Controls on Coastal Development - Jurassic to Tertiary Periods As is true for much of the Tasmanian coast, at the largest scale the gross plan form of the coast of the NRM North and Cradle Coast region reflects the influence of tectonic faulting and disruption of these bedrock sequences during the break-up of Gondwana from Jurassic to Tertiary times (particularly in the period between circa 170 and 40 million years ago; see Morrison et al. in: Burrett & Martin 1989, p. 341-347). The predominantly linear plan form of the west and southwest coasts evidently reflects the parallel marginal faults of the offshore Sorell Basin, an extensional graben developed due to crustal stretching and rifting as Antarctica separated from Tasmania. The Macquarie Graben, a downthrown basin underlying Macquarie Harbour that has filled with Tertiary-age sediments, is an onshore extension of the Sorell Basin. Similarly, the gross form of the northwest coast (Devonport to Woolnorth) broadly parallels fault trends in the extensional Bass Basin to the north, which also developed as a failed rift zone during the separation of Australia and Antarctica, albeit subsequent volcanism and sedimentary deposition have somewhat masked the large scale tectonically-controlled coastal form.

During much of the Tertiary Period (65 – 1.8 million years ago), the large graben structures were lowlying depositional basins in which thick sequences of fluvial (river), lacustrine (lake), mass movement and some marine sediments were deposited. Owing to their relatively young geological ages, these Tertiary sediments are mostly only semi-lithified materials, typically gravely or bouldery sequences with high proportions of soft clays that are prone to rapid wave erosion or slumping when exposed on the shoreline. Because the Tertiary sediments typically formed infillings within the Tertiary graben basins, they are mostly exposed where the present coastline transects the graben basins. This situation occurs more commonly in eastern and south-eastern Tasmania than in the Cradle Coast region, however semi-lithified Tertiary sediments are well exposed on the north shore of Macquarie Harbour and in the Wynyard area.

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Quaternary Geological Development of the NRM North and Cradle Coast Region West Coast This study validated the section of coast from Macquarie Heads at Strahan heading north to Woolnorth Point. Present day geology shows vast expanses of Holocene sands +/- vegetative stability throughout the Western NRM North and Cradle Coast region. Coastal dune systems varying between mobile parabolic Holocene and stable Pleistocene aged dominate south of Trial Harbour. The mainly high cliffed coast between Trial and Granville Harbours comprises of alkali-feldspar granite and granite/adamellite of Devonian age. The rocky shore platforms extending north of Granville Harbour are formed of unmetamorphosed quartzwacke turbite sequences. Further north to Ahrberg Bay consists of younger foreshore dunes backed and underlain by older (Pleistocene aged) dune systems.

The striking elongate columns and bedrock surrounding Conical Rocks is dominantly adamellite to granitic and encapsulates the headland to Hardwicke Bay. The section of coast north of Hardwicke Bay to Sandy Cape is dominated by dark, laminated, commonly pyritic siltstone and mudstone of Cowrie Siltstone and similar sequences for the southern part. The northern section extending to Sandy Cape is largely dominated by Holocene parabolic and transgressive dune systems, segregated by outcrops of grey siltstone and pale quartz siltstone-fine quartz sandstone. Sandy Cape itself is dominantly alkali-feldspar granite. Sharples (2007) validated a large section of coast extending north from Sandy Cape to Arthur River in previous work by and as such was an exclusion zone for the present project. This region is dominated by long (~20km) sandy beaches, parabolic and transgressive dune systems separated by rocky shores of finely interlaminated siltstone, quartz and sandstone and pyritic siltstone and mudstone.

North of Arthur River there are alternating sequences comprising of quartzite, coastal sands and gravels and marine limestone intertidal platforms through to Mount Cameron West where basalt (Hawaiite, with other related pyroclastic rocks) protrudes. North of Mount Cameron coastal sands continue to dominate backed and underlain by older stabilised Aeolian sand of predominantly coastal plain, with underlying marine sands. Maxies Point to Studland Bay consists of sandy beaches and dunes separated by lower to upper intertidal sections of thin bedded laminated siltstone and mudstone with interbeds of cross-laminated and oscillation ripple-marked quartzarenite. Occasional pockets of laminated dolomitic siltstone are also present as is silicified quartzarenite that is well bedded with minor horizons of laminated siltstone.

Bluff Point marks the main cluster of crudely bedded basaltic pyroclastic rocks from the Marrawah Volcanics association which includes massive-columnar, olivine basalt lavas that forms high-cliffs along the coastline rising to greater than 100 m ASL. Isolated beaches and embays comprised of basalt gravel beaches are separated by marine limestone and basalt rocky shore platforms and headlands. The final section of the west coast encompassing the far North-western tip of Tasmania around to the start of the north coast is Woolnorth Point, almost entirely comprising dominantly orthoquartzite sequences of the Rocky Cape Group.

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North Coast to West Head The north western part of Tasmania’s north coast contrasts the high energy west coast with tidal and salt marsh flats replacing expanses of rock shore platforms and near shore rocks and reefs; fine silt and paralic clay in sheltered estuaries replacing high energy bays with fine to medium grain sands.

The coastline from Murkay Islets through to Smithton is predominantly uniform in geology, comprising paralic clay, silt , sand and minor gravel deposits associated with tidal flats and modern salt marshes in the more sheltered bays and coastal segments. The majority of the coastline and extending landward, is dominated by older stabilised Aeolian sand of predominantly coastal plain, underlain by marine sands that may include relict landform features including terraces, lunettes, linear or barchan dunes and beach ridges. The Stony Point outcrop is reddish-brown weathering, interbedded lithic wacke, litharenite, lithic conglomerate and laminated siltstone-mudstone that is generally well bedded with an upward-fining cycle which is partly turbidic and of late Cambrian age. Closer to Stanley sections of massive and amygdaloidal, dominantly tholeiitic basalt (commonly with pillows) occurs. Coastal sands, marine sediments and gravel dominate many of the beaches and inlets on the western side of Stanley.

The shore around Stanley is a mix of Basalt (tholeiitic to alkalic) and related pyroclastic rocks along the rock cliffs and shorelines and the volcanic neck of ‘The Nut’. Coastal sediments dominate much of Stanley which is a tombolo comprising costal sands and gravels and other marine sediments. Sections of talus slopes exist around ‘The Nut’ and are both vegetated and active. The eastern side of the Stanley tombolo is dominantly sand and sediments of lacustrine and littoral origins. From Stanley to Rocky Cape the lithology is dominated by sands of stabilised longitudinal beach dune ridges, fine to medium grained sands and pyritic siltstone and mudstone that is laminated and commonly dark. Rocky Cape comprises well-bedded and cross-bedded orthoquartzite and subordinate siltstone from the Detention Subgroup.

The section of coastline from Rocky Cape to Wynyard is largely dominated by Basalt flows tending north easterly. Sections of older stabilised Aeolian sands and coastal plains are underlain by marine sands but are less common throughout this section of coastline. The other main lithology comprises orthoquartzite and subordinate siltstone as found around Rocky Cape. The elevated monolith of Table Cape is a Crinanite volcanic neck. .Immediately to the north, and east of Wynyard to Somerset the present sea platform comprises outcrops of indurated Permian tillite, minor basalt extrusions and sand beaches with longitudinal beach dune ridges.

Wynyard east to Penguin is primarily backed by Basalt as previous sea cliffs, however, only a few small pockets of Basalt reach the ocean. Much of the coastline is a mix of consistently alternating bedrock extrusions intermixed between older stabilised sands. Precambrian interbedded diamictite, pebbly mudstone and laminated mudstone, with minor conglomerate and sandstone, quartzwacke turbidites and Agglomerate and tuff, form much of the coastline outcrops that inter-space the sandy and/or gravely beaches and older stabilised dune systems. Burnie is however, built upon a minor outcrop of Olivine tholeiite, and comprises a section of fabricated structure/deposits connecting the terrestrial and marine environments. Two small sections of Cambrian Dolerite outcrop between Somerset and Burnie.

Penguin to Ulverstone similarly to the previous section comprises of Basalt flows in the distal backshore as older sea cliffs, the upper and lower intertidal zone however differs somewhat in diversity. Large blocks of chert, quartzite, basalt, limestone, siltstone, mudstone and jasper in a matrix of lithicwacke and mudstone and conglomerate are present on the coastline immediately north of Penguin. Tholeiitic basalt lava and chert, quartzwacke turbidites, schistose conglomerate, volcaniclastic sandstone-siltstone-mudsone-chert-minor carbonate sequences with intercalated tholeiitic basalt flows, phyllite and quartz are interspaced and irregularly occurring east of Penguin through to Ulverstone.

Ulverstone to Port Sorell is backed and underlain by marine sediments. East to Devonport much of the coast is interspaced with deeply weathered basalt and quartz-mica and mica-quartz schist. The section November 2008

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from Devonport to Port Sorell consists of stabilised dunes and beach systems in the upper and lower intertidal zone with Devonport Bluff and Port Sorell occurring as projecting dolerite intrusions. Port Sorell itself is comprised of coarse, fine grained and pebbly sand with sections of paralic clay, silt and minor gravel deposits associated with salt marshes and tidal flats, with minor section of quartz sandstone and shale, stream alluvium and talus associated with dolerite boulders. From Port Sorell east to West Head at the top of the Tamar Estuary the coastline is moderately uniform consisting of stabilised and active longitudinal beach ridges with or without gravel deposits that are separated by Badger Head - a sandstone, slate and phyllite protrusion and West Head which is comprised of Dolerite on the exposed marine interface and non marine gravel, sand, silt, clay and regolith on the estuarine entrance to the Tamar Estuary.

North Coast - Tamar Estuary to Weymouth The Tamar ‘River’ is dominated by non marine gravel, sand, silt, clay and regolith and dolerite throughout much of the northern reaches. Other minor occurrences include basalt, human modified sections, minor talus deposits, fossiliferous sandstone, siltstone, mudstone and limestone - with or without minor conglomerate marine fossils, cross-bedded quartz sandstone and shale and stream alluvium and swamp deposits around creek mouths and embayments away from the main channel. The southern part of the Tamar river from Gravelly Beach to Launceston has minor sections of dolerite (with or without weathering), sand and siliceous pebble gravel less than 10m above sea level and poorly consolidated clays, silt/sand with gravels, some deposits with iron oxide-cemented layers and concentrations and others containing leaf fossils. By far, the most dominant lithology are deposits of estuarine silt, mud, sand and gravel in generalised tidal to sub-tidal environments and submerged to emergent estuarine deposits of similar composition.

Low Head is a dolerite intrusion and marks the eastern tip of the Tamar estuary. Low Head to Weymouth is principally uniform in lithology with vast beaches and dune systems backed by windblow sands. The beaches are separated by basalt outcrops and micaceous quartzwacke turbite sequences from the Mathinna Group.

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Figure 2 Distribution of the softer coastal landform types in the NRM North and Cradle Coast region, which were the priority focus of fieldwork during this project (see Section 1.1). This map was created using the shoreline geomorphic types line map (tascoastgeo_v5gda) that was upgraded during this project using fieldwork results from many of the areas highlighted here. Note that the small scale of this map results in loss of much of the finer mapping detail that the map actually contains.

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Figure 3 Many coastlines in the NRM North and Cradle Coast region are moderate to steeply sloping hard-rock shores, such as that shown here north of Trial Harbour, western Tasmania. These shores tend to be highly robust and present few geomorphic management issues. However when these shores and their backshore areas are more or less undisturbed, they may have high conservation value for a variety of reasons including the importance of undisturbed geomorphic process systems, scenic values and in providing natural habitat for flora and fauna.

Figure 4 Shores of mixed sensitivity, such as the semi-lithified rocks and gravels intermixed with sandy substrates shown here at Doctors rocks south of Wynyard in northern Tasmania, are prone to progressive erosion, and may present a range of geomorphic management issues, particularly with sea level rise, even though they are less mobile than sandy beach shores.

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2.3 COASTAL LANDFORM TYPES AND GEOMORPHIC PROCESSES IN THE NRM NORTH AND CRADLE COAST REGION There are four distinct geomorphic coastline types that comprise the North and Western coastlines of Tasmania. The west coast from Macquarie heads north to Marrawah has long expanses of bedrock coastline in various stages of in situ breakdown, separated by vast deposits of wind-blown Holocene and Pleistocene dune systems. The far north-west coastline between Mt Cameron and Cape Portland alternates between long fine-medium grained beaches with common bedrock outcropping and high cliffed coastline with basalt extrusions. Between Robbins Island and east of Stanley, there is a marked change in physical exposure with vast expanses of tidal sand flats backed by salt marshes. Rocky shore platforms are still present; however, bedrock extrusion and expanses of bedrock coastline with in situ breakdown are greatly reduced comparative to the West coast. The remainder of the coastline comprises fine to medium grained beaches separated by rocky headlands (this is a lower energy coastline, as distinct from the high-energy west coast), and large estuaries that consist of mixed substrates and fluvio-lacustrine deposition, examples of which are seen in the Mersey and Tamar Rivers.

Hard Rock Shorelines There are known to have been two glacial events dating back to the Pleistocene that are responsible for carving many of the mountains, deep gorges and rivers throughout much of Western Tasmania. Post glaciation the sea around Tasmania reached its present level around 6000 BP and since, the hard bedrock coastline has remained unaltered (Banks Colhoun and Chick, 1977). The west coast of Tasmania receives significant storm surge due to dominantly westerly frontal weather systems. High seas have further shaped sections of the west coast, post glaciation. This has occurred firstly, through the initial weathering (chemical and physical) of the parent rock, leading to break-down in the form of collapse (mass-movement) caves, rock arches and ledges. Further in situ weathering leads to the development of secondary formations, such as, rocky shores, dissected shores (ridges run parallel to the coastline), incipient (ridges run perpendicular to the coastline) and shore platforms. These coastal rocky shorelines grade from coarse to smooth (such that a 4x4 vehicle could drive across a shore platform; Bird, 2008). Tasmania’s west coast contains significant expanses of each of these shoreline types, while the northern coastline contains a predominance of [flat] shore platforms (Figure 5).

The area north of Trial harbour is remarkably straight, possibly due to a geological fault. This section of coast is subject to very heavy wave attack and consists mainly of granitic, rocky expanses, such as the area encompassing Conical Rocks and between Trial and Granville Harbours (Banks, et al., 1977).

Granville harbour and some sections of coastline further to the north contain good examples of incipient and dissected shore platforms, while the Bluff Point property and sections of the north-west coastline between Stanley and Wynyard contain good examples of shore platforms and sub-horizontal low tide shore platforms. The latter of which, tend to be exposed only at low tide, slope ocean-ward and may contain algal growth and an ocean fronting ledge or cliff (Bird, 2008). Areas of the northern coastline also contain rocky shore examples similar to the western facing Bluff Point and occur between Table and Rocky Capes. In these locations steep slopes descend to rounded wave washed boulder cobble beaches that are intermixed or underlain with bedrock outcropping or shore platforms.

Around Wynyard and further north, the rocky shore platforms are backed by small weathered cliffs that have been subsequently undermined from wave activity, which has led to block failure and coastline recession of the cliff line.

Larger rocky buttresses and high sea cliffs are also present across the west coast, particularly sections between Ocean Beach and Granville Harbour, further north along the coastline between Mt Cameron and Cape Portland Properties and between Stanley and Table Cape. The dissected buttresses between

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Trial and Granville Harbours are likely to have been formed through periglacial 2 dissection and subsequent erosion and weathering that causes residual massive rock formations that have survived frost shattering and are now weathered by slower cool climate chemical weathering and more physical weathering such as strong winds carrying fine debris and storm surges. Some paraglacial 3 activity may lead to mass movement, however this is unlikely to have played a role in the development of the Cradle region coast since there is no known evidence of Pleistocene glaciers having reached as far as any part of the present day coastline.

Figure 5 Typical rocky shore platform of Northern Tasmania. Many of the shore platforms on the northern coastline are flat and extensive, comparative to rocky shorelines on the west coast of Tasmania.

In the period since the mid-Holocene end of the post-glacial marine transgression, periglaciated coastal slopes have been stabilised from vegetative growth and subsequently undercut by marine erosion, causing steep or vertical basal cliffs (Bird, 2008). Good examples of such undercutting and periglacial frost shattering activity exist throughout much of the West and North West coastline. Mt Cameron West north to Cape Grim is comprised of Basalt, a volcanically derived rock type, and block failure in these regions is likely attributed to volcanic activity that has subsequently weathered.

Coarse and Depositional Material Storm surges can deposit material that is generally coarser than that deposited by fluvial or long-shore drift. Typically the material is delivered in a single event (Bird, 2008) which can hurl material in large quantities up onto the upper-intertidal shore-face and backshore. Evidence of such a storm surgesplaying cobble to boulder size material is visible between Arthur River and Marrawah. While cobble to boulder sized deposition may occur in a single event, the material is often well rounded as small to medium storm events mobilise the material on the ocean floor, grinding away rough edges into a uniform rounded cobble or boulder (Figure 6). Additionally, some of the material may have travelled a 2

Environments that reside outside the boundaries of glaciers and are subject to extreme freeze-thaw activity that causes rocks to crack and/or shatter from the temperature extremes (French, 2007)

3

Slopes that have been left over-steepened as glaciers have supported the slopes; however as the glacier retreats an unstable rock face remains (French, 2007).

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short distance from the escarpment through weathering and subsequent fluvial transport during times of high river discharge, typically at bank-full stage via a thalweg shift (Brierley and Fryirs, 2005).

Figure 6 Cobble boulder berm (left) with evident landward splaying of depositional material (right). This site is recommended for listing on the Geoconservation database as an outstanding example of a geomorphic landform (Bluff Hill Pt berm and splay) likely caused by an extreme storm event or tsunami.

Semi-Consolidated Shorelines Some Tasmanian shorelines are comprised neither of hard bedrock nor soft sand, but of intermediate "semi-consolidated" materials. These include clayey-gravely sediments of Tertiary-age, and steep shores of semi-consolidated slope and landslide deposits. These shores have their own distinct characteristics and management issues.

The softer semi-lithified Tertiary-age bedrock sequences – typically clays, clayey-gravels or sandstones and unconsolidated boulder beds – tend not to exposed on open coast shores directly exposed to swell and storm, where they have generally long ago been eroded to a low profile and covered by sand (as is the case at Ocean Beach, for example). Within the Cradle Coast region, a long shoreline of exposed and cliffed Tertiary clays and gravels occurs on the north side of Macquarie Harbour, an inlet not directly exposed to ocean swells.

However, some open coast shores underlain by Tertiary bedrock (e.g., sediments associated with basalts at Bluff Point, and the Wynyard limey sandstones) have shores of unconsolidated clayeygravely sediment or weathered sandstone facies. Cliff slumping in the Wynyard area occurs in sandstone bedrock and slumping is directly related to wave and wind action eroding the softer shoreline in the lower and upper intertidal zones. Coastal weathering of the unconsolidated sediments in the Bluff Point area, however, is generally void of direct impacts from wave activity as the sediments occur above the cliffs line. Slumping is therefore not associated with wave activity in these areas, but rather, other processes such as wind, climate and physical disturbance.

Some shores are also mantled by younger unconsolidated bouldery slope deposits (colluvium) which are the product of both Pleistocene mass movement processes and relatively rapid Holocene marine erosion on steep exposed rocky coasts. In the NRM North and Cradle Coast region this type of unstable coastline is found on steep exposed high energy basalt coasts at Mt Cameron, and basalt colluvium shores are also common between Stanley and Devonport, in some cases creating significant coastal management problems as at Boat Harbour for example

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Sandy Coast Landforms and Processes (excluding dunes) Beaches A beach is generally an accumulation of loose, unconsolidated sediment, consisting of a range of sizes from fine sand to pebbles and occasional boulders, often intermixed with shelly material. Shelly material will often be more prevalent in the presence of off-shore rocks which can support shellfish growth. Evidence of this is shown by the carbonate content of beaches. Ocean Beach has a very low carbonate composition (0.6-2.5 per cent) comparative to pocket beaches to the north and south (3-38 per cent) that contain offshore rocks and rocky (shellfish-supporting) coasts (Banks et al. 1977).

Beaches form the seaward fringe of barriers, which are banks of deposited beach material that can be deposited across and around inlets, embayments, lagoons and swamps. Beaches occur long, short, curved or straight and are present in both sheltered bays and exposed coastlines. Most beaches exhibit rapid change especially from storm events; however, some beaches are fairly stable for periods of years to decades. Additionally, beaches gain, or loose sediment from prograding or eroding wave action or see sediment migrating down the coastline (Bird, 2008). Wind activity on wide sandy beaches can cause features such as small barchans 4 to form, a combined result of wind gusts and unvegetated backshore sands that migrate downwind (onshore, seaward or alongshore). Small barchans are a notable feature of the wide beach just north of Sandy Cape, and barchans have been observed to form on Tatlow Beach at Stanley on the north coastline of Tasmania during gale events (Bird, 2008).

Post sea-level stabilisation, adjustments in the coastline have occurred with the outline and surface form of Ocean Beach being reshaped due to sand transported by wind and waves activity (Banks et al.

1977). Similar transformations are likely to have also occurred further north to the vast expanses of Holocene dune systems between Interview River and Sandy Cape; while the presence of sea terraces to the west of the Norfolk Range are likely indicators of previous sea level height >100m above present day sea levels.

Storm surges can induce more rapid alterations of sandy coastlines totally reshaping and removing beaches in single events (Bird, 2008). There was evidence on field work (2008) of recent erosion around Macquarie Heads, at the start of Ocean Beach. Photos were compared from a 2006 (scenic) visit to that of the 2008 project trip. In 2006 Macquarie heads could be described as a transitional zone characterised by net deposition with a wide (~200m) slightly prograding beach front (intertidal zone) and a moderately sloping dune upper-intertidal and backshore. As is often the case, the erosion is likely the cause multiple occurrences. Firstly, a local caravan park owner recalls several king tides at the beginning of winter 2007; and secondly, anecdotal evidence from flood hydrographs indicate several large floods pulsing through western draining rivers. The combination of these events has meant that at the time of the 2008 field validation visit, Macquarie Heads was an erosional zone characterised by a receding shoreline (barely 50m wide), steep dune cliffs (>15m in parts) with an actively eroding face and a flat intertidal zone (Figure 7).

4

A barchan refers to a sand mound with lateral trailing arms in a down-wind direction, typical of formations seen in a desert. They can form up to 30 m high with laterally trailing arms up to 350 m long (Bird, 2008).

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Figure 7 Ocean Beach at Macquarie Heads. The left picture was taken during a scenic visit in 2006 and shows an incipient dune between the car and the foredune, indicating a process of progradation (building) of the beach profile. The picture on the right shows no incipient dune present and a large erosional scarp that has cut deep into the foredune, indicating that processes have altered from depositional to erosional.

Coastline alteration has been aided through sediment delivered to the coast during Pleistocene times, from the large high-energy west coast river systems. Due to high rates of glacial erosion in western Tasmania, glacial outwash rivers delivered large quantities of sediment to the continental shelf, which was reworked landwards by wave and wind action, and by rising seas at the end of each glacial phase.

Once this fine-grained sediment reached the present coast it was redistributed by long-shore processes and aeolian transport (dune mobilisation). There were also significant sediment inputs from northern rivers, such as the Cam, Leven, Emu, Forth and Mersey Rivers, as evident from the extensive beaches adjacent to the river mouths or further alongshore in the direction of long-shore drift. The processes that have formed beaches on the northern coastline are less severe however, than their western counterparts. To the north of Ocean Beach, embayment and beach pockets tend to contain higher carbonate content, causing beach material to coarsen, a reflection of the hardened off-shore rock structures that support a greater proportion of shellfish.

Depositional Spits and Barriers (Beach Lobes) Spits, also called barriers or bars, are beaches that have built up above the high tide level and diverge from the coast, typically with a landward hook or recurves. Spits grow in the predominant direction of longrore drift caused by oblique wave action on the coastline. The source of sediment supply for spit formation can be from a range of environmental contributors; such as, glacial outwash, down-drift from eroding cliffs or from the sea floor during marine transgression (Bird, 2008). Within the NRM North and Cradle Coast region there are three primary landform features observed. The river-mouth spits that are attached to land at one end are present at Ocean Beach caused by southerly deflection of both the Henty and Little Henty Rivers on the western coastline and the Black River on the Northern coastline. Saltmarshes and swamps often develop on the landward side of spits (notably) between the recurves due to the shelter provided by these areas from storm surge (Bird, 2008).

There are several rivers on the Northern coastline where river-mouth spits would be expected to occur, but are absent. This is likely attributed to human modification of the coastline in the form of sea defence walls, which restrict or remove the long-shore drift processes from developing spits. Examples of river mouths where natural processes have been restricted occur at the mouth of the Inglis, Leven and Mersey Rivers. Interestingly, the Emu River near Burnie, which has a sea defence wall, has had a spit develop; though this is in the opposite direction to long-shore drift and may be attributable to current circulation effects from the bay. Due to the presence of numerous shore platforms on the northern coastline, some spits are restricted in their development due to the bedrock, examples of this occur at Curries River at Beechford and Pipers River at Weymouth.

There are some specific differences in the wind transport and ocean redistribution of sediment on the west and northern coastlines, as distinct from southern Tasmania, particularly the high energy western November 2008

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coastline. These processes include the dominant long-shore regimes and the presence of deposited material that is linked to storm surge events and dominant wind and wave refraction. Ocean Beach is one such example of the above processes and forms an uneven curvature spanning 32km from Trial Harbour to Macquarie Heads.

The beach is almost totally straight between Trial Harbour and the mouth of the Henty River. Longshore drift has caused the river mouths of the Little Henty and Henty Rivers to deflect to the south.

This results from the sediment transported down rivers such as the Little Henty and Henty Rivers to be deposited along the shorelines further south. This is supported by the presence of fewer heavy minerals and the surprisingly uniform grains of sand along Ocean Beach (Banks et al. 1977).

Southerly long-shore drift is visually evident at the Little Henty and Henty Rivers from a fly-over where beach lobes have formed and have pushed the river mouth exits further south from their expected coastal exit. Interestingly, Bird (2008) notes that “Beach lobes are not found on swashdominated high wave energy coasts”, however with few off-shore structures, Ocean beach is clearly a high-energy swash dominated coastline.

Sandy isthmuses and tombolos Sandy isthmuses and tombolos link islands together or link islands to land, they formed in response to wave refraction and wave approach to shore. Generally, tombolos are formed in response to wave refraction in the lee of the tombolo. There are three notable tombolos within the NRM North and Cradle Coast region.

The best example of process-response in the formation of a tombolo in the NRM North and Cradle Coast region is The Nut at Stanley (Figure 8), where a wave washed tombolo connects The Nut with the mainland. Robbins, Hunter and 3 Hummock Islands shelter westerly dominant wave attack that enters Perkins Bay, which is further subdued by the sandy inlet of West Inlet. This results in the extensive sand flats of Anthony Beach and salt-marsh formation within West Inlet. To the east of the Stanley Isthmus, Sawyer Bay is sheltered by the Black River Beach before entering East Inlet where salt-marshes are also present. Sediment replenishment for the area is likely derived from sand trapped in the Robbins Island ‘sand trap’ region. This is likely to have been derived during the Pleistocene, where glacial processes delivered the sediment to the west coast. Subsequent movement of this sand around and across north-west tip of Tasmania has occurred by a combination of longshore drift and aeolian transport during the course of repeated glacial – interglacial cycle.This area is sheltered from SW swells and acts as a large sand trap. The current stability of the area is evident from the presence of saltmarshes, which are unable to establish in areas of strong wave action.

Figure 8 The Nut at Stanley on the north coast of Tasmania is a good example of a tombolo, see text for explanation.

Other features present within the study area that have more island type formation (as opposed to isthmus) are: Robbins Island which is linked to land by a low lying sand-flat with salt marsh present at the edges of land. It is possible to access Robbins Island with a 4x4 vehicle via the extensive sand flats; and Perkins Island connects to land via a sand flat that is part of Perkins Channel. Similar to Robbins Island salt-marshes are present at the land edges and 4x4 vehicular access to the island is possible at low tide.

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Dune Processes and Formation Coastal Holocene dunes occur in four bedform categories in the Northern NRM Cradle Coast region, these are foredunes, parallel to shore dunes, Parabolic and blow-out dunes and transgressive dune fields. Typically, dune formation will be limited by sediment supply, but presuming sediment supply is not limiting, the process of dune formation occurs as follows, incipient dunes form above the high water mark and become vegetated. As the beach progrades with sand the incipient dunes become foredunes. Alternating sequences of dune degradation from storm events separated by periods of progradation by onshore aeolian sands (winds blown sands) can lead to multiple dune ridges forming that are separated by swales (depressions); these alternating ridges are referred to as parallel dunes (Bird, 2008). Increasing aridity or stronger more frequent wind scouring can cause vegetation to become weakened on dunes previously stable, leading to the mobilisation of aeolian sands. As strong wind gusts continue the vegetated fore and parallel dunes scour and migrate landward in a concave shape known as a blow-out. If the blow-out length reaches greater than three times its mean width, it is referred to as a parabolic (or sometimes U-dune). Parabolic dunes contain trailing arms of partly vegetated sand on either side that form the axial excavated corridor. As sand continues to migrate landward, parabolic dunes may loose their trailing vegetated arms through fire, trampling or other blowouts merging, this results in a wider elongated sediment body referred to as a transgressive dune (Bird, 2008). This process is shown in Figure 9.

Figure 9 Process of dune formation and subsequent transition from parallel dunes via a blow-out into transgressive dunes (Bird, 2008:257).

Incipient dunes In front of the foredune, vegetation can stabilise sands that have been blown onshore by strong winds or from sediment delivered along the coast. These low lying stabilised sand ridges are referred to as incipient dunes. They represent the most seaward and immature dunes within the dune system (DEWHA, 1990). These incipient dunes can further develop forming the new foredune, leaving older foredunes as an older dune ridge. During storm events however, incipient dunes may be completely removed, shown along Ocean Beach at Macquarie Heads (Figure 7), indicating the highly sensitive nature of these geomorphic features. The presence of an incipient dune is a good indication that the beach is currently in a process of accretion or progradation, that being sand is accumulating along this part of the coastline. However, if an erosion scarp is present along the face, this may indicated a transition from accumulating sands to shifting sands from longshore drift.

Foredunes Foredunes are ridges of sand that have built up at the back of a beach or on the crest off a sand or cobble berm, where vegetation has colonised, and traps wind blown sand (Figure 10). The vegetation that colonises acts as a baffle reducing wind velocities at or close to the ground level, thus creating a sheltered environment for aeolian sands to become deposited and stabilise. The dune system is typically vegetated by native Spinifex sp. or the European marram grass (Ammophila arenaria) A November 2008

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foredune may grow higher and wider as additional sand becomes trapped. The amount of growth of the foredune will be dependant on aeolian sediment supply and progradation along the coastline. A foredune may become initiated due to high spring tides that deliver seed-bearing vegetation to the coastline (Bird, 2008). Ironically, however, these same spring tides that initiate the development of a foredune (as an immature incipient dune), especially when coinciding with other storm based events, can also be the same processes that cause their destruction or substantive erosion, as was evident along Ocean Beach.

Parallel dunes Some coasts have multiple dune ridges present, usually running parallel to the coastline behind the foredune. The multiple dune ridges form as a result of successive foredune formation behind a prograding sandy beach from cut and fill sequences on an intermittently prograding shore.. The presence of intervening elongated swales or troughs is what distinguishes parallel dunes apart from prograding backshore terraces. The incipient dune forms from aeolian sands, building a new foredune seaward of the existing foredunes. Storm events erode back the seaward margin of the frontal dune, which is again repaired during calmer conditions, where waves restore the beach and initiate new incipient dunes with an unvegetated swale between the existing foredune and the incipient dune. As foredunes begin to stabilise the swales separating these parallel foredunes may be increased by wind that eddies on the lee (sheltered) side of each developing ridge. Swales are excavated by the wind to the point that vegetation is undermined and roots become exposed and lay bare. Some of the better examples of parallel dunes exist between Smithton and Stanley.

Blowouts and Parabolic dunes Blowouts are erosional bedforms, frequently resembling keyholes when viewed from elevation in that they have a narrow neck through which the wind funnels and then reduces momentum as it flows around an elongated circle, scouring sediment from the walls. Blowouts are a natural feature and transport sand from the beach and foredune inland. They can develop into large features that rework the sediment that forms the dune.

Large, wide examples of parabolic dunes are present on the west coast of Tasmania. Onshore gales for this region vary in direction from north-west through west to south-west, causing a wide dispersal of sand characteristic to the coastline of western Tasmania. Conversely, the north coast has northwesterly predominant winds producing narrow hairpin dunes and blow-outs (Bird, 2008). Good examples of parabolic dunes exist inland from ocean beach and including Henty Dunes (along with transgressive dune fields), north from Interview River to Sandy Cape, Ahrberg Bay, Kenneth Bay, Mt Cameron Beach and Studland Bay. Transgressive dune fields The transgressive dune fields within the NRM North and Cradle Coast region generally have very large volumes of sand. Transgressive dune fields often start as a blowout that becomes a parabolic dune, as more of these parabolic dunes develop they merge into a large dune system that transgress across pre-existing landscape features and engulfing any features within their path. Transgressive dunes will work previously emplaced sediments, such as those described above for the Henty Dunes.

Due to the large volume of sand contained within a transgressive dune field there are often secondary features present within transgressive dune fields, such as, blowouts, parabolic dunes, and barchan dunes that reflect diversity of forms within the dune field. Aside from the Henty Dune system, examples of complex transgressive dune fields are also present south of Sandy Cape and north at Kenneth Bay. Inland from Ocean Beach wind action has caused a number of major vegetated dunes to form complex minor blow-out features and minor longitudinal sand ridges on transgressive dune fields of progressively increasing age from northwest to southeast. Some of these dunes closer to Strahan are surprisingly deep in the A2 horizon, so much so they must be depositional in origin, as opposed to pedogenic. The younger (Holocene) of these dune systems have been advancing at a rate of 17m per annum since 1953, with sand derived from the beach and frontal dune systems (Banks et al. 1977).

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Some transgressive dune systems in the Cradle Coast region occupy backshore areas to landwards of rocky shorelines, particular in the Arthur-Pieman coastal strip. The causes of this seemingly anomalous situation (a dune field with no shoreline sand source) have not been properly investigated on Tasmanian coasts. A likely explanation, however, is that these represent the inland parts of formerly more extensive Pleistocene dune fields which thinly blanketed bedrock over extensive areas of the continental shelf during the low sea stands that accompanied arid glacial climatic phases. When subsequent rising sea levels scoured the thin sand mantle off the underlying bedrock during interglacial phases, to form rocky coasts, dune fields were left in backshore areas isolated from their former sand sources. This sort of coastal system (sometimes characterised by “cliff-top dunes”), forms a coastal region of mixed sensitivity to natural or artificial disturbances: whilst the rocky shore may be robust and unlikely to erode or change significantly over human time frames, the inland sand sheets may be sensitive to significant mobility as a result of either natural or artificial processes.

Soft Sediment Sheltered Shores The western section of the north coast, from Robbins Island and east to the Tamar River, comprises a variety of coastlines. These range from exposed bedrock headlands and beaches to embayed, sheltered beaches and estuarine environments. This is not to say that such features are not present on the west coast, they are, however not to the diversity or size found on the northern coastline. The more sheltered nature of the north coast has meant that coastal formations are not as heavily weathered from wind and shoreline erosion from heavy sea waves.

As the wind and weather systems dominating Tasmania are predominantly westerly, headlands on the northern coastline tend to have a sheltered leeward side, especially where bays have formed from some of these environs. Some examples of sheltered beaches viewed on the northern coastline include Duck Bay around Smithton, West and East Inlet below Stanley, Burnie Beach at Emu River exit, East Devonport Beach behind the artificial breakwater at Frederick Head and Port Dalrymple at the mouth of the Tamar River.

The high energy longshore and onshore processes that dominate the West Coast are notably different from the lower energy coastal process systems across the north coast. In particular Robbins Passage around Robbins Island and Perkins Channel near Perkins Island, both provide good examples of sheltered low-energy shallow marine and intertidal sediment flats. This area is a notable ‘sediment trap’, sheltered from the strong south-westerly swells by the far NW tip of Tasmania and by Hunter Island. Sand is evidently driven into this region from sand-rich west coast regions, possibly by longshore drift around Tasmania’s northwest tip, but probably more significantly by extensive headland-bypassing mobile aeolian sandsheets during arid Pleistocene glacial climatic phases (see the accompanying Quaternary coastal sediment polygon mapping). However, once in the wave-sheltered ‘sediment trap’ area, there has been little potential for continued longshore drift to remove sand from the region, which has consequently accumulated some of the most extensive intertidal and shallow subtidal sand flats found on the Tasmanian coast.

Salt marshes and lagoons are common in the sheltered coastlines and backshores of the Cradle Coast region. Examples of salt marshes exist throughout most of Robbins Passage, Perkins Channel, West and East Inlets, in the sheltered bay between Penguin Point and Lodders Point in North East Arm (Port Sorell) and in the Tamar River, in particular, around Tamar Island. Backshore Salt marsh lagoons are limited in the study area. The best examples of backshore salt marsh lagoons occur near Robbins Passage in the north opposite Robbins Island (Figure 11) and on the west coast extending north of the Henty River in the proximal backshore of Ocean Beach.

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Figure 10 Sandy shores backed by dune fields on low-lying soft sediment plains, such as the example below from north-western Tasmania that shows a stabilised foredune, are amongst the most sensitive and mobile coastal landform types in Tasmania (see Section 3.3).

Figure 11 Salt marshes on sheltered muddy-silty or sand-flat coasts, as shown here on the north coast opposite Perkins Island, are amongst the more sensitive coastal landform types in the NRM North and Cradle Coast region, and are typically associated with biological communities of high bioconservation value.

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3.0 KEY GEOMORPHIC MANAGEMENT ISSUES FOR THE NRM NORTH AND CRADLE COAST REGION COAST This section provides introductory discussion of a number of key issues regularly faced by land managers in regard to coastal landforms and land-forming ("geomorphic") processes. These are key issues whose management is intended to be supported by the mapping tools provided as an outcome of this project.

3.1 INTRODUCTION – COASTAL LANDFORM MANAGEMENT PHILOSOPHIES AND STRATEGIES This section identifies key coastal planning and management issues related to geomorphic processes, which arise given the nature of the NRM North and Cradle Coast region coast as described in Section 2. No attempt is made here to provide all the scientific and technical information necessary to plan for and manage these issues, however further information on these issues can be found in the references cited in the following discussions.

Coastal geomorphic management issues can be broadly considered as falling into two classes, namely the maintaining the conservation values of natural coastal geological features, landforms and landform processes (Geoconservation), and the management of hazards to human coastal development or use that result from coastal geomorphic processes. These issues are dealt with in, respectively, Section 3.2 and Sections 3.3 – 3.5 below; however in practical terms they are inter-related so that many coastal management issues require attention to both aspects.

In a broad sense, the objective of coastal geoconservation is to protect or maintain a diversity of coastal geological sites, landforms and ongoing land forming (geomorphic) processes that are considered significant for a variety of reasons including the integral role they play in maintaining the broader natural values of coasts. In contrast, the objective of coastal hazards management is to avoid, minimise or remedy the potential impacts that coastal geomorphic processes (such as erosion, dune mobility, flooding, etc) may have on human developments, infrastructure or uses in the coastal zone.

Such impacts can result either from the operation of ongoing natural processes such as natural coastal erosion, or may be the result of developments unintentionally triggering a coastal geomorphic process which then threatens the same or other developments (as in the case where developments or inappropriate uses trigger artificially accelerated dune mobility in the form of blowouts, which then threaten those developments with undermining by erosion or inundation with blown sand).

Although the following sub-sections treat coastal geoconservation values and geomorphic hazards as conceptually separate issues, it must be recognised that these issues overlap and have many linkages.

For example, natural dune mobility may be regarded as a hazard for certain developments and uses of the coast, there is also a strong geoconservation argument for allowing such dune mobility to continue unhindered since it is a normal and natural ongoing process in coastal evolution. In the past there have been many attempts to halt dune mobility by artificial means such as the planting of marram grass.

Dune mobility was typically considered to be primarily an artificially-triggered land degradation problem requiring a remedy, and there was often little appreciation of the degree to which large scale episodic dune mobility occurs as an entirely natural phenomenon (Cook 1986). Accordingly, the prevailing philosophy was to manage the hazard of dune mobility by halting it (Steane, 1996).

However, many such attempts have largely failed, and moreover have had unforeseen consequences such as causing erosion to be triggered in nearby areas due to the artificial interference with coastal sand budgets that occurs when naturally mobile sands are stabilised. An example of anthropogenic impact is evident in Macquarie Harbour as the King River delta, where a massive tailings slug, continues to prograde into Macquarie Harbour. Significant tailings from the Mt Lyell Mine have travelled down the King River into the larger Queen River before being deposited into Macquarie Harbour. There are however, few other examples of this sequential adjustment occurring in the NRM North and Cradle Coast region as much of the western coastline is undeveloped and the Northern

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coastline consists of many rocky shores which reduce the impact of shoreline erosion and deposition processes.

In recent decades, coastal management philosophies world-wide have moved away from the idea of trying to manage coastal hazards by artificially controlling them, partly due to numerous experiences that have demonstrated the difficulty of successfully achieving this aim, and partly due to increasing recognition of the nature conservation value of allowing coastal processes to continue to operate and evolve in their own way. Today, it is widely recognised that the simpler (and nearly always more costeffective) means of managing coastal geomorphic hazards is to identify those parts of the coast where natural geomorphic processes such as dune mobility and erosion will create hazards for development, and avoid allowing inappropriate developments in those areas. This achieves the dual goal of maintaining active natural coastal processes and evolution (Geoconservation) – since the "hazardous" coastal areas are simply those parts of the coast where natural geomorphic change is most rapid whilst at the same time avoiding exposure of infrastructure to potential hazards (geomorphic hazards management).

However, while it is desirable to avoid coastal hazards by avoiding future development in hazardous areas, many coastal managers are faced with the problem that a great deal of coastal infrastructure, development and usage already exists in areas subject to hazards. The available strategies for managing existing developments in areas now known to be hazardous can be summarised as: • • • •

Do nothing (deal with problems as they become an issue) Protection (strengthen defences against hazards – usually an engineering response) Adaptation (continued use with adaptation, e.g., modifications to infrastructure to withstand hazards) Retreat (phased changes in land use as hazard becomes a problem)

Each of these approaches has advantages and disadvantages, and each approach will be more appropriate in some circumstances but less appropriate in others. The optimal management strategy is to identify which of these approaches is most appropriate for a given location, in consideration of the full range of geomorphic, conservation, social and economic circumstances applying in that location.

For example, where an existing building on an eroding shore is of high social or economic value, and protection from erosion can be achieved by a local engineering solution (e.g., a rock wall) that will not significantly modify coastal processes further alongshore, then Protection may be the appropriate solution. However, where infrastructure has been built immediately behind a long sandy shore subject to ongoing erosion, and the only means of successfully protecting against that erosion would be a long artificial wall that would considerably modify both the aesthetics and geomorphic processes of the beach, then a more appropriate strategy may be to consider a phased retreat involving moving infrastructure out of the erosion hazard zone over a period of years or decades.

The purpose of the Decision Support Tools provided by this project is to provide a means for managers to identify locations where the mix of landform values and coastal hazards imply a need to consider a range of differing management responses.

3.2

GEOCONSERVATION VALUES

The key focus of this project has been the provision of tools to assist in managing coastal areas to maintain the nature conservation values of coastal landforms, geological features and the ongoing natural geomorphic processes of coastal landform development. These values can be termed "geoconservation values".

Geoconservation is "the identification and conservation of geological, geomorphological and soil features, assemblages, systems and processes (geodiversity) for their intrinsic, ecological or heritage values" (Eberhard, 1997).

Geoconservation complements biodiversity conservation November 2008

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("Bioconservation") as two equally essential components in any properly holistic approach to Nature Conservation. Not only do the living parts of the ecosystem depend on the substrates and natural processes of the non-living parts, but the non-living parts – geological features, landforms, geomorphic processes and soils – have their own values that are equally worthy of conserving.

Geoconservation is explicitly recognised by the Australian Natural Heritage Charter (AHC 2002) and Tasmania's Nature Conservation Strategy (DPIWE 2002) as an important element of Nature Conservation, and current Tasmanian Government legislation (Nature Conservation Act 2002) requires that all formal conservation reserves in Tasmania have the conservation of "Geological Diversity" (i.e., geodiversity) as one of their key management aims.

Further information on principles of Geoconservation are available from the DPIW website (see http://www.geoconservation.info ), and have been summarised by Sharples (2003). Kiernan (1997) has provided a detailed discussion of geoconservation in particular regard to coastal landforms.

Ten (10) potential coastal geoheritage sites were identified within the NRM North and Cradle Coast region during this project. Seven (7) of these sites are already listed on the Tasmanian Geoconservation Database (TGD), while another three (3) new sites have been identified. The newly identified sites are Bluff Hill Point (a boulder berm and splay), Conical Rocks (granite conical shaped pillars) and an incipient shore platform to the south of Interview River. Additionally, the West Point Cobble Berm was updated with additional information. The West Point Cobble Berm is listed on the Tasmanian Geoconservation Database (see Section 4.5) and has been updated to recognise its representative values. However, many coastal landforms contribute significantly to coastal conservation values not in virtue of any unusual characteristics, but simply in virtue of their geomorphic processes continuing to function more-or-less naturally, and so contributing to the overall nature conservation value of coastal areas.

Although landforms are often thought of as robust and not in need of active protection in the same way that biotic values are, in many cases this is far from being the case. Coastal landforms are amongst the most dynamic and rapidly changing landforms on earth, and these active processes – such as dune and beach mobility, shoreline erosion, or sea cliff slumping – are sensitive to disturbances which can quickly cause them to change in ways which significantly modify the natural processes. Such interference – for example, mobilisation of naturally stable dunes by land clearance, or stabilisation of naturally mobile dunes by marram grass planting – can not only degrade the natural values of a coastal region but also create hazards for human use of the coastal zone by changing the natural patterns of erosion and deposition. Following sections describe some of the more dynamic coastal landform processes, which are natural parts of coastal landform processes, but can become hazards for human use of the coast if interfered with, or if human infrastructure is placed in naturally hazardous areas.

Having emphasised the dynamic and mobile nature of many coastal landforms, it must also be recognised that some coastal landforms are relatively robust and stable, at least in the context of human time frames. These include many moderately-sloping hard rocky shores. However, robust rocky shores may contribute to the conservation values of coasts just as much as softer mobile shores where they remain in good condition with intact vegetation and soil cover in the backshore area.

Although disturbance of rocky coastal types may be less likely to significantly modify coastal geomorphic processes, they may nonetheless contribute significantly to broader coastal conservation values such as providing undisturbed habitat for coastal biological communities.

The geoconservation of at least representative and outstanding natural coastal geological sites, landforms, ongoing geomorphic processes and soil systems should be an integral part of any coastal management strategy. To be effective, geoconservation must focus not only on protecting natural features – e.g., the forms of the coastal landforms, but must also focus on maintaining the natural processes such as erosion, sediment transport and deposition which maintain the natural landforms.

This objective not only contributes to maintaining broader conservation values of the coastal zone (e.g., biodiversity and landscape values), but also informs a more appropriate treatment of hazard November 2008

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issues in the coastal region as noted in Section 3.1 above. In tandem with bioconservation, geoconservation in the coastal zone serves to maintain the intrinsic natural values, ecological systems, amenity and landscape values of the coast, and as such constitutes one of the objectives of the Tasmanian State Coastal Policy (both in its original 1996 form, and in its current (2008) draft review form). Geoconservation in the coastal zone is important not merely within coastal conservation reserves, but more broadly as an objective to be integrated with and balanced again the range of other development and management objectives for the coast generally.

Tools for coastal management provided with this report include map datasets aimed at facilitating management of the coastal zone for the maintenance of its geoconservation values (see Sections 4.5, 4.6, & 5.0). Coastal geoconservation values information is presented in two ways by the mapping accompanying this report: 1. Recognised Geoheritage sites are presented as maps layers derived from the Tasmanian Geoconservation Database (see Section 4.5). These layers identify features recognised as having particular significance; however it must be recognised that these comprise only a very incomplete and very much "under development" list of particular features that have been identified as having special values.

2. Geoconservation Priority ("Indicative Geovalues") mapping (Section 4.8) provides a more comprehensive but broader indicator of coastal geomorphic conservation values based on the sensitivity of coastal landforms to disturbance, and their condition, or degree of existing artificial disturbance (see Section 4.6).

3.3

COASTAL DUNE MANGEMENT ISSUES

Coastal dunes are prone to sand mobilisation by wind erosion. Wave activity normally only impacts the ocean facing side of a dune system, having few direct impacts associated with landward progression of dune systems, aside from the impacts of sea level rise. Wind activity, by comparison, has the potential to mobilise and saltate grains resulting landward progression of a dune system.

Vegetation is in some cases able to stabilise dune systems and the introduction of exotic marram grass into coastal areas has caused wide spread stabilisation of dunes. Anectotal evidence from local surfers in the Marrawah region suggests that this has resulted in swell changes due to increased quantities of sand being bound up in stable dune systems.

Dune mobility is commonly a natural process that is triggered by wave erosion and/or climatic variations including reduced precipitation (vegetation dieback) and increased wind speeds (increased wind erosion stress). Phases of dune mobility and stabilisation may naturally alternate as a result of minor climatic variations or simply due to sediment supply replenishment or exhausting (see Cook 1986) However, erosion of naturally stable dunes can occur due to human impacts like fire and vehicle tracks. Situations of accelerated erosion resulting from human induced impacts can lead to blowouts occurring. These situations can be particularly problematic if development is directly behind the frontal dune system or proximal backshore. Careful management is required in such instances to ensure recreational or development impacts do not disturb natural systems. If natural systems become disturbed and threaten infrastructure, management may need to consider stabilising the dune system through revegetation programs or soft engineering approaches. This type of ‘management’ however, then causes sediment to become ‘bound up’ in vegetated dunes (temporarily) removing it from the system, which would otherwise contribute to aeolian processes, long-shore drift – possibly causing sediment starvation to other areas of the coastline, which can then lead to coastal erosion. Hence, dune management is complex – some dune mobility is natural, some is artificially triggered, it can be problematical to determine whether we should be managing to prevent dune mobility or allow it to continue. Getting it wrong either way can impact upon other natural processes.

In the past there has been an assumption that most coastal dune mobility in Tasmania is caused by human (eg, grazing, burning) disturbance, and that we should therefore stabilise dunes. Marram grass November 2008

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has been introduced in an attempt to do this; however, it has proven to be an invasive weed which created problems of its own (e.g., binding sand up in large dunes, which starves coastal systems of sand and causes coastal erosion to occur in other areas). This process typically functions by long-shore drift eroding sand from one beach and depositing it further along either the beach or coastline. Sand withheld from this process is likely to result in an area being eroded, as there is no sand available to replenish that lost. While, as discussed above, this naturally occurs, stabilising dunes artificially or interfering in the natural system of sediment supply and erosion is likely to have flow on effects that may accelerate both the rate of sediment supply or loss and the time scales in which they operate.

The optimum approach would be to simply leave coastal dunes alone and let their processes continue to change naturally; however, it is unfortunate that in many places development and recreational pressures on coastal dunes has foreclosed this option, leaving coastal managers, councils and landowners with a suite of complex management problems.

Finally, a significant natural control on dune mobility or stability is the balance between effective precipitation (encouraging vegetation to stabilise dunes) and maximum wind speeds (encouraging dune erosion if the vegetation becomes sparser). It is likely that with climate change, some Tasmanian coasts will become windier and drier (encouraging increased dune mobility), while it is possible that others will become wetter and less windy, encouraging dune stabilisation. This coastal process should be recognised and allowed to natural function, remaining unaltered by human ‘management’.

3.4

COASTAL SLUMPING, EROSION & SHORELINE RECESSION

Most coasts are prone to erosion for entirely natural reasons. Few if any coasts on Earth have reached a final stable equilibrium form in relation to sea level, which only stabilised at roughly its present level circa 6,500 years ago. Most coasts are continuing to progressively adjust their form in response to continual wave, tide and current action, typically by eroding, but sometimes by accretion (deposition) of sediment. Even without any further sea level changes, most coasts would continue to naturally adjust their form for a geologically-long period into the future.

Many hard bedrock shores show only negligible erosional change over human lifetimes, but the fact that even hard rock shores are continuing to erode is demonstrated by occasional natural coastal rock falls, and by the degree of shore platform and sea cliff erosion that has evidently occurred on many rocky shores since sea level stabilised. Vertical sea cliffs tend to exhibit more instability and erosional recession than moderately sloping bedrock shores, while steep shores of strongly fractured bedrock or of only semi-consolidated sediments such as old talus deposits or Tertiary-age clayey-gravelly fluvial sediments, may occasionally slump dramatically in response to wave attack at their base. Lower profile shores of semi-consolidated clayey-gravelly sediment may simply erode progressively landwards at rates that can reach well over a metre per century.

In addition to such long term progressive adjustment of shorelines, the softer and more mobile shores particularly sandy shorelines – tend to respond to short or medium term variations in wave climate and current action by rapidly changing their form on a daily, seasonal and inter-annual or inter-decadal basis. Such changes can involve repeated phases of both erosion and accretion (or prograding) of sand in response to individual storms, periods of greater or lesser average storminess, variations in wave climate and tides caused by cyclic processes such as the El Nino Southern Oscillation (ENSO), and for other natural reasons. Episodic or cyclic changes can lead to the frequently repeated cycles of beach and foredune erosion followed by progradation or accretion that is commonly referred to as the "cut and fill" cycle, as well as long term changes related to increased or decreased sandy sediment supply to a beach. See the preceding Section (3.3) for further discussion of the high degree of mobility and erosion that is particularly characteristic of sandy beach and dune systems.

However, historically, there has been a widespread failure to recognise that natural landforms, including coastal landforms, are commonly subject to natural physical change including erosion over relatively short time periods – and that this is characteristic of most coasts even without any major November 2008

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changes. Examples of this are seen in renewed sea level or artificial interferences with coastal systems.

An incorrect notion that coastal landforms "should" be quite stable and unchanging has lead to widespread development and construction of infra-structure right up to the waterline on numerous coasts throughout the world. Such development has been relatively unproblematic where it has occurred on hard rock shores whose rates of change are negligible over human lifetimes, however all too often development has taken place on softer shores where soon after development there is a realisation that ongoing shoreline erosion is placing infrastructure at risk.

The usual response to a realisation that erosion is placing coastal infrastructure at risk has been an engineering response of either a "hard" or "soft" sort. Hard engineering responses include the construction of seawalls to halt shoreline erosion and groynes to arrest the natural drift of sand along a coast. Soft engineering responses include repeated replenishment of sand on a beach to replace eroded sand, thereby maintaining a protective sand buffer between the sea and developments at the back of the beach.

Engineering responses such as these can in principle halt coastal erosion, however all too often they have failed to do so as a result of inadequate understanding of the coastal erosion processes, or because insufficient funding of coastal protection works resulting in the building of structures that were inadequate to contain the erosion problem. Soft approaches such as beach replenishment can also succeed, but these require an ongoing commitment to repeatedly replenish beach sands at regular intervals, since the mere replenishment of sand on a beach does not itself halt the erosion process. A further problem with both hard and soft engineering approaches to halting coastal erosion is that, because such action necessarily involves interfering with a natural coastal process of erosion, it is common for this to have unforeseen consequences elsewhere on a coast. For example halting natural erosion on one part of a sandy coast may result in depletion of sand on another part of the coast that formerly received sand from the eroding area, with the result that the erosion problem is simply shifted along the coast to another site.

As noted in Section (3.1) above, the high cost and long term commitment required for effective artificial protection of developments on eroding shores has resulted in a gradual shift of philosophy away from a reliance on artificial coastal protection and towards avoidance of development in hazardous coastal areas in the first place. Of course this shift of emphasis does not solve the problem of protecting existing coastal developments. In some parts of the world such as the Norfolk coast of England the cost of effective coastal protection has proven so great and unsupported that a policy of abandoning all but the highest value coastal assets to natural erosion is now being seriously considered (see http://www.northnorfolk.org/acag/default_smp.html).

The problems associated with coastal erosion are currently being exacerbated by renewed global sea level rise. There is no longer any reasonable doubt that sea level has begun to rise again after 6,500 years of relative stability, and 10 – 20 cm of renewed sea level rise has been observed around the world in the last century (IPCC 2001). Anywhere between 0.09 and 0.88 of a metre in further vertical sea level rise is now expected to occur by 2100 (IPCC 2001). Sea level rise is expected to cause an acceleration of existing natural shoreline erosion rates on most types of shores. However, erosion and landwards recession of the shoreline is expected to be most marked on soft sandy shores. On these shores the average degree of landwards recession is likely to be in the order of 50 to 100 times the vertical rise in water level (see Sharples 2006 and references therein for a more detailed discussion of these issues). Sharples (2006 and accompanying digital maps) has provided indicative coastal vulnerability mapping that identifies Tasmanian sandy coastal areas potentially vulnerable to accelerating erosional recession of the shoreline in response to sea level rise (see also Section 4.7).

The vulnerability of many Tasmanian coasts to erosion, particularly with renewed sea level rise, and the problems of coping with coastal erosion in developed areas, mean that there is a major need for planners and other responsible bodies to give serious consideration to appropriate strategies for managing development in erosion-prone coastal areas (see also Section 3.1).

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3.5

COASTAL FLOODING (STORM SURGE INUNDATION)

Coastal storms may produce a rise of water levels at the coast, known as a storm surge. This can occur due to a combination of low atmospheric pressures, onshore winds and waves "piling up" water against the shore, and the run-up of individual waves. The results of this can be water levels reaching several metres above the normal high tide levels, particularly if the maximum intensity of a storm surge coincides with a spring tide (Hubbert & McInnes, 1999).

One of the consequences of sea level rise over the next century and beyond is that the vertical height of storm surges will increase. The magnitude of storm surge will increase proportionately to the vertical rise in mean sea level relative to the land. Thus, by 2100 storm surges of a given return period could potentially flood to levels around 0.88 metres higher than they do at present, if the maximum sea level rise currently predicted by IPCC (2001) for 2100 eventuate. It is also possible that future climate change may result in increased intensities of storms of a given return period (Pittock, 2003); although no systematic increases in storm intensities have been detected for the Tasmanian region. However, it is known that storm activity in eastern Australia has been episodic during the Twentieth Century, with frequent large storms occurring during the 1970's in NSW (Thom & Hall 1991) and less storm activity during other periods. Historically, periods of more frequent and/or intense storm activity have caused increased flooding and coastal erosion (ibid.). Furthermore, such episodes are likely to occur in the future; both as an element of the "normal" long-term storm variability, and possibly as an effect of long-term climate change.

Coastal areas most at risk of flooding during storm surges are low-lying, low profile coastal flats immediately backing the high water mark. Many such coastal areas exist in the NRM North and Cradle Coast region, and some such areas support valuable infrastructure including roads and houses.

Hence, storm surge flooding is a significant hazard for coastal land use and development in some parts of the NRM North and Cradle Coast region.

In Tasmania one of the highest storm surge water levels historically recorded by a tide gauge was a water level of 1.32 metres above AHD 5. This was reached at the Hobart Tide Gauge on 25th July 1988, and was 0.66m above the predicted tide level for that day ("The Mercury" newspaper, 26th July 1988 p. 1, DELM 1996, p.1). This storm surge caused flooding at Lauderdale and Bicheno Street (Pipe Clay Lagoon), covered waterfront reserves at Sandy Bay (Marieville Esplanade), pushed water to the doorsteps of homes at Kingston Beach, flooded through a house at Old Beach, covered part of the Huonville to Cygnet Road, submerged some Battery Point Streets and flooded several basements on Hobart's waterfront ("The Mercury" newspaper, 26th July 1988 p. 1). Several other storm surges during the 1960's to 1990's period were also reported to have risen over roads at Lauderdale (Sharples, 2004: 18).

The fact that historical storm surge flooding has occurred in areas of current residential development under conditions associated with historical sea levels, highlights the increased flooding vulnerability for these same areas under future conditions of higher mean sea levels. Sharples (2006, and accompanying maps) provides further discussion of the factors in storm surge vulnerability for Tasmania’s coastline. Included in this work is indicative flood hazard mapping for the entire Tasmanian coast which specifically identifies coastal areas potentially subject to storm surge flooding, both under present conditions and with future sea level rise (see also Section 4.7 below).

5

AHD = Australian Height Datum, which for the Southern NRM region corresponds to the mean sea level measured at Hobart in 1972.

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4.0

COASTAL GEOMORPHIC DATASETS AND DECISION SUPPORT TOOLS

4.1 INTRODUCTION The key purpose of the NRM project described by this report is to provide tools and datasets to assist in better coastal land management and land use planning, particularly in regard to conserving natural coastal landform values and planning appropriate responses to coastal geomorphic hazards such as dune mobility, shoreline erosion and flooding. The management tools (data sets) provided by or in association with this project are briefly listed and their purposes are explained in the following subsections. Detailed technical descriptions, as necessary, of these datasets are provided in Appendices One & Two of this report. The following Section 5 constitutes a manual, the purpose of which is to describe how the tools and datasets described below can be used in practice for improved planning and land management in the coastal zone.

In summary, the datasets described in the sub-sections following below comprise: Coastal Geomorphic (Landform) Descriptions, as: •

Geomorphic Shoreline Types line map (Complete mapping of all coastal landform types for the entire Tasmanian coast, but only in a line-map format and with ongoing ground-truthing). See Section 4.2.

•

Coastal Sediment and Geomorphic Types polygon map (Mapping of aerial extent and types of Quaternary coastal sediment bodies and "soft" coastal landforms, now complete at 1:50,000 to 1:25,000 scale for much of the Tasmanian coast from Macquarie Harbour clockwise to South-East Cape, but still incomplete for the remaining south-west coast. See Section 4.3.

•

Coastal Photography (A photographic collection of coastal landform features, sub-features and substrate throughout the NRM North and Cradle Coast region. The photography includes a near complete digital series of photos between Ocean Beach and Sandy Cape. The remainder of the coastline from Macquarie Heads to [and including] the Tamar Valley has been photographically recorded ‘as visited’, in-conjunction with opportunistic polygon boundary photography. See Section 4.4.

Coastal Geomorphic Hazards and Condition mapping, as:

•

Coastal Geomorphic Sensitivity and Condition mapping (Zoning of the coast according to overall sensitivity of landforms to degradation through artificial disturbance, and mapping of current condition of coastal landforms, i.e., degree of degradation of coastal landforms or landform processes that has occurred as a result of artificial disturbances; subject to ongoing revision with additional ground truthing and/or land use changes). See Section 4.6.

•

Coastal Geomorphic Hazard (Vulnerability) mapping (Indicative mapping of coastal areas vulnerable to specific coastal geomorphic hazards. Dune mobility vulnerability mapping is contained within the Coastal Sediment and Geomorphic Types polygon map described above; Sharples (2006a) provided coastal erosion, slumping and storm surge flooding vulnerability mapping data separately from the current NRM project). See Section 4.7.

Coastal Geomorphic (Geoconservation) Values mapping, as:

•

Coastal Geoheritage Sites mapping (mapping of particular coastal landforms, geological sites and soil sites that have been identified as having special geoconservation values). See Section 4.5.

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•

Geoconservation Priority (Indicative Geovalues) mapping (broader and more comprehensive mapping of likely ("indicative") geoconservation values based on the sensitivity and condition of coastal landforms). See Section 4.8.

4.2

COASTAL GEOMORPHOLOGY – DESCRIPTIVE LINE MAP

Background The Tasmanian Shoreline Geomorphic Types line map, provided with this report as an ESRI Arcview shapefile (tascoastgeo_v5gda.shp), is the fifth version of a digital (GIS) map providing geological and geomorphic (landform type) descriptions of the entire Tasmanian coastline. The map identifies and locates large to medium-scale Tasmanian coastal landform types using a primarily descriptive (form and fabric) format (e.g., "sandy beach", "rocky shore platform", "sloping rocky shore", etc), rather than a more genesis- or function-based classification (e.g., "barrier beach", "mid-bay spit", "reflective beach", etc). As such, this map provides the only currently available digital description of the landform types (as opposed to the simple topography) of the entire Tasmanian coast. Geomorphic data suitable for a wide variety of uses is provided (which to date has included assessment of oil spill management responses (see below) and mapping of potential vulnerabilities related to sea level rise (Sharples 2006a).

The Tasmanian Shoreline Geomorphic Types line map (tascoastgeo_v5gda.shp) is copyrighted by the Tasmanian Department of Primary Industries & Water (DPIW). Custodianship and management of the map is vested in the Senior Earth Scientist (or equivalent manager responsible for the Earth Science Section) DPIW. The data is presented as a line map (the LIST 6 digital coastline map of Tasmania as at 2000, supplied

by DPIW 7, which nominally represents the Mean High Water Mark line at 1:25,000 scale), which has been sub-divided into over 12,000 geomorphically distinct line segments, ranging from several kilometres long to as little as 20m or so in length. Although the coastal landform data is presented as a simple line, the attached digital attribute table allows each distinctive segment of the line map to be attributed with geomorphic attributes describing the landform types in the lower intertidal, upper intertidal, backshore and distal zones adjoining that line segment, as well as the underlying bedrock geology and a range of other geomorphic attributes. In this way, considerably more information is encoded within each coastal line segment than is apparent at first glance, hence this coastal data mapping format is now sometimes referred to as “Smartline” mapping. Appendix One provides detailed descriptions of the structure (Data Model) and attributes (lookup tables) of the Shoreline Geomorphic Types line map.

The entire Tasmanian coastline, all major islands including the Bass Strait islands, and most minor islands above approximately 1 hectare in area (but not including Macquarie Island) have been described and attributed in this way, amounting to over 7000 km of shoreline at 1:25,000 scale.

However, a number of coastal lagoons and estuaries (connected to the sea) are not included in the dataset since they were not included in the LIST coastline map that formed the basis for the original (2000) version of this map. These inlets are included in a separate LIST theme (estuaries), and should be added to the shoreline geomorphic types map in the future.

The current (version 5) data set builds upon the four previous versions of the Tasmanian Shoreline Geomorphic Types digital line map. Sharples (2000) originally prepared this for the Australian Maritime Safety Authority's (AMSA) Oil Spill Response Atlas (OSRA) and the Australian Coastal Atlas. Version 1 was based on previous (paper) air photo interpretation mapping of Tasmanian coastal landforms at 1:50,000 scale by Munro (1978), the most recent available geological mapping and 6

Land Information System Tasmania.

7

Department of Primary Industries & Water, Tasmania.

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1:25,000 topographic mapping, published coastal geomorphology descriptions (especially Cullen 1998), a significant amount of new air photo interpretation (API) by C. Sharples (between Scamander and Recherche Bay), and limited ground-truthing. A subsequent Version 2 incorporating new ground truthing data was prepared in the course of coastal mapping for the South East Tasmania Integrated Coastal Management Strategy (Sharples 2001). Version 3 incorporated the results of additional ground truthing by C. Sharples in a number of areas subsequent to 2001. Version 4 incorporated coastal geomorphic mapping and ground-truthing undertaken in southern, eastern and north-eastern Tasmania

by Chris Sharples and Frances Mowling during 2005 - 2006. That work focussed in particular on ground-truthing shorelines composed of Tertiary age sediments and basalts, and other non-sandy shores thought likely to be sensitive to slumping and erosion hazards. The current Version 5 of the line map incorporates further field validation by Hydro Tasmania Consulting staff, covering the coast between Macquarie Heads and the Tamar Valley, which occurred during March-June 2008.

The current status of the Tasmanian Shoreline Geomorphic Types line map (tascoastgeo_v5gda.shp) can be described as complete for the entire Tasmanian coast including the entire NRM North and Cradle Coast region, but still requiring ground-truthing in some areas such as the far south-west coast.

Ongoing and future work on developing and upgrading the Tasmanian Shoreline Geomorphic Types line map should focus on continued ground-truthing of the map, with accompanying refinement of the geomorphic classifications used to describe coastal landforms in the map attribute table. The previous version 4 of the line map (tascoastgeo_v4) has been incorporated into a new national coastal geomorphic map under preparation for Geoscience Australia and the Department of Climate Change (see also Section 1.1). It is envisaged that the current tascoastgeo_v5 line map with its new Cradle Coast data will be incorporated into version two of the Tasmanian tile of the national map Map Data Structure and Attributes The data attributes of the Tasmanian Shoreline Geomorphic Types line map (tascoastgeo_v5gda.shp) are described in detail in Appendix One. This section provides a brief overview of the key information encoded in the map.

The line map provides a range of geomorphic information pertaining to each segment of coast as attributes tagged to line segments nominally representing the High Water Mark line. The line map is split into segments wherever a significant change occurs in any of the attributes. The map attributes refer to geomorphic characteristics of the coast found not only at the shoreline itself (the HWM), but also in backshore areas to landwards of the line and lower intertidal areas to seawards of the line.

Whilst this has some drawbacks in terms of visualising the coastal landforms of each coastal segment, it has significant advantages in terms of providing a simple and cost-effective means of recording coastal geomorphic data, and in terms of analysing that data for a range of purposes in a GIS context.

Note that a key drawback of the geomorphic line map is that, while it indicates the presence of soft coastal sediment bodies (dunes, etc) in the backshore, it does not indicate their landwards extent and form. The Quaternary Coastal Sediment polygon map described in Section (4.3) below was developed to address this key deficiency.

The line map describes coastal landforms through a number of attribute fields which each describe a key element of the coastal landform systems. The attributes are represented as descriptive codes, since some require a sentence to fully specify the landform characteristic. The descriptive codes and associated numerical codes are listed as "lookup tables" in Appendix One. While this may appear at first sight to be a complex means of representing the data, it is in reality a simple means of capturing a wide range of geomorphic data. These attributes can be merged to provide simplified descriptions of coastal landforms, which is how the Sensitivity and Geoconservation Priority attributes in this report were derived (sections 4.6 and 4.8), and is also how the coastal vulnerability mapping provided by Sharples (2006) was created. However, any such simplification always involves some loss of information. The data structure used in the geomorphic line map was developed because it allows for the recording of significant amounts of coastal geomorphic detail this can then be queried in a variety of ways to create simplified descriptions of coastal landforms for a wide variety of purposes.

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Appendix One provides a full description of all attribute fields tagged to each segment of the Tasmanian Shoreline Geomorphic Types line map (tascoastgeo_v5gda.shp). Many of these attributes will not be relevant to some users, however the following are the geomorphic attribute fields likely to be of most interest to planners and land managers (see also Appendix One for details of each attribute): • • • • • •

Upper Intertidal Zone (Upperint): A description of landform types found in the upper intertidal zone. This corresponds to the coastal landform types most commonly thought of as characterising a shoreline type (e.g., sandy beach, sloping rocky shore, rocky cliff, etc) Lower Intertidal Zone (Lowerint): A description of landforms characterising the lower intertidal tidal zone (e.g., rocky shore platform, intertidal sand-flats, sloping sandy or rocky bottom, etc).

Backshore (Backshore): A description of landform types occurring immediately to landwards side of the upper intertidal zone (e.g., dunes, low marshy sediment plains, sloping bedrock + soil surface, etc).

Profile (Profile): A broad generalised description of the immediate backshore topography or slope to landwards of the shoreline (low-lying plain, moderately rising ground, steeply rising ground, high cliffs) Bedrock (Bedrock): A simply categorisation of the hard bedrock type forming or underlying the shore, even where it is buried by sand or other sediment (e.g., dolerite, sandstone, quartzite, etc) Exposure (Exposure): The degree of exposure of the shoreline segment to wave energy (as three broad categories – sheltered, semi-exposed and exposed).

Figure 14 and Figure 15 provide examples of the information contained in some of these attributes and the means by which this information can be displayed by the line map. Competent GIS users will be able to analyse the data to display maps of the coast giving a wide range of geomorphic information.

4.3

COASTAL GEOMORPHOLOGY – DESCRIPTIVE POLYGON MAP

Background The Quaternary Coastal Sediment polygon map provided with this report as an ESRI Arcview shapefile (tascoastsed_v5gda.shp), is the latest version of a digital (GIS) map providing mapping of Quaternary-age (i.e., geologically recent) coastal soft-sediment bodies and landforms for parts of the Tasmanian coast including the NRM North and Cradle Coast region. This map was initially produced by combining polygon coverage's of unconsolidated coastal sediments on the West-North-West coasts of Tasmania (digitised in 1999 for Tasmania's West North West Councils from 100K maps supplied

by Sharples 1998), and on the South-East coast of Tasmania (prepared by Sharples (2001) for the South East Tasmanian Integrated Coastal Management Strategy). It should be noted that there is a difference in scale that these two areas were mapped: the WNW polygons were digitised at a nominal 1:100, 000 scale, whilst those in the SE were digitised at a nominal 1:25,000 scale. Further mapping of coastal Quaternary sediment bodies in southern, eastern and north-eastern Tasmania by Frances Mowling has subsequently (2005 - 2006) was added to the data set during two previous NRM projects (DTAE 2007a, b), to produce the fourth version tascoastsed_v4gda.shp).

The current version (tascoastsed_v5gda.shp) was produced during the NRM North and Cradle Coast project by incorporating new mapping of coastal sediments in the Arthur-Pieman Conservation Area (APCA), prepared by Sharples (2007), and adding to this further mapping based on air photo interpretation by Dax Noble of areas outside the APCA All previous mapping has been incorporated into the one layer (tascoastsed_v5gda.shp), maintaining only the most current polygon extents for all areas. Older versions of the tascoastsed_v5gda.shp layer will still contain historical mapping that

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shows beach and dune spatial and temporal alterations, should a user interrogating the data require comparisons.

The mapping associated with the current update (tascoastsed_v5gda.shp) has been updated for the western, north western and northern areas. API digitising of beaches, foredunes, hummocky dunes, parabolic and transgressive dunes and estuarine areas has been mapped at 1:10,000 scale accuracy for the western coastline and 1:4,000 scale accuracy, or better, for much of the northern coastline. The difference in aerial photography scale for the images used, meant that in order to preserve the same level of digitised accuracy as was mapped on the west coast, polygons on the north coast needed to be ‘zoomed into’ further. This polygon map is similar in format to available geological mapping, and in part, maps some of the features mapped by existing geological mapping (namely, Quaternary-age sediment deposits). However, the Quaternary Coastal Sediment polygon map (tascoastsed_v5gda.shp) does not simply duplicate existing geological mapping, but rather is different in two respects: Currently available Tasmanian geological mapping (including GIS formats) depicts both hard bedrock and overlying superficial soft Quaternary sediments in a single layer. As a result, in many areas the geological mapping omits surface Quaternary sediment bodies known to be present, in order to be able to depict the underlying bedrock. Thus, the geological maps arbitrarily omit some areas of soft surface sediments, whose presence is critical information for land management. In order to remedy this, the Quaternary Coastal Sediment polygon map (tascoastsed_v5gda.shp) has been designed to ignore bedrock geology and depict only the full extent of soft Quaternary sediment bodies insofar as these can be determined.

Current geological mapping in most areas captures only broad classifications of the landform types comprised by the Quaternary sediments mapped. The Quaternary Coastal Sediment polygon map (tascoastsed_v5gda.shp) endeavours to provide a more detailed classification and delineation of Quaternary sediment landforms (e.g., dune types), and additionally provides other management relevant data not provided by traditional geological mapping (e.g., dune mobility data).

The Quaternary Coastal Sediment polygon map (tascoastsed_v5gda.shp) is copyrighted by the Tasmanian Department of Primary Industries (DPIW). Custodianship and management of the map is vested in the Senior Earth Scientist (or equivalent manager responsible for the Earth Science Section) DPIW. Map Data Structure and Attributes The Quaternary Coastal Sediment polygon map (tascoastsed_v5gda.shp) provides information on coastal landforms in a traditional map polygon format, however whereas the geomorphic line map (described above) describes all landform types in the coastal zone, the polygon map is focussed on providing information on the extent, types and mobility of only soft sediment coastal landforms. These are typically the most sensitive landforms in the coastal zone, hence the need for a map not only identifying their presence (as the geomorphic line map tascoastgeo_v5gda does), but also delineating their landwards extent and form. The Quaternary Coastal Sediment polygon map (tascoastsed_v5gda.shp) provides such information.

Appendix One provides a full description of all attribute fields tagged to each segment of the Quaternary Coastal Sediment polygon map (tascoastsed_v5gda.shp). Many of these attributes will not be relevant to some users, however the following are the geomorphic attribute fields likely to be of most interest to planners and land managers (see also Appendix One for details of each attribute): •

Individual Landform types (Bedform): A description of individual landform types, based on form and fabric (composition). Includes beaches, dune types, intertidal sand flats, backshore sediment plains, etc.

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• • • •

Larger scale landform assemblages (Landform): This attribute was introduced to allow mapping of larger scale landforms comprising assemblages of several bedform types (e.g., "spits", which may comprise beaches, foredunes, parallel dunes and other bedform features) Dune Mobility (Mobility): A measure of dune sand mobility at the date of the imagery or fieldwork used to perform the mapping. Based on assessment of percentage vegetation cover by fieldwork or interpretation of aerial photography.

Present-day Dune Mobility (Currmob): A measure of dune sand mobility at present day, based on assessment of percentage vegetation cover by fieldwork and interpretation of recent aerial photography by Frances Mowling in eastern Tasmania Historic Dune Mobility (Histmob): A measure of past dune mobility (during the 1940s – 1950s era) based on assessment of percentage vegetation cover from interpretation of 1940s – 1950s aerial photography by Frances Mowling in eastern Tasmania.

Figure 15 provides an example of some of the information provided by the Bedform attribute of the Quaternary sediment polygon map.

The dune mobility attributes have not to date been applied uniformly across the entire tascoastsed_v5gda.shp dataset. The dune mobility attributes currmob & histmob were developed by Frances Mowling during the northern and southern NRM coastal values mapping projects (DTAE 2007a), but have only been applied to coasts of the eastern half of Tasmania. These attributes are intended to provide a means of assessing the susceptibility of a sand dune to becoming mobile. For example, dunes which are fixed (fully vegetated) in both the currmob and histmob attributes are likely to be relatively stable dunes, whereas dune that have been vegetated during one period but mobile during another, are likely to be more susceptible to repeated phases of sand mobility (both natural and triggered by inappropriate human land uses). In contrast, the attribute mobility simply gives a measure of the observed dune mobility (as estimated % vegetation cover) at the time of mapping (or date of aerial photography used); this attribute was applied by Sharples (2007) to track changes in dune mobility between photos of the Arthur-Pieman area dunes at different epochs, and so far has only been applied in some western portions of the map (tascoastgeo_v5gda.shp). Some rationalisation of these various mobility attributes is desirable in the future.

See further discussion of coastal dune mapping issues below: Holocene and Pleistocene Coastal Dunes & Mapping Issues The Quaternary period is comprised of the Pleistocene and the Holocene, the latter of which covers the past 10,000. In western Tasmania, there is a distinct sequence of younger Holocene dunes being present and more continuous along the coastline, while older Pleistocene aged dunes occur inland and more discontinuous. Holocene dunes have a bolder outline and often have an accretion of quartzose sand still occurring. They may be stable from vegetative encroachment or occur as large transgressive masses where mobile sands are still advancing inland. The sand granules often appear a bright yellow or brown in colour from the small shell or iron oxide content that is yet to be leached out by rainwater.

However, areas of weathered granite consist of beaches of almost entirely grey quartzose sand without the iron oxide staining. This also occurs in areas where Holocene dunes have been podsolised beneath heath vegetation, leaving behind an older appearing grey Holocene dune (Bird, 2008); examples of such Holocene systems are evident in the distal backshore dune systems north of Granville Harbour Pleistocene dunes by comparison have comparatively subdued topography (to Holocene dunes) with percolating rainwater leaching out calcareous sediments and shell fragments up to over a metre in depth during podzol profile development. The junction between the old and new dune systems is often well developed, especially where transgressive dunes are advancing across older subdued topography (Figure 12). The distinction between Australia and areas such as Europe, where dunes are also present, is that in Australia the dune systems (Pleistocene and Holocene) usually abut, while the European equivalent contains Holocene dunes that overlie older Pleistocene dunes systems (Bird, 2008). This often means that the distinction between older and younger dune systems is more readily identifiable, November 2008

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especially from aerial photography, when vegetation has not entirely covered the dune system, as in areas of western and northern Tasmania. In Pleistocene dune systems that are highly vegetated, the distinction between boundaries becomes difficult to identify from aerial photography and ground investigations are necessitated, though not always feasible.

Figure 12 Mobile parabolic and transgressive dunes inland from Ocean Beach on the west coast of Tasmania.

These dune systems are highly active and driven by largely natural processes, therefore providing some of the best examples of large active dune systems in Tasmania.

Some of the issues associated with identifying polygon boundaries include the use of vegetation as an indicator of polygon boundary. Vegetation is not entirely accurate for identifying boundaries between Holocene and Pleistocene sands as local hydrological and climatic conditions may have a stronger influence of vegetation community type and structure. This is also true for overlaying soils whose genesis may not be directly associated with the underlying geology. Additionally, modified vegetation from pre-European type, condition and cover further diminishes it as a reference for local geology and sediment polygon extent. As such, validation of polygons from API was limited to Holocene formed features, with only limited boundary validation of Pleistocene dunes and sand sheets.

4.4

COASTAL PHOTOGRAPHY

A collection of coastal photographs are provided on DVD in the data accompanying this report and are intended to provide an illustrative key of images for coastal landform types and a spatial and temporal reference point for future reassessment in the NRM North and Cradle Coast region,. The aim is to provide: • • • •

Illustrative examples of the diversity of coastal landform types characteristic of the NRM North and Cradle Coast region; Examples of coastal geoconservation values; Examples of coastal landform types prone to various coastal geomorphic hazards (flooding, erosion, etc), and examples of the effects of those hazards.

Spatial and temporal condition if a specific coastal segment needs to be reassessed

The photography for the NRM North and Cradle Coast region has been captured in two different ways, oblique and terrestrial. Oblique photography is the photography that has been collected from the helicopter validation between Ocean Beach and Sandy Cape. The coverage of photography for this area is very comprehensive, as, due to the vast array of ground coverage in a helicopter, it is not possible to complete a validation while airborne. Therefore, oblique photo’s are collected for later November 2008

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desk based validation. By comparison, terrestrial photography is that which has been captured on the ground, while completing an in-field validation of a particular line segment. The terrestrial photography completed as part of the current (2008) project is quite comprehensive and highly representative of much of the coastal segments visited however, not as comprehensive as the oblique photography as the terrestrial photography was captured only as a reference point, not for later desk based validation.

It must be emphasised that while the photos provided for the NRM North and Cradle Coast region are quite comprehensive, the NRM North and Cradle Coast region photo collection currently remains far from constituting a comprehensive set of images, but rather provides key coastal landform features indicative of the region. The photos provided for the current (v5) update of the coastal geomorphic mapping project were captured during field mapping using terrestrial and oblique photography (from helicopter) of coastal landforms. Since the project scope allowed for mapping of a prioritised selection of coastal sites and types, access within the region to some of the sites was limited. Despite some limited access, a substantial coverage of photos has been obtained for the north west of Tasmania.

Currently, the collection of photos provided concentrates mainly on the following coastal types in the NRM North and Cradle Coast region: • • • • • • •

Actively eroding sediment shorelines Holocene sediment bodies Unconsolidated sediment shorelines (where present) Salt marsh & estuarine shores Sandy beaches, dunes & spits Sediment boundaries and extent (Potential and current) geoheritage sites

Ideally, it is intended that future ongoing development of the datasets provided by this project will allow the photographic image collection to be expanded for the rest of Tasmania, to provide a representative collection of images for the collection described above captured as part of this project.

Additional information on how the photography has been compiled and can be viewed is contained in Appendix Two. 4.5

COASTAL GEOCONSERVATION VALUES MAPPING

The geoconservation values of coastal geological and landform features, and of ongoing natural coastal land-forming processes, are represented in the map data accompanying this report in two ways, namely: •

by the identification of a suite of specific coastal geological and landform features that have been identified as having special conservation ("geoheritage") value; and

•

by the classification of the entire project area coast into areas of differing sensitivity, condition and – derived from these – differing Geoconservation Priorities ("indicative geovalues").

This section describes the mapping of features specifically identified as having special conservation values, whilst the following Sections 4.6 and 4.8 describe the broader indication of conservation values through sensitivity, condition and Geoconservation Priority mapping.

The Coastal Geoconservation Values point and polygon maps (geoconareas_gda and geoconpts_gda) delineate coastal geological sites, landforms and landform assemblages, and soil sites which have been identified as having special Geoconservation (or "Geoheritage") significance (the data structure and attributes of these maps is detailed in Appendix Sections A1.2.3 and A1.3.3). The areas and sites

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delineated on these maps comprise all coastal features in all Tasmanian regions that are registered on the current version of the Tasmanian Geoconservation Database (TGD) 8.

The Tasmanian Geoconservation Database is a GIS-based register of sites of geoconservation significance, which is maintained by the Department of Primary Industries & Water, and which is regularly reviewed by an expert panel, the Tasmanian Geoconservation Database Reference Group (TGDRG). The TGD was initially compiled in the course of studies undertaken for the TasmaniaCommonwealth Regional Forest Agreement (Dixon & Duhig 1996), but has subsequently undergone revisions and upgrades under the direction of the TGDRG. The current version of the TGD is Version 6.0 (2008). The TGD is the primary record of sites, areas and features in Tasmania, which have been assessed as having special geoconservation value; however, the listing of a site on the TGD has no legal implications. That is, the listing of a site on the TGD serves an advisory function by identifying sites of geoconservation value, but does not in itself confer legal protection on the listed sites.

Despite its lack of legal status, the TGD is the primary tool for planning and prioritising efforts to manage and protect features and systems of special geoconservation value in Tasmania. The specific management practices and prescriptions needed to maintain the conservation value of sites on the TGD (and on the derived geoconareas_gda and geoconpts_gda maps) vary widely depending upon the particular nature and values of each site. For example, the value of the large site NUG32: "Frederick Henry Bay Beach Alignment" resides in the large-scale plan form of the coast, and this value is unlikely to be degraded by any likely artificial developments short of very extensive engineering realignment of the coastline. Hence, few conceivable coastal developments would degrade the values of this site. In contrast, site DCX12 "Mickey's Bay Elephant Skin Jointing" comprises shoreline sandstone outcrops valued for their delicate surface weathering features, and hence protection of the value of this site requires exclusion of small scale artificial excavations, filling or covering of the outcrops concerned. The level of management and protection needed to protect the values of a listed site are broadly implied by the sensitivity rating contained within the map attributes (see A1.3.3), but should be specifically assessed by a relevant expert in the course of planning for the protection of any specific feature.

It must be emphasised that the TGD, and the derived geoconareas_gda and geoconpts_gda maps, do not identify all coastal landform features worthy of some level of management to protect their geoconservation values, but rather emphasise a suite of sites recognised as having special or outstanding geological or geomorphic characteristics. Many other natural landforms and ongoing natural geomorphic processes are present on the coast and, whilst their geoconservation values may be individually more of a locally representative nature than outstanding, the maintenance of the natural landscape, amenity and ongoing natural processes in any coastal region as a whole requires that natural coastal geomorphic features and processes generally be managed to maintain their geoconservation values insofar as is possible. It is the purpose of the geomorphic sensitivity and condition mapping described in Section (4.6) below and the Geoconservation Priorities mapping described in Section (4.8) below to provide an indication of these broader geoconservation values.

4.6

COASTAL GEOMORPHIC SENSITIVITY AND CONDITION MAPPING

The attributes Sens and Cond provided in the coastal geomorphic line map tascoastgeo_v5gda that accompanies this report, give an indication of the sensitivity of coastal landforms to artificial disturbance, and the degree to which natural coastal landforms and land-forming processes have already been modified by human activities.

8

With the exception of site SWA16 (Pleistocene Marine System High Level Relict Shorelines). This is an extensive area within which uplifted shoreline features occur at certain specific locations, however no polygon has been drawn for this site as yet. It is currently proposed that this large area will be withdrawn from the TGD, and replaced with a number of smaller sites identifying known specific uplifted coastal landforms.

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The Sens and Cond attributes are described in detail in Appendix section (A1.3.4). This section provides an overview of the purpose of these attributes.

Sensitivity is the inherent susceptibility of a feature, process or system to degradation resulting from disturbances caused by human activities, irrespective of any existing threats of such disturbance actually occurring. Landforms more sensitive to human disturbance tend also to be those more prone to change and erosion due to natural causes, however a corollary of this is that the more sensitive landforms may rapidly change in ways that would not occur naturally, if they are artificially disturbed.

In the context of coastal landforms, sensitivity primarily refers to the susceptibility of a landform or landform system to accelerated wave or wind erosion (and/or accelerated sediment mobility and deposition) because of human disturbances to the coastal landform system. By convention, sensitivity as mapped for this project (Sens) refers to sensitivity to local or regional artificial disturbances, but not specifically to the effects of global anthropogenic climate change and sea level rise, which for the purposes of this indicator are treated as if they were natural changes.

Sensitivity has value for management of coastal geomorphic values by indicating areas where natural landform values are likely to be most easily degraded. It simultaneously has value for coastal hazards management, by indicating areas which, in virtue of their sensitivity, are likely to be most prone to hazards such as erosion and dune mobility (as noted in Section 3.1, this is one of the ways in which management of coastal landform values is inextricably linked with management of coastal hazard issues).

For the purposes of providing a simple indicator of sensitivity that will provide guidance to planners and managers, coastal landforms have been grouped into four simple categories as follows (see also Appendix section A1.3.4): 1.

High Sensitivity: Primarily coasts dominated by soft sediments (sand or mud) which are prone to significant degradation and management problems through inappropriate activities.

2.

Mixed Sensitivity: Coasts with significant components of differing sensitivity (e.g., hard rock shores backed by soft dunes). Disturbance may significantly degrade some but not all elements of these coasts.

3 Moderate Sensitivity: Coasts composed of semi-consolidated materials intermediate in their sensitivity to disturbance between soft (sandy) and hard (bedrock-dominated) coasts. Human disturbance may cause some modification of natural landforms and processes, which may be locally significant (e.g., slumping) but is generally of a lesser scale than on high sensitivity coasts.

4.

Low Sensitivity: Primarily coasts dominated by hard bedrock. Some human disturbance can occur on such coasts without substantially altering natural geomorphic processes, albeit soils may be vulnerable and other natural values (including biological and aesthetic values) may be degraded by disturbance.

These categories have been determined in a rule-based fashion (using GIS query functions) for the entire Tasmanian coast from the detailed geomorphic mapping (tascoastgeo_v5gda and tascoastsed_v5gda), which contains the geomorphic information needed to assign coastal areas to one of the four sensitivity classes above.

The division of coastal landforms into four simple categories of sensitivity has the advantage of providing planners with a simple indicator of sensitivity to disturbance. The downside of this is that the sensitivity rating does not provide details of specific disturbing activities that might degrade the conservation values of particular coastal features, the purpose of the sensitivity rating is the flag areas more likely (or less likely) to warrant further consideration of the impacts that human activities might have on the natural (geoconservation) values of particular areas. In general, a high sensitivity rating (Sens = 1) indicates that a range of management activities are likely to arise in respect to human November 2008

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activities on the coast, such that any proposed new activities warrant careful consideration of possible impacts on coastal landforms. On the other hand, a low sensitivity rating (Sens = 4) suggests that only the most highly disturbing human activities are likely to be problematical from the perspective of maintaining natural coastal landform values.

Condition is the degree of naturalness, or of artificial disturbance by human activities, of coastal geological features, landforms, soils and geomorphic or soil processes. The condition attribute Cond is an overall condition summary for bedrock, landform and soil features within each shoreline segment, encapsulating the cumulative impact of all known artificial disturbances on the naturalness of landforms or geomorphic processes of the coastal segment in question. By convention, Cond refers to the effects (or otherwise) of local or regional artificial disturbances, but not to the effects of global anthropogenic climate change and sea level rise. Disturbances, for the purposes of this indicator are treated as if they were natural changes (e.g., some sandy shores in southwest Tasmania are eroding rapidly for reasons probably related to global (anthropogenic) sea-level rise, but are otherwise undisturbed and so are categorised as being in essentially pristine condition Cond = 1).

The condition attribute provides an indicative means of making a preliminary assessment of the conservation value of coastal landforms in the absence of more detailed and systematic assessments of geoconservation value over long stretches of coastline (as noted in Section 4.5 above, coastal geoconservation values have to date only been assessed for a limited suite of outstanding sites on the Tasmanian coast, and no comprehensive assessment of geoconservation status for the Tasmanian coast is available). In the absence of more rigorous systematic assessments, coastal landforms in good condition are taken to have geoconservation significance for that reason – i.e., they are natural systems that have conservation value because they retain much or all of their natural forms and functions.

For the purposes of providing a simple indicator of condition that will provide guidance to planners and managers, coastal landforms have been grouped into four simple categories as follows (see also Appendix section A1.3.4): 1.

Highly Natural: Coasts whose landforms and land-forming processes are wholly or essentially undisturbed. If any human disturbances are present, these have not notably affected coastal landforms.

2.

Partly Disturbed: Coasts whose landforms are largely natural, and dominated by natural land-forming processes, although minor modification of natural land-forming processes may have occurred (e.g., hard-rock shores with roads and building in the backshore, but little change to the coastal landforms).

3 Significantly Disturbed: Significantly disturbed coasts which still posses some natural landform elements (e.g., essentially natural beaches with significantly disturbed or built-over dune and backshore areas, or dunes with roads or marram grass that has notably modified natural dune processes).

4.

Highly Modified: Coasts where natural landforms and land-forming processes have been modified to the extent they contribute little to nature conservation values (e.g., artificial shorelines dominated by reclaimed land, rock walls, port facilities, etc).

The condition classification Cond was manually attributed to the northern and southern NRM region coasts by Chris Sharples and Frances Mowling during 2006, by reference to relevant disturbance mapping (roads, infrastructure, and land clearance) and to field inspections during and prior to this project. Condition attributes have subsequently been similarly applied to parts of the NRM North and Cradle Coast region by the Hydro Tasmania Consulting Team in 2008. This condition classification takes account of both the degree of conservation of natural landform morphologies (shapes, surface disturbances), and of ongoing natural land-forming (geomorphic) processes such as natural erosion and sediment mobility. That is, the geomorphic condition of a segment of coast is taken to depend on November 2008

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both the degree to which natural geomorphic processes have been disturbed (or not), and the degree to which natural coastal forms have been artificially altered (or not).

Note that geomorphic condition is generally taken to be independent of vegetation condition for the purposes of this classification: the geomorphology and soils may be essentially intact despite some weed species being present or native species absent. However, where weed species have affected the geomorphic processes, as may occur for example where marram grass (Ammophila arenaria) infestation has altered the sand mobility and profile of dunes, a poorer geomorphic condition classification is applied.

4.7

COASTAL GEOMORPHIC HAZARD (VULNERABILITY) MAPPING

One of the datasets provided with this report provides coastal dune mobility data, which constitutes a tool to assist planning for management of dune mobility hazards (coastal sediment polygon map tascoastsed_v5gda, see Section 4.3 above). However, tools for specifically identifying other coastal geomorphic hazards such as coastal erosion, recession, slumping and storm surge flooding (see Sections 3.4 & 3.5 above) have not been provided in the data accompanying this report. The exception to this is the sensitivity indicator (Section 4.6), which provides a generalised indicator of potential sensitivity to these or other hazards. The provision of information aimed at assisting coastal managers to plan for and manage other coastal geomorphic hazards is instead the objective of work undertaken by the Climate Change Project within the Strategic Policy Division of DPIW. Rather than duplicate that work here, it is intended that coastal managers and planners should refer to the separate coastal hazard mapping in conjunction with the dune mobility hazard information provided with this NRM project report (see Sections 4.3 & A1.3.2).

In 2004 – 2006, the Strategic Policy Division of DPIW commissioned the preparation of maps providing an indicative assessment of sandy coast erosion and recession vulnerability, slumping and other erosion hazards, sea cliff instability and storm surge flooding vulnerability, for the entire Tasmanian coast. The indicative vulnerability mapping is available on the LIST website (http://www.thelist.tas.gov.au) and is fully described in the vulnerability project report (Sharples 2006), which is also available on the DPIW website (http://www.dpiw.tas.gov.au or http://www.coastalvulnerability.info).

In brief, the indicative vulnerability mapping provided by Sharples (2006) identifies shores potentially vulnerable to shoreline erosion or slumping, or to flooding during coastal storm surges, under both present day climate and sea level conditions, and under predicted future sea level rise conditions to the year 2100. The indicative mapping of sandy shore erosion and recession vulnerability is based on the same coastal geomorphic descriptive line map that is described in Section 4.2 above 9. This is compared to the indicative storm surge flooding vulnerability mapping, which is based on the 25 metre Digital Elevation Model (DEM) of Tasmania in conjunction with the analysis of Tasmanian tide gauge records by Dr John Hunter (ACE CRC & University of Tasmania) to extract historic storm surge levels on the Tasmanian coast. It is important that users of the indicative coastal vulnerability mapping be aware of the caveats and limitations on the use of that mapping, as described by Sharples (2006).

Planners should also note that subsequent to 2006, further (more detailed) assessments of coastal vulnerability to sea-level rise and climate change have been and are continuing to be undertaken by (within Tasmania) DPIW and the Antarctic Climate & Ecosystems CRC, and (nationally) by Geoscience Australia and the Department of Climate Change. These organisations should be contacted for advice on the most up to date coastal vulnerability information for any specific sites of interest.

9

Note that whilst the sandy shore erosion vulnerability mapping is based on the same descriptive geomorphic line map that is provided with this NRM report, the erosion vulnerability classification attributes are provided only in the version prepared for the Strategic Policy Division of DPIW as described by Sharples (2006).

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4.8

GEOCONSERVATION PRIORITY ("INDICATIVE GEOVALUES") MAP

The attribute Geovalues provided in the coastal geomorphic line map tascoastgeo_v5gda that accompanies this report is a high-level (i.e., generalised) indicator of geoconservation management priorities, which has been derived from lower-level (i.e., more specific) geomorphic attributes classified in the tascoastgeo_v5gda.shp map. The Geovalues attribute is described in detail in Appendix section (A1.3.4). This section provides an overview of the purpose of the attribute.

The purpose of the Geovalues attribute is to highlight coastal segments which are most likely to warrant more detailed consideration of the appropriate management of their geomorphic or geological (geoconservation) values. If the Geovalues attribute highlights a coastal segment as warranting some attention, the first step is therefore to examine the underlying Sensitivity, Condition and Geomorphic attributes, which gave rise to the Geovalues classification. This is necessary to obtain a better indication of why a coastal segment has been assigned a higher (or lower) geoconservation priority, and consequently, the sort of geoconservation management issues that may arise for that segment (see Section 3.0) 10.

The Geovalues attribute is a simple indicator that assigns higher or lower Geoconservation Priority to particular coastal segments. High Geoconservation Priority landforms are those which are either in more natural condition (and thus make a greater contribution to existing regional conservation values) or of higher sensitivity to disturbance (and thus of higher priority for conservation management, even if already somewhat disturbed, because of their propensity for significant further degradation of regional geomorphic values if inappropriately managed).

For the purposes of providing an indicator of geoconservation priority that will provide guidance to planners and managers, coastal segments have been grouped into four simple categories as follows (see also Appendix section A1.3.4): 1.

High Geoconservation Priority: Coastal segments having either the highest sensitivity to disturbance, and/or the most natural condition. The highest geoconservation priority will apply to sensitive (e.g., sandy) coasts in pristine condition, however a significantly disturbed sensitive (e.g., sandy) coastline may also fall into this category because, despite its existing disturbance, continued inappropriate management may continue to cause or increase coastal geomorphic management problems regionally.

10

It is worth noting that during the course of the prior Northern and Southern NRM Coastal Values projects,, an attempt was made to combine the Geovalues (Geoconservation Priority) indicator with an equivalent Biovalues (Bioconservation Priority) indicator developed by NorthBarker Ecosystem Services for a parallel NRM Coastal Biological Values Project, so as to produce an overarching "Natural Values Priority Indicator". However, it was found that in doing so, the natural values priority indicator generalised information about geo- and bio-values to such an extent that the resulting indicator provided little assistance in differentiating coastal areas of greater and lesser priority for conservation (an effect of the process was to give a great preponderance of coastal areas a uniformly high priority, which is of precious little use for differentiating between management priorities along the coast!).

The cause of this problem is that both the Biovalues and Geovalues indicators are themselves generalised from more detailed underlying data, with some loss of information but a result that remains useful for indicating priorities. However, in taking these already-generalised indicators, and combining them to produce, - in effect - a generalisation of a generalisation, further information was lost to the extent that the resulting Natural Values indicator was of little use.

We consider that the Biovalues and Geovalues priority indicators are best used separately but in parallel, rather than in a fully combined fashion.

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2.

Moderate Geoconservation Priority: Intermediate category – coastal segments of either moderate sensitivity or in moderately natural condition. The same considerations as for Geovalues = 1 apply, at a lower level of priority.

3 Moderate to Low Geoconservation Priority: Coastal segments whose sensitivity is moderate to low, and whose condition is moderate to poor, but which still retain some natural landform or process elements that may be further degraded or result in geomorphic hazards if subjected to some types of inappropriate activities, and which thus still warrant some management consideration in regard to landform values or processes.

4.

Low Geoconservation Priority: Coastal segments of low sensitivity to disturbance yet which are significantly disturbed nonetheless (mainly refers to hard rock shores that have been extensively built over and modified by dock facilities, urban development to the waterline, etc). Geoconservation issues will rarely arise for these shores, which have essentially lost all natural geoconservation values, and whose continued disturbance will generally not result in additional environmental degradation to that which already exists.

The Geoconservation Priority Geovalues attribute was assigned by means of automated GIS queries on the Sens And Cond attributes on which it is based, as described in Appendix section (A1.3.4). This attribute was provided for most of the northern and southern NRM region coasts by Chris Sharples and Frances Mowling during 2006 (DTAE 2007a,b), and subsequently in 2008 by Josh Hawkins of Hydro Tasmania Consulting for those parts of the NRM North and Cradle Coast region where both Sens and Cond attributes were completed.

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5.0

PUTTING IT ALL TOGETHER – USING THE COASTAL MANAGEMENT DECISION SUPPORT TOOLS

5.1

THE PURPOSE OF THE COASTAL GEOMORPHIC VALUES DECISION SUPPORT TOOLS The mapping and information provided with this report constitute a set of Decision Support Tools that are a means of quickly identifying the potential for management issues and problems related to coastal landform processes (geomorphology) arising in relation to human activities or proposed developments in particular coastal areas. These tools are high level (i.e., generalised) indicators of coastal geomorphic management issues, and as such they will not eliminate the need for more detailed specialist assessments of particular coastal management issues where high-priority issues arise. Rather the purpose of these tools is to provide means of more efficiently determining whether problems are likely to occur, and to give an indication of their nature, so that any need for assessments that are more detailed can be more readily identified and focussed. Thus, these tools should be seen as decision support tools, not decision-making tools.

These tools represent the first attempt to provide a set of high-level management tools for dealing with coastal geomorphic management issues in Tasmania. As such, it is inevitable that these tools will be subject to refinement in future, as experience with their use reveals needs and potentials for their further improvement.

This section outlines an approach to using the Decision Support Tools to inform decision making and Land Management Zoning in regard to coastal landform management issues such as those described in Section 3 of this report, in particular those issues related to conserving natural values in coastal areas.

It is envisaged that this approach will be utilised in tandem with parallel approaches to other coastal management issues including biodiversity values management. The approach described here is a suggested approach, and it is possible that some users will develop other means of using the tools provided.

5.2 THE DECISION SUPPORT TOOLS The geomorphic map layers described by this report provide coastal geomorphic data and management guidance at three levels of detail, namely a base level of detailed geomorphic mapping, a mid-level of management-relevant information (Sensitivity and Condition, abstracted from the detailed mapping), and a high level Decision Support Tool (Geoconservation Priority or "Indicative Geovalues") which functions as an indicator of coastal areas most likely to present management issues for the conservation of coastal geomorphic values. As is always the case with information hierarchies of this nature, some of the more detailed information is lost at each rising level, but a clearer and simpler guide to management action is provided.

Each of these levels of information is described in more detail elsewhere in this report as noted in Table 1, which summarises the availability and sources of more descriptive information for each data layer. In addition to these layers, layers of indicative coastal geomorphic hazard vulnerabilities are provided separately to this project; these are also noted in Table 1.

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Table 1: Data layer maps (Decision Support Tools) described by this report, and sources of maps and information for each.

Data Level

Data Layer (Decision Support Tool)

High Level Indicators

Geoconservation Priority (Indicative Geovalues) Coastal hazard vulnerability Indicative Mapping (flooding & erosion)

Mid-Level Management Information

Detailed Level Base Data

Data Purpose info (Section no.s, this report)

Data Structure info

4.8

A1.2.1

(Section no.s, this report)

A1.3.4 Sharples (2006) plus more recent information

Sharples (2006) plus more recent information

Geomorphic Sensitivity (to disturbance)

4.6

A1.2.1

Geomorphic Condition (degree of disturbance)

4.6

Coastal landform Line Map

4.2

A1.3.4 A1.2.1 A1.3.4

A1.2.1 A1.3.1

GIS Layer

Online Availability

(CD accompanying this report) Geovalues attribute in tascoastgeo_v5gda

LIST website

Accompanying Sharples (2006) plus more recent information

LIST website

Sens attribute in tascoastgeo_v5gda

LIST website

Cond attribute in tascoastgeo_v5gda

LIST website (www.thelist.tas.gov.au)

Geomorphic attributes in tascoastgeo_v5gda

LIST website

(www.thelist.tas.gov.au)

(www.thelist.tas.gov.au)

(www.thelist.tas.gov.au)

(www.thelist.tas.gov.au) & Coastal Atlas website (www.atlas.tas.gov.au)

Coastal Landform Polygon Map

4.3

Coastal Geoheritage Sites (TGD)

4.5

A1.2.2

tascoastsed_v5gda

A1.3.2

LIST website (www.thelist.tas.gov.au)

A1.2.3

geoconareas_gda

TGD:

A1.3.3

geoconpts_gda

LIST website (www.thelist.tas.gov.au)

5.3 USING THE DECISION SUPPORT TOOLS The Decision Support Tools (Table 1) comprise a hierarchy of increasingly simplified information at each rising level, each based on more detailed data levels lower in the hierarchy, but each rising level providing a clearer indication of the management priorities arising from the more detailed data at lower levels in the hierarchy. The intended method to use this information is to consider first, the highest level, and then "drill down" through the more detailed levels (guided by the priorities and potential issues indicated by the higher levels). The guidance obtained at each level directs the management priorities and types of information that needs to be collected at the lower levels.

Figure 13 diagrammatically represents the Decision Support Process, each step is briefly described below. The following Section 5.4 provides an example of the use of this Decision Support Process.

The following Decision Support Process is described specifically from the perspective of managers seeking to maximise the conservation of natural coastal geomorphic values. This process should be conducted in tandem with parallel decision processes about other conservation values (e.g., November 2008

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biodiversity), and other management priorities such as assessing coastal hazards to infrastructure and assets (erosion, flooding, etc); these other processes are described elsewhere.

1.

Decision Required

Development Proposal?

Zoning? Land Use?

2.

Hazards Assessment Needed?

3.

High Level Assessment (Determine priority of Geo issues)

Involves infrastructure or artificial assets?

N

Determine Geoconservation Priority (Geovalues indicator)

4

1–3 4.

Mid Level Assessment (General types of issues likely)

5.

Detailed Assessment (Specifics of issues, likelihood of needing specialist advice)

6. Implications and Actions

Y

Geoconservation issues unlikely

Coastal vulnerability assessment

Tandem process, see Sharples 2006 & newer resources.

Site Indicatively vulnerable? More assessment may be needed.

1 – 3 indicates likely importance and priority of geoconservation issues

Determine Sensitivity and Condition Determine broad management issue types

Refer Table 2: Geoconservation priorities arising from Sensitivity & Condition (i.e., reasons for Geoconservation Priority rating)

Review base geomorphic mapping and geoheritage data

Landform types?

Landform mobility?

Soft sediment areas?

Geoheritage sites?

Issue types confirmed?

Landform types correspond to issues and priorities? (Table 2) Y

N

Review landform types present in light of possible issues (Section 3.0)

Obtain preliminary specialist advice

Draw possible implications for decision needed

Likely importance of issue indicated by Geoconservation Priority (above)

Specialist Advice (if needed)

Lower Priority issues: preliminary advice sufficient?

Higher priority issues: may require detailed specialist advice

Figure 13: Simplified representation of the decision making process for using the Decision Support Tools described in this report to make management or zoning decisions aimed at maximising the conservation of natural geomorphic values (geoconservation values) in the coastal zone.

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Decision Making Process The following paragraphs provide a succinct description of the decision making process outlined on Figure 13.

1 Decision Required The decision-making process commences with a requirement to make a decision on coastal land use or zoning. This may arise because of a Development Proposal for a particular location, a proposal for changed land use, a need to zone coastal land according to the most appropriate uses for different areas, or for some other reason. As noted above, the decision making process described here is based on the assumption that a goal of the decision making process is to maximise the conservation of natural coastal landforms and landform processes – i.e., that the decision making process has Geoconservation as a key objective. In general, this decision-making process will be conducted in tandem with assessment of other issues including bioconservation priorities.

2 Hazards Assessment Required?

If the decision involves infrastructure or other artificial coastal assets, then an indicative assessment of vulnerability to coastal hazards including flooding, erosion, and the potential for increased flooding or erosion with sea level rise, should be undertaken in tandem with the values assessment described here.

For Tasmanian shores, an indicative assessment of coastal vulnerability may be undertaken using the indicative coastal vulnerability mapping of Sharples (2006, see Table 1), and additional more recent information. Such an assessment is not the primary focus of this report; however, the implications of the results would relate to and inform the values assessment described here (see also discussion in Section 3.1).

For example, if the site of a proposed coastal infrastructure development is shown to be indicatively vulnerable to flooding or erosion, and the geomorphic values of the site are in good or moderate condition, then this would lend weight to a decision to prioritise coastal conservation over development at the site, since the hazards are typically a part of natural coastal processes and evolution, whereas they will constitute a difficulty for proposed developments which might better be planned for a less vulnerable location. On the other hand, if retention or construction of infrastructure at a site indicated to be potentially vulnerable were still favoured for other reasons, or because of a high level of existing disturbance reducing the geoconservation priority of the site, then this would trigger a need for a more detailed assessment of vulnerability.

Note that a coastal site vulnerable to hazards such as erosion is likely to have a high or moderate Sensitivity indicated by the Sensitivity map (Sens) Decision Support Tool described below; however a site vulnerable to flooding (by reason of low topography) may have a low sensitivity in other respects (e.g., to erosion).

3 High Level Assessment - Geoconservation Priority The first step in the geomorphic values assessment is to obtain a preliminary indication of the likely priority of the site from a geoconservation values perspective. The Geoconservation Priorities indicator provides a high-level indication of this (Geovalues attribute of tascoastgeo_v5gda map; see Sections 4.8 & A1.3.4). Figure 14 provides an example of the Geoconservation Priority indicator (Geovalues) viewed as a map layer.

A geoconservation values priority level 4 indicates that the site is both heavily disturbed from a natural values perspective (e.g., artificial or built-over shore), and also of low sensitivity such that further disturbance is unlikely to significantly increase existing levels of degradation of natural geomorphic values locally. Such sites are unlikely to warrant further assessment from a geoconservation values perspective.

However, sites having Geoconservation Priorities of 1, 2 or 3 may all retain some level of natural geomorphic values and contribute to the overall level of coastal geomorphic values locally or November 2008

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regionally. The type and significance of these values may vary, and will not always rule out artificial disturbance or development; however, the likely significance of the geomorphic issues relative to other considerations is likely to be greater for areas having Geoconservation Priority 1, and less for areas having Geoconservation Priority 3. The Geoconservation Priority level is thus an indicator of the weight likely to need to be placed on further assessment of the geomorphic values issues. An area of geoconservation priority 3 may warrant only a preliminary assessment, whilst an area of Geoconservation Priority 1 is likely to have major implications for any decision that is made and should be considered carefully.

4 Mid-Level Assessment - General Types of Issues Likely The Geoconservation Priority indicator (Geovalues) is based on the indicative geomorphic Condition and Sensitivity of a site. However, sites may have the same level of indicative Geoconservation Priority for quite different reasons, and hence the next stage of assessment is to identify the broad types of geomorphic values issues pertaining to a site, by considering the particular Condition and Sensitivity attributes of the site.

The Condition and Sensitivity attributes can be viewed as map layers using the Cond and Sens attributes of the tascoastgeo_v5gda map (see Sections 4.6 & A1.3.4). Figure 14 provides an example of the Condition and Sensitivity attributes viewed as a map layer. When the particular mix of Condition and Sensitivity values pertaining to a coastal site have been determined, Table 2 can be used as a matrix designed to provide an appreciation of the general nature of the geomorphic issues that pertain to the site and which inform its Geoconservation Priority ranking.

In general, sites having high sensitivities will have high priority for careful planning consideration even when somewhat degraded – because of the high propensity for artificial disturbance to result in landform and geomorphic process degradation. Even where a high sensitivity site is already highly disturbed, poorly planned disturbances can further exacerbate degradation of natural processes for the local or regional coastal area.

Sites with more natural condition (better Condition ranking) will also warrant more consideration of their natural geomorphic values in virtue of the greater contribution they make to maintaining natural coastal values. This is most important in the case of highly sensitive sites that remain in good natural condition, but low sensitivity sites in good natural condition (e.g., undisturbed robust rocky shores) also have high conservation value since – even though many disturbances will not greatly degrade their geomorphic values per se – their natural condition supports a range of other coastal conservation values including habitat and biodiversity.

5 Detailed Assessment - Specifics of the Issues Having established the Geoconservation Priority of a site, and formed a general picture of the management issues likely to arise from the Condition and Sensitivity attributes of the sites geomorphology, the detailed geomorphic information provided in the geomorphic map layers tascoastgeo_v5gda (line map) and tascoastsed_v5gda (polygon mapping of soft sediment landforms), and in the Geoheritage map layers (geoconareas_gda and geoconpts_gda, or current online TGD version) should be reviewed. These maps provide details of the actual landform types present at the site, and any special geoheritage values that may have been previously recognised.

In particular, the following information from the detailed mapping layers may be particularly useful in appreciating the nature of any issues arising: • • •

Broad types of landforms present - soft sandy or muddy? Hard bedrock? Intermediate clayeygravelly or colluvial types? (Upperint, Lowerint & Backshore attributes of tascoastgeo_v5gda line map, Bedform and Landform attributes of tascoastsed_v5gda polygon map).

Bedrock types (Bedrock attribute of tascoastgeo_v5gda line map) Coastal topography - steep slopes? Moderate slopes? Low-lying plains? (Profile attribute of tascoastgeo_v5gda line map) November 2008

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• • •

Degree of exposure to wave energy (Exposure attribute of tascoastgeo_v5gda line map).

If soft (sandy or muddy) sediments present, the extent of these and any history of past dune mobility recorded by the dune mobility attributes (currmob and histmob attributes of tascoastsed_v5gda polygon map; see Sections 4.3 & A1.3.2).

Any recognised Geoheritage sites present, noting especially the nature and sensitivity of any such sites (geoconareas_gda and geoconpts_gda maps, or current online TGD version)

The purpose of reviewing the detailed geomorphic mapping is to confirm more specifically the nature and extent of the issues flagged as potentially arising in consideration of the Condition and Sensitivity of the site (above). The specific types of landforms occurring at the site should be considered in terms of the coastal landform management issues identified in Section (3.0) of this report to determine whether the potential issues arising are pertinent for the decision requiring to be made in each particular case.

This review of the base geomorphic data is intended to clarify the specific nature of the broad issue types that were identified in the Mid-Level Assessment (above) by consideration of the Condition and Sensitivity ratings. To some extent, this stage of the Decision Making Process will inevitably require some appreciation of the geomorphic response of various coastal landform types to a range of potential disturbances, in order to assess the implications of the Condition and Sensitivity of the particular landform types present to the types of land uses that are under consideration. The discussions in Section (3.0) of this report are intended to provide a basic overview of the implications, however there will inevitably be cases where these implications are not obvious to the user of these Decision Support Tools. Where this is the case, users should seek preliminary advice from appropriate specialists.

6 Implications and Actions In summary, the high level Geoconservation Priority attribute indicates the overall likelihood that a coastal site is important in the maintenance of coastal geomorphic values, and the Condition and Sensitivity attributes indicate the general types of issues that need to be considered in planning for the site or area to maximise the conservation of geomorphic values at the site and in the surrounding local or regional zone. The specific geomorphic attributes – and any geoheritage sites listed for the coastal segment - will confirm and provide details of the geomorphic management issues arising – or if they do not, will indicate the need for at least a preliminary specialist overview of the site to clarify whether any issues are present. A tandem indicative coastal hazards vulnerability assessment will indicate additional geomorphic constraints that should be considered if the planning issue under consideration involves infrastructure or other artificial assets.

With all this information in hand, it is intended that planners and managers will by this stage have a reasonably clear picture of the sorts of geomorphic issues arising that may influence the decision required where it is a planning objective to maximise the conservation of coastal geomorphic values locally and regionally. If the picture remains unclear at this stage, planners should seek preliminary specialist advice.

However, where (as is intended) the nature of the geomorphic planning issues arising is clear, it will be possible to make some decisions at this stage. If the planning decision to be made will clearly not affect the geomorphic values present at the site, it may be possible to proceed with the decisionmaking process without further consideration of geomorphic issues. On the other hand, if the site has a high Geoconservation Priority rating, and the decision to be made may affect the geomorphic values present, it is likely that this will be a trigger for either rejecting a proposal which may have detrimental effects on coastal geomorphic values, or alternatively seeking specialist advice on the likely specific impacts on geomorphic values, and any means of ameliorating those impacts that may be available.

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Table 2: Condition – Sensitivity matrix, provides a succinct summary of geoconservation management priorities that typically arise for each combination of Sensitivity and Condition when viewed from the perspective of managing to maximise the conservation of coastal geomorphic (geoconservation) values.

Condition

Sensitivity (& typical landform types and natural geomorphic processes)

1 High Sensitivity Dominantly soft coasts – beaches, dunes, salt marsh, muddy estuarine shores, backed by soft sediment plains.

- Dune mobility - Shoreline erosion & deposition

2 Mixed Sensitivity Shores with hard and soft elements – e.g., beaches backed by hard bedrock, rocky shores backed by dunes.

3 Moderate Sensitivity Shores dominated by semi-consolidated materials – e.g., clayey-gravelly shores, colluvium, landslide deposits - Slumping, landslides - Progressive shoreline erosion

4 Low Sensitivity Dominantly hard-rock shores – sloping or cliffed hard-rock shores backed by bedrock ± soil.

- Mostly stable - Some cliff rock-fall (hazards).

- Backshore soils may be vulnerable

1 Highly Natural

2 Largely Natural

3 Partly Natural

Negligible disturbance of landforms and geomorphic processes.

Dominantly natural landforms and geomorphic processes – minor disturbances only.

Significantly disturbed but retaining some natural geomorphic elements.

Landforms and geomorphic processes dominantly degraded.

Highest priority for protecting natural landforms & sediment dynamics Avoid artificial modification, mobilisation or stabilisation of soft sediments.

Avoid disturbance of natural landforms & sediment dynamics Avoid or minimise artificial modification, mobilisation or stabilisation of soft sediments.

Minimise ongoing disturbance of landforms & geomorphic processes Some artificial modification acceptable but prefer avoidance of naturally mobile areas to artificial protection of assets.

Some artificial modifications may be acceptable, but avoid increased modification of geomorphic processes in broader region.

Protect assets from geomorphic hazards consistent with avoiding broader impacts.

High priority for protecting natural landforms and processes As above for soft landform elements, as below for hard landform elements.

Avoid disturbance of natural landform processes dynamics As above for soft landform elements, as below for hard landform elements.

Minimise ongoing disturbance of geomorphic processes As above for soft landform elements, as below for hard landform elements.

Artificial modifications may be acceptable, but avoid increased modification of geomorphic processes.

As above for soft landform elements, as below for hard landform elements.

High priority for protecting natural landforms and processes Avoid physical disturbance on these potentially mobile shores.

Avoid disturbance of natural landform processes dynamics Avoid or minimise physical disturbance on these potentially mobile shores.

Minimise ongoing disturbance of geomorphic processes Some artificial modification acceptable but prefer avoidance of natural hazard areas to artificial protection of assets.

Artificial modifications may be acceptable, but avoid increased modification of geomorphic processes.

Geomorphic hazards may still threaten artificial assets, avoid triggering hazards.

High priority for protecting natural landforms and processes Shores largely robust but avoid soil erosion or clearance in backshore areas.

Avoid disturbance of natural landforms and processes Shores largely robust but avoid or minimise soil erosion or clearance in backshore areas, any disturbance should avoid hazards (e.g., cliffs)

Minimise ongoing disturbance of geomorphic processes Some artificial modification acceptable, but avoid natural hazards (e.g., cliff edges) and minimise soil erosion.

Dominantly robust and artificial shores, geoconservation issues unlikely

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Using the Coastal Geomorphic Management Decision Tools

5.4 EXAMPLE OF DECISION SUPPORT TOOL USE The following case study involves a planning issue, which in this instance is imaginary, but is similar to many planning issues that arise in Tasmanian coastal areas. The coastal location considered is however real, and the maps accompanying this case study are drawn from the mapping and Decision Support Tools described in this report.

Case Study The case study location is a stretch of typical Tasmanian coast adjacent a regional town, comprising beaches backed by small dunes and low-lying sediment plains, interspersed between headlands of sloping to cliffed rocky shores backed by moderately rising bedrock substrates with soil mantles.

The case study area comprises several differing coastal landform types represented by different segments in the coastal line map (see Figure 15). In this instance, it is necessary to compare the geomorphic characteristics of several coastal segments to determine which is any of them are suitable – from a geomorphic perspective – for a particular land use.

Key outcomes of this case study are summarised in Table 3, and each step leading to these outcomes is described below: 1 Decision Required Increasing pressure for urban development requires rezoning to create a new area for residential development on the outskirts of the neighbouring town. Three adjoining coastal segments (shown as A, B & C on Figure 14 and Figure 15) are under consideration for rezoning as a residential area.

Which is the three areas is most optimal for residential development in the context of minimising disturbance and degradation of coastal geomorphic (geoconservation) values in the local coastal region?

2 Hazards Assessment Required?

Because the required decision relates to infrastructure development, an assessment of indicative vulnerability to coastal hazards (erosion, flooding) is essential. Indicative coastal vulnerability mapping (e.g., Sharples 2006, or more recent information) indicates that coastal segment A is backed by sufficiently low-lying ground that it may be subject to storm surge flooding, although it has a hard rock shoreline which is not particularly prone to erosion. Segment A is a soft shoreline backed by low plains, and is thus potentially prone to both coastal erosion and flooding. However, Segment C is a moderately rising hard-rock shore with little indicative vulnerability to either erosion or flooding. See Figure 14.

This indicative vulnerability assessment indicates that, if either segment A or B were favoured for residential development on other grounds, then a more detailed assessment of their vulnerability to flooding and/or erosion would be necessary. However, if Segment C is favoured for residential development, then the existing Indicative vulnerability mapping indicates that a hazard of flooding or shoreline erosion is unlikely and a detailed hazard assessment is probably un-necessary.

3 High Level Assessment - Geoconservation Priority As the initial step is assessing geoconservation value issues for the proposed rezoning, the Geoconservation Priority levels for the three coastal segments are determined by reviewing the Geovalues attribute of the tascoastgeo_v5gda map (see Figure 14). This indicates that geomorphic values (geoconservation issues) are likely to be most problematic for the residential zoning proposal in coastal segment B (Geoconservation Priority 1), somewhat problematic for segment A (Geoconservation Priority 2), and least problematic for segment C (Geoconservation Priority 3).

This high-level assessment suggests that, from a geomorphic values perspective, segment C is likely to prove most suitable for the proposed rezoning. If segment A or B are preferred for residential zoning on other grounds, then the high-level indication is that this will result in a greater impact on local or regional geomorphic values.

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Figure 14: High and Mid-Level Indicative mapping layers for the Case Study area. Top: Geoconservation Priority, Geomorphic Condition and Geomorphic Sensitivity maps (derived respectively from the Geovalues, Cond and Sens attributes in the tascoastgeo_v5gda map); Bottom: Indicative coastal hazard vulnerability mapping (from Sharples 2006), indicating soft sandy shores at risk of erosion and recession, cliffed shores at risk of rock-falls, and sloping bedrock shores with minimal hazards vulnerability.

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4 Mid-Level Assessment - General Types of Issues Likely The next step is to review the Condition and Sensitivity ratings for the three coastal segments. These are determined by reviewing the Cond and Sens attributes of the tascoastgeo_v5gda map (see Figure 14). This indicates that Segments B and C are both significantly modified by human activities (roads, land clearance, some buildings), while Segment A is only slightly modified and remains in mostly natural condition (see Table 3). In terms of sensitivity, Segment B is highly sensitive (sandy beach with foredune and backing soft sediment plain), but that Segments A and C have low sensitivity, (hard rocky shores backed by bedrock and soil). See Table 3.

By using Table 2 to identify the general sorts of geomorphic management issues likely to arise from these combinations of Condition and Sensitivity, we find the following: Segment A:

Although this segment is geomorphically robust, its good condition (which explains its moderate Geoconservation Priority rating) suggests that activities involving clearance or potential soil disturbance in the backshore should be avoided because its existing good condition makes it a natural asset from a geomorphic values and broad conservation perspective.

Segment B:

Although this segment is significantly disturbed by land clearance and roads near the shore (see Figure 14), its high sensitivity (which accounts for its high Geoconservation Priority) means that it is preferable to avoid activities that may be detrimentally affected by, or cause an increase in, existing natural landform mobility (e.g., beach & dune erosion). In the context of this potentially mobile site, disturbances such as roads and housing are likely to result in increased disturbance of these natural mobility processes.

Segment C:

This segment is both in significantly modified condition (in terms of backshore disturbances) and is robust (low sensitivity). This combination of factors accounts for its moderate to low Geoconservation Priority. This is the sort of geomorphic environment in which some additional disturbance (such as housing) will not significantly degrade local or regional coastal geomorphic values to any greater extent than they are already disturbed. However, it will be important to avoid any hard-rock coast hazards such as cliff edges, and do manage disturbances to avoid issues such as significant backshore soil erosion.

5 Detailed Assessment - Specifics of the Issues At this point, the detailed geomorphic mapping is consulted to determine whether the actual nature of the coastal landforms in each segment will indeed result in management issues relating to those identified by consideration of the higher-level Condition and Sensitivity ratings (above). Reviewing the geomorphic line and polygon maps (tascoastgeo_v5gda and tascoastsed_v5gda) we find the following (compare Figure 15): Segment A: This turns out to be a hard rock shoreline backed by a low profile bedrock (+ soil) backshore; this suggests little potential for erosion, mobility, slumping or other issues identified in Section (3.0) of this report, apart from some flooding potential due to the low profile. These geomorphic factors are consistent with and confirm the low sensitivity rating of this site.

Segment B: This is a sandy beach backed by a foredune that in turn is backed by a low plain of soft (floodplain) sediments. This is the sort of soft coast that is potentially prone to significant beach & foredune erosion, and to progressive shoreline recession with sea level rise (as described in sections 3.3 and 3.4). These geomorphic factors are consistent with and confirm the high sensitivity rating of this segment.

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Segment C:

The geomorphic mapping shows this to be a hard rock shoreline (without significant cliffs) rising at a moderate slope in the backshore; this suggests little potential for erosion, mobility, slumping, flooding or other issues identified in Section (3.0) of this report. These geomorphic factors are consistent with and confirm the low sensitivity rating of this site.

Checking the Geoheritage mapping, we find no listed Geoheritage sites in the area of these coastal segments.

6 Implications and Actions The geomorphic mapping data confirms that the sensitivity ratings for each segment are appropriate, and give an indication of the sort of sand mobility issues likely to arise from disturbance of Segment B.

Figure 15: Detailed geomorphic map layers for the case study area, showing soft Quaternary sediment landforms from the Quaternary Sediment polygons map (tascoastsed_v5gda) and the Backshore and Upper Intertidal attributes from the geomorphic line map (tascoastgeo_v5gda). A range of other attributes from these maps can also be displayed, including dune mobility (mobility, or currmob & histmob) from the tascoastsed_v5gda polygon map and Lower Intertidal, Exposure, Profile and Bedrock Geology attributes from the line map. No Geoheritage sites are listed on the Tasmanian Geoconservation database for this area; hence, the Geoheritage map layers are not depicted.

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Using the Coastal Geomorphic Management Decision Tools Table 3: Summary of information obtained for the case study area through the Decision Making Process described here, and the decisions flowing from that information. The case study coastline segments are named as per Figure 14 & Figure 15.

Coastal segment A Hazards (vulnerability)

Geoconservation Priority

Potentially vulnerable to storm surge flooding (hard shore but low-lying)

B Potentially vulnerable to both erosion (soft shore) and flooding (low-lying backshore)

C Not significantly prone to flooding or shoreline erosion (hard moderately rising shore)

2

1

3

(Moderate)

(High)

(Moderate to Low)

2

3

3

(slightly modified)

(significantly modified)

(significantly modified)

4

1

4

(low sensitivity / robust)

(high sensitivity)

(low sensitivity / robust)

Likely Issues

Although this segment is geomorphically fairly robust, its good condition suggests that activities involving clearance or potential soil disturbance in the backshore should be avoided because its existing good condition makes it a natural asset from a geomorphic values or geoconservation perspective.

Although this segment is significantly disturbed, its high sensitivity means that it is preferable to avoid activities that may be detrimentally affected by, or cause an increase in, existing natural landform mobility (e.g., beach & dune erosion). Disturbances such as roading and housing are likely to result in increased disturbance of these natural mobility processes.

This segment is both in significantly modified (backshore) condition and yet is a geomorphically robust shore (low sensitivity). This is the sort of geomorphic environment in which some additional disturbance may not significantly degrade geomorphic values to any greater extent than they are already disturbed, provided hazards such as soil erosion are avoided.

Geomorphic descriptive mapping

Hard-rock shore backed by relatively low-lying bedrock + soil surface.

Sandy beach backed by a low dune, which in turn is backed by a low-lying soft sediment plain (floodplain sediments).

Hard-rock shore (not cliffed) backed by moderately rising bedrock + soil slopes.

Implications for Decision - making

The geomorphic mapping confirms the low sensitivity of the segment. However, the relatively good condition of the segment, together with its potential vulnerability to coastal flooding, makes this location better suited to low impact land uses which allow its existing relatively high value for geoconservation (which accounts for its moderate Geoconservation Priority) to be maintained.

In spite of its already-modified condition, the high sensitivity of this segment, together with its vulnerability to flooding and shoreline erosion, means that this coastal segment is less suited to high value infrastructure such as housing, which may lead to ongoing geomorphic process degradation. In the light of its high Geoconservation Priority (due to its sensitivity) it is better suited to lower impact uses (e.g., recreation) which result in less ongoing landform degradation and thus contribute more to maintaining rather than further degrading the coastal landform conservation values of the region.

The existing disturbance and low sensitivity of this segment (which account for its moderate to low Geoconservation Priority), together with its low vulnerability to flooding or shoreline erosion, make this coastal segment the most suitable for coastal housing development resulting in the least loss of existing geomorphic values.

Condition Sensitivity

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At this point, all the information gathered from the Decision Support Tools points towards Segment C as the favoured site for residential rezoning (see Table 3): it is already significantly modified, yet as a shoreline geomorphic type is essentially robust such that disturbances like new housing are unlikely to cause significant further reduction of geomorphic coastal values in the area. This conclusion is consistent with the moderate to low Geoconservation Priority initially indicated for the segment. The segment is also probably not vulnerable to coastal flooding and erosion hazards, and has no listed Geoheritage sites. In terms of geomorphic values, Segment C is likely to be suitable for residential zoning, and if this option is adopted, probably warrants only preliminary site inspections from a geomorphic specialist. Note that this assessment refers only to geomorphic values, and other conservation values (e.g., biodiversity) may potentially over-ride this assessment.

In contrast, Segment B is less appropriate for residential zoning because of its high sensitivity (accounting for its high Geomorphic Priority) which means that – despite its existing disturbance – further disturbance of this erodible and potentially mobile geomorphic environment is better avoided (the alternative, if residential development is permitted, will to be expect to have to deal with ongoing geomorphic problems in future, such as foredune erosion and shoreline erosion threatening houses).

Finally, although Segment A is similarly geomorphically robust to Segment C, it is more vulnerable to flooding than Segment C, and in a less disturbed, more natural condition (which accounts for its moderate Geoconservation Priority). Thus, geomorphic values (geoconservation) will be less impacted and any potential flooding hazards to housing in this zone will be avoided, providing this segment is zoned for low impact uses that consider its contribution to local coastal geomorphic (and other) conservation values.

In essence, in this case, the high level Geoconservation Priority indicator has proven a useful guide to the best planning decision outcome for this section of coast from the perspective of maintaining coastal geomorphic values.

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Bibliography

BIBLIOGRAPHY AHC, 2002: Australian Natural Heritage Charter for the Conservation of Places of Natural Heritage Significance; Australian Heritage Commission & Australian Committee for the International Union for the Conservation of Nature (ACIUCN), Canberra.

BANKS, M.R., COLHOUN, E.A., and CHICK, N.K., 1977: A Reconnaissance of the Geomorphology of Central Western Tasmania, in: Banks, M.R. and Kirkpatrick, J.B., Landscape and Man, The proceedings of a symposium organised by the Royal Society of Tasmania, November, 1976.

BIRD, E., 2008. Coastal Geomorphology An Introduction, Second Edition. John Wiley and Sons Ltd, The Atrium, West Sussex, London, 411p BURRETT, C.F. & MARTIN, E.L., (eds),1989: Geology and Mineral Resources of Tasmania; Special Publication 15, Geological Society of Australia, Inc., 574 pp.

COOK, P.G., 1986: A review of coastal dune building in Eastern Australia; Australian Geographer, Vol. 17, p. 133-143.

CULLEN, P., 1998: Coastal Dune Systems of South-Western Tasmania: Their Morphology, Genesis and Conservation; Nature Conservation Report No. 98/1, Parks & Wildlife Service, Tasmania.

DAVIES, J.L., 1959: Sea Level Change and Shoreline Development in south-eastern Tasmania: Papers and Proceedings of the Royal Society of Tasmania, Volume 93, Royal Society of Tasmania, Hobart, Tasmania.

DAVIES, J.L., 1978: Beach sand and wave energy in Tasmania; in: Davies, J.L., & Williams, M.A.J., (eds), Landform Evolution in Australasia, ANU Press, Canberra.

DELM, 1996: The Vulnerability of the Coastal Zone to Climate Change in Tasmania; Coastal and Marine Program, Department of Environment and Land Management, Hobart, June 1996, 142 pp.

DEWHA, 1990: NSW Coastline Management Manual, Available at: www.environment.com.au/coasts/publications/nswmanual.html, Accessed 06-08-2008, Department of the Environment, Water, Heritage and the Arts, Australian Government.

DIXON, G., & DUHIG, N., 1996: Compilation and Assessment of Some Places of Geoconservation Significance; Report to the Tasmanian RFA Environment and Heritage Technical Committee, Forestry Tasmania, 78 pp.

DPIW, 2007: Arthur-Pieman Conservation Area Vehicle Tracks Assessment: Geoconservation, Flora and Fauna Values and Impacts; Report to the Tasmanian Parks and Wildlife Service, by Resource Management and Conservation Division, Department of Primary Industries & Water, Hobart, 230p.

DPIWE, 2002: Tasmania's Nature Conservation Strategy 2002 – 2006; Department of Primary Industries, Water & Environment, Hobart.

DTAE, 2007a, Vegetation, Fauna Habitat and Geomorphology Coastal Values Information of the Southern Tasmania NRM Region, Interpretation Manual. Coastal and Marine Branch, Department of Tourism, Arts and the Environment, Tasmania.

DTAE, 2007b, Vegetation, Fauna Habitat and Geomorphology Coastal Values Information of the Northern Tasmania NRM Region, Interpretation Manual. Coastal and Marine Branch, Department of Tourism, Arts and the Environment, Tasmania.

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Bibliography

EBERHARD, R. (Ed.), 1997: Pattern & Process – Towards a Regional Approach to National Estate Assessment of Geodiversity; 1997 Technical Series No. 2, Australian Heritage Commission & Environment Australia, Canberra, 102 pp.

FISH, G.J. & YAXLEY, M.L. 1966: Behind the scenery. The geological background to Tasmanian landforms. Teaching Aids Centre Publication No. 62, Education Dept. Tasmania.

FRENCH, H.M., 2007. The Periglacial Environment. Wiley, Chichester HARRIS, P.T., SMITH, R., ANDERSON, O., COLEMAN, R., and GREENSLADE, D., 2000: GEOMAT – Modelling of Continental Shelf Sediment Mobility in Support of Australia's Marine Planning Process; AGSO Record 2000/41, Geoscience Australia.

HOUSHOLD, I., SHARPLES, C., DIXON, G., & DUHIG, N., 1997: Georegionalisation – A more systematic approach for the identification of places of geoconservation significance; in: Eberhard, R., (ed), Pattern and Process – Towards a Regional Approach to National Estate Assessment of Geodiversity; 1997 Technical Series no. 2, Environment Australia, Canberra, p.

65 – 89.

HUBBERT, G.D., & McINNES, K.L., 1999: Modelling Storm Surges and Coastal Ocean Flooding; in: Noye, B.J., (ed), Modelling Coastal Sea Processes, World Scientific Publishing Co., p. 159188.

IPCC, 2001: Climate Change 2001: The Scientific Basis. Summary for Policymakers; A Report of Working Group I of the Intergovernmental Panel on Climate Change (a United Nations committee). (http://www.unep.ch/ipcc) KIERNAN, K., 1997: The Conservation of Landforms of Coastal Origin; Forest Practices Unit, Hobart, 273 pp.

MOWLING, F.A. 2006: The Influence of Wind Flow Over a Long-Walled Asymmetric Coastal Parabolic Dune – Morphodynamic Feedback, Evolution and Migration. Ph.D Thesis, University of Tasmania.

MUNRO, R.A.A., 1978: Tasmanian Coastal Study; Unpublished original 1:50,000 coastal geomorphology maps of Tasmania, Tasmanian Conservation Trust, Hobart (Original maps held

by Earth Science Section, Nature Conservation Branch, DPIWE, Hobart).

PITTOCK, B., (ed.), 2003: Climate Change: An Australian Guide to the Science and Potential Impacts; Australian Greenhouse Office, Canberra, 239 pp.

POFF, N. L., ALLAN, J. D., BAIN, M. B., KARR, J. R., PRESTEGAARD, K. L., RICHTER, B., SPARKS, R, and STROMBERG, J., 1997. The natural flow regime: a new paradigm for riverine conservation and restoration. BioScience 47:769-784.

POND, S., & PICKARD, G.L., 1983: Introductory Dynamical Oceanography; Second Edition, Pergamon Press.

SCANLON, A.P., FISH, G.J., & YAXLEY, M.L., (eds), 1990: Behind the Scenery: Tasmania's Landforms & Geology; Department of Education and the Arts, Tasmania, Australia, 163 pp.

SHARPLES, C., 1998: West North West Tasmania Coastal Management Plan: Geomorphology & Geoheritage; Unpublished report to Tasmania's West North West Councils.

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Bibliography

SHARPLES, C., 2000: Tasmanian Shoreline Geomorphic Types and Oil Spill Response Types: Data Dictionary; Report to accompany digital data set, Department of Primary Industries, Water and Environment, Tasmania.

SHARPLES, C., 2001: Geomorphology; Explanatory Report for the South East Tasmania Integrated Coastal Management Strategy, Clarence, Sorell and Tasman Councils, October 2001.

SHARPLES, C., 2003: A Review of the Geoconservation Values of the Tasmanian Wilderness World Heritage Area; Nature Conservation Report 03/06, Nature Conservation Branch, Department of Primary Industries, Water & Environment, Hobart.

SHARPLES, C., 2004: Data Dictionary for the Tasmanian Coastal Geomorphic Maps Digital (GIS) Dataset Version 3.0 (2004); Department of Primary Industries, Water & Environment (Tasmania).

SHARPLES, C., 2006a: Indicative Mapping of Tasmanian Coastal Vulnerability to Climate Change and Sea Level Rise: Explanatory Report, 2nd Edition; Report to Department of Primary Industries & Water, Tasmania, 173 pp. plus accompanying digital mapping.

SHARPLES, C., 2006b: Data Dictionary for the Tasmanian Shoreline Geomorphic Types Digital Line Map Version 4.0 (2006) (Tascoastgeo_v4gda); Report for Department of Primary Industries & Water (Tasmania), December 2006.

SHARPLES, C., 2006c: Data Dictionary for the Tasmanian Quaternary Coastal Sediments Digital Polygon Map Version 4.0 (2006) (Tascoastsed_v4gda); Report for Department of Primary Industries & Water (Tasmania), December 2006.

SHARPLES, C., 2007: Data Dictionary and Explanatory Notes for Mapping of Changes in Mobile Dunes and Vehicular Tracks, 1953 to 2001: Arthur Pieman Conservation Area, North-western Tasmania; Report to Tasmanian Parks & Wildlife Service, March 2007.

SHORT, A.D., 1996: Beaches of the Victorian Coast & Port Phillip Bay; A Guide to their Nature, Characteristics, Surf and Safety; Coastal Studies Unit, Department of Geography, University of Sydney.

SHORT, A.D., 2006: Beaches of the Tasmanian Coast and Islands; A Guide to their Nature, Characteristics, Surf and Safety; Sydney University Press, 353 pp.

STEANE, D., 1996: Some man-induced geomorphic changes in the coastal environment of Northeast Tasmania since European settlement and some related observations on coastal vegetation; Records of the Queen Victoria Museum and Art Gallery, No. 103, Launceston, p. 65-71.

THOM, B.G., & HALL, W., 1991: Behaviour of beach profiles during accretion and erosion dominated periods; Earth Surface Processes and Landforms, vol. 16, p. 113-127.

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Appendix One – Data Dictionary for Mapping

APPENDIX ONE: DATA DICTIONARY FOR DIGITAL GEOMORPHIC MAPPING A1.1 INTRODUCTION This appendix provides technical details (metadata) describing the digital (GIS) map files that accompany this report. The mapping has been prepared as ESRI Arcview shapefiles which are projected in metric MGA (Zone 55) co-ordinates using the GDA94 datum.

The nature and purposes of these maps are described in the body of this report (see Section 4.0). This appendix provides the detailed descriptions of data structure and attributes that are necessary to usefully interpret and display the mapping in a GIS system.

These metadata comprise: • a Data Model (Section A1.2) for each GIS map layer, which lists and describes the attribute fields associated with each layer; and •

Attribute Tables (Section A1.3) listing the attribute codes for each attribute field whose attributes cannot be easily listed in the Data Model.

The digital maps described in this appendix existed as earlier versions prior to the 2008 NRM North and Cradle Coast Region coastal values mapping project (see Section 4), but each has been extended or upgraded with additional data during the course of this project. Since these maps were created prior to this NRM project, and will continue to be used for purposes beyond the scope of this project, they contain a number of attributes which are not directly relevant to this project. For completeness, all attributes in the provided mapping are detailed in this data dictionary, however the attributes which are most directly relevant to this project are identified in Section (4.0) of this report.

All the mapping described here is copyrighted by the Tasmanian Department of Primary Industries & Water (DPIW). Custodianship and management of the geomorphic maps described below is vested in the Senior Earth Scientist (or equivalent manager responsible for the Earth Science Section) of DPIW. A1.2

DATA MODELS

A1.2.1 Shoreline Geomorphic Types, Sensitivity and Condition line map Shapefile: tascoastgeo_v5gda.shp (geo-registered to GDA94 datum) Type: Line Description: Line map of entire Tasmania shoreline (LIST 1:25,000 High Water Mark map) divided into geomorphically distinct segments. Data records tagged to each segment contain geomorphic descriptions and data pertaining to the shoreline segment.

Field

Type

Width

Attributes (see attribute tables in following section)

Comments

Feat_id

number

6

Consecutive unique numbers for each unique shore segment.

Legacy field inherited from version 1 of this map (2000).

Some original line segments have been split; these split segments have all retained their original feat_id numbers, which consequently are now duplicated in some cases.

Beachno

string

16

Beach number as per Short (2006), else:

This field was created previously for future attribution, but has not been used to date.

Intended to allow cross-

00 = Not a beach

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Appendix One – Data Dictionary for Mapping 99 = Sandy shore not numbered as a beach by Short (2006). (All sandy shores are currently labelled "99"; these are to be given beach numbers from Short 2006).

referencing (and database linking) with Short (2006), who has provided comprehensive descriptions and data on Tasmanian beaches.

Feat_len

number

6 (+ 2 decimal places)

Length of line segment in metres

Calculated automatically in Arcview

Confidence

string

2

Identifies whether segment has been ground-truthed & by whom, or identifies where geomorphic classification is based only on map data, other published data and /or air photo interpretation.

Refers to ground-truthing actually undertaken during the course of editing any version of this data set.

Updated

string

10

See attribute table: Section (A1.3.1)

Date of data currency or last update, as a string in format "DD/MM/YYYY" (e.g., 07/04/2001 for 7th April 2001)

Shoreline geomorphic (landform) type descriptors: Upperint

string

2

Upper intertidal zone landform type

See attribute table: Section (A1.3.1)

Lowerint

string

2

Lower intertidal zone landform type

See attribute table: Section (A1.3.1)

Backshore

string

2

Backshore landform type

See attribute table: Section (A1.3.1)

Exposure

string

1

Shoreline segment exposure

Exposure of the individual coastal segment to swell wave energy. Not to be confused with amount of wave energy received by the coastal region (Wavenzn); See attribute table: Section (A1.3.1) and discussion.

Slope

string

1

Intertidal zone slope

See attribute table: Section (A1.3.1)

Sedbudg

string

2

Sediment budget

Applied to sandy shorelines, indicates whether gaining sand (prograding), losing sand (receding) or stable (equilibrium); applies as at date of data currency, but intended to record long-term sand budget (i.e., short term "cut & fill" or "beach rotation" cycles not considered). See attribute table: Section (A1.3.1)

Geomorphic system control classifiers: Time

string

2

Relevant time period

Always 'present day' for this project. See attribute table: Section (A1.3.1)

Bedrock

string

2

Shoreline bedrock type

Includes inferred bedrock underlying soft sediment

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Appendix One – Data Dictionary for Mapping coasts where bedrock is not exposed.

See attribute table: Section (A1.3.1) Profile

string

1

Hinterland slope/topography class

See attribute table: Section A1.3.1)

Wavenzn

string

2

Wave energy zone of the Tasmanian coast, as defined by Davies (1978).

Semi-quantitative measure of wave energy received by a coast. Not to be confused with exposure to wave energy (Exposure); See attribute table: Section A1.3.1) and discussion.

Process

string

1

Geomorphic process

Always 'marine/coastal' for this map. See attribute table: Section A1.3.1)

Field geomorphic measurement records: (provided for some ground-truthed segments only) Cliffht

number

4

Total height of cliffs (upper intertidal + backshore) in metres

as above

Slopedeg

number

2

Modal Slope in actual degrees measured

as above

Geomorphic Sensitivity, Condition and Geoconservation Priority Descriptors: Sens

string

1

Geomorphic sensitivity of shoreline segment to artificial disturbance or degradation of coastal bedrock, landform or soil features or processes (four – level indicative sensitivity classification).

Sensitivity categories generated by queries, based on geomorphic types.

Cond

string

1

Geomorphic condition of shoreline segment (four-level overall condition classification).

Condition categories applied manually, based on assessment of available information.

By convention, refers to sensitivity to local or regional artificial disturbances, but not to the effects of global anthropogenic climate change and sea level rise, which for the purposes of this indicator are treated as if they were natural changes.

See attribute table: Section (A1.3.4) Summarises the cumulative impacts of all known artificial disturbances to coastal landforms or geomorphic processes in a coastal segment. By convention, refers to the impacts of local or regional artificial disturbances, but not to the effects of global anthropogenic climate change and sea level rise, which for the purposes of this indicator are treated as if they were natural changes.

See attribute table: Section (A1.3.4).

Condnotes

string

100

Explanatory notes on shoreline segment condition.

Generally used to briefly list factors leading to overall assessment of segment condition.

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Appendix One – Data Dictionary for Mapping Geovalues

string

1

Indicative geomorphic values of shoreline segment (four-level indicative classification).

Geovalues categories generated by queries, based on combination of Sensitivity and Condition.

High-level indicator of geoconservation priority of the shoreline segment, based on assigning highest values to shores which are either in the most natural condition, or which are most sensitive to disturbance.

See attribute table: Section (A1.3.4).

Other: Notes

string

200

General notes and comments pertaining to the coastal segment.

Generally used to note special geomorphic issues or mapping issues pertaining to the segment.

Reference

string

200

Bibliographic citation for published or other data sources.

Reference to published or other data sources where these are the primary source of data for all or specified attributes of a particular coastal segment.

Full bibliographic citation provided where possible, in preference to referring to a separate bibliographic list.

See also Confidence attribute – no Reference provided where information largely derived from air photo interpretation and/or fieldwork during editing of this data set.

Note: attribute created in version 4, thus not yet attributed for most coastal segments.

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A1.2.2 Quaternary Coastal Sediment Polygon Map This map theme is described in Section (4.3) of this report.

Shapefile: tascoastsed_v5gda.shp (geo-registered to GDA94 datum) Type: Polygon Description: Map of thick unlithified Quaternary coastal sediment accumulations (landforms) in the coastal region, including dune fields, sand sheets, intertidal/subtidal sediment flats, beaches, etc.

This map is intended to be a map of those "soft" elements of the coastal zone (Quaternary sediment accumulations) which are typically the parts of the coast most susceptible to human-induced changes and alteration of natural processes.

Field

Type

Width

Attributes

Comments

Default

string

3

"on" or "off"

Legacy field, inherited from ArthurPieman mapping (Sharples 2007) which included overlapping mobile sand polygons mapped from air photos at different epochs; only the 2001 polygons were incorporated into this dataset. Hence, all polygons are “on” for tascoastsed_v5gda.shp.

The Default attribute is "on" where only one polygon has been mapped for a given location.

Where multiple overlapping polygons representing differing landform configurations at different epochs have been mapped at a given location, the Default attribute for the polygon representing the most recent mapping epoch is "on", and for the older (overlapping) polygons is "off".

Year

string

4

Year for which the data on which the mapped polygon is based was current (e.g., "2000"). If the year is unspecified or unknown, this field is attributed "unsp". If the year is unknown but the decade is known, this is indicated by a final "X", e.g., the 1990's would be indicated as "199X".

String entered manually, day & month not specified, only the year.

This attribute allows polygons of differing epochs to be separated out in areas where multiple overlapping polygons for different epochs have been mapped.

The attribute "unsp" generally (but not always) refers to the most current data available that was used for mapping purposes (as specified in Source and Reference attributes) at the date specified in the Updated field, and this mostly refers to data current circa 2001 – 2006.

Updated

string

10

Sed_area

number

10 (+ 2 decimal places)

string

3

Age

Date of last data update, as a string in format "DD/MM/YYYY" (eg, 07/04/2001 for 7th April 2001)

String entered manually. Refers to date of updates to GIS data, not to the date for which the data is/was current (which is given by the Year field).

Area of polygon in square metres

Calculated automatically in Arcview

Age of sediments or landforms

String entered manually.

Age given as Quaternary

See attribute table: Section (A1.3.2).

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Bedform

string

3

Classification of coastal Quaternary sediment and landform units.

String entered manually.

See attribute table: Section (A1.3.2).

Landform

string

2

Classification of larger scale coastal Quaternary landforms (typically assemblages of bedform units).

String entered manually

See attribute table: Section (A1.3.2).

Mobility

string

2

Mobility status of coastal dunes at the epoch represented by the mapped polygon (classified according to % vegetation cover).

Used for polygons of a specified Year, to refer to dune mobility as at that year.

String entered manually.

Field introduced by C. Sharples (Used in Cradle Coast NRM project & preceding Arthur-Pieman project (Sharples 2007))

See attribute table: Section (A1.3.2).

Currmob

string

2

Current mobility status of coastal dunes (classified according to % vegetation cover).

String entered manually .

Field introduced by Frances Mowling.

Used for polygons of Year "unsp" (unspecified), to refer to dune mobility as at the unspecified (nominally "current") year represented by the polygon.

See attribute table: Section (A1.3.2).

Histmob

string

2

Historic mobility status of coastal dunes (classified according to % vegetation cover).

Used for polygons of Year "unsp" (unspecified), to refer to mobility in 1940's – 1950's period, determined from historic air photos

String entered manually .

Field introduced by Frances Mowling.

See attribute table: Section (A1.3.2).

Sedrate

String

2

Rate of sediment supply to estuary from river catchment. Broad semiquantitative estimate derived from air photo interpretation and field observations.

String entered manually .

Field introduced by Frances Mowling.

See attribute table: Section (A1.3.2).

Source

string

2

General source of mapped information: includes field or airphoto interpretation by specified people,

NOTE that bibliographical details of specific data sources used should be given in the Reference

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Appendix One – Data Dictionary for Mapping previous geological mapping, etc.

field.

See attribute table: Section (A1.3.2).

Reference

string

200

Bibliographic citation or details of specific data sources used to map polygon, where relevant.

E.g., citation of published works, numbers & capture dates of aerial photographs, etc.

See also Source field; no Reference details given where the Source is (otherwise unpublished) fieldwork by a specified person, etc.

Other: Notes

string

200

Notes and comments pertaining to the coastal segment or to the data sources used.

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A1.2.3 Coastal Geoheritage Maps This map theme is described in Section (4.5) of this report. Coastal sites and areas of recognised geoheritage significance in the Southern, Northern & NRM North and Cradle Coast regions have been mapped as two map layers, namely a polygon (area) layer (geoconareas_gda) and a point (site) layer (geoconpts_gda). These layers have been extracted from the current version (6.0) of the Tasmanian Geoconservation Database. Several additional sites of potential geoconservation significance have also been identified during the NRM North and Cradle Coastmapping project, and have been recorded as point sites in geoconpts_gda.

Significant Features Map (areas) Shapefile: geoconareas_gda.shp Type: Polygon Description: Significant geoheritage features map (areas). Linear features are included, mapped as long thin polygons, rather than lines.

Field

Type

Width

Attributes

(see attribute tables)

Comments

updated

string

10

Date of data currency or last update, as a string in format "DD/MM/YYYY" (eg, 07/04/2001 for 7th April 2001)

String entered manually.

giscode

string

6

GIS Code used for the feature in the Tasmanian Geoconservation Database (TGD).

Indicates feature listed on TGD:null value used where feature not on the TGD

areaname

string

200

sigbasis

string

4

Type of geoconservation value (code)

The type of thing about the feature that gives it geoconservation value, as codes (see attribute table).

signif

string

3

Significance category

As recorded for feature in TGD, else assigned by source (see attribute table)

Name of feature (verbal)

(i.e., representative or outstanding) siglevel

string

10

Significance level

As recorded for feature in TGD, else assigned by source (see attribute table).

(i.e., world to local) sigsens

string

2

Sensitivity to degradation of values by artificial disturbances.

10-point sensitivity scale as used in Tasmanian Geoconservation Database, as distinct from 4-point sensitivity scale used in tascoastgeo_v5gda attribute Sens (see attribute table).

degrad

string

12

Degree of degradation of the particular values for which the feature is considered to be of geoheritage value.

Related to Cond in tascoastgeo_v5gda, but classified according to the system adopted in the TGD (see attribute table).

source

string

2

Source of judgement that feature is of geoconservation significance.

Records whether feature is listed on TGD, RNE, other prior source, or newly determined to be significant in the course of this project (see attribute table).

comment

string

200

Comments on geoconservation values of feature.

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Significant Features Map (points) Shapefile: geoconpts_gda.shp Type: Points Description: Significant geoheritage sites map (point features). As for geoconareas_gda.shp, however this theme is used to map sites too small to be properly mapped as polygons.

Field

Type

Width

Attributes

(see attribute tables)

Comments

updated

string

10

Date of data currency or last update, as a string in format "DD/MM/YYYY" (eg, 07/04/2001 for 7th April 2001)

String entered manually.

giscode

string

6

GIS Code used for the feature in the Tasmanian Geoconservation Database (TGD).

Indicates feature listed on TGD:null value used where feature not on the TGD

ptname

string

200

Name of feature (verbal)

sigbasis

string

4

Type of geoconservation value (code)

The type of thing about the feature that gives it geoconservation value, as codes (see attribute table).

signif

string

3

Significance category

As recorded for feature in TGD, else assigned by source (see attribute table).

(i.e., representative or outstanding) siglevel

string

10

Significance level

As recorded for feature in TGD, else assigned by source (see attribute table).

(i.e., world to local) sigsens

string

2

Sensitivity to degradation of values by artificial disturbances.

10-point sensitivity scale as used in Tasmanian Geoconservation Database, as distinct from 4-point sensitivity scale used in tascoastgeo_v5gda attribute Sens (see attribute table).

degrad

string

12

Degree of degradation of the particular values for which the feature is considered to be of geoheritage value.

Related to Cond in tascoastgeo_v5gda, but classified according to the system adopted in the TGD (see attribute table).

source

string

2

Source of judgement that feature is of geoconservation significance.

Records whether feature is listed on TGD, RNE, other prior source, or newly determined to be significant in the course of this project (see attribute table).

comment

string

200

Comments on geoconservation values of feature.

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Appendix One – Data Dictionary for Mapping

A1.2.4 Coastal Photography Digital photography of both landform features, substrate and profile was collected throughout the duration of field validation work for both the coastal line segments and sediment polygon layers. The photos comprise both oblique view photography (taken from helicopter) and terrestrial view photography (land based). See section 4.4 or Appendix Two for further information.

Photo Log (points) Shapefile: Tascoastgeomaps_v52008gda94_PhotoLog_shp Type: Points Description: Photo log of sites visited (point features). This layer contains a list of linked photos (clicking the information of a particular photo point opens a table with an imbedded link to the photo) collected throughout the field validation Field

Type

Width

Attributes

(see attribute tables)

Comments

PhotoID

Long

4

Point ID of photo, note some photo points reference more than one photo

String automatically generated

PhotoNumbers

string

255

Photo numbers recorded by each site, may contain more than one photo per site, comma separated.

Photo numbers will be entered more than once if more than one photo is collected from one point.

Name

string

255

Name of feature (numerical), unique number per photo

Individual photo name generated from the camera in use (Olympus u770 SW and Cannon IXUS 80 IS)

PhotoPath

string

255

Link to photo storage path

Relative file path records photo location.

Description

string

255

Field description regarding photograph

Any specific notes during photographing segments were collected in this field

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A1.3

ATTRIBUTE TABLES

A1.3.1 Shoreline Geomorphic Types Line Map Descriptors Degree of Ground Truthing (Confidence) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Confidence Field type: string (character) Field width: 2 Explanation: Provides indication of whether segment has been ground-truthed since 2000 for the purpose of compiling or checking any version of this dataset, or whether geomorphic classification is based only upon on existing published data including map data, and/or on air photo interpretation.

Attribute summary: Characters (00 - 99)

Degree of ground-truthing (Confidence)

00

Not ground truthed during editing of this coastal data set (mostly based on combinations of airphoto, topographic and geological map interpretation, as described in Sections 1.1 & 4.1)

01

Field inspection (ground-truthing) by Chris Sharples in the course of editing this coastal data set.

02

Field inspection (ground truthing) by Frances Mowling, incorporated during editing of this data set.

03

Field inspection (ground truthing) by Cliff Massey, incorporated during editing of this data set.

04

Field inspection (ground truthing) by Brad Smith and Dax Noble, incorporated during editing of this data set.

05

Field inspection (ground truthing) by Dax Noble and Cliff Massey, incorporated during editing of this data set.

06

Field inspection (ground truthing) by Brad Smith, incorporated during editing of this data set.

07

Field inspection (ground truthing) by Dax Noble, incorporated during editing of this data set.

Geomorphic Descriptors The geomorphic descriptors used in tascoastgeo_v5gda are classified as either Geomorphic System Controls (independent controls such as bedrock and wave energy which have controlled the development of coastal landforms) or as Shoreline Geomorphic Type Descriptors which describe the types of coastal landforms that have developed in response to the system controls. See discussion of this conceptual distinction further below. The following figure provides a diagrammatic explanation of these descriptors:

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Figure 16: Diagrammatic representation of key attribute fields of the Shoreline Geomorphic Types Map (tascoastgeo_v5gda).

The following tables list the attributes and attribute codes pertaining to fields in the data model provided in Section (A1.2.1). Attribute tables are not provided for fields that are adequately explained in the Data Model itself.

Shoreline Geomorphic Type Descriptors: These attribute fields provide a simple description of coastal landforms within each distinctive coastal segment. The descriptors are based on the form and fabric (constituents) of the coastal landforms, rather than upon their genesis. These descriptors describe the types of landforms that have been produced by the broader geomorphic system controls that have influenced each coastal segment.

Some (but not all) of the geomorphic system controls that have determined the landform development of each coastal segment are classified in the attribute fields listed as "georegion (geomorphic system control) classifiers" in the Data Model (Section A1.2.1) and further below.

Note that, for the purposes of achieving a relatively simple landform description system, a number of generalised conventions have been adopted. For example, where rocky shore platforms are present, these are in all cases recorded only in the Lower Intertidal Zone landform type descriptor (lowerint), despite the fact that many rocky shore platforms do actually extend into the upper intertidal zone.

Again, the "Upper Intertidal Zone" landform type descriptor nominally describes landform types extending up to the Mean High Water Mark only, however in reality it has been used to describe landforms extending up to the limits of occasional storm wave action (e.g., shingle beach storm berms, which may extend well above the actual MHWM).

Upper Intertidal Zone Landform Type (Upperint) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Upperint Field type: string (character) Field width: 2 Explanation: Landform types forming the upper intertidal zone (nominally up to high water mark, but actually up to the limits of occasional storm wave action in many cases). This is the part of the shoreline zone most commonly thought of as characterising a "shoreline type".

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Attributes 00 – 12 were used in the original shoreline mapping (v.1) by Sharples (2000); all other attributes are more detailed sub-divisions which have been added subsequently, but as yet have not been applied in all parts of the Tasmanian coast. In general, the more detailed (sub-divided) attributes have been applied mainly in areas that have been ground-truthed or otherwise re-mapped since 2000.

Since the new attributes are all sub-divisions of those used previously, it is possible to "retro-fit" the more detailed categories defined here back to the broader undifferentiated categories used previously.

The original 12 attribute categories are numbered in bold on the following table, while the newer subdivided category numbers are indicated by normal numbers.

Note that some sub-divided attribute codes have been re-ordered and re-numbered as compared to the codes used in the earlier version tascoastgeo_v3. This was done to create a more logical coding system; all codes within the data set have been systematically re-assigned in accordance.

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Attribute summary: Characters (00 - 99) 00 01 02 21 22 23 03 31 32 33 34 35 36 37 04 41 42 43 44 45 46 47 48 49 05 51 06 61 07 71 08 81 09 10 11 12

Upper Intertidal landform type

(Upperint)

Shoreline type unknown Cliffs (dominantly vertical or very steep to at least 5m above high water mark) Rocky (bedrock) shoreline undiff. (in situ bedrock, may include small cliffs rising to <5m above high water mark) unconsolidated sediment accumulations absent or minor Rocky (bedrock) shore covered by in situ bedrock breakdown material (angular to subrounded pebble/cobble/boulder shores, commonly with bedrock outcrop) Angular boulder (± cobble/pebble) shores (colluvium, collapses, slumps) Angular boulder (± cobble/pebble) shores (colluvium, collapses, slumps) - with common bedrock outcrop protruding Shell, pebble, cobble ('shingle') or boulder (undifferentiated) beach or shoreline rounded (wave washed) shell/pebble/cobble/boulder (undifferentiated) shores wave washed shell beaches or shorelines wave washed shell beaches or shorelines - with common bedrock outcrop protruding rounded (wave washed) pebble/cobble beaches or shores rounded (wave washed) pebble/cobble beaches or shores - with common bedrock outcrop protruding rounded (wave washed) cobble/boulder beaches or shores rounded (wave washed) cobble/boulder beaches or shores - with common bedrock outcrop protruding Mixed fine- medium sandy and undifferentiated shell, pebble, cobble or boulder beach or shoreline mixed fine – medium sandy and undifferentiated shell, pebble, cobble or boulder beach or shoreline - with common bedrock outcrop protruding mixed fine – medium sandy and shell beach or shoreline mixed fine – medium sandy and shell beach or shoreline - with common bedrock outcrop protruding mixed fine – medium sandy and undiff. pebble/cobble beach or shoreline mixed fine – medium sandy and undiff. pebble/cobble beach or shoreline - with common bedrock outcrop protruding mixed fine – medium sandy and (rounded, wave washed) cobble/boulder shore mixed fine – medium sandy and (rounded, wave washed) cobble/boulder shore – with common bedrock outcrop protruding mixed fine – medium sandy and angular (collapse or breakdown) boulder (± cobble/pebble) shore mixed fine – medium sandy and angular (collapse or breakdown) boulder (± cobble/pebble) shore - with common bedrock outcrop protruding Sandy beach or shoreline - grainsize undetermined sandy beach or shoreline - grainsize undetermined – with common bedrock outcrops protruding Sandy beach or shoreline - coarse grained (coarse sand = grain diameters > 0.5mm; Pettijohn et al. 1973) sandy beach or shoreline - coarse grained – with common bedrock outcrop protruding Sandy beach or shoreline - fine to medium grained ( = grain diameters 0.0625 – 0.5mm; Pettijohn et al. 1973) sandy beach or shoreline - fine to medium grained – with common bedrock outcrop protruding Muddy or silty shoreline (may be pebbly or cobbly; typically fine sands with high mud (silt/clay) content, darker in colour than sandy shores) muddy or silty shoreline – with common bedrock outcrops protruding Permeable artificial shoreline, e.g., rip – rap, boulders, gravel fill.

Impermeable artificial shoreline, e.g., concrete sea walls, wooden walls.

Other artificial shoreline (including excavated shorelines), undifferentiated Artificial shoreline - type unknown

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Lower Intertidal Zone Landform Type (Lowerint) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Lowerint Field type: string (character) Field width: 2 Explanation: Landform type comprising the lower intertidal zone. This element is water covered for a significant proportion of the tidal cycle. Note that attributes (04) and (45) have been added to the attribute table subsequent to compilation of the original shoreline geomorphic mapping (v.1, Sharples 2000); most lower intertidal zones now classified as (04) or (45) were previously classified as (99).

Note that by convention, all rocky shore platforms are recorded as Lower Intertidal Zone landforms using the Lowerint attribute field, despite the fact that many rocky shore platforms do actually extend into the upper intertidal zone.

Attribute summary: Characters (00 - 99) 00 01 02 03 04 45 05 07 08

09 10 11 12 20 22 23 25 27 28

30 32 33

98 99

Lower Intertidal landform type (Lowerint) with unknown lower intertidal characteristics with rocky shore platform with near shore rocks or reefs (exposed at low tide, can be up to 500m offshore) with rocky shore platform plus near shore rocks or reefs (can be up to 500m offshore) sloping sandy bottom (Âą submerged bottom rocks) in lowest intertidal to subtidal zone sloping rocky bottom in lowest intertidal to subtidal zone with intertidal or shallow subtidal flats - grainsize undetermined with intertidal or shallow subtidal sand flats with intertidal or shallow subtidal mudflats (may include marshy vegetated intertidal mudflats).

(Note: Mudflats are typically fine sands with high mud (silt/clay) content, darker in colour than sandy shores) with permeable artificial structures, e.g., rip-rap. with impermeable artificial structures, e.g., concrete sea walls with other artificial structures (including excavated shorelines or wrecks) with artificial structures - type unknown with intertidal or shallow subtidal flats - grainsize undetermined - plus rocky shore platform with intertidal or shallow subtidal sand flats plus rocky shore platform with intertidal or shallow subtidal mudflats plus rocky shore platform. (Note: Mudflats are typically fine sands with high mud (silt/clay) content, darker in colour than sandy shores) with intertidal or shallow subtidal flats - grainsize undetermined - plus near shore rocks or reefs (can be up to 500m offshore). with intertidal or shallow subtidal sand flats plus near shore rocks or reefs (can be up to 500m offshore). with intertidal or shallow subtidal mudflats plus near shore rocks or reefs (can be up to 500m offshore). (Note: Mudflats are typically fine sands with high mud (silt/clay) content, darker in colour than sandy shores) with intertidal or shallow subtidal flats - grainsize undetermined - plus rocky shore platform and near shore rocks or reefs (can be up to 500m offshore). with intertidal or shallow subtidal sand flats plus rocky shore platform and near shore rocks or reefs (can be up to 500m offshore). with intertidal or shallow subtidal mudflats plus rocky shore platform and near shore rocks or reefs (can be up to 500m offshore). (Note: Mudflats are typically fine sands with high mud (silt/clay) content, darker in colour than sandy shores) pending mapping with no distinctively different lower intertidal shoreline element (upper intertidal zone grades continuously down to subtidal zone without significant substrate change)

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Backshore Landform Type (Backshore) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Backshore Field type: string (character) Field width: 2 Explanation: Landform types occurring immediately above high water mark and the limits of occasional storm wave activity. This does not refer to the hinterland, but simply records the landform types present immediately inland of the intertidal zone itself.

Most attributes are as used by Sharples (2000) in the original (V.1) shoreline mapping, with the exception that attributes 15 – 18, 21 – 26 and 31 - 34 have been added (to sub-divide artificial backshores by indicating those fronting unconsolidated sediment plains, to provide sub-types of rocky shores dominated by colluvium & weathered bedrock, and to sub-divide dune-backed shores into several sub-categories, respectively). As with, Upperint, the newer attributes sub-divide certain original broad categories into sub-types, but can be lumped back into the original broader types if necessary. The original (v.1) categories are numbered in bold on the table below, while the newer sub-divisions are indicated by normal numbers.

Attribute summary: Characters (00 - 99) 00 01 02

21 22 23 24 25 26 03 31

32 33 34 04 05 06 07 10 15 11

Landforms immediately inland of Intertidal Zone (Backshore) Unknown Cliffs (rising at least 5m above high water mark) – mainly bare bedrock Bedrock ± soil (not notably cliffed but may include small cliffs rising to <5m above high water mark; no dunes) undifferentiated – may include bedrock, colluvium, slumps and soil.

NOTE "bedrock" may include unlithified non-marine sediments where Bedrock = 01 Colluvium (including slumps & cliff collapses) with or without soil development (undifferentiated) Colluvium (including slumps & cliff collapses) with little or no soil development Colluvium (including slumps & cliff collapses) with significant soil development Colluvium (undifferentiated) associated with significant Cliffs Slopes of deeply weathered bedrock (bedrock ± soil, where bedrock is softened and erosionprone due to intense fracturing ± deep chemical weathering).

Cliffs of deeply weathered bedrock (where bedrock is softened and erosion-prone due to intense fracturing ± deep chemical weathering).

Dunes & aeolian sandsheets undifferentiated (one or more dune ridges, or aeolian sand sheet, back-dune area types undifferentiated) Dunes (one or rarely more dune ridges, backed and/or underlain by bedrock ± soil substrate in immediate back dune area, no significant unconsolidated sediment plain behind or underlying dunes) Dunes (one or more dune ridges, with unconsolidated sediment plain in immediate back dune area and/or underlying any back dunes) [sediment plains <50m to >>100m wide] Dunes (one or more dune ridges, with lagoon(s) and unconsolidated sediment plain in backdune area) [sediment plains <50m to >>100m wide] Aeolian sandsheets (generally thin, with or without some dune forms) mantling bedrock in the backshore.

Sediment flats, unconsolidated or unlithified (may be sandy plain, but no notable dunes in backshore zone) [sediment flats may range from ~10m to >>100m wide] Marshy low-lying supratidal sediment flats; mostly saltmarsh ( = sediment flats subject to inundation) [sediment flats may range from ~10m to >>100m wide] CURRENTLY UNUSED CLASSIFICATION Lagoon (usually where impounded by low sand spit without dunes) Reclaimed land (artificially filled) Artificial fill over unconsolidated sediment plain [sed. plains <50m to >>100m wide] Permeable artificial structures, e.g., rip rap

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permeable artificial structures, e.g., rip rap, fronting unconsolidated sediment plain with or without dunes [sed. plains <50m to >>100m wide] Impermeable artificial structures, e.g., concrete sea walls impermeable artificial structures, e.g., concrete sea walls, fronting unconsolidated sediment plain with or without dunes [sed. plains <50m to >>100m wide] Other artificial structures (including excavations and roads) other artificial structures (including excavations and roads), fronting unconsolidated sediment plain with or without dunes [sed. plains <50m to >>100m wide] Artificial structures - type unknown Pending mapping

Intertidal Zone Slope (Slope) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Slope Field type: string (character) Field width: 1 Explanation: The slope of the intertidal zone (only), estimated in degrees. By convention, the slope is the angle of a line drawn from high water mark to low water mark irrespective of intervening irregularities. Where the slope has been measured in the field with a clinometer, the actual measurement in degrees is provided in the separate field Slopedeg. The slope categories used are based on formats previously used for the AMSA/OSRA Oil Spill Response Atlas, and this attribute was created to satisfy those formats. Note that intertidal zone slopes on sandy beaches may vary seasonally or in response to storm wave action; thus the slope should be measured from high to low water mark only, and may be subject to some variation. This attribute therefore provides only a very broadly generalised indicator of intertidal zone slope, and no greater accuracy than this should be assumed.

Attribute summary: Character (0-9) 0 1 2 3 4 5 6 7

Shoreline slope (intertidal zone only) (Slope) unknown steep >30° moderate 30° - 5° flat <5° steep >30° (unconfirmed) moderate 30° - 5° (unconfirmed) flat <5° (unconfirmed) pending mapping

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Shoreline Segment Exposure (Exposure) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Exposure Field type: string (character) Field width: 1 Explanation: Shoreline exposure is a rough qualitative measure of the degree to which a particular shoreline segment is exposed to whatever wave energy impinges on the broader coast of which it is a part, over time.

Note that exposure to wave energy is not a quantitative measure of the amount of wave energy received by a shoreline, but simply an indicator of the degree of exposure to whatever wave energy impinges on the relevant stretch of coast. Thus an "exposed" coastal segment in western Tasmania will probably receive considerably more wave energy over time than an equally "exposed" segment in eastern Tasmania. The separate geomorphic system control attribute Wavenzn (see below) provides an indicator of the actual amounts of wave energy received over time along different regions of the Tasmanian coast. Thus, it is roughly true to say that two equally exposed coastal segments in the same wave energy zone (Wavenzn) will receive about the same amount of wave energy over time, whereas two similarly exposed segments in different wave energy zones will receive different amounts of energy over time.

Exposure to wave energy is here presented as a Shoreline Geomorphic Type Descriptor rather than as a Geomorphic System Control, on the basis that the processes of coastal landform development, influenced by geomorphic system controls, have produced local variations in exposure as a function of the intricate shape of shoreline bays and headlands as they have actually developed in response to system controls such as bedrock structure and wave climate (wave energy).

Wave energies received by Tasmanian coastlines may derive from ocean swells or more localised and shorter-term storm and wind waves. The most important source of both oceanic swells and storms affecting Tasmanian coasts are the strong and constant swells and storm waves which arrive on Tasmania's south and west coasts during all seasons from a south-westerly or westerly direction (Davies 1978), and which refract eastwards through Bass Strait and northwards up the east coast (see Figure 17). These waves and storms are generated by mid-latitude cyclonic systems in the "Roaring Forties" region of the Southern Ocean, south of Tasmania (Short 1996, p. 15, 17, 26), and generate moderate to high swell waves which dominate the south and west coasts all year round. The exposure attribute Exposure is currently classified in this dataset mainly based on the degree of exposure of shorelines to these direct or refracted south-westerly swells and storms, and were manually classified by visually estimating exposure to these swell and storm wave approach directions.

Note however, that this exposure classification requires updating and improvement for the north-east, east and southeastern coasts of Tasmania. Whereas the south-westerly swells and storm waves are at all times the dominating wave energies received by the west, northwest, southwest and southern coasts of Tasmania, and refraction of these waves impinges on the south-eastern, eastern, northern and northeastern coasts as shown in Figure 17 below, the latter coasts are also strongly affected by infrequent but intense easterly and south-easterly storms generated by low pressure systems (East Coast Cyclones) moving south-eastwards through the Tasman Sea, to the east of Tasmania (Short 1996, p.15, 26). Southeasterly, and to a lesser extent easterly storm and swell wave approach directions produced by these east coast low pressure systems have a major influence on Tasmania's eastern, south-eastern and northeastern coasts, hence it is important that the current shoreline exposure attribute (Exposure) for these coasts should as soon as possible be reviewed and reclassified to account for exposure to easterly and south-easterly storm waves and swells, as well as to refracted southwesterly swells.

An additional caveat on this exposure classification results from the fact that shores relatively sheltered from the most important storm wave directions may still be exposed to other less frequent, but still important, storm wave approach directions. This should also be reflected in future updates of this attribute.

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Figure 17: Map of Tasmania indicating diagrammatic oceanic swell wave crests and approach directions assumed in mapping shoreline exposure (based on refraction of the dominating south-westerly swell around Tasmania). Swells only refract over the continental shelf where they begin to "feel bottom" at about 120m water depth, and not in deep ocean waters. Note that this map, and the exposure attribute Exposure based on it, remain in need of future upgrading in the eastern, north-eastern and south-eastern coastal regions of Tasmania, to take into account exposure to the south-easterly and easterly swells and storm wave approach directions which are significant in those regions.

Attribute summary: Character (0-9)

Shoreline segment exposure (Exposure)

1

exposed

2

semi-exposed

3

sheltered

4

pending mapping

(aspect of shoreline segment faces towards within 45º of important swell and storm wave approach directions) (aspect of shoreline segment faces between 45º - 135º from important swell and storm wave approach directions) (aspect of shoreline segment faces >135º from, or is sheltered from, important swell and storm wave approach directions)

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Sediment Budget (Sedbudg) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Sedbudg Field type: string (character) Field width: 2 Explanation: Sediment budget for sandy shorelines. This characteristic applies only to sandy shorelines, and applies as at the date of data currency, but is intended to identify the long-term sand budget. The Sedbudg attribute is intended to identify whether sand is being permanently lost from a sandy shoreline segment (recession), is being progressively added to the shoreline segment's sand budget (progradation), or is in long-term equilibrium (in which case any sand lost from the system is being balanced by sand added to the system).

Short term "cut & fill" beach cycles in which sand is lost from the upper beach during storm erosion, dumped in the near-shore sub-tidal zone, then later returned to the beach (onshore-offshore sand movements) are not intended to be considered. Similarly, "beach rotation" whereby sand may episodically be moved laterally along a beach for a period, then moved back for a period, is also not intended to be considered. However, without long-term monitoring or some other clear evidence of a long term trend 11, beach sediment budgets may be difficult to determine with certainty. For example, the presence of incipient foredunes is not necessarily evidence of progradation, as these commonly form on equilibrium or receding beaches during intervals between major storms. Similarly erosion scarps may not necessarily be evidence of recession, but can be simply a brief phase of erosion superimposed on a longer term progradation trend.

As a result, some sediment budget attributes recorded in this dataset may prove to be incorrect.

However, in the absence of long-term studies providing more confident sediment budget assessments for Tasmanian beaches, the sediment budget attributes recorded in this dataset are useful as an indication of beaches considered likely to be receding, in equilibrium or prograding on current knowledge.

The sediment budget attributes provided in version 4 (tascoastgeo_v4gda) and later have partly been based on information provided by Frances Mowling (University of Tasmania) and Mike Pemberton (formerly Senior Earth Scientist, Tasmanian Department of Primary Industries & Water), based on their field observations of many Tasmanian beaches over the last decade or so, with the exception of south-west Tasmanian beaches where the attributes were obtained from Cullen (1998). Many Tasmanian beaches have not yet been given a Sedbudg attribute due to lack of suitable information.

Attribute summary: Character (00-99) 00 01 02 03 99

Sediment budget (sandy shores) (Sedbudg) Not a sandy shoreline, or segment not classified Receding sandy shore (net sand loss from shoreline system) Stable sandy shore (any sand lost from shoreline system is balanced by sand gained) Prograding sandy shore (net sand gained by shoreline system) Sandy shore, sediment budget undetermined.

11

For example, studies of historical records including air photos, or stratigraphic evidence of progradation or recession.

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Georegion ("Geomorphic System Control") Classifiers In contrast to the Shoreline Geomorphic Type Descriptors (above), which give a simple form and fabric – based description of the coastal landforms developed in each coastal segment, the following Geomorphic System Control Classifiers identify some (but not all) of the broader characteristics ("system controls") of each coastal region that have influenced or determined the type of coastal landforms that have actually developed in each region. A key distinction between the two groups of attributes is that, whereas the shoreline geomorphic type descriptors describe the types of coastal landforms that have developed in response to coastal processes, the geomorphic system controls are independent variables which were not produced by coastal processes, but which exert an influence upon coastal geomorphic processes and the development of coastal landforms.

This distinction between "system controls" which influence landform development, and geomorphic type descriptors which describe the landforms that have actually developed, underpins the concept of "Georegionalisation". Georegionalisation (Houshold et al. 1997) provides a means of characterising (and predicting) the distribution of shoreline landform types at a broader level than that provided by the shoreline geomorphic type descriptors. Coastal georegions are defined by identifying the parameters (system controls) influencing the development of coastal landforms, and mapping the spatial variation in each of these. Each georegion then consists of one or more cells (or segments of coastline) having a unique combination of influences (system controls) influencing and determining coastal landform development. It can then be predicted that each unique georegion, because of its unique set of controlling parameters, will have certain characteristic associations of coastal landforms (although there will of course be many coastal landform types common to many georegions).

In effect, the coastal georegions map out the influences controlling shoreline landform development, whilst the shoreline geomorphic type descriptors map the actual landforms that have developed in response to those georegion controls. One consequence of this is that, whereas the shoreline geomorphic type descriptors used in this dataset classify landforms within the intertidal and immediate backshore zone specifically, the georegions refer to a broader coastal zone (including some nearcoastal hinterland elements and offshore wave climate characteristics) which has exerted an influence on the development of the intertidal zone itself.

The geomorphic system controls classified in this data set are listed below: • • • • •

Time Bedrock Geology Coastal Profile (topography) Wave Energy (climatic controls) Geomorphic Process

However, it is recognised that these system controls are not sufficient to fully characterise coastal georegions, and it is envisaged that more work will be undertaken in future to further develop this georegional approach to coastal landform classification. In particular, it is envisaged that it will be necessary to develop a "Geomorphic History" system control attribute to supplement the above system controls. A geomorphic history system control would allow a georegional model of coastal development to take into account such things as sand supply sources (e.g., past glacio-fluvial sand outwash to the coast) which are not modelled by the currently attributed system controls, yet play a major role in coastal development by determining the availability of sand to build beaches and dune systems.

However, notwithstanding that the system controls classified to date in this data set do not fully describe coastal georegions, most of them are nevertheless of immediate value for a range of coastal research and management purposes independent of georegional modelling.

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Each geomorphic system control is a separate field in the data model. The system control fields are discussed below, with a listing of the categories (attributes) which each parameter has been divided into for the purposes of this dataset.

Relevant Time Period (Time) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Time Field type: string (character) Field width: 2 Explanation: Landform development has varied over geological time, and it is possible to analyse landforms in terms of their development at different stages in geological history. For the purposes of this project the coast is being analysed in terms of its present day status and ongoing development.

The field Time is included in this analysis purely in order to make the data compatible with possible future work which may extend the landform development analysis to other time periods.

This field (attribute) would become useful if, for example, Last Interglacial coastal landforms were being mapped and differentiated in the dataset; a different value of Time could be used to identify these landforms and allow them to be plotted or analysed separately from the present day coastal landforms.

Attribute summary: Characters (00-99) 00

Time period (Time) present day

Shoreline Bedrock Type (Bedrock) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Bedrock Field type: string (character) Field width: 2 Explanation: Bedrock geological type occurring at the shoreline. Where the shoreline comprises unconsolidated Quaternary sediments that have accumulated in response to coastal or estuarine processes, the bedrock type is that type known or inferred to underlie the shoreline. Bedrock types are based on a lithostructural classification developed by Dixon & Duhig (1996) and Houshold et al.(1997), which broadly groups Tasmanian bedrock types according to their differing erosion and weathering characteristics (based on their lithologies and structural styles), and thus their effects on landform development. The attribute categories used for this field are as used by Sharples (2000), with the exception that two further categories (41 & 45) have been added; these sub-divide category 04 (undifferentiated) into two sub-categories where these have been mapped (currently, these subcategories have only been applied in south-eastern Tasmania).

Bedrock geology, particularly lithology and structure, strongly influence coastal landform development in a variety of ways. Such controls include the influence of geological structures and lithological variations on coastal erosion rates, and hence on coastal plan form and profile development, and the influence of bedrock lithology on the amounts and type of coastal sediment derived from local bedrock erosion.

Previous work (Dixon & Duhig 1996, Houshold et al. 1997) identified 11 broad lithostructural (rather than primarily stratigraphic) categories into which Tasmanian bedrock associations can be grouped so as to reflect major differences in their structural and lithological characteristics, and thus in their response to erosion. Essentially, it can be expected that the differing lithostructural characteristics of the rocks grouped in each category will give rise to somewhat differing types of landforms. The same 11 categories are used in this project.

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It is important to note that, although the lithostructural "bedrock geology" categories listed below can include some relatively unlithified or unconsolidated sedimentary sequences (e.g., parts of "01 Terrestrial sediments"), they do not include presently accumulating or geologically-recent sediments of coastal or estuarine origin, but rather sediments which were deposited in previous (non-coastal) environments at a location which later became coastal. The purpose of the Bedrock Geology system control classifier is to identify the bedrock materials upon which the coast has formed - that is, the bedrock system controls on coastal development - but not the sedimentary products of coastal development in response to those system controls.

Essentially, if a bedrock material (lithified or unlithified) predates and/or has actually or potentially controlled coastline development, then it is a georegion system control; however if it has been produced by coastal processes, then it is not a independent system control and is not used to classify georegions.

Attribute summary: Characters (00-99) 00 01

02 03 04 41 45 05 06 07 08 09

10 11

Bedrock type (Bedrock) unknown terrestrial sediments, variably lithified (mostly unlithified or only semi-lithified) and mostly undeformed.

(Gravels, sands, clays, boulder beds, tuffs; mostly Tertiary age, but including some un-lithified or semi-lithified Quaternary sediments that are not themselves the product of Holocene coastal processes. Thus, may include terrestrial fluvial, glacial or colluvial sediments deposited over hard bedrock during Pleistocene glacial phases when sea level was much lower, and now forming the substrate into which the present shoreline has eroded) undeformed, largely unfaulted basalt (mostly Tertiary age, some Jurassic and Triassic) dolerite (mostly Jurassic age) or Cretaceous syenite masses â&#x20AC;&#x201C; large bodies flat-lying dominantly arenite/lutite sequences undifferentiated (mostly Permo-Triassic Parmeener Supergroup) Âą sub-ordinate small dolerite or syenite intrusions Permo-Carboniferous dominantly glacio-marine tillite, sandstone, siltstone and shale sequences (Lower Parmeener Supergroup) Late Permian and Triassic dominantly terrestrial sandstone- mudstone sequences (Upper Parmeener Supergroup) folded dominantly arenite/lutite sequences (mostly Mathinna and Eldon Groups) folded, structurally dismembered sedimentary and volcano-sedimentary sequences (mostly Late Precambrian - Cambrian sequences) mafic/ultramafic complexes (mostly Cambrian) folded, dominantly lutite sequences (mostly the lower-middle Rocky Cape Group and correlates) folded, quartzite/schist associations and quartzose clastic sequences (includes Precambrian quartzites, quartzite/schist associations, Owen Group conglomerates, upper Rocky Cape Group, etc) carbonate rocks (limestones or dolomites of all ages) granitoids (all ages)

For these reasons, the bedrock type mapped in each coastal segment is the bedrock or substrate underlying any superficial Quaternary coastal sediments, including extensive areas of coastal sands and dunes. In some areas there is very little coastal or near-coastal bedrock outcrop and the bedrock geology is unknown, but in most such parts of the Tasmanian coast it has proved possible to infer the bedrock geology from interpretation of the regional geology. Where a coastal stretch is comprised of a sea cliff which exhibits several different rock types in vertical succession, the coastal bedrock type is classified as the lowest rock type, upon which most wave energy impinges. For example, near Deep Glen Bay (SE Tas) Permian sedimentary rocks overlie Devonian granite which outcrops to only a few metres above sea level. The coastal bedrock type is classified as granitoid, since nearly all wave energy impinges on the granites, rather than directly on the overlying sedimentary rocks.

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Hinterland Topography Class (Profile) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Profile Field type: string (character) Field width: 1 Explanation: A qualitative indication of the broad topographic type of the immediate coastal hinterland zone (extending inland beyond the immediate backshore zone). This field is categorised into broad topographic types likely to have had differing influences on the development and nature of the intertidal zone.

Existing topography is an important control on geomorphic processes since it determines the degree to which gravitational, wave, wind and other energies can perform work at a given location. A number of topographic variables are relevant to coastal landform development, including submarine topography, shoreline plan form, and coastal profiles. For the purposes of a broad-based geomorphic system control analysis it is neither possible nor necessary to take into account all possible topographic variables. In the present analysis, submarine topography is not directly integrated, the large scale effects of shoreline plan form on coastal processes are implicit in the Bedrock system control, and in the Geomorphic History system control (which has yet to be incorporated into this dataset). Many smaller scale effects are implicit in the Bedrock geology system control (e.g., in determining the relative positions of headlands on resistant rocks or embayments in less resistant rocks).

For the purposes of this coastal geomorphic system control approach, the topographic parameter considered most important to deal with as an independent variable controlling coastal development is that of coastal Profile, that is, the generalised gradient or slope of the immediate hinterland backing the intertidal shoreline.

Attribute summary: Character (0-9) 1 2 3 4

Coastal profile (coastal hinterland slope / topography class) (Profile) plains 0° - 6° gentle to moderate slope terrain 6° - 20° steep slope terrain >20° high cliffed coast (Bedrock cliffs, sometimes mountainous, rising well above maximum zone of direct wave impact (typically >50m high cliffs), regardless of profile angle inland of cliff tops. This profile category is indicative of resistant coastal rock types that tend to form steep shoreline profiles particularly where exposed to high wave energies)

The coastal profile is important in coastal landform processes since it partly determines the degree to which gravitational energy interacts with marine processes such as wave energy to either erode bedrock or deposit sediments to landwards, and the degree to which aeolian processes can erode, transport and deposit sand inland.

Coastal Profile (Profile) refers to the generalised slope of the coastal hinterland, not that of the intertidal zone, since whereas the intertidal zone slope (Slope) is a product of coastal landform development, the hinterland slope (Profile) is more generally a pre-existing or independent control on coastal processes. Partly because of the differing implications of intertidal (shoreline) and hinterland (system control) profile slopes, the categories of each are defined differently.

The categories (attribute values) of coastal profile used here are those used by Sharples (2000), which are closely similar to the georegion topographic categories originally defined by Dixon & Duhig (1996).

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Wave Energy Zone (Wavenzn) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Wavenzn Field type: string (character) Field width: 2 Explanation: Climatic conditions are one of the most important major independent "system controls" influencing the nature and development of any geomorphic (landform) system (Houshold et al. 1997). Climatic variables which may affect coastal geomorphic systems include wave climate (wave energy, exposure to wave energy, frequency, intensity and direction of storms), prevailing and storm winds, temperature, effective precipitation, and others. However, most of these have not proven practical to use as system controls in this dataset 12.

The climatic system control which has been considered most important, and has been used in this dataset, is the wave climate parameter wave energy (Wavenzn). Wave energy impinging on coasts is by far the most important energy source driving the development and evolution of coastal landforms.

The Wave Energy attribute Wavenzn as used in this dataset is an indicator of the average wave energy received over time by a stretch of coast. Note that wave energy zones (Wavenzn) are clearly distinguishable from "exposure" zones (Exposure), in that the latter simply indicate the degree to which a certain shore is exposed to whatever wave energy is available, whereas Wavenzn provides a indication of how much wave energy actually is available on (or received by) a given stretch of Tasmanian coast over time. Thus, for example, a "highly exposed" coast in a high wave energy zone will receive considerably more wave energy over time than a "highly exposed" coast in a low wave energy zone.

Comprehensive measured quantitative data on this parameter is unavailable for Tasmanian coasts, however Davies (1978) used geomorphic criteria including beach sand sorting, grainsize, and other characteristics to derive a qualitative indication of the relative amounts of wave energy received by different parts of the Tasmanian coast. Davies (1978) scheme has been used to divide the Tasmanian coast into 8 broad wave energy zones (see Figure 18A), which have been used to create the wave energy attribute Wavenzn for this dataset.

An additional ninth category is reserved for coastal lagoons and estuaries substantially sheltered from oceanic swell and storm waves in all coastal regions of Tasmania. These are coastal water bodies which do not receive significant wave energy directly from the ocean. Wave energies within these embayments depend mainly on wind waves generated across their fetch, and the energy of these may vary considerably between these embayments, depending on local conditions.

However, whilst little measured data on wave energy is available for the Tasmanian coast, Harris et al. (2000) have produced a digital model of annual average (mean) wave heights around the Tasmanian coast (see Figure 18B). Wave energy varies as the square of wave height (Pond & Pickard 1983), hence average annual wave height can be used as an indicator of average annual wave energy.

The annual average wave height model for the Tasmanian coast (Harris et al. 2000) shows a 12

Effective precipitation influences river discharge and hence supply of sediment to coasts, and also influences establishment or dieback of dune vegetation which can strongly influence coastal dune mobility or fixing.

However, this variable has not at this stage been integrated into the system controls used in this dataset, partly due to difficulties in deciding whether it is precipitation at the coast or in the coastal river catchment areas which should be used, and partly because this variable is likely to be less influential than the wave climate parameters which have been used (below). Similarly, temperature has not been used as it is likely to be less significant as an independent variable. Wind strengths and directions are very significant in the development of sandy coast landforms, especially dunes, however this variable has not been used here as an independent system control variable. This is partly because it is likely to be less significant for the non-sandy coasts that make up much of Tasmania's coast, and also because it is likely to correlate significantly with the wave climate system controls that have been used (given that waves affecting the coast are also largely a wind-driven phenomenon).

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reasonable correlation with the wave energy zones derived from Davies (1978) - compare Figure 18A & B â&#x20AC;&#x201C; and in addition provides a continuously-variable and semi-quantitative indicator of average wave energies received by coastal regions.

It is envisaged that in future improved wave height modelling could be used to create a more quantitative and regionally-variable attribute indicating average wave energy variations around the Tasmanian coast than is currently provided by the Wavenzn attribute used in the present dataset.

Attribute summary: Character (00-99) 0 1 2 3 4 5 6 7 8 9

A

Wave Energy Zone (from Davies 1978) (Wavenzn) Not classified Highest energy coast (West Coast South) High energy non-embayed coast (West Coast North) High energy embayed coast (South Coast) High-moderate energy coast (East Coast South) Moderate energy coast (East Coast North) Low- moderate energy coast (Bass Strait East) Low energy coast (Bass Strait West) Lowest energy coast (D'Entrecasteaux Channel) Sheltered coastal lagoons and estuaries on all coasts (special category for coasts not exposed to oceanic swells and storm waves)

B

Figure 18: Wave Energy Zones around the Tasmanian coast: A: Adapted from Figure 7.1 of Davies 1978, showing Wavenzn (and sediment compartment zones) numbering presently used in tascoastgeo_v5gda data set as per attribute table above ; B: A model of average annual wave heights around the Tasmanian coast (adapted from Figure 7A of Harris et al.

2000). Wave energy is proportional to the square of wave height (Pond & Pickard 1983), hence this model can be used as an indicator of average annual wave energies received around the Tasmanian coast. This model shows a reasonable correlation with the wave energy zones derived from Davies (1978) (A), and could in future be used to produce a more semi-quantitative and regionally - variable wave energy attribute than the broadlyzoned Wavenzn attribute currently used in this dataset (A above).

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Geomorphic Process (Process) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Process Field type: string (character) Field width: 1 Explanation: Landforms develop in response to a variety of different geomorphic processes, of which only the "marine/coastal" process group is relevant to this data set. The field Process is included in this analysis purely in order to make the data compatible with possible future work which may extend the landform analysis to other geomorphic process systems.

Attribute summary: Character (0-9) 0 1 2 3 4 5

Geomorphic process (Process) fluvial aeolian (terrestrial, non-coastal) marine/coastal (includes coastal aeolian processes) glacial periglacial karst

Field Geomorphic Measurement Records A limited number of fields have been provided to allow for recording of actual quantitative field measurements.

Total Cliff Height (Cliffht) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Cliffht Field type: Number Field width: 4 Explanation: The total cliff height from sea level, including both upper intertidal and backshore cliffs. Where cliff height varies along a shoreline segment, a modal value is estimated.

Attribute summary: Modal cliff height in metres.

0 = not measured or not applicable to shoreline segment in question.

Intertidal Zone Slope (Slopedeg) Used in shapefile/theme: tascoastgeo_v5gda.shp Field name: Slopedeg Field type: Number Field width: 2 Explanation: Modal Slope in actual degrees measured. As defined for Slope, the slope is a line from the high water mark to the low water mark; where this varies within a shoreline segment, a modal value is estimated.

Attribute summary: Modal intertidal slope in degrees.

0 = not measured for shoreline segment in question.

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A1.3.2 Quaternary Coastal Sediment Polygon Map Descriptors These geomorphic descriptors are used in the Tasmanian Quaternary Coastal Sediment polygons map (tascoastsed_v5gda).

Geological Age of Sediment Bodies and Soft Sediment Landforms Used in shapefile/theme: tascoastsed_v5gda.shp Field names: Age Field type: string Field width: 3 Explanation: Geological age of sediment bodies and landforms, expressed as chrono-stratigraphic time period names, not as ages in years (i.e., "Holocene", not "000 years BP" for example) All sediments mapped in this dataset are attributed as "Quaternary undifferentiated" unless evidence is available to allow a more specific age to be attributed.

Attribute summary: Character (000 - 999) 000 010 020 030

Geological age (Age) Unclassified Quaternary undifferentiated Pleistocene Holocene NOTE that sub-divisions of "Pleistocene" and 'Holocene" can be added to this attribute table as needed, by using the third digit to create sub-divisions within the existing categories

Sediment & Landform Types Used in shapefile/theme: tascoastsed_v5gda.shp Field name: Bedform Field type: string Field width: 3 Explanation: Classification of Quaternary sediment and landform types used to attribute polygon map of sediment areas. Includes beaches, inland sand sheets, dune fields, onshore quaternary marine deposits, intertidal and subtidal mud and sand flats, intertidal estuarine or deltaic deposits, and estuarine fluvial floodplain deposits. Generally refers to thick or low-lying unlithified Quaternary sediment accumulations (which are most susceptible to changes induced by human activities).

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Attribute summary: Character (000 - 999)

Coastal sediment and landform types – polygons

000

Sediment or bedform type unknown or unclassified

100 110 120 130 140

Beaches undifferentiated (may include mix of sand, shell or cobbles) Beaches - sand Beaches – sand and shell Beaches – sand and cobble (typically sand beach with cobble berm) Beaches – cobbles and/or boulders

200

Onshore (aeolian) sands undifferentiated (aeolian sand sheets ± dunes, some are thin sheets over bedrock) Aeolian sand sheets (no dune forms, some are thin sheets over bedrock) Aeolian sand sheets with distinct dune forms (some are thin sheets over bedrock)

210 220 300 310 315 320 330 340 400

(Bedform)

Dunes undifferentiated Foredune ± incipient dune Undifferentiated foredunes, other parallel dunes or hind dunes & beach ridges to lee of current foredune.

Parallel dunes or beach ridges to lee of current foredune Hummock dune system Transgressive and parabolic dune systems

410 411 420 430 440 450 451

Backshore / supratidal sediment body (plain or basin) undifferentiated (includes estuarine backshore environments and backshore sediment bodies not placed in any other category) Backshore / supratidal sandy/pebbly sediment body Backshore / supratidal cobble sediment body Backshore / supratidal sandy sediment body Backshore / supratidal sandy/silt sediment body Backshore / supratidal silt/mud sediment body Drained and artificially filled sediment plain or basin Cut & formed roads, into dune or backshore sediments, or on reclaimed land.

500

Not currently used

600

Fluvial deposits (mainly supratidal: floodplain, channel & fluvial delta sediments)

700

Onshore Quaternary marine sediment deposits (e.g., Last Interglacial marine sediments)

800

Intertidal-subtidal sediment bodies undifferentiated (includes estuarine and sheltered embayment deposits) Intertidal-subtidal sandy sediment body Intertidal-subtidal sandy/silt sediment body Intertidal-subtidal silt/mud sediment body (may include a sand fraction)

810 820 830 900

Colluvial deposits undifferentiated (includes coastal cliff collapse and slumping deposits, unlithified older (e.g., Last Glacial) landslide deposits, currently active coastal landslide deposits, vegetated coastal escarpment slope deposits, etc)

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Larger Scale Coastal Landforms or Landform Assemblages Used in shapefile/theme: tascoastsed_v5gda.shp Field names: Landform Field type: string Field width: 2 Explanation: Larger scale coastal landforms, generally including an assemblage of differing bedforms and landforms classified individually in the Bedform field (above).

Attribute summary: Character (00 - 99) 00 11 12 13 14 15 16

Coastal landform assemblage type (Landform) unclassified Spit (narrow accumulation of beach and dune deposits; one end connected to land, the other end extending into a large body of water) Tombolo (a bar or spit connecting an island to the mainland) Isthmus (a narrow spit connecting two areas of land) River delta (fluvial sediment transport & deposition) Estuary Tidal delta (marine / tidal sediment transport & deposition, typically at the ends of a tidal channel)

31

Headland by-pass dune system (classified under "landform" attribute rather than "bedform" attribute, since headland by-pass dune systems may include a range of specific dune types classified under "bedform".

50 51 52 53

Lagoons undifferentiated Lagoon – impounded (intermittently or permanently separated from the sea) Lagoon – tidal (connected to sea by open tidal channel) Area subject to inundation (above MHWM and/or backshore, generally refers to marshy wetlands)

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Dune Mobility Status Used in shapefile/theme: tascoastsed_v5gda.shp Field names: Mobility Field type: string Field width: 2 Explanation: Dune mobility status of dunes mapped for a specified Year, as determined by fieldwork and/or examination of aerial photography of the relevant year.

Mobility quantified as a measure of proportion of vegetation cover on dune surface (i.e., proportion of fixed dune surface). See detailed discussion of the dune mobility attributes in Section (4.3).

Attribute summary: Character (00 - 99) 00 01 02 03 04 05 06

Dune mobility status at specified Year (Mobility) Unclassified 100% vegetation cover 70% - 100% vegetation cover 50% - 70% vegetation cover 30% - 50% vegetation cover 10% - 30% vegetation cover <10% vegetation cover

(fixed dune) (transitional) (transitional) (transitional) (actively mobile dune) (actively mobile dune)

Current Dune Mobility Status Used in shapefile/theme: tascoastsed_v5gda.shp Field names: Currmob Field type: string Field width: 2 Explanation: "Current" dune mobility status where the "current" epoch represented by the mapped dune is unspecified (Year = "unsp"), as determined by fieldwork and/or examination of "current" aerial photography. Field introduced and attributed by Frances Mowling for Northern & Southern NRM region coasts, not yet applied to all mapped dunes.

Current mobility quantified as a measure of proportion of vegetation cover on dune surface (i.e., proportion of fixed dune surface). See detailed discussion of the dune mobility attributes in Section 4.3.

Attribute summary: Character (00 - 99) 00 10 11 12 20 21 22

Current dune mobility status

(Currmob)

Unclassified 100% vegetation cover (fixed dune) 70% - 100% vegetation cover (transitional) 50% - 70% vegetation cover (transitional) 30% - 50% vegetation cover (transitional) 10% - 30% vegetation cover (actively mobile dune) <10% vegetation cover (actively mobile dune)

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Historic Dune Mobility Status Used in shapefile/theme: tascoastsed_v5gda.shp Field names: Histmob Field type: string Field width: 2 Explanation: Historic dune mobility status where the "current" epoch represented by the mapped dune is unspecified (Year = "unsp"), as determined by examination of aerial photography from 1940's or early 1950's. Field introduced and attributed by Frances Mowling for Northern & Southern NRM region coasts, not yet applied to all mapped dunes.

Historic mobility quantified as a measure of proportion of vegetation cover on dune surface (i.e., proportion of fixed dune surface) evident from historic air photo's. See detailed discussion of the dune mobility attributes in Section 4.3.

Attribute summary: Character (00 - 99) 00 30 31 32 33 34 35

Historic dune mobility status Unclassified 100% vegetation cover 70% - 100% vegetation cover 50% - 70% vegetation cover 30% - 50% vegetation cover 10% - 30% vegetation cover <10% vegetation cover

(Histmob)

(fixed dune) (transitional) (transitional) (transitional) (actively mobile dune) (actively mobile dune)

Rate of Sediment Supply to Estuaries Used in shapefile/theme: tascoastsed_v5gda.shp Field names: Sedrate Field type: string Field width: 2 Explanation: Rate of sediment supply to estuary from river catchment. Broad semi-quantitative estimate derived from air photo interpretation and field observations. Field introduced and attributed

by Frances Mowling for Northern & Southern NRM region coasts, not yet applied to all mapped estuaries.

Attribute summary: Character (00 - 99) 00 10 20 30

Rate of sediment supply to estuaries (Sedrate) Unclassified Small rate of sediment supply Moderate rate of sediment supply Large rate of sediment supply

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Mapping Data Sources Used in shapefile/theme: tascoastsed_v5gda.shp Field names: Source Field type: string Field width: 2 Explanation: General source of information used to map polygons in sediment type map (tascoastsed_v5.shp). Where particular geological map sheets, aerial photos or other specific reports have been used, a bibliographic reference should be cited in the References field. This has not been consistently done in the past, but should be done in future, and the relevant information progressively attributed to older polygons based on particular geological maps or other sources.

Attribute summary: Character (00 - 99) 00 01 02 03 04 05 06 07 08 09 10 11 12 13

General data sources (Source) Unknown Fieldwork plus airphoto and geological map interpretation, by C. Sharples Fieldwork only, by C. Sharples Airphoto and geological map interpretation only, by C. Sharples Davies (1959) 100K maps in Sharples (1998), digitised in 1999 for WNW Councils 250K Digital Geological Map of Tasmania Fieldwork plus airphoto &/or geological map interpretation by Frances Mowling Fieldwork only by Frances Mowling Airphoto &/or geological map interpretation only by Frances Mowling LIST 25K maps coastal flats and tidal zone polygons Cullen (1998) Fieldwork only, by Cliff Massey Fieldwork plus airphoto and geological map interpretation, by Dax Noble

A1.3.3 Coastal Geoheritage Map Descriptors Type of geoconservation value Used in shapefile/theme: geoconareas_gda.shp & geoconpts_gda.shp Field name: sigbasis Field type: string (character) Field width: 4 Explanation: Classifies the type of thing the feature is valued for as geoheritage. That is, this is not a descriptive field, but rather identifies the main aspect of the feature for which it is considered to have geoconservation value. The categories used are as per the Tasmanian Geoconservation Database.

Code

Type of geoconservation value (sigbasis)

geol geom soil geo all

Geological (bedrock) values Geomorphic (landform) values Soil values Geological and geomorphic values Geological, geomorphic and soil values

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Significance category Used in shapefile/theme: geoconareas_gda.shp & geoconpts_gda.shp Field name: signif Field type: string (character) Field width: 3 Explanation: Geoconservation significance category, as per the convention used in the Tasmanian Geoconservation Database.

Code

Significance category (signif)

U L R O R/O

Unknown Low Representative Outstanding Both Representative and Outstanding

Significance level Used in shapefile/theme: geoconareas_gda.shp & geoconpts_gda.shp Field name: siglevel Field type: string (character) Field width: 10 Explanation: Level of geoconservation significance, as per the convention used in the Tasmanian Geoconservation Database.

Code

Significance level (siglevel)

unknown local regional Tasmania Australia world

Unknown Local Regional Tasmania Australia World

Sensitivity category Used in shapefile/theme: geoconareas_gda.shp & geoconpts_gda.shp Field name: sigsens Field type: string (character) Field width: 2 Explanation: Sensitivity to artificial disturbance (irrespective of whether or not disturbance has actually occurred), using the same 10-point sensitivity scheme (Kiernan 1997) as used in the Tasmanian Geoconservation Database. Note that this 10-point sensitivity classification serves a somewhat different purpose to that which the 4 – point Sens attribute (Section A1.3.4) encoded in the Tasmanian Shoreline Geomorphic Types map (tascoastgeo_v5gda) serves, and should not be confused with the latter. The 10-point scheme used in the Tasmanian Geoconservation Database provides a level of detail which is possible and useful for describing the sensitivity of particular sites with known particular characteristics; in contrast the 4-point sensitivity scheme used in the Sens attribute is a broader “indicative” assessment of sensitivity which is appropriate for describing potential geoconservation values where specific sites are not identified.

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Code

Sensitivity category

(0-10)

(sigsens)

0 01

02

03

04

05

06

07

08

09

Unassigned Features or values sensitive to inadvertent damage caused simply by diffuse, free ranging human pedestrian passage, even with care.

Example: fragile surfaces that may be crushed underfoot, such as calcified plant remains.

Features or values sensitive to effects of more focussed human pedestrian access even without deliberate disturbance.

Examples: risk of entrenchment & erosion by pedestrian tracks; coastal dune disturbance; drainage changes associated with tracks leading to erosion by runoff; risk of damage as a result of changes caused by changes to fire regimes.

Typically soft (sandy, muddy) coasts with some relief (eg, dunes) exposing sediments to wind or water erosion triggered by pedestrian trampling, or similar.

Features or values sensitive to damage by scientific or hobby collecting or sampling, or by deliberate vandalism or theft.

Examples: some fossil and mineral sites; accessible speleothems in sea caves or coastal karst.

Features or values sensitive to damage by remote processes.

Examples: degradation resulting from hydrological or water quality changes associated with the clearing or disturbance of catchments; fracture/vibration damage due to blasting in adjacent areas (e.g., to stalactites in caves).

Includes shorelines sensitive to coastal siltation and turbidity resulting from catchment land clearance and soil erosion, and soft sediment shores sensitive to changes in intertidal currents or sediment movements caused by structures elsewhere on the coast.

Features or values sensitive to damage by higher intensity shallow linear impacts, depending upon their precise position.

Examples: features whose values would be degraded by vehicular tracks, minor road construction or excavation of ditches or trenches.

Typically soft (sandy, muddy) coasts with low relief (broad flats, no dunes, etc), or soft shores with bedrock/soil backshores, thus less susceptible to wind and water erosion, but may be impacted significantly by vehicles and roads.

Features or values sensitive to higher intensity but shallow generalised disturbance on site (this might involve either the removal or addition of material).

Examples: features whose values would be degraded by clearfalling of forests and replanting, but without stump removal; land degradation such as soil erosion due to bad management practices; revegetation, stabilisation or covering of naturally exposed substrates by human-promoted site rehabilitation (resulting in covering of significant exposures or interference with natural sand movement patterns on beaches and dunes).

Typical of rocky shores with bedrock plus soil backshore (susceptible to backshore soil erosion), boulder beaches with bedrock & soil backshore, and natural colluvium or slumpdebris shorelines (susceptible to soil erosion and accelerated slumping).

Features or values sensitive to deliberate linear or generalised shallow excavation.

Examples: values which may be degraded by minor building projects, simple road construction or shallow excavations. e.g., rocky shore with low/moderate height cliffs (generally 50m high or less) having soil above the cliffs.

Features or values sensitive to major removal of geo-material, or large scale excavation or construction.

Examples: values which may be degraded by quarries or large construction sites.

Typical of rocky shores without soil in immediate backshore (eg, high energy rocky shores and high rocky cliffs).

Features or values sensitive only to very large scale contour change.

Examples: values which may be degraded by very large quarries or excavations.

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Special cases.

Examples: existing wholly artificial shorelines (sensitivity might still be relevant from engineering perspective, but is irrelevant from nature conservation perspective since negligible natural value remains).

Degree of degradation of geo-conservation values Used in shapefile/theme: geoconareas_gda.shp & geoconpts_gda.shp Field name: degrad Field type: string (character) Field width: 12 Explanation: Degree of degradation (if any) of the particular values for which the feature is considered to be of geoconservation (geoheritage) value. Note that it is possible for a feature to be degraded in some other respects, but to be classified as un-degraded or only minimally degraded under this criterion if the particular geoheritage values themselves are un-degraded. This criterion is closely related to the Geomorphic Condition Classification (Cond) used in the coastal landforms description field (tascoastgeo_v5gda), but is here classified according to the convention used in the Tasmanian Geoconservation Database. Whereas Cond refers broadly and indicatively to all geological, geomorphic and soil characteristics of a coastal segment, degrad refers to specific features identified as being of special geoconservation (or geoheritage) value.

Code

Degree of degradation of geoconservation values (degrad)

unknown none slight significant advanced total

Unknown None Slight Significant Advanced Total

Source Used in shapefile/theme: geoconareas_gda.shp & geoconpts_gda.shp Field name: source Field type: string (character) Field width: 2 Explanation: Identifies the source of the judgement that the feature is of geoconservation significance.

Code

Source of judgement of geoconservation value

(00-99)

(source)

00 10 20 21 30

Unknown Listed on Register of the National Estate (including Interim list) Listed on the Tasmanian Geoconservation Database (TGD) v6, 2008.

Interim listed on TGD v6 (2008) - under consideration.

Listed on both the Register of the National Estate and the Tasmanian Geoconservation Database v6, 2008.

Individual geoconservation worker (unidentified or identified in Comments field) Chris Sharples (2000 â&#x20AC;&#x201C; 2006) Frances Mowling (2006)

50 51 52

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A1.3.4 Coastal Geomorphic Sensitivity, Condition and Geoconservation Priority Map Descriptors The Sensitivity and Condition Descriptors detailed below were originally developed for use in the South East Tasmanian Integrated Coastal Management Strategy (Sharples 2001), during which they were created in version 2.0 of the Tasmanian Shoreline Geomorphic Types Dataset. However, note that whilst the Condition descriptor Cond remains a 4 – level coastal landform condition indicator as originally defined for Version 2.0, the Sensitivity descriptor Sens has been condensed from the original 10 – level coastal landform sensitivity indicator (as used in versions 2.0 and 3.0), to a simpler 4 – level indicator in version 4.0 & 5.0.

The Geoconservation Priority (Geovalues) descriptor was created during and for the purposes of the 2005 – 2008 NRM coastal values mapping projects described by this and previous reports (DTAE 2007a,b).

Sensitivity of Coastal Geomorphic and Geological Features (Sens) Used in shapefile/themes: tascoastgeo_v5gda.shp Field name: Sens Field type: string Field width: 1 Explanation: Sensitivity is here considered as the inherent susceptibility of a feature, process or system to degradation resulting from disturbances caused by human activities, irrespective of any existing threats of such disturbance actually occurring. Landforms more sensitive to human disturbance tend also to be those more prone to change and erosion due to natural causes, however a corollary of this is that the more sensitive landforms may rapidly change in ways that would not occur naturally if they are artificially disturbed. In the context of coastal landforms, sensitivity primarily refers to the susceptibility of a landform or landform system to accelerated wave or wind erosion (and/or accelerated sediment mobility and deposition) as a result of human disturbances to the coastal landform system. By convention, Sens refers to sensitivity to local or regional artificial disturbances, but not specifically to the effects of global anthropogenic climate change and sea level rise, which for the purposes of this indicator are treated as if they were natural changes.

The 4 – level sensitivity scale detailed below is a condensed version of an earlier 10-level sensitivity scale previously applied in versions 2.0 & 3.0 of the Tasmanian Shoreline Geomorphic Types Dataset.

The original 10-level sensitivity scale was based on an indicative scale of sensitivity initially developed by Kiernan (1997, Table 15.2) for coastal (and other) landforms. This scale of sensitivities has also been adopted for more general use with the Tasmanian Geoconservation Database (Dixon & Duhig 1996).

The 10-level sensitivity scale indicates particular hazards that would degrade the geomorphic values of specific features having known values and characteristics; thus it is most useful when applied to particular features, which is how it is used in the Tasmanian Geoconservation Database. The 4-level scale used in tascoastgeo_v5gda is a more generalised indicator of sensitivity where the details of the values and characteristics of particular features are not specified or are not known; this is in general the case with the geomorphic mapping encoded in tascoastgeo_v5gda – the general types of coastal landforms present are classified in the map, but specific values and details of specific features are not identified.

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Attribute summary: Character (0 - 9)

Sensitivity of coastal geomorphic and geological features (Sens)

0

Sensitivity unclassified Includes many artificial shorelines

1

High Sensitivity – soft sediment shores backed by soft sediment backshores Coasts dominated by soft unconsolidated and highly mobile sediment substrates (usually sand and/or mud) in both the intertidal and backshore zones. These include sandy beaches backed by sand dune systems, muddy estuarine or deltaic shores backed by soft sediment plains, pebble or cobble shores backed by soft sediment plains, or other combinations of soft sediments. These shores are typically highly susceptible to wave erosion, and associated dunes may be susceptible to wind erosion either naturally or if disturbed. Includes shorelines sensitive to coastal erosion and recession, siltation and turbidity resulting from catchment land clearance and soil erosion, and soft sediment shores sensitive to changes in intertidal currents or sediment movements caused by structures elsewhere on the coast.

Examples: Sand dunes – erosion of loose unconsolidated sediments due to exposure to wind resulting from pedestrian trampling, excavations, loss of vegetation cover, fires, or to water erosion triggered by waves, or similar.

Sandy or muddy shorelines susceptible to erosion and recession due to storm surge or undercutting; risk of coastal dune mobility or slumping; risk of entrenchment and erosion by pedestrian/vehicular tracks; risk of damage resulting from changes to fire regimes.

2

Mixed Sensitivity – Coasts with significant components of widely differing erodibility Typified by coasts having soft sandy or muddy shores immediately backed by harder bedrock backshores, or conversely, hard bedrock shores backed by extensive sand dune systems (e.g., cliff top dune systems) prone to wind erosion. Elements of these coasts may be prone to significant erosion either naturally or if disturbed, whilst other elements remain robust and erode only very slowly either naturally or in response to disturbance.

Examples: Sandy beaches backed by bedrock, which are susceptible to shoreline erosion but little recession.

Rocky (robust) shores backed by overlying mobile dunes (susceptible to increased sand erosion)

3

Moderate Sensitivity – Shores of soft bedrock or semi-consolidated materials Coasts where soft mobile sediments (sand or mud) are minor or absent in the backshore zone, but the coastal substrate is softer than well-lithified bedrock types. These shores may include shores dominated by clayey-gravelly Tertiary-age sediments, Quaternary-age colluvial (landslide deposit) shores, or deeply-weathered and/or intensely fractured shores of formerly well-lithified bedrock. These shores are prone to slumping or noticeable erosion on human timescales, but are significantly less mobile than unconsolidated sand or mud shores having soft backshores.

4

Low Sensitivity – Hard bedrock coasts Coasts where hard lithified bedrock dominates the intertidal zone and backshore (± a soil mantle).

May include low profile, moderately sloping or cliffed hard rock shores. Dominantly cobble or boulder beaches backed by rising bedrock surfaces have also been included in this sensitivity category. These are shores that will generally erode slowly by human time scales, and would require intense artificial disturbance to significantly modify their forms (e.g., deliberate excavation or use of explosives).

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Geomorphic Condition Classification (Cond) Used in shapefile/themes: tascoastgeo_v5gda.shp Field name: Cond Field type: string Field width: 1 Explanation: Condition is here considered as the degree of naturalness, or of artificial disturbance by human activities, of coastal geological features, landforms, soils and geomorphic or soil processes.

Cond is an overall condition summary for bedrock, landform and soil features within each shoreline segment, encapsulating the cumulative impact of all known artificial disturbances on the naturalness of the landforms or geomorphic processes of the coastal segment in question. By convention, Cond refers to the effects (or otherwise) of local or regional artificial disturbances, but not to the effects of global anthropogenic climate change and sea level rise, which for the purposes of this indicator are treated as if they were natural changes (e.g., some sandy shores in southwest Tasmania are eroding rapidly for reasons probably related to global (anthropogenic) sea-level rise, but are otherwise undisturbed and so are categorised as being in essentially pristine condition Cond = 1).

This is a simple four - level classification which takes account of both form and process as important criteria of the naturalness of coastal landforms; that is, the geomorphic condition of a segment of coast is taken to depend on both the degree to which natural geomorphic processes have been disturbed and the degree to which natural coastal forms have been artificially altered. The accompanying text string field Condnotes is used to briefly indicate issues giving rise to the overall condition classification.

For the purposes of this condition classification, the coastal zone under consideration is taken to encompass a coastal strip extending roughly 200m inland from the High Water Mark. While processes operating further inland (eg, catchment erosion) may affect the coast, it is the condition of the coastal strip itself which is being classified here.

Note that geomorphic condition summary is taken to be independent of vegetation condition for the purposes of this classification: the geomorphology and soils may be essentially intact despite some weed species being present or native species absent. However, where weed species such as marram grass (Ammophila arenaria), have altered the profile of dune bedforms, a poorer geomorphic condition classification is applied.

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Attribute summary: Character (0 - 9) 0

Overall geomorphic condition (Cond)

1

Areas of coast that are highly natural in their geomorphic character and where there is little threat from processes on adjacent or other areas which would affect the natural geomorphic integrity of the identified area. Intertidal zone and backshore landforms and soils entirely or essentially undisturbed within 200m of shoreline.

Condition unclassified

These are areas where there has been little or no disturbance to landforms or soils, and is little threat from existing processes or actions. In these areas natural geomorphic and soil processes and forms are largely intact, and they generally are of significant geoheritage value in providing intact examples of ongoing landscape processes characteristic of their georegion type, and in providing an archive of information relating to landscape history and natural processes.

This classification represents a limited need for conservation management intervention other than protection from overt disturbance and un-natural processes such as nutrient enrichment, unsustainable fire regimes, grazing, dumping of refuse and garden waste and other sources of pollution.

2

Areas of partly disturbed coast whose landforms and soils are largely natural, or where natural processes have been re-instated and there is an expectation that natural processes will dominate further landform development. Intertidal zone and backshore landforms and soils largely intact, but with some minor disturbance. Active protection and further restoration of natural conditions likely to be a worthwhile and practical option for maintaining regional conservation values.

These areas may contain significant areas of geomorphic or soil disturbance but still include features of high geomorphic or geoheritage significance, or relatively un-degraded landforms and soils which provide habitat for significant natural species. Examples may include undisturbed rocky shorelines (intertidal zone) with vegetation clearance or minor vehicular or foot tracks in the backshore zone, but no significant accelerated soil erosion or other contour changes (landform degradation); sandy beaches and dunes with minor foot or vehicular tracks but little marram grass or major erosion, etc.

These areas may retain 'archives' or important information regarding past and ongoing landform processes, and/or be largely capable of being managed to provide examples of ongoing natural geomorphic or soil processes.

This category implies a need for active conservation management intervention to prevent further degradation and may require active rehabilitation in parts to restore natural processes (eg, erosion control, weed control, revegetation, etc).

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Areas of significantly disturbed coast that still possess some elements of natural landforms or soils, but where ongoing landform or soil processes are likely to be dominated or at least significantly modified by unnatural factors. Intertidal zone or backshore significantly altered, but still with significant natural elements intact. Restoration to natural conditions may be possible in some cases, but will generally be worthwhile only where such actions will contribute strategically to nature conservation values.

Examples might include relatively undisturbed beaches (intertidal zone) backed by dune systems (backshore) that have been largely cleared of native vegetation and replanted with exotic species, eg, marram grass or pines, with resulting geomorphic changes in the dunes; or undisturbed rocky shores (intertidal zone) with significant accelerated soil erosion in the backshore zone resulting from vegetation clearance or track erosion, or with roads or other structures causing significant changes to landforms in the backshore.

Although these areas might retain significant recreational values they are sufficiently altered or degraded as to have limited value for nature conservation. These areas may be strategically rehabilitated or restored where they will contribute significantly to nature conservation, but this process may require a high level of intervention and a significant expenditure of resources.

4

Highly modified areas of coast in which landforms and soils have generally been modified or degraded to such an extent that they contribute little to the maintenance of geoconservation values. Intertidal and backshore zones both significantly altered. Restoration to natural condition is not normally a practical option.

Such areas may retain some bedrock geological features of geoheritage significance, but generally their landforms and soils will be significantly disturbed and altered by human activities, for example by clearing, accelerated erosion, structures, covering or excavations in both the intertidal and backshore zones These areas may need to be actively managed to ensure they continue to contribute to other environmental amenity parameters such as water quality and erosion control, or so they do not pose a threat to other more intact natural environments. These areas should only be restored or rehabilitated for nature conservation purposes if they are of high strategic value.

Geoconservation Priority ("Indicative Geovalues") of Coastal Segments (Geovalues) Used in shapefile/themes: tascoastgeo_v5gda.shp Field name: Geovalues Field type: string Field width: 1 Explanation: This attribute is a high-level (i.e., generalised) indicator of geoconservation management priorities, which has been derived from lower-level (i.e., more specific) geomorphic attributes classified in the tascoastgeo_v5gda.shp map. The purpose of the Geovalues attribute is to highlight coastal segments which are most likely to warrant management attention in the context of management regimes aimed at maximising the maintenance of regional geoconservation values and/or minimising the threat of geomorphic hazards to human activities & infrastructure.

This is a simple four - level classification which attributes higher Geoconservation Priority to coastal segments whose landforms are either in more natural condition (and thus make a greater contribution to existing regional conservation values) and/or of higher sensitivity to disturbance (and thus of higher priority for conservation management â&#x20AC;&#x201C; even if already significantly disturbed â&#x20AC;&#x201C; because of their propensity for significant further degradation of regional geomorphic values if inappropriately managed).

The Geovalues classifications have been automatically derived from the Sensitivity (Sens) and Condition (Cond) attributes above by GIS queries as illustrated in the matrix below:

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Sensitivity

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Condition 2 3 1 1

1

1 1

4 1

2

1

2

2

2

3

1

2

3

3

4

1

2

3

4

Table 4: Matrix demonstrating the derivation of geoconservation priority (Geovalues) from Sensitivity (Sens) and condition (Cond) attributes. In effect, each coastal segment is assigned a geoconservation priority corresponding to the highest value of either sensitivity or condition for that segment.

Attribute summary: Character (0 - 9) 0

Geoconservation Priority (or, "Indicative Geovalues") of coastal segments (Geovalues)

1

High Geoconservation Priority

Geoconservation Priority unclassified

Coastal segments having either the highest sensitivity to disturbance, and / or the most natural condition. The highest geoconservation priority will apply to sensitive (e.g., sandy) coasts in pristine condition, however a significantly disturbed sensitive (e.g., sandy) coastline may also fall into this category because, despite its existing disturbance, continued inappropriate management may continue to cause or increase coastal geomorphic management problems regionally.

2

Moderate Geoconservation Priority Intermediate category â&#x20AC;&#x201C; coastal segments of either moderate sensitivity or in moderately natural condition. The same considerations as for Geovalues = 1 apply, at a lower level of priority.

3

Moderate to Low Geoconservation Priority Coastal segments whose sensitivity is moderate to low, and whose condition is moderate to poor, but which still retain some natural landform or process elements that may be further degraded or result in geomorphic hazards if subjected to some types of inappropriate activities, and which thus still warrant some management consideration in regard to landform values or processes

4

Low Geoconservation Priority Coastal segments of low sensitivity to disturbance yet which are significantly disturbed nonetheless (mainly refers to hard rock shores that have been extensively built over and modified by dock facilities, urban development to the waterline, etc). Geoconservation issues will rarely arise for these shores, which have essentially lost all natural geoconservation values, and whose continued disturbance will generally not result in additional environmental degradation to that which already exists.

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Appendix Two â&#x20AC;&#x201C; Coastal Photography

APPENDIX TWO: COASTAL PHOTOGRAPHY â&#x20AC;&#x201C; NRM NORTH AND CRADLE COAST REGION As the photography collected throughout the NRM North and Cradle Coast region is quite comprehensive, the photos have been provided as part of the mapping requirements for this project contained on the DVD attached, not as thumbnails presented within this section.

In total 646 photos have been collected and are provided in two different ways, oblique (from helicopter) and terrestrial (during field validation on ground). The photos are linked in the layer tascoastgeomaps_v52008gda94_PhotoLog_shp. The photos can be viewed one of two ways; firstly by accessing the photos folder on the DVD; or through the tascoastgeomaps_v52008gda94_PhotoLog_shp layer in ArcGIS (by clicking the information of a particular photo point opens a table with an imbedded link to the photo, which can be selected to view a photo of that location). If viewing the photo log layer in ArcGIS the Polyline or Polygon layers can be overlain to review the geomorphic classification of that section of coastline while viewing the site photograph(s).

The information contained in this document has been carefully compiled, but Hydro Tasmania Consulting takes no responsibility for any loss or liability of any kind suffered by any party, not being the intended recipient of this document, in reliance upon its contents whether arising from any error or inaccuracy in the information or any default, negligence or lack of care in relation to the preparation of the information in this document.

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