Page 1

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-2Use of this publication and disclaimer: Reproduction of this publication, or portions of this publication is authorised for educational or non-commercial purposes only provided the source is fully acknowledged. Use of best practices found within this manual does not guarantee approval for a development as all developments are required to follow the laws and regulations found within the VI Planning Act, 2004 and approval is only granted through the VI Planning Authority. This BMP Guide has been prepared solely for informational purposes. The practices contained herein are to be utilized solely by those competent to evaluate the significance and limitations of its content and specific site requirements where applied and who can take full responsibility for the application of the practices set forth herein. The authors, contributing authors and all other agencies and organizations cooperating in the development of this BMP Guide, strive for accuracy, but disclaim any and all responsibility for the application of the stated practices or for the accuracy of the content or sources and shall not liable for any loss or damage arising from reliance on or use of any content or practices contained in this BMP Guide.Â

Citation Gore, S, Leoniak, L, et al. (2013). Best Management Practices: Reducing Erosion in the British Virgin Islands. Government of the Virgin Islands, Road Town, Tortola, British Virgin Islands.152pp. This publication can be downloaded at: http://www.bvidef.org Main Cover Photo: L. Jarecki. Northern coast of Tortola after heavy rainfall. Book Layout and Design by Wilbert Chambers


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Best ManageMent Practices: A Guide for Reducing Erosion in the British Virgin Islands This publication was made possible with funding and technical support from:

Overseas Territories Environment Programme, Office of the Governor The Nature Conservancy Jack Setton (Little Bay Property Holdings Limited) Split Holdings (Moskito Island Development)

OF

DISASTER M

AN

ve Go

sla nd s

NT

ENT EM AG

DEPAR TM E

Quorum Island (BVI) Limited

rn I me n nt of the Virgi


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-5Principal Authors Shannon Gore, PhD

Conservation & Fisheries Department

Lain Leoniak, Esq.

The Nature Conservancy

Contributing Authors Edwin Adams

Jon Grant

Clive Petrovic

Ron Beard

Jameal Georges

Garymar Rivera

Edwin Adams Architecture Co. Ltd.

Town & Country Planning Department

AJ “Bones” Blake A. J. Blake BVI LTD.

Lisamarie Carrubba, PhD

National Oceanic & Atmospheric Administration

Wilbert Chambers

Conservation & Fisheries Department

Val Corrington

Trunk Bay Development

Sharleen Dabreo

Department of Disaster Management

Jose DeCastro, RA, LEED AP Public Works Department

Winston Donavan Survey Department

Joel Dore

Conservation & Fisheries Department

Thor Downing, BA Barch (Hons) Roger Downing & Partner Co. Ltd.

Steve Fox, RIBA, LEED AP Onions, International

Gary Frett

Conservation & Fisheries Department

Zoco Engineering, Inc

Ministry of Communications & Works

Mervin Hastings

Conservation & Fisheries Department

David Hildred, BSc (Hons) AnneMarie Hoffman The Nature Conservancy

Aaron Hutchins

The Nature Conservancy

Kelvin Penn

Conservation & Fisheries Department

Bertrand Lettsome

Lettsome Consulting Inc.

Jerry McCrain, PhD Atkins Global

Daryll Murphy

Kraus-Manning, Inc.

Nancy Pascoe

National Parks Trust

Dylan Penn

Town & Country Planning Department

Perry Penn

Public Works Department

E-Concerns Ltd.

Department of Disaster Management

Joshua Silwimba

Public Works Department

Devon Skelton

Public Works Department

Susan Smith

The Nature Conservancy

Ronald Smith-Berkeley

Ministry of Natural Resources & Labour

Scarlett Steer Manine’s

Paul Sturm

Ridge to Reefs Inc.

Susan Zaluski

Jost Van Dyke Preservation Society


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Message FrOM His eXceLLencY, BOYD MccLearY, cMg, cVO, tHe gOVernOr OF tHe BritisH Virgin isLanDs I am pleased that the Governor’s Office, through access to the UK Government’s Overseas Territories Programme Fund, has been able to support the Virgin Islands Government in its efforts to achieve the right balance between environment and development, by sponsoring Best Management Practices: A Guide For Reducing Erosion In The British Virgin Islands. We are all dependent on our environment, particularly those of us who live on small islands. The environment provides us with food and water. It protects us from extremes of weather and even protects us from ourselves by dealing with our waste products. Here in the Virgin Islands, where the beauty of our surroundings is one of the Territory’s greatest assets, the value of the natural environment should be obvious to us and yet we sometimes take it for granted. Our coral reefs and soft sand beaches attract thousands of visitors and protect the coastline. Sea-grass beds and mangroves act as fish nurseries. Forested slopes protect property from flooding and prevent reefs from being covered in sediment. Good planning decisions and utilising sustainable land development practices will be essential components of our economy going forward. Equally important will be communicating to everyone who lives in these islands the value of these practices and their positive impacts on the environment. This Guide is a good place to start and is intended for a wide cross-section of people involved in the land development process from the public to the private sectors, professionals and non-professionals alike. The Guide identifies various best practices to reduce erosion, prevent flooding, and property damage, and many cost savings techniques. It also provides a better understanding of island watersheds and how these best management practices are connected to the health of our terrestrial, coastal and marine environments. In closing, I would like to sincerely thank all those in government, participating non-profit organisations and the development community of the Virgin Islands, whose time and expertise made this Guide possible.

Boyd McCleary, CMG, CVO Governor


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Message FrOM Dr. tHe HOnOUraBLe KeDricK PicKering DePUtY PreMier anD Minister OF natUraL resOUrces & LaBOUr On behalf of the Government and the People of the Virgin Islands I am pleased to introduce Best Management Practices: A guide for reducing erosion in the British Virgin Islands. The Virgin Islands comprises over sixty stunning and unique islands and cays and are home to endless white sand beaches, coral reefs and countless tropical marine species. People travel from all over the world to enjoy the natural beauty of our country. Preserving the breathtaking natural beauty of this special place requires good stewardship from all of us who are fortunate to call the BVI home. Each and every citizen of this country must understand the vital importance of our environment and that if we protect and preserve it for ourselves and our visitors, it will give back to us tenfold and enable us to continue to pay for the services we enjoy today. We must take responsibility for our actions and understand that what we do affects the natural world around us. The Best Management Practices Guide provides valuable resources and information for planners, developers, builders and home owners along with several best practices well suited to our challenging island topography to prevent soils and waste from developments from entering ghuts and coastal waters thus damaging property, beaches and threatening the health of coral reefs and marine life. This Guide compliments the on-going efforts of my Ministry to lead by example through initiatives such as the development of a Climate Change Trust Fund that will make monies available for environmental protection and preservation programmes and to declare more National Parks and Marine and Fisheries Protected Areas to preserve and protect these areas for citizens and visitors alike. I encourage professionals in the construction industry and current and future property owners to make use of the important resources provided in this Guide to work together to leave a legacy of a healthy natural environment for future generations.

Dr. Kedrick Pickering, Deputy Premier and Minister of Natural Resources & Labour


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taBLe OF cOntents Preface & acknowledgements

10

acronyms & abbreviations

11

1.

2

3

intrODUctiOn

13

1.1 Reality Check 1.2 Worst Case Scenario

14 15

WatersHeDs 101: aLL YOU neeD tO KnOW

19

2.1 In a “Perfect Watershed� World 2.2 What is a Watershed? 2.3 Watershed Anatomy 2.4 Where Does Water Go? 2.5 Requirements for Developing in a Watershed

20 21 22 25 26

DeVeLOPMent PLanning

29

3.1 Introduction 3.2 Application & Approval Process 3.3 Technical Planning 3.4 Design Planning 3.5 Physical Characteristics 3.5.1. Topography 3.5.1.1. Slopes 3.5.1.2. Soils 3.5.1.3. Vegetation Types 3.5.1.3.1. Endangered Species 3.5.1.3.2. Locally Important Species 3.5.1.3.3. Invasive & Problematic Species 3.5.1.4. Rock Outcroppings 3.5.2. Hydrology 3.5.2.1. Ghuts 3.5.2.2. Wetlands 3.5.3. Coastal Features (If Applicable) 3.5.3.1. Beaches 3.5.3.1.1. Seasonal Beach Behaviour 3.5.3.1.2. Historical Beach Behaviour 3.5.3.2. Mangroves

30 32 33 34 35 35 35 35 35 37 38 40 41 42 42 43 44 44 47 48 49

3.5.3.3. Seagrass Beds 3.5.3.4. Coral Reefs 3.5.3.5. Oceanographic Processes 3.5.4. Anegada 3.5.4.1. Dune Systems 4. cOnstrUctiOn 4.1. Preconstruction 4.1.1. Phasing & Scheduling 4.1.2. Protective Measures 4.1.2.1. Preserving Natural Vegetation 4.1.2.2. Footprints 4.1.2.3. Setbacks/Buffers 4.1.3. Housekeeping BMPs 4.1.3.1. Feral Animals 4.1.4. Implementation of BMPs 4.2. Erosion Controls 4.2.1. Roads 4.2.1.1. Cut & Fill 4.2.1.2. Road Drainage 4.2.1.3. Paving 4.2.2. Stabilization 4.2.2.1. Construction Site Entrance 4.2.2.2. Clearing the Site 4.2.2.2.1. Land Grading 4.2.2.2.2. Gradient Terracing 4.2.2.3. Holding the Soil in Place 4.2.2.3.1. Mats, Nets & Blankets 4.2.2.3.2. Mulching 4.2.2.3.3. Temporary Seeding 4.2.2.4. Slope Protection 4.2.2.4.1. Soil Retention Walls 4.3. Sediment Control 4.3.1. Stormwater Diversion 4.3.1.1. Perimeter/Interceptor Dike & Swales 4.3.1.2. Check Dams & Berms

50 51 53 54 57

59

61 62 64 65 66 67 69 70 71 72 72 72 74 76 77 77 78 79 79 80 80 82 83 84 84 85 86 87 88


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5.

4.3.2. Stormwater Conveyance 4.3.2.1. Lined Channels (Drainage Swales) 4.3.2.2. Drainage Protection 4.3.3. On-Site Detention Systems 4.3.3.1. Temporary Sediment Basin 4.3.3.2. Sediment Traps 4.3.4. Bioretention Systems 4.3.5. Filters & Barriers 4.3.5.1. Silt Fencing 4.3.5.2. Brush Barriers 4.3.5.3. Filters/Buffer Strips 4.3.5.4. Curtains 4.4. Shoreline Developments & Erosion 4.4.1. Shoreline Stabilization 4.4.1.1. Beach Nourishment 4.4.1.2. Shoreline Stabilization Implications 4.4.2. Land Reclamation 4.4.3. Marina Construction BMPs 4.4.3.1. Dredging BMP’s

88 88 89 90 90 92 93 93 94 95 95 96 97 98 99 101 102 103 104

POst cOnstrUctiOn

107

5.1. Introduction 5.2. Post-Construction Review Plan 5.2.1. Pre- & Post-Development Hydrologic Analysis 5.2.3. Pollutants of Concern 5.2.4. Pollution Prevention Measures 5.2.5. Stormwater Treatment & Controls 5.2.6. Proof of On-Going Maintenance 5.3. Permanent Seeding & Planting 5.3.1. Acceptable Vegetation 5.4. Permanent Retaining Walls 5.5. Permeable Pavers 5.6. Rain Gardens 5.7. Maintenance of Best Practices 5.8. Conclusion

108 109 110 111 112 113 114 114 115 118 120 122 124 126

6.

aPPenDiX 1: elements & Use of environmental impact assessment (eia)

128

7.

aPPenDiX 2: elements & Use of Hazard Vulnerability assessment (HVa)

130

8.

aPPenDiX 3: Developer’s checklist for Planning

132

9.

aPPenDiX 4: erosion, sediment & Pollution Prevention Plan

134

10.

aPPenDiX 5: the environmental Managment Plan 136

11.

citatiOns, WeBsites & iMage creDits

140


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Preface & acknowledgements Increased development of buildings and roads within steep watersheds on small islands reduces permeable surface areas. In undeveloped areas, rainwater is absorbed and filtered by thick vegetation and distributed or captured through natural hydrological pathways (ghuts or wetland areas). But in developed areas, rainwater and everything transported in it as runoff now flows directly into coastal waters. This excessive volume of unfiltered, muddy waters results in flooding of low lying areas and reduces coastal water quality. This increases health risks in bathing waters near popular tourist beaches, reduces the tourism value of what once were white sand beaches and clean clear waters, and threatens the sustainability and health of our nearshore coral reefs and seagrass beds. In 2012, the Conservation & Fisheries Department was awarded a grant for a project entitled ‘Building Community Capacity to Reduce Island Erosion” through the Governor’s Office under the Overseas Territories Environmental Programme. The purpose of the project was to raise awareness of: 1) the cumulative impacts caused by watershed developments that ultimately have a negative impact on our beaches and coastal waters and 2) how individual property owners, buyers or large scale developers can reduce their impacts during the planning, construction and post-construction phases of their development. A one-day workshop was held in November 2012 to set the stage for a wide range of stakeholders directly involved in various developments throughout the Territory to come together to discuss watershed management and erosion control. The workshop enabled stakeholders to learn about what best practices are used in our neighbouring islands, as well as to discuss the obstacles we currently have in the BVI that do not allow for improved watershed management. The discussions from this workshop helped shape the contents of this guide. If not for the funding from the Governor’s office, Jack Setton, Split Holdings, Quorum Island (BVI) Ltd., the support of the Ministry of Natural Resources & Labour and the Conservation & Fisheries Department, and the technical advice from The Nature Conservancy, this project would have never been initiated. Additionally, the participation and roles of contributing authors have helped to create this one-of-a-kind publication that will not only provide accountability towards making better decisions but will also contribute to the future sustainability of our beautiful islands. Lastly, a special thank you to Jon Tattersall, co-founder of the Ten Project for inspiring Ms. Colette Tittley’s Form 1G students from St. George’s Secondary School, Tortola to draw some of the wonderful illustrations found within this Guide.


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acronyms & abbreviations ASLA BMP BVI CCMA CFD DCA DDM EIA EPA ESA ESAPPP FCO GBR GIS HDS HVA IRF IUCN NOAA PICP TCP TNC UNESCO

American Society of Landscape Architects Best Management Practices British Virgin Islands Center for Coastal Monitoring & Assessment Conservation & Fisheries Department Development Control Authority Department of Disaster Management Environmental Impact Assessment Environmental Protection Agency Endangered Species Act (United States) Erosion, Sediment & Pollution Prevention Plan Foreign Commonwealth Office Great Barrier Reef Geographic INformation Systems Hydrodynamic Separation Devices Hazard Vulnerability Assessment Island Resource Foundation International Union for Conservation of Nature National Oceanographic and Atmospheric Administration Permanent Interlocking Concrete Pavement Town & Country Planning Department The Nature Conservancy United Nations Environmental, Scientific and Cultural Organisation


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1.

intrODUctiOn “The environment defines a development; development cannot define the environment” -Anonymous

No development is too big or too small to use the best practices found within this Guide. Whether you are a developer, a planner, a builder, a designer, a property owner or just concerned about the natural environment, there is something for everyone to consider as a ‘best practice’ to implement at any type of building site. Even if you have already built your dream home or still trying to decide what to build, this Guide will help you make informed decisions that will mitigate a development’s negative contribution to island erosion and coastal sedimentation.


- 14 1.1

reality check

Imagine an island with flourishing coral reefs and sugary white sand beaches. Imagine during periods of heavy rainfall, coastal waters remain crystal clear and clean. Imagine never having to worry about flooding in low lying areas or landslides ending up in your backyard. Now consider reality. Throughout the Caribbean, live coral coverage has declined an average of 80% since the late 1970’s [1]. Beach erosion, poor water quality and increased coastal development have become common island issues [2, 3, 4]. In the future, impacts from climate change such as sea level rise and an increase in the frequency and intensity of storms [5], will become more prevalent and further reduce the quality of the coastal environments to protect us and generate a sustainable island tourism economy. In general, people’s actions are to blame for the deterioration of our natural environment but there is no reason or time to sit around and complain as to who did what and when. Now is the time to change the way of thinking that got us into this situation in the first place. Can we continue to develop and reduce our impact on the environment? We can. It is time to start using known “best” practices that have been proven to reduce erosion and sedimentation instead of continuing those practices that have had detrimental impacts on our natural resources and resulted in increased development costs over the long run. The quality of our environment is reflected in our attitude towards it. Why put great efforts into making your development (within property boundaries) the best it can be when it fails to be the best it can be as part of the wider surrounding environment? While you may think your development doesn’t contribute to any kind of wider environmental degradation, your personal opinion may not hold up against scientific fact or your neighbour’s opinion, especially if they are impacted by your development. Your property and development will suffer over time if your surroundings are degraded. This is one of the reasons why this Guide was developed, to bridge the gap between current knowledge and sound final decisions. This Guide provides the most current scientific knowledge (of the BVI) and technologies used in best practices today. However, as new information comes available, this publication will need to be reviewed at least every 5 years.


- 15 1.2

Worst case scenario

The “worst case scenario” is more than just the unsightly, mud-filled coastal waters after a heavy rainfall. It includes the long-term effects from not controlling the sediments that are washed away from upland developments. Unfortunately, there are numerous examples from around the world. European settlement in Australia during the late nineteenth century led to land clearing for livestock and agriculture [6], which subsequently led to increased sedimentation along the coast. In one coastal city, the loss of vegetation and development upland from a particular beach resulted in soils washed down to the coast and turned a once sandy beach into a mud flat [7]. While this is only one known sandy beach to forever be changed, there is also the impact increased sedimentation has had on the world’s largest coral reef (350,000 km2), the Great Barrier Reef (GBR). European settlement (from the late 1800’s) has been linked to the cause of a previously undetected historical collapse in nearshore coral communities prior to formal monitoring of the GBR beginning in 1985 [8]. This raises the question of how “pristine” the reef really was in 1985 when live coral coverage was 28%. Since 1985, half the reef has died; by 2012 live coverage had declined to 13.8% [9].

Closer to home in the Caribbean, a similar story exists. The mass loss of the coral species Acropora1* in the early 1900’s [10, 11, 12, 13] implies land clearing for intensive agriculture and other local human impacts have played an earlier role in Acropora decline than previously realized [14]. This decline took place before the more recent (1970s-present) phenomena of mass coral disease [15] and bleaching events [16] attributed to anthropogenic climate change effecting already weakened coral populations due to human impacts [17, 18, 19]. This has led to the U.S. population of acroporid corals being listed under the U.S. Endangered Species Act (ESA) and the current proposal to list an additional seven coral species under the ESA. Continued poor land use and development practices continue to be the primary cause of reef degradation in the BVI. *

The Acropora species of corals, also known as elkhorn and staghorn corals, were the dominant reef building species in the Caribbean.


- 16 Land clearing is not the only action capable of impacting the environment. Infilling land where wetlands once existed has also created negative local effects. One of the main functions of wetlands is to mitigate erosion control and retain sediments and nutrients prior to their entering coastal waters [20, 21, 22]. The loss of more than 84% of the original wetlands in the BVI for development purposes [23] coupled with reduced vegetation on steep hillsides from developments and unpaved cut roads [24.25] has contributed to localized flooding in low-lying areas [26]. This has significantly increased the hazard vulnerability of BVI communities during heavy rainfall events. This resulting flooding often causes erosional gullies to form in which sediment-laden stormwater breaches a beach from the landward side and enters coastal waters. Subsequently, some of these sediments end up being trapped by the sand, which is likely the reason that residents claim some beaches have lost their bright lightgolden appearance [27].

The underlying message here is that there is a very strong link between what we do on land and the impacts it will have on our coastline and near shore coral reefs.


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2

WatersHeDs 101: aLL YOU neeD tO KnOW “The whole is greater than the sum of its parts” - Aristotle


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in a “Perfect Watershed” World

In order to really understand what we are trying to achieve as part of a greater community, we have to recognize and adopt a shared vision of what would help to create a perfect watershed. Therefore, the following goal is what all developments in the BVI, no matter how big or small should strive to achieve. “Our built environment is properly designed, managed and enforced according to localized physical characteristics using best practices in order to maintain functional hydrological systems that will in turn, promote reduced flooding in low lying areas and sediments from entering coastal waters.” This goal was first created as part of a capacity building workshop held in 2012 based on a sustainable development framework developed by The Natural Step™ (www.naturalstep.org ). This framework provided the necessary tools to help local BVI stakeholders develop a sustainable development framework for the Territory. UNESCO provided Green VI funding for this project and more information can be found at www. greenvi.org .


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What is a Watershed?

Simply put, a watershed is the area of land where all of the water that falls within it eventually drains off into a shared location. A watershed carries water “shed� from the land after rain falls. Drop by drop, water is channelled and filtered through vegetation, runs over or percolates through underlying rock and soils, down ghuts, and eventually makes its way to a low lying wetland or directly into the sea. A healthy watershed is characterized by a series of processes that convey, store, distribute, and filter water that, in turn, sustains terrestrial and aquatic life. Water is affected by all that it comes in contact with, including the land it traverses, and the soil and rock through which it travels. The important thing to remember about watersheds is that what we do to alter natural landscapes can affect everything within the watershed, as well as everything nearshore in the sea below. Little information exists specifically on BVI watersheds except for a single report by Abul Alam (circa 1990) [28] but that information is limited and is now outdated. However, more information on watersheds has been recently collected by the Island Resource Foundation (IRF) in their Environmental Profiles, but information is currently limited to certain islands. Reports on Jost Van Dyke [29] Virgin Gorda and surrounding islands [30], and Anegada [31] can all be downloaded at www.irf.org .


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Watershed anatomy

Every watershed has the hydrologic function of capturing, storing, and releasing water. How well a watershed performs these functions is dependent upon how well each individual part (that makes up the whole of a watershed) is able to perform. Each part or landform of a watershed has its own specific job. If a landform becomes ecologically altered or degraded, the overall hydrologic function of a watershed becomes impaired and unable to perform properly [32]. The watershed, as a whole, is only as effective as the function of its weakest or most degraded part or landform. Low lying areas in tropical islands often have localized flooding during periods of rainfall partly because of reduced vegetation on steep hillsides, inadequate drainage channels, blockage and / or inadequate development control mechanisms. The integration of structural (ponds, on-site retention basins, rain gardens) and non-structural measures (use of hydrologic modelling, warning systems, public education) throughout the management process as well as integrating the views of all the relevant parties (i.e. town planners, emergency services, engineers, contractors, etc.) are key components for improved watershed management and island sustainability [26]. NOTE: A watershed on the steep volcanic islands* of the BVI differs from Anegada’s watershed due to the island’s underlying geology. More information about Anegada’s features is in Sec. 3.5.4. Anegada. *

The term “volcanic islands” is used to differentiate between the steep islands (volcanic) and the flat coral islands (e.g. Anegada, Sandy Spit).


- 23 a.

The ridge to reef concept states that both upland areas and receiving coastal waters (coral reefs and seagrass beds) are affected by land-use within the watershed [33].

b.

Watersheds are delineated by the islands’ topography. Drainage is divided at hilltop ridges which create the upper boundaries of a watershed. One watershed can be divided into several sub-watersheds but for simplicity, land areas that all drain into a shared location form a “watershed”.

c.

Upland areas are simply the upper hillsides of watersheds and include the forested slopes. Uplands receive water from rain that permeates through the terrain, sinking into soils. Because trees are closely intertwined with soils, they help absorb incoming water. Forests are considered to be “sponges” during storm events, capable of absorbing and storing huge amounts of water, thereby reducing runoff that contributes to flooding. If the ground is saturated from rain, water will run over the soil surface as runoff, to a low point, or until it is absorbed.

d.

In the BVI soil layers are generally thin (2-6in and rarely up to 12in) and include both organic matter and minerals which are influenced by the underlying bedrock, climate, vegetation, microorganisms, and topography. During development, any vegetation that is removed exposes and loosens soils which subsequently contribute to localized flooding in low-lying areas [26]. Additionally, the low organic content of soils means soils that are exposed due to vegetation removal often are not recolonized and even replanting is very difficult, leading to more erosion and sediment transport. (See also Sec.3.5.1.2. Soils)

e.

Bedrock is the consolidated rock found under soils. The type of bedrock that forms the islands of the BVI is classified by composition resulting from volcanic activity or in the case of Anegada, Pleistocene reef production. Since bedrock composition varies greatly throughout the islands, understanding bedrock characteristics (or the geologic characteristics of an area) is vital in the planning and design stages of a development, especially since some areas are more prone to landslides than others. (See also Appendix 2: Elements and Use of a Hazard Vulnerability Assessment on how you can find out more about the geology underlying your development).

f.

A ghut is the local term used for the watercourse in which surface runoff (or stormwater) flows towards the ocean along a natural drainage pathway or channel. Most ghuts are generally dry most of the year but flow during periods of heavy rainfall. Filling in or altering the direction of a ghut could lead to localized flooding. (See also Sec.3.5.2.1. Ghuts)

g.

Mangrove wetlands are continuous mangrove ecosystems that may include a salt pond, the pond’s shoreline and its fringing mangroves [23], or form at the mouth of ghuts where the ghut meets the sea. Wetlands exhibit a richer diversity of plants and animals, and greater biological productivity, than non-wetland areas around them. Wetlands play significant roles in cleaning runoff waters. First, vegetation slows the speed of incoming water, and sediments carried along in the water drop out and are deposited in the wetland area. In this way, wetlands effectively reduce flooding and filter contaminants such as sediment from waters before these sediment-laden waters reach the sea. (See also Sec.3.5.2.2. Wetlands)

h.

i.

Salt ponds are coastal seawater ponds that accumulate sea-salts by evaporation [23]. They provide a place for stormwater to naturally pool and filter out the nutrients and sediments that have “shed” from hillsides during heavy rainfall. Filling or destroying a salt pond eliminates a natural buffer and filtration feature between uplands and the ocean. (See also Sec.3.5.2.2. Wetlands) Mangroves are trees that have developed special adaptations in order to grow in salt

water / coastal conditions by tolerating salt. Red mangroves (Rhizophora mangle) grow nearest the water’s edge and are the most productive of the mangrove species. Moving from the shore, the succession of mangroves includes black mangroves (Avicennia germinans), white mangroves (Laguncularia racemosa), and the button mangrove (Conocarpus erectus). Not all mangroves are associated with mangrove wetlands, instead, they may fringe the coastline and in some cases, such as the southern coast of Tortola, the mangroves form mangrove cays (i.e. Slaney Point). These types of mangroves provide the ecologic service of reduced wave energy and erosion control during storms, and are highly valued by boat owners for use as hurricane shelters. Red mangroves also provide physical habitat and nursery grounds for fish, lobster, and other marine organisms as well as nesting and roosting sites for birds. (See also Sec.3.5.3.2. Mangroves) j.

Flood prone areas (also called flood zones) are defined as areas of normally dry land whose general and temporary condition of partial or complete inundation by water occurs due to storms. Flood prone areas can include: Overflow of inland or tidal waters Unusual and rapid accumulation of runoff of surface waters from any source Mudslides caused by flooding Collapse or subsidence of land along the shore as a result of erosion or undermining caused by waves or currents Increase or rise of water table (groundwater level) The term ‘floodplain’ is more often used in other countries but not commonly used in the BVI. However, floodplains, like flood prone areas are both described in terms of statistical frequency. A “100-year event” (“event” could be replaced with storm, flood, etc.) describes an event subject to a 1% probability of happening in a given year. In other words, it does not mean it happens once every 100 years; there is a chance of 1 in 100 that it will occur in a given year.

k.

In simple terms, a beach is the strip of land next to a body of water where loose materials (sediments) such as muds, sand, stones, gravels, shingles, coral fragments, or boulders have accumulated. The landward boundary of a beach is where there is a drastic change, such as a line of vegetation, solid rock, the edge of another body of water (such as a salt pond), or even a building or a road. Seaward, the beach extends to the water depth at which waves are not capable of moving sand landward (also called the ‘depth of closure’). In the BVI, this is roughly at a water depth of 20-30m. (See also Sec.3.5.3.1 Beaches)

l.

Nearshore coastal waters represent the marine ecosystems that include bathing waters, sandy flats, seagrass meadows, algal beds, colonized hardbottoms, and coral reefs. (See also Sec. 3.5.3.3 Seagrass beds and Sec. 3.5.3.4 Coral Reefs)

m. The wearing away of soil by water, wind, or gravity is called erosion. In many cases, erosion is a man-made problem caused by exposing bare earth during construction or land clearing. In the BVI, runoff of soil during erosion often ends up in the ocean with negative impacts to water quality and marine life. Gully erosion is erosion resulting in a relatively deep incision of the soil surface caused by concentrated overland runoff. Rill erosion is small eroding channels produced by surface runoff. n.

Turbidity is a measure of the ability of a water sample to transmit light. High turbidity (poor light transmission) is normally caused by the presence of suspended matter such as clay, silt, fine organic matter, and microscopic organisms. Turbidity is a generally associated with “muddy water” often seen in coastal waters after a storm.


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2.4

Where Does Water go?

When rain falls on dry ground, some of the water soaks in to the soil. Some water that infiltrates the soil will remain in the shallow soil layer, where it will gradually move downhill, through the soil, and eventually enter the sea. The amount of water that will soak into the soil over time depends on several watershed characteristics: •

Soil characteristics: Clay and rocky soils absorb less water at a slower rate and behaves as an impermeable layer. Soils absorbing less water result in more runoff overland into the sea. In BVI, soils form a shallow layer and are limited in the amount of water they can absorb. (See also Sec.3.5.1.2. Soils)

Soil saturation: Like a wet sponge, soil already saturated from previous rainfall cannot absorb much more because of water table rise. So, more rainfall will become surface runoff.

Land cover: Some land covers have a great impact on infiltration and rainfall runoff. Impervious surfaces, such as parking lots, roads, and developments, act as a “fast lane” for rainfall to flow into watercourses and storm drains that lead directly to wetlands or the sea. Flooding becomes more prevalent as the area of impervious surfaces increases but can be mitigated if pervious materials are used in places such as parking lots to allow the infiltration of water. Unpaved areas that have been cleared of vegetation lead to more erosion, sediment, and pollutants entering coastal waters.

Slope of the land: Water falling on steeply-sloped land runs off more quickly than water falling on flat land. (See also Sec. 3.5.1.1. Slopes)


- 26 -

2.5

requirements for Developing in a Watershed

The following list provides some of the key legislation and recommendations but is not exhaustive. It is up to the property owner of developer to know all the applicable BVI laws, regulations and policies prior to development. •

Protection of Trees and Conservation of Soil & Water, 1954 / 1965 (Cap 86): Legislation that sets forth provisions for the protection of forested areas, water areas and trees.

Virgin Islands Planning Act, 2004; Schedule II Part IV (Amenities) Sec. 8: Prohibiting, regulating and controlling the deposit or disposal of waste materials and refuse, the disposal of sewage and the pollution of rivers, lakes, ponds, gullies, beaches and the seashore.

Virgin Islands Statutory Instrument 1999 No. 55, Buildings Ordinance (Cap. 234) – Building Regulations 1999, Sec. 174: Land drains linked to septic tanks shall be laid in open areas not surfaced with impervious materials in accordance with the following requirements: (e) no pipe runs shall (i) be located within 4 feet of one another or of a building or a site boundary; and (ii) be located within 50’0” of any well or stream or open water source.

Virgin Islands National Park Act, 2006: Part VII (Controlled Activities) Sec. 49: (1) A person shall not, within a park or other protected area established under Part III of this Act, (b) obstruct, pollute, or divert any ghut river, coastal waters or other body of water.

Virgin Islands Fishery Act, 1997. Part V Conservation Measures Sec. 39: (1) The Minister may, having regard to any other enactment relating to the prevention or control of marine pollution, take such measures as he considers necessary (a) to prevent, reduce and control pollution of the fishery waters and the marine environment generally from any source; and (b) to ensure that activities in the fishery waters are so conducted as not to cause damage or adversely affect the living resources of the fishery waters or the waters of the other States.

Department of Disaster Management Hazard and Vulnerability Assessment (HVA) recommendation for building near natural drainage ways (ghuts): DDM’s recommendations for mitigation measures is to undertake a survey of the ghut at the site by a qualified professional to support the development of a drainage plan in order to determine the impact of the development on natural drainage patterns in the surrounding area. Based on this survey, a ghut reserve has to be defined using a minimum setback of 30ft. (10m) from the edge of the ghut to reduce or avoid any impact to the watershed. (See also Appendix 2: Elements and Use of a Hazard Vulnerability Assessment).

Developments must also adhere to the goals and objectives outlined in the Climate Change Adaptation Policy, the VI Wetlands Policy and the VI Beach Policy.


- 27 -


- 28 -


- 29 -

3

DeVeLOPMent PLanning

“There is nothing wrong with change if it is in the right direction� -Winston Churchill


- 30 3.1

introduction

Planning problems we face today result from mismatches between land use and our physical environment. These ‘mismatches’ originate from (1) poor land use decisions early in the planning process of projects due to a lack of scientific knowledge about the environment, like a landowner who unwittingly builds a house on an unstable slope; (2) negative impacts from environmental change after development has occurred, as illustrated by a property owner plagued by flooding caused by a new development upland from his or her site; (3) social change, as represented by a resident living on a narrow street that was once used by donkeys but is now used by SUVs or once quiet areas now plagued by noise, air pollution, and safety problems and; (4) violations of human values concerning the environment exemplified by the eradication of a species, destruction of ecosystems, and the alteration of historically valued landscapes [34]. When planning a development, it is important to identify goals in order to guide the process. For all developments in the BVI, no matter how small or large, the watershed goal described in section 2.1* is essential for property owners, developers and other stakeholders to strive to attain. In order to achieve attainable results, development planning must include techniques and practices that provide the developer and stakeholders the ability to reach this and other goals.

*�Our built environment is properly designed, managed and enforced according to localized physical characteristics using best practices in order to maintain functional hydrological systems


- 31 that will in turn, promote reduced flooding in low lying areas and sediments from entering coastal waters.”

This chapter identifies what needs to be considered during the early stages of a development prior to any land being cleared. In many cases, people clear their property in order to get a better view of the area, but this is considered “development” as defined by the Virgin Islands Planning Act of 2004 and is illegal without permission from the Planning Authority. Under this Act, development is defined as the “carrying out of building, engineering, mining, earth moving or other operations, in, on, over or under land...”. The primary components of development planning are: (1) application and approval process, (2) technical planning, and (3) design planning, described in the following sections.

However, planning in general should not be regarded as a linear sequence of events but as an interrelated circuit of activities that occur before any land is cleared or construction even begins. An effective planning process includes continuously repeating the circuit in which a check and balance relationship often emerges among decision makers, technical planners, and designers [34].


- 32 3.2

application & approval Process

Whether you are an owner or a buyer, you may already have an idea of what you want to build. However, until the property has been surveyed, it is likely that no one knows for sure what is on the property. Having the property surveyed, accompanied by an engineer is the first step, even if you have not purchased the property. This will save you money when it comes to the design of your home or development. It is much less expensive to adapt your home or development to the existing environment rather than try to re-create the environment after the fact. With up-to-date surveys, the architect will be able to create designs based on the topography that will subsequently minimise erosion. Once you have an idea of what you want to do, talk with Town & Country Planning Department (TCP) before doing anything else. Understanding the application and approval process early on in your development will save you time and money. The application and approval process is a sequence of events that will need to be completed or signed-off prior to any final decisions by the Planning Authority or Cabinet. The figure below is a simplified flow chart of the process and is based on the Virgin Islands Planning Act of 2004 and the Development Planning (Environmental Impact Assessment) Regulations, 2012. Applicant/Agent submits application to TCP (including drawings and fees)

TCP presents application to the Development Control Authority (DCA) for consideration and a decision

Processing of application: Review, site inspections, public consultation and recommendations

DECISION

APPROVED

Return approved application to applicant/agent

TCP monitors progress of development

Applicant commences construction within one year, providing other approvals have been received.

APPROVED WITH CONDITIONS

TCP informs applicant/agent of conditions and the required amendments

Agent modifies drawings to meet DCA conditions of approval

DEFERRED

TCP informs applicant/agent of reasons for deferral

Agent modifies drawings to meet DCA requirements

REFUSED

TCP informs applicant of reasons for refusal

Applicant may appeal refusal or submit new application


- 33 3.3

technical Planning

Once you have spoken to TCP, they will direct you to the next step in the process. In many cases a pre-development discussion (usually referred to as a ‘pre-planning’ meeting) will be recommended by TCP. This meeting allows for the different government agencies to identify any issues or concerns they may have prior to an application being submitted for review. This meeting will also help the property owner or developer better understand what may be required in order to be granted approval, such as submission of an environmental impact assessment (EIA) (see also Appendix 1: Elements & Use of an Environmental Impact Assessment). The scale of the development and its location (hillside or coastal) will determine the stakeholders that may be included in the discussions. The following lists provide some of those stakeholders that are recommended to be present:

Any development • • • • •

Developer/Property Owner(s) Town & Country Planning Department Surveyor Engineer Architect

Additional stakeholders may include (depending on the scale of the development): • • • • •

Member of the Planning Authority Department of Disaster Management (for Hazard Vulnerability Assessment) Geotechnical engineer Environmental Health Department National Parks Trust

Coastal Developments may also include (depending on the scale of the development): • • •

Conservation & Fisheries Department Coastal Engineer Oceanographer and/or Marine Biologist

Understanding the application and approval process can help you save time and money. The pre-planning meeting may further help to reduce future or unnecessary costs, as well as speed up the process for approval. Additionally, technical experts in the various Government agencies can provide a wealth of information in these early stages of your development.


- 34 -

3.4

Design Planning

As mentioned earlier, the planning process is an interrelated circuit of activities. Once the first wave of technical information has been identified (in a pre-planning meeting as discussed above), design planning may begin. However, more technical information may be required, creating this ‘loop’ of activities between technical planning, design planning, and the application process. The rest of this chapter describes the physical characteristics in a watershed that, in part, make up a significant portion of the technical information required prior to development and why this information should be identified before clearing a property. Knowing the physical characteristics of a site also allows the designer and builder to incorporate these physical features into the design of the development. Collecting the information at this early stage will also greatly reduce costs by minimizing problems caused by erosion and additional costs from clearing more land than just the footprint of a development. You may also want to review Disaster Management’s “Handbook for Homeowners & Property Developer” available on their website (www.bviddm. com) under ‘Publications’.


- 35 3.5.

Physical characteristics 3.5.1.

Topography

A thorough understanding of the site’s topography is important. This allows the building designer and contractor to work with the natural contour of the land to reduce erosion, minimize excavation, reduce flooding, and minimize costs. Topographic site features that should be mapped for the site include: slopes, soils, vegetation, rocky outcrops, hydrological characteristics (i.e. ponds), and (if applicable) coastal features. 3.5.1.1.

Slopes

The loss of topsoil due to erosion can affect the growth of crops and native plants, and can clog ghuts and other waterways with displaced soil. Causes of soil erosion include gravity, wind, and fast moving water. 3.5.1.2.

Soils

Identifying and understanding soil composition on site, prior to construction (or even purchase), is critical in order to prevent costly mistakes. Varying soil types are better suited to some uses than others. For instance, some soils are appropriate for use with septic systems, construction fill, road beds, and building foundations, while others are not. Soils are made up of different percentages of sand, silt and clay. Numerous websites provide simple do-it–yourself soil testing to determine what types of soils you have on your property. Soils sustain life. Without it, we are unable to produce food or even develop antibiotics to fight illness. Soil is a nonrenewable resource and therefore, important to protect. 3.5.1.3. ‘

Vegetation Types

‘Vegetation’ is the collective plant coverage and ‘vegetation types’ are named categories of plant communities defined on the basis of shared composition (floristic) or structural (physiognomic) characteristics that distinguish them from other kinds of plant communities or vegetation[35]. Being familiar with the vegetation types within a development is a best practice since some types tend to play a special role in erosion control or hydrologic function. Knowing the vegetation on a property also allows for identification of any endangered, threatened, vulnerable, or locally important species. The following list is not the complete list of vegetation types found in the BVI but identifies their role in erosion control and will require a plan in place in order to protect, minimize, or repair any disturbances to the vegetation within these areas.


1

- 36 1. Coastal Wetlands and Fringing Mangroves: holds runoff (sediments, pollutants) from upland areas prior to entering coastal waters and are critical coastal barriers that protect inland areas from storms and high tides 2. Native Grasslands: are highly threatened by foraging livestock but provide a thin cohesive coating of the top layer of the soil in grass among grass clumps which prevents wind and water erosion [36].

2

3. Dry Coastal Scrub and Woodlands: have been reduced by years of agriculture, livestock grazing and deforestation which have caused soil depletion and island erosion. 4. Dry Coastal Forests: are similar to dry coastal scrub and woodlands and suffer from the same problems but this vegetation type also contains dense stands of trees. 5. Coastal Beach Foredune: is the first dune ridge forming at the back of the beach and plays an important role in storing sediment and protecting the land from extreme wave and tide conditions. 6. Coastal Dunes: represent “storages� of sand trapped by vegetation so when vegetation is removed, the loose sand can be easily carried away by wind and waves thus causing severe beach erosion. (See also Sec. 3.5.4.1. Dune Systems).

3

4

7. Coastal Hedges: form a low line of vegetation immediately behind a beach and are often dominated by seagrape (Coccoloba uvifera), button mangrove (Conocarpus erectus), seaside mahoe (Thespesia populnea), beach morning-glory (Ipomoea pes-caprae) and other low shrubs and vines, all of which help control beach erosion as well as provide habitat for nesting hawksbill (Eretmochelys imbricata) sea turtles.

5

6

7


- 37 3.5.1.3.1.

Endangered Species

All plants found in this section are found on the IUCN’S Red List (Critically endangered and endangered) and must be protected prior to any development. 1. “Pokemeboy” (Vachellia anegadensis) is a spiny tree in the bean family and only occurs on Anegada, nowhere else on Earth. Status: Critically Endangered 2. “Kiaerskov’s Lidflower” (Calyptranthes kiaerskovii) is a tree that was originally described in 1895 from a single specimen found in Tortola but is now believed to only be found in the Gorda Peak National Park. It may still exist in Puerto Rico, but evidence is limited. Status: Critically Endangered

1 2

3. “Thomas’ Lidflower” (Calyptranthes thomasiana) is an evergreen tree up to 4m and occurs in moist forest. It is currently only found in the Gorda Peak National Park. Status: Endangered 4. “Puerto Rico Manjack” (Varronia rupicola) is a small woody shrub, originally described as endemic to Puerto Rico but populations there have rapidly declined, though, apparently, a few specimens continue to exist. It is found in western Anegada. Status: Critically Endangered 5. “Commoner Lignum Vitae” (Guaiacum officinale) is a very slow-growing tree found in lowland dry forests. A number of lignum vitae trees were cut down on Beef Island when the runway was extended in the early 2000’s. Also found in the wild on Anegada. Status: Endangered

3

6. “Sebucan” or “Prickly Web” (Leptocereus quadricostatus) is a large bushy cactus 3-4m high originally described as endemic to Puerto Rico but a sub-population was found in the Western Salt Pond complex in Anegada. Status: Critically Endangered 7. “Alfillerilo” (Machaonia woodburyana) is a small multi-stemmed, spiny evergreen shrub 1.5-3m in height occurring in dry forest and coastal thickets. It is found on the edge of the Gorda Peak National Park, and a few scattered locations at Leverick Bay and likely on the forested slopes immediately to the west on Virgin Gorda. Status: Critically Endangered 7

6

5

4


8

- 38 8. “Caribbean Mayten” (Maytenus cymosa) is a rare flowering tree that occurs in dry, coastal woodland in Puerto Rico, the US and BVI. The largest population is in the Gorda Peak National Park but a single tree was once found at Savannah Bay, Virgin Gorda. Status: Endangered 9. “Wire Wist” (Metastelma anegadense) is unique to the sand dunes of Anegada. A population of Metastelma found at Leverick Bay is likely this species and represents are first record for the species on Virgin Gorda. It twines itself around shrubs that cover the area. Status: Critically Endangered

9

10. “St Thomas Pricklyash” (Zanthoxylum thomasianum) is an evergreen shrub tree found in Puerto Rico, the USVI and BVI in dry forests and shrublands. Status: Endangered 3.5.1.3.2.

Locally Important Species

All plants found in this section should be protected or relocated as they are an important species to BVI although they may not currently be listed under the IUCN’s Red List of endangered species. They are also recommended for re-vegetation in the appropriate locations suitable for their survival.

10

1. “Silver Palm”, “Thatch Palm”, “Tyre Palm” or “Broom Palm” (Coccothrinax alta) is now a synonym of Coccothrinax barbadensis, a species found from Hispaniola to Trinidad. It is found primarily along the north coast of Tortola, Guana, Scrub and Moskito Islands. The leaves of the palms were used to make crafts such as hats and brooms. It usually grows between six and ten feet and prefer sandy, limestone, non-acidic soils. Native palms do not require much if any fertilization. 2. “Turpentine” (Burseria simaruba) is a tree with a shiny dark red bark and serves as excellent wind protection. 3. “White Cedar” (Tabebuia heterphylla ) native to the BVI and the national tree is often planted in the islands as an ornamental tree bearing masses of pale pink trumpet blossoms in the spring. The wood is traditionally used in construction and for the ribs of boats. 1

2

3


- 39 4. “Calabash Tree” (Crescentia cujete) have fruits that are widely used for crafts such as bowls, cups, as well as ornaments and musical instruments.

5. “Mampoo” or “Loblolly” (Pisonia subcordata) is often the largest species in the dry forest environment and is able to resist long periods of drought.

6. “Bullet wood” (Manilkara bidentata) is a hardwood tree used for construction materials.

7. “Century Plant” (Agave’ missionum) can withstand such hardships as salt spray, steep hills, strong winds, poor soil, low rainfall and full intense tropical sun. However, many have died or are dying as the result of a disease that scientists continue to research. It was named because it was thought they only flowered once every one hundred years and then died after flowering. Recent evidence has shown that the flowering usually takes place on average after 28 years and the plant itself will live approximately 50 years. 8. “Butterfly Orchid” (Psychillis macconnelliae) is an epiphyte on small trees and shrubs in a variety of habitats. The flowers bloom in various shades of red to lavender. Little is known about this orchid or what its habitat requirements are, but as with most orchids, it is likely that it is threatened by habitat loss and illegal collecting.

9. “Indian Mallow” (Bastardiopsis eggersii) is tree that grows 10-15m in height and has somewhat heart shaped leaves covered in short soft hairs which gives it a silvery velvet like look from a distance. It was once recorded on Tortola but is now only found on Jost Van Dyke and Little Jost Van Dyke.

10. “Barrel Cactus” or “Turk’s Cap Cactus” (Melocactus intortus) is often found as ground cover and found throughout the Caribbean. The name of the plant itself comes from its spiny red cap, thought to resemble a fez.

11. “Fishlock’s Croton” (Croton fishlockii) was discovered by W. C. Fishlock in 1919. A small shrub considered to be a Virgin Gorda “belonger”.


- 40 3.5.1.3.3.

4 1

Invasive & Problematic Species

Reducing the number and presence of invasive species is considered a best practice since it is the second greatest global threat to biodiversity, after habitat destruction [37]. As hotel and resort developments increase in number and scale, native plant species and their habitats are disappearing. Many of the native species are better adapted towards reducing erosion and therefore need to be protected. Native species also assist with water conservation because they are adapted to our climate and do not require frequent watering, unlike most exotic plants imported for use in landscaping. Of the many introduced and problematic species, the following are those of concern and should be removed from a development and replaced with native vegetation:

2

1. “Beach Cabbage”, “Sea Lettuce”, “Beach Naupaka” or “Hawaiian Sea Grape” (Scaevola taccada or its synonym is Scaevola sericea) is a beach shrub originally from the Indo-Pacific and introduced as a landscaping plant pushing away the native Caribbean “beach berry” or “inkberry” (Scaevola plumieri). The native species has a similar flower but has black fruits while the invasive species has white fruits. 2. “Tan tan”, “Guinea Tamarind” or “Wild Tamerind” (Leucaena leucocephala) displaces native vegetation and is a low quality wildlife habitat since the flowers and fruit are not food for wildlife.

5

3. “Guinea grass” (Megathyrsus maximus) displaces native species by dominating areas and preventing other plants from growing. 4. “Coral Vine” (Antigonon leptopus) forms dense mats that can smother plants on which it grows.

3

5. “Purple rubber vine” (Cryptostegia madagascariensis) is originally from Madagascar and introduced as an ornamental and threatens waterways, pastures, forests, and mangroves.

6 7

6. “Water hyacinth” (Eichhornia crassipes) is one of the worst aquatic weeds in the world with populations known to double in as little as 12 days with infestations that can block waterways. 7. “Casuarina” or “Australian Whistling Pine” (Casuarina equisetifolia) is an evergreen tree that can grow up to 115 feet in height and was originally from Australia and introduced as a shade tree. Where it establishes it may form dense stands with negative impacts on native flora, fauna, soil character and dynamics. Commonly found in Anegada.


- 41 8. “Neem” (Azadirachta indica) crowds out native vegetation. NOTE: Although the neem bears the label of “an invasive” it has several positive attributes. The neem tree a close relative to the Mahogany, is sturdy and resistant to drought. It is an important honey tree and extracts of neem have been found to cause sterility in insects. It is used for medicine, in cooking and neem oil is a very effective pesticide that can be used safely in the garden with no negative effects on the environment. 9. “Manchineel” (Hippomane mancinlla) is a species of flowering plant native to the Caribbean. The name “manchineel” (sometimes written “manchioneel”) is from Spanish manzanilla (“little apple”), from the superficial resemblance of its fruit and leaves to those of an apple tree. A present-day Spanish name is in fact manzanilla de la muerte, “little apple of death”. This refers to the fact that manchineel is one of the most poisonous trees in the world. Its milky white sap contains phorbol and other skin irritants, producing strong allergic reactions. Standing beneath the tree during rain will cause blistering of the skin from mere contact with this liquid (even a small drop of rain with the milky substance in it will cause the skin to blister). Burning the tree may cause blindness if the smoke reaches the eyes. The fruit is said to be possibly fatal if eaten.

3.5.1.4.

Rock Outcroppings

In the BVI, we have a few quite colourful terms to refer to the large but beautiful rock outcroppings common to the area that give many contractors and earth-movers headaches during development. Instead of cursing them, use these rock outcrops to create interesting aesthetic design features that also serve the very important purpose of anchoring steep slopes and preventing soil erosion. In some instances, the rock needs to be removed from steep slopes to avoid future slides, therefore, an assessment needs to be made as to whether or not the rock outcropping is stable or not. Some ‘boulder fields’ also provide a desert-like habitat that contain very rare plant species that are native to the BVI.


- 42 3.5.2.

Hydrology

Hydrology is the occurrence, circulation, distribution and properties of water. Understanding the hydrology of a site is a best practice in order to take the necessary steps to minimize flooding, erosion, and property damage both on and off site. Important information to identify, define, and map include the location(s) of any water pathways (or potential water ways) within the property and whether or not the property is prone to flooding during periods of heavy rainfall. If it is prone to flooding, it is important to understand why it is prone to flooding; particularly if poor development practices upland of the development is the primary cause. 3.5.2.1.

Ghuts

It is important to remember that a ghut is a ghut. These natural water paths found within a property, including those on adjoining parcels must be identified, defined and mapped, their locations included in the designer’s or drafter’s plans and shared with all stakeholders in order to minimize and avoid damage or to anticipate expensive preventive or corrective measures. Identification of natural water paths (even if water has not been seen in it recently) on the master plan allows for the maintenance of natural drainage patterns and, if disruption of natural patterns occurs, allows for restoration of the natural water paths during the post-construction phase. This is particularly important in the case of ghuts that rarely have running water. These ghuts are natural “contingency” plans for stormwater drainage during extreme events. As future development continues, these dry ghuts most likely will eventually be reactivated as wet ghuts. If it is normally dry, expect it to be wet at some point in the future! Construction in ghuts is a poor practice. In fact, a ghut reserve is defined using a minimum setback of 30 ft. (10m) from the edge of the ghut in order to reduce or avoid any impacts to the ghut (See also Appendix 2: Elements and Use of a Hazard Vulnerability Assessment). Paving ghuts and natural drainage pathways is also a poor practice since it significantly eliminates the filtering effect and velocity control of water flowing down the hillsides, overwhelming the existing drainage system. A hydraulic and hydrological study is recommended for ghut development if a road is going to be built through the ghut. Bridges are usually going to be a better practice than the use of culverts. Watersheds will become more impervious (from increased development) and ghuts may need to be enlarged (or engineered) to cope with flash flood situations. This requires an overall development plan of that watershed designed by experienced engineers! Love your ghut! Healthy ghuts reduce erosion, minimize property damage and flooding, and create habitats for wildlife. The ghuts in the Virgin Islands have been severely damaged by either human activities such as removal of vegetation, altering the natural flow of water paths, or by filling and paving of ghuts. The impacts of the loss or alteration of ghuts and related soil and slope destabilization and loss of native habitat can drastically increase flooding, landslides, beach erosion, smothering of corals and seagrasses, as well as roadway erosion.


- 43 3.5.2.2.

Wetlands

Mangrove wetlands and salt ponds are described in section 3.2 (Watershed Anatomy) and we refer to either term here as simply “wetlands”. It is important to know that wetlands are defined by the presence of three factors: hydric soils, hydrology (water at/on the surface or within 1 ft/.3m of the surface for 12.5% of the growing season) and water loving (hydrophytic) plants so mudflats, depressional areas and some low areas bordering ghuts may be considered ‘wetlands’. When identifying and mapping wetlands for a development, it is best practice to demarcate the wetland and associated vegetation (particularly mangroves) and to also provide a fixed distance between the wetland and the development where nothing is allowed to be altered in any way or form. This area or the ‘buffer zone’ (also sometimes called a greenbelt), is simply a separation area between land use (external pressures such as development) and the wetland [38]. Many countries require buffer zones by law (at least 50ft/15m from the outer line of mangroves in the BVI) because of their great importance for flood control. Since wetlands act as basins for stormwater, extreme events could cause the wetland to “overflow”. Therefore, providing the space for such an event will reduce future costs from property damage caused by flooding. In order to determine an appropriate buffer zone, you may contact DDM or CFD. More information is available at: http://wetlandinfo.derm.qld.gov.au/resources/static/pdf/buffer-guide/wetland-buffer-guideline-final-221111.pdf It is also important to understand that as development continues throughout the Territory, the functional capabilities of wetlands may begin to decrease. Absorption of stormwater upland through soils and vegetation will decrease because of the increased number of impermeable surfaces (roads, buildings). Greater volumes of water (as well as increased solid waste and chemicals) will reach the bottom of hillsides and wetlands may not be able to accommodate all the stormwater. This supports the need for increased buffer zones, but additional areas may require some form of environmental engineering to improve the functionality of the wetland. Even more reason to use best practices upland to reduce the amount of water flowing down the hillsides!


- 44 3.5.3.

Coastal Features (If applicable)

Coastal features include all habitats found near the shoreline and include beaches, mangroves, seagrass beds and coral reefs. All of these can be affected by developments along and upland of the development. During the planning and design phase, the location of the site in relation to coastal features should be assessed and plans made to prevent erosion, sediment, and other pollutants from entering these waters where they will harm reefs, seagrass beds, and other marine species and habitats. Additionally, dredging or development of structures built over the water will require detailed reports of habitats and associated species that will be impacted as well as possible changes or impacts to coastal dynamics and oceanographic conditions. Issues such as “shading” caused by over the water structures will cause the corals to “bleach” [39] and reduce the productivity (photosynthesis) of seagrasses from lack of light [40], ultimately killing off those species. Other issues such as the development of groins may cause adverse impacts to neighbouring coastlines and even much further (1km+) from the development site.

3.5.3.1.

Beaches

A beach is the strip of land next to a body of water where loose materials (sediments) such as muds, sand, stones, gravels, shingles, coral fragments, or boulders have accumulated. The landward boundary of a beach is where there is a drastic change such as the line of vegetation, solid rock, the edge of another body of water (such as a salt pond), or even a building or a road. Seaward, the beach extends to the water depth at which waves are not capable of moving loose materials on the seafloor landward (also called the ‘depth of closure’). In the BVI, this is roughly at a water depth of 20-30m. In a review of the ecology and processes along landforms of tropical coasts, Spencer and Viles [41] contend that “a better understanding of the spatial and temporal complexities present in carbonate beach and shallow marine environments is an important precursor to effective coastal zone management”. Therefore, understanding the geographical, physical and historical differences of a beach (and its marine habitats) adjacent to a proposed development is an important element for designing and implementing the appropriate best management practices.


- 45 Beaches in the BVI are remarkably different from each other across the 60+ high volcanic islands and further complicated by the existence of low reef islands (i.e. Anegada, Sandy Spit). Beaches can be made up of materials that derive either from eroded rock landward of the beach and/or from marine particles (carbonate) such as molluscs, foraminifera (tiny marine animals with shells), and coral. Depending on the orientation of a beach to incoming wind and waves, and habitats that lie in front and behind the beach, not only does the amount of eroded rock found within beach sediments differ, but even the size of the sediment particles (sand, pebbles or boulders) that make up the beach differ from island to island. As a general rule of thumb, beaches along the north shores of the northern island chain—Tortola, Guana, Camanoes, Dog Islands, and Anegada—have the most amount of carbonate in the sediment [27]. This is primarily due to the highly productive Horseshoe Reef and the carbonate bank between Tortola and Anegada that produces large amounts of carbonate sands. With prevailing trade winds and waves, carbonate sediments are simply driven onshore to create most of the beaches in the BVI. Beaches along the southern island chain—from Norman Island to Virgin Gorda—have carbonate sediments but have been diluted with eroded rock such as quartz from the hillsides over millions of years. Additionally, larger sediment sizes, produced from coral rubble, pebbles, and boulders, are more commonly found along the southern shorelines because waves are not as energetic from the south to break down marine particles to smaller sand grain sizes [27]. Numerous beaches throughout the BVI are turtle nesting beaches. Removal of vegetation on a nesting beach will reduce the chances of nesting sea turtles, particularly hawksbill turtles. Therefore, development along a nesting beach requires special consideration to ensure sea turtles continue to nest on a particular beach. (More information about turtle nesting beaches in the BVI is available through the Conservation & Fisheries Department. Best practices on nesting beaches can be found at: http://www.barbadosseaturtles.org/documents/manual.of.best.practices. safeguarding.nesting.beaches.pdf


- 46 Mainland Attached Beaches

Oil Nut Bay East

Rogues and Trunk Bay

Linear

Embayed

George Beach Cuspate (Tombolo)

Spits

The shapes of beaches in the BVI, seen from a bird’s eye view, can be classified into three major categories (mainland attached, barrier or spit) and further subdivided into linear, embayed or cuspate forms [27]. These characteristics provide insight into a range of characteristics about the beach such as wave exposure, water transport pathways, formation of littoral cells, temporal morphologic changes and sedimentary characteristics.

Blu at South Sound

Sprat Point Barrier Beaches

Anegada Linear

South Bay, Salt Island Embayed

Dead Chest

Cuspate (Foreland)


- 47 3.5.3.1.1.

Seasonal Beach Behaviour

It is a best practice to understand a beach’s seasonal and long-term behaviour for all developments located near a beach. Like the physical differences of beaches in the BVI, they also behave differently from each other. Beaches appear to come and go as seasons change. This is caused by accretionary waves that bring sand to the beach during the summer and erosional storm waves that take sand offshore during the winter [42]. This is a natural process that allows the shoreline to protect itself from the higher energy conditions of the winter. Additionally, there are occasional storm events that reshape beaches. These are more dramatic, but are still part of the natural process. Just because a beach appears to severely erode after a storm doesn’t mean it is gone forever. Similarly, just because a beach appears to gain sand after a storm doesn’t mean it has increased in size forever. Either way, it could take a few years for the beach to return to its steady size and shape. It is important to remember a sandy coast adjusts its shape based on its response to wind and waves, as well as whether or not there is a supply of sand available. This ability to change shape is why beaches (which are just loose piles of sand) can survive when other structures such as walls and cliffs collapse (see also Sec. 4.4.1.2. Shoreline Stabilization Implications).

Sandy Spit

Sandy Spit


- 48 3.5.3.1.2.

Historical Beach Behaviour

Understanding long term changes on small tropical islands is vital for management purposes, but only a few Caribbean islands have consistent data sets spanning a five-year period [3]. However, long term changes (10+ years) can be determined through the use of aerial photography and a powerful mapping programme called Geographic Information Systems or GIS for short. This information and technology is available in the BVI through various Government agencies such as TCP, CFD, and DDM that make up the National GIS council.


- 49 A number of beaches on the volcanic islands in the BVI have been studied to determine long-term changes using aerial photography with GIS. The results show that these beaches are generally stable except where permanent structures have been built close to the shoreline or where extensive mining has occurred [27] (see also Sec. 4.4.1.2. Shoreline stabilization implications). If your development is near a beach, collecting this information (either through Survey, DDM or CFD) is extremely important to determine the best possible setback to protect your property based on the historical behaviour of the beach (see also Sec. 4.1.2.3. Setbacks & Buffers). Long-term beach behaviour on Anegada is entirely different to that found on the volcanic islands. This is due to its underlying geology, orientation to wind and waves, and the existence of the Horseshoe Reef. Because Anegada has unique characteristics vulnerable to coastal erosion, a special section was created in this manual (see also Sec. 3.5.4. Anegada). Future changes in beach behaviour should also be taken into consideration during the planning stages of a development. Sea levels are expected to rise .7in (0.018m) – 23in (0.590m) in the Caribbean by 2099 [43]. The frequency and intensity of storms are expected to increase [5] and even worse, if coral reefs continue to decline, reefs that protect the coastline will no longer be capable of slowing incoming waves [44]. 3.5.3.2.

Mangroves

Mangroves may not always be associated with wetlands, but can merely fringe the coastline. These fringing mangroves also serve to slow incoming waves and stabilize the land areas behind them from the erosive forces caused by storms [45]. Mangroves such as the ones in Paraquita Bay also serve a unique function of protecting millions of dollars’ worth of yachts during the hurricane season. Like buffer zones mentioned earlier for wetlands, it is a best practice to provide an area of space (buffer zone) between fringing mangroves and a development in order to protect the mangroves from accidental destruction. In other countries, this buffer zone ranges from 26ft (8m) in Ecuador to 66ft (20m) in the Philippines [46]. When the issue of “obstruction of view” comes into play, mangroves can easily be pruned without destroying their vital root systems that hold the shoreline in place. For best practices in pruning see: http://manatee.ifas.ufl.edu/seagrant/pdfs/Mangrove_Trimming_Guidelines.pdf .


- 50 3.5.3.3.

Seagrass Beds

Seagrasses are usually regarded as an eyesore for developers and most people hate the feeling of slimy grass under their feet. However, removal of seagrasses can significantly alter beaches [47] because seagrasses help to slow down incoming waves [48], as well as stabilize the seafloor [49]. Consequently, removal of seagrass destabilizes the seafloor, which will cause water to become cloudy (turbid) and increase the risk of beach erosion [50]. Additionally, dead seagrasses found on the beach itself help to hold sand in place, as well as enhance dune formation [51, 52]. Dead seagrasses also provide a home to fauna that subsequently serve as food for seabirds [53, 54]. “Cleaning� the beach, usually by raking, not only reduces the numbers of shorebirds present but can also increase the amount of flies on a beach [55].


- 51 -

3.5.3.4.

Coral Reefs

Fringing coral reefs surround every island and Anegada’s Horseshoe Reef covers an area of 133km2, making this one of the largest contiguous reefs in the Caribbean. It is also the most productive reef in the BVI [56]. Coral reefs serve as a source of the sand we see on our beaches, as well as protect the shoreline by slowing down incoming waves [44] . Although reefs have been drastically declining since the late 1970’s from causes such as coral disease, hurricanes, and bleaching, this does not mean we cannot do anything locally to help protect those remaining healthy reefs. Best practices of reducing the amount of sediments and pollutants entering coastal waters will help increase the resiliency or the ability of a reef (or any natural resource) to resist or adapt to change and maintain key functions and processes [57, 58].


- 52 -

Lamarck’s Sheet Coral (Agaricia lamarcki)

When planning a coastal development, all reef-building corals (stony corals) must be identified within the boundaries of an in-water development, or those just offshore of a land-based development. Special attention must be paid to endangered coral species (similar to those plants that need to be identified on a property during the planning stage). The following coral list includes those species listed as critically endangered, endangered, or vulnerable on the IUCN’s Red List (http://www.iucnredlist.org/).

Staghorn Coral (Acropora cervicornis)

The National Oceanic and Atmospheric Administration (NOAA) currently lists two (the first two on the list below) of those identified by the IUCN as critically endangered as ‘threatened‘ under the US Endangered Species Act (ESA) of 1973, while seven other species are proposed to be added to the ESA. The ESA listing of elkhorn and staghorn corals is proposed to be changed to endangered. Regardless of classification by various governments or organisations, all reef-building corals need to be protected from erosion or impacts caused by developments.

Elliptical Star Coral (Dichocoenia stokesii) Mountainous Star Coral

(Montastraea faveolata)

Elkhorn Coral (Acropora palmata) Pillar Coral (Dendrogyra cylindrus)

Star Coral (Montastraea franksi)

Boulder Star Coral (Montastraea annularis)

Rough Cactus Coral (Mycetophyllia ferox)


- 53 3.5.3.5.

Oceanographic Processes

Developments along the coast, in or over the water require special consideration because building in these areas is not the same as developing upland. These projects include, but are not limited to, marinas, docks, over-the-water structures, dredging, land reclamation, and coastal stabilization. The dynamic processes of oceanographic conditions such as wind and waves vary from island to island. Understanding these processes (the nature of the forces acting on the coast) is a best practice and a vital component to designing a sustainable development. In the majority of these types of developments, a team of experts will be required (marine biologist, oceanographer, coastal geomorphologist, and a coastal engineer) to carry out studies on the specific location in which a plan is being proposed. A development design will be required to have minimal impacts on the marine environment, ensure there will be no adverse impacts down or up-shore from the development (erosion or accretion), not be at risk of overwash from waves (especially from high energy waves due to swell, hurricanes or extreme swells) and have considered climate change impacts and future sea level rise.


- 54 3.5.4.

Anegada

Unlike the volcanic islands in the BVI, Anegada formed as part of a massive coral reef system between 119,000 and 130,000 years ago [59, 60] when sea levels were in the range of 8ft (2.5m) to 49ft (15m) higher than today’s sea level [60]. After this period, the climate cooled and led to the last ice age, when sea levels dropped on an average global scale of almost 395ft (120m) [61, 62, 63], a time in which you could walk from Anegada to Puerto Rico [64]. The massive coral reef system died off and began transforming into a solid slab of limestone from years of exposure to sun, wind, rain and the many other elements of nature. Then about 20,000 years ago, sea levels began to rise to the sea level we see today [65, 66, 67]. As the sea levels were rising, a fringing reef to the north of Anegada, patch reefs to the south and a barrier reef to the southeast of the island formed into what is collectively known as the Horseshoe Reef and covers an area of approximately 51 sq. miles (132km2). The island of Anegada is geologically divided into two parts, the Anegada Limestone Formation (ancient coral reef) on the eastern half of the island and the Anegada Ridge Plain Formation that rims the north-eastern part of the Limestone Formation as well as makes up the entire western half of the island. The Ridge Plain is a large sand dune system that surrounds seven interconnected ponds that make up one of the largest mangrove wetlands in the Caribbean [68, 23] (see also Sec. 3.5.4.1. Dune Systems) While the island is geologically divided into two parts, the approximate 30 miles (48km) of shoreline exhibits four distinctive coastlines [27]. This is based on the coastline’s orientation to prevailing wind and waves as well as each coastline’s long-term behaviour. While each of the four coastal sections of Anegada exhibit specific behaviours, the entire sedimentary systems works as one entity and is capable of adjusting to changing wind, waves and sea levels.


- 55 Littoral sand movement is generally westward along the northern shoreline with circulation cells that move sand onshore from the reef as well as through outflows in reef channels. Long-term changes also indicate continued sediment production and that the island’s sandy coastline is rotating in a counter-clockwise motion. However, this represents the island’s historical resiliency by its ability to aggressively adjust to change. Near-shore coastal development, particularly shoreline stabilization along the Anegada Ridge Plain Formation will permanently disrupt Anegada’s natural sedimentary behaviour. Long-term implications from developments would include the island’s inability to naturally adjust to impacts such as sea level rise, increased number and intensity of storms caused by climate change [69,70] as well as accelerated erosion down-drift (up to several miles) of the development. (See also 4.4.1.2. Shoreline Stabilization Implications).


- 56 -


- 57 -

3.5.4.1.

Dune Systems

The Anegada Ridge Plain Formation is the largest dune system found in the BVI. (Long Bay-Belmont, Tortola and Savannah Bay in Virgin Gorda are the only other dune systems in the BVI that have not been disturbed by development). These dune systems formed from the accumulation of large volumes of sand by wind and wave action over a long period of time. As sand accumulated, vegetation was able to trap the sand and hold it in place. Over time, numerous ridges formed on the western side of Anegada and are clearly visible from aerial photos. Since dune systems are flexible barriers which absorb wave energy by moving and adjusting their shape and position, this dynamic behaviour of dunes and beaches inevitably conflicts with development. Because dunes and beaches are interdependent of each other, they have to be managed together and cannot be viewed in isolation from other components of the coastal sedimentary system. The following list identifies best practices that must be adhered or expect to have severe erosion within your development. • • • • • •

Anegada requires a 200ft (61m) setback from the high-water mark; however, the vegetation line is a more suitable location in which to measure from since the vegetation line is stable over long periods of time. The high-water mark changes as often as on a daily basis. Developing on dunes must be done on pilings. Solid structures will not allow the movement of sand and will ultimately result in erosion. Pathways must be designated in order to reduce the amount of trampling on dune vegetation. Re-vegetation projects for denuded areas are crucial to conserve dune systems (see list of recommended dune plants in Sec. 5.3.1. Acceptable Vegetation). Stairs to the beach must be temporary structures such as stairways built out of wood. Although sand mining was once a common practice throughout the Caribbean, advancement in the scientific understanding of sedimentary systems reveals mining from dune systems and beaches is an exceptionally poor management practice.


- 58 -


- 59 -

4

4.

CONSTRUCTION

cOnstrUctiOn

“For every action, there is an equal and opposite reaction”. -Sir Isaac Newton


- 60 One of the most serious and potentially costly problems associated with land development is the increase in the amount and rate of runoff that reaches waterways and coastal waters. “Runoff” occurs when rainwater is not absorbed by the ground but flows downhill on the surface. This runoff includes not only the rainwater (often called stormwater) but also all the sediments (soils), nutrients, fertilizers, rocks, garbage and anything else that the flowing water can carry with it down the hillsides. The process of rainfall, or even wind, wearing away the land surface is called erosion. Erosion is accelerated by human activities such as removing vegetation, compacting or disturbing the soil, changing natural drainage patterns, and by covering the ground with impermeable surfaces (pavement, concrete, buildings). When the land surface is developed in this manner, stormwater cannot seep into the ground and measures must be put into place in order to ensure runoff doesn’t leave the property during the construction phase, except when free from sediment and in a controlled manner so as to protect the watershed and environment below. ‘Erosion controls’ are the structural and non-structural practices used during the construction process to protect and hold soils in place and facilitate the establishment of vegetation within the construction site. Erosion controls are the primary means of preventing sediment transport in runoff but these controls work best when used in combination with ‘sediment controls’ as a second line of defence that can trap eroded sediments moved by stormwater before it leaves the construction site. The following chapter provides a number of different examples of best practices for erosion management and sediment controls as well as pollution prevention practices that can be used on a construction site. It is best to pick those combinations of practices that work together and are most suitable for the site. Just remember, it is much less expensive to prevent or control erosion and pollution at the beginning of the construction phase of a development than it is to control sediments once they leave a construction site. If in doubt seek advice. Time spent on recon is seldom wasted!!

EROSION CONTROLS + SEDIMENT CONTROL= BEST PRACTICE!!!


- 61 4.1.

Preconstruction

Several best practices for erosion control can be implemented between the development planning and construction phases of a development. In some cases, obtaining approval from the Planning Authority or Cabinet may still require additional information under a ‘condition of approval’ letter prior to starting construction. No matter what size the development, it is a best practice (in many countries, a requirement) to create an Erosion, Sediment and Pollution Prevention Plan (ESAPPP) prior to breaking ground. (These plans may also be called drainage plans, stormwater management plans, erosion control plans, etc., but they all mean the same thing). Understanding, documenting and implementing best practices before clearing for construction can save you time, money and a lot of headaches. (Especially since clearing land is considered ‘development’ under the Planning Act and is illegal without permission from the Planning Authority) These plans don’t have to be long and drawn out. They can even be just a series of simple, non-technical maps. Additionally, these maps can be useful for contractors and construction workers to understand where protected areas are located and what erosion and sediment control measures are in place. (See Appendix 4 for an example outline and explanation of an Erosion, Sediment & Pollution Prevention Plan). It is important to remember your ESAPPP needs to be based on accurate and up-to-date topographical maps of the existing conditions as well as the location of the development in order for BMPs to work. Otherwise you may spend a lot more money than you expect!


- 62 4.1.1.

Phasing & Scheduling

Figuring out what is going to happen and when it is going to happen can sometimes be complicated by the timeframe for Planning and Building Authority approval, scope of the project and by the time of year when construction starts. Phasing a project is a non-structural practice that can help reduce erosion considerably by minimizing the amount of disturbed soil when only a small portion of the site is exposed at any one time and reducing the amount of time that disturbed soil is vulnerable to erosion which includes but is not limited to, reducing the amount of time between clearing the footprint and putting control measures into place. Examples: • If you were developing a 15 acre housing project, rather than clear the entire 15 acres at the start of construction, only clear a 3 acre par cel, grade the area, install the utilities, pave the roads, construct the houses, landscape and seed the lawn areas, then move on to the next 3 acre parcel. • Limit vehicle traffic to designated areas or active construction work areas to preserve vegetation. • Use a chipper on tree clearing waste material and spread chips over exposed area to protect exposed soils until grading begins (See also Sec. 4.2.2.3.2 Mulching). Along with phasing the project, scheduling these different phases is a best practice. The following list identifies certain times of the year in which construction may be delayed or special measures must be taken into account; however, bad weather can happen at any time: 1. Try to plan site clearing during dryer times of the year. • Hurricane season extends from June 1 to November 30th, with August and September being the most active [71]. • The height of the wet season in the Virgin Islands typically occurs from August to December [29, 71] and coincides with the hurricane season. • May often has an isolated rainy peak [29, 72]. 2. Plan certain aspects of the project to avoid disturbance of wildlife reproduction if the development is in/over the water or near the coast line. • Coral spawning occurs ~6-10 days after the 1st full moon in July, August & September [73] and is disrupted by poor practices that result in sedimentation in coastal waters, pile driving or dredging near coral reefs. • While pile driving can cause sedimentation and is harmful to spawning corals, older techniques of pile driving can also cause harm to marine mammals and sea turtles by causing behavioural disturbance and reducing their acoustic activity [74]. Humpback whales (Megaptera novaeangliae) migrate annually through the Territory from January to May. Although not an erosion control measure, best practices to mitigate noise and vibration are highly recommended such as vibratory and jetted piles, the use of bubble curtains, cushion blocks, cofferdams or temporary noise attenuation piles. (More information can be found at: http://warrenappleton.com/bmp/ pile-driving.php). • Depending on the species, sea turtle nesting season and hatchling emergence generally occurs from February to October in the BVI. Any construction on a nesting beach during this period should be avoided or nests should be clearly marked to avoid disturbance of hatchlings. For other best practices on sea turtle nesting beaches see: http://www.barbadosseaturtles.org/documents/manual.of.best.practices.safeguarding.nesting.beaches.pdf


- 63 -


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4.1.2.

Protective Measures

Prior to land clearing, physically marking features (such as with bright coloured flagging survey tape), that are to remain untouched ensures contractors and construction workers do not accidentally remove the protective vegetation or exceed the boundaries of the intended development. Be sure flagging or other markers are placed at a height that will be viewable by heavy equipment operators.


- 65 4.1.2.1. Preserving Natural Vegetation

Preserving existing vegetation is the most effective way to control erosion. Plant cover reduces erosion and saves money by: • Protecting the soil surface from the impact of falling rain drops, • Slowing runoff and allowing sediment to settle out, • Physically holding the soil in place with plant roots, • Increasing infiltration rates by improving the soil’s composition. Identifying and clearly marking trees to preserve and protect them requires special attention. The following practices should be applied: • Do not nail boards or other materials to trees. • Build sturdy fences, wood or steel barriers around valuable vegetation to protect it from construction equipment, but be careful not to damage the roots. • Place barriers far enough from trees so that tall equipment such as backhoes and dump trucks do not injure branches. • For narrow-canopied trees and shrubs, convert the stem diameter in inches to feet (ex.10in to 10ft) and double (10ft x 2), so that a 10in diameter tree is protected to 20ft. • Identify and clearly mark construction areas to exclude equipment or building materials. • Prune obstructive and broken branches properly. As the site is being developed, it is also important that the following measures are followed: • Avoid heavy equipment damage to tree trunks and roots during land-clearing. • Use terraces to protect tree and shrub roots when lowering grades. In some cases, this will only work when the following recommendations are considered: • Not more than 3 inches of soil over existing tree and shrub roots. • Lowered grades begin outside the tree drip-line. • No trenches across tree root systems within the drip line (the outermost circumference of a tree canopy where water drips from).


- 66 4.1.2.2.

Footprints

A building footprint is the area on a project site used by the building structure, defined by the perimeter of the building plan. Parking lots, parking garages, landscapes, and other non-building facilities are not included in the building footprint; however, must be included when it comes to considering runoff. Locating the footprint of a development to minimize parking lots and driveways not only aids in reducing erosion but will also save you money. In order to clear only the minimum amount of land necessary, walk the property, preferably with a land surveyor, and physically mark the limits of site clearing activities with visible flagging tape or flags, placed at eye level for equipment operators. Determine all necessary equipment and vehicle access points and routes within and around the footprint. The excavator should be closely monitored by the supervising engineer in order to avoid excessive clearing which could be costly and destroy all best practices for erosion and sediment controls on the first day of construction. Extra costs, such as the need for creating retaining walls not in the original plans have been known to be incurred because of improper excavation. Why pay good money to have your team design and position your development to minimize costs only to have it all lost in as little as a few hours due to unsupervised clearing? Clearing the entire parcel of land can raise your costs significantly.


- 67 4.1.2.3.

Setbacks/Buffers

A ‘setback’ is defined as the minimum distance a structure is built away from a particular location or feature such as a road, shoreline or protected area. However, a development ‘setback’ in the BVI is legally defined under the Land Development Control Guidelines, 1972 as: “the minimum horizontal distance between the street, rear or side lines of the lot and the front, rear or side lines of the building;”. Please remember that this only defines the minimum between a building and road. Several Government agencies recommend and often require developments to follow setback guidelines listed below: Ghuts • Buildings must be 30ft (10m) from the edge of the ghut • Waste water disposal and absorption fields must be 50ft (15.25m) from the edge of the ghut Wetlands • Buildings must be at least 50ft (15.25m) from the highest water level • Waste water disposal and absorption fields must be 100ft (30.5m) from the highest water level Shorelines (although there is a legal minimum setback, it is a best practice to have an assessment of the coastline due to its dynamic nature (see also Sec. 3.5.3.1. Beaches) • Buildings must be 50ft (15.25) from the high water mark (it is better to use the vegetation line when measuring since it does not change as often as the high water mark!) • Buildings in Anegada require a 200ft (61m) setback due to the dynamic behaviour of the coastline (see also Sec. 3.5.4. Anegada).


- 68 Setbacks also provide buffer zones between buildings (or land use) and protected areas such as National Parks, Marine or Fishery Protected Areas, historical sites, beaches, dunes, wetlands, mangroves or ghuts. Buffer zones (sometimes also called greenbelts) can be an area of vegetation that is left undisturbed during construction, or a strip of newly planted vegetation (see also Sec. 4.3.5. Filters & Barriers). The use of “buffer zones” or swaths of land (or sea) next to protected areas are becoming increasingly important to ensure indirect impacts on protected areas are reduced but also as an important hazard mitigation measure in sensitive areas. These zones help decrease the velocity of stormwater runoff that subsequently improves coastal water quality. Alternatively, buffer zones can help protect a property in the event of flooding. The loss of natural ecological buffers such as mangroves, wetlands, beaches and coral reefs increases the vulnerability of an area to natural disasters. Setbacks along coastlines provide buffer zones between the sea and buildings to allow natural movement of sand. Buffer zones help reduce damage to beachfront properties during high wave events, provide access along the beach and help to provide privacy for beachfront properties and for the enjoyment of the beach resource user. For many small islands in the Caribbean, setback distances are not based on current scientific data such as the historical changes of the beach, influences of storms or from sea level rise predictions [75]. Many setbacks are fixed [i.e. 200ft (61m) in Anegada and 50ft (15.2m) for the rest of the BVI] and are often not far enough from the shoreline. This has subsequently led to accelerated beach erosion because the dynamic shoreline is unable to adjust to changes [76]. BEST PRACTICES FOR FIGURING OUT AN APPROPRIATE SETBACK • • • • •

Identify the geologic characteristics and historical changes within the broader sedimentary system and the potential of sea level rise from climate change. Ask the Survey Dept. or DDM for information regarding historical use of air photos to help determine an appropriate setback. Use the vegetation line along the coast to measure landward for the appropriate setback. Refrain from removing vegetation along the coastline as this helps hold the sand in place and reduce erosion; trim it instead. Remember the property you save from future storm surge and erosion impacts may be your own!


- 69 4.1.3.

Housekeeping BMPs

Stormwater runoff is capable of picking up construction site waste and depositing it into watercourses and coastal waters, particularly during heavy rainfall. Since construction projects can accumulate large volumes of waste, managing it is critical. The Virgin Islands Fisheries Act, 1997; Part V – Conservation Measures, Sec. 39. (1) states: “The Minister may, having regard to any other enactment relating to the prevention or control of marine pollution, take such mea sures as he considers necessary (a) to prevent, reduce and control pollution of the fishery waters and the marine environment generally from any source; and (b) to ensure that activities in the fishery waters are so conducted as not to cause damage or adversely affect the living resources of the fishery waters or the waters of the other States. Additionally, the Virgin Islands Fishery Regulations, 2003; Part IV – Conservation Measures, Sec. 32. (1) states: “No person, company, or their employees or agents shall put or cause to be put any poison, noxious substance or other pollutant into the fresh, estuarine or fishery waters of the Virgin Islands”. There are six key pollution prevention principles for good housekeeping on the construction site and include: • • • • • •

Provide for waste management Establish proper building material storage and staging areas Designate proper paint and concrete washout areas Establish proper equipment/vehicle fuelling and maintenance practices, including construction entrances/exits Control equipment/vehicle washing and allowable non-stormwater discharges Develop a spill prevention and response plan

In order for these pollution prevention principles on the construction site to be effective, they need to be established early on, be easily accessible and used appropriately to prevent pollution and reduce impacts and costs.


- 70 -

4.1.3.1.

Feral Animals

Feral animals, particularly feral goats, are devastating to island ecosystems, causing direct and indirect impacts through overgrazing, which often results in ecosystem degradation and biodiversity loss. They deplete the soil’s protective cover of vegetation and break up the soil crust with their hooves. This leads to wind erosion during droughts, water erosion during rain storms and can cause slips in steep areas. Increased erosion rates can have a significant long-term impact on biodiversity through the removal of soil and nutrients, and the alteration of soil structure leading to reduction in potential productivity. Feral goats may also affect perennial vegetation by feeding on established plants and by preventing the regeneration of seedlings. These goats, by foraging, can kill established plants by defoliation. They affect the regeneration processes indirectly when they reduce the ability of plants to produce seeds and directly when they eat young plants, and can have detrimental effects to insular ecosystems like the BVI, where native plants have evolved in the absence of these animals. Eradication measures coupled with diligent monitoring efforts and government-run management plans are widely accepted best practices and have had favourable results in restoring native ecosystems. However, in lieu of a goat eradication program or government management plan, property owners with goats and other grazing animals should keep them properly secured or penned to prevent the type of damage described above. If feral goats are encountered, property owners should contact the Department of Agriculture for more information about management of these animals.


- 71 -

4.1.4.

Implementation of BMPs

An important best practice is to notify the community of any construction that is about to start. Be a good neighbour! Once an ESAPPP has been developed and documented, and the construction site has been demarcated for areas to preserve, footprints and location of buffers or setbacks; you are ready to begin implementing the best practices that make up the rest of this chapter. However, your construction workers and subcontractors may not be familiar with the BMPs you are implementing and may not understand their role. One of the most effective BMPs you can use is to train your staff in the basics of your erosion, sediment and pollution prevention plan. The ESAPPP (see also Appendix 4) can be an effective tool for everyone involved in the construction process to ensure best practices are being effectively implemented.


- 72 4.2.

erosion controls

Once a development breaks ground, the cleared areas expose soils which become highly vulnerable to erosion from either wind or rain. How a site is cleared and what measures are put into place prior to and immediately following clearing are important considerations for erosion and sediment controls. It is important to remember, the best practices found within this chapter have to adapt to changing site conditions that occur and if something does not work or stops working, you will have to change the measures you are using to something more suitable. If for some reason construction activities have temporarily or permanently stopped, erosion control practices must continue because exposed soils must be stabilized. 4.2.1.

Roads

Roads cut in the BVI can either end up as obvious scars in the hillside or barely noticeable. If they are barely noticeable, the roads were designed by a qualified engineer that used best practices. How to specifically engineer cut roads and calculate volumes is not within the scope of this manual but concepts are provided to better understand why some of our roads leave obvious scars or fail, while others do not. 4.2.1.1.

Cut & Fill

Best management practices pertaining to road cuts and fills are important and serve many purposes. Cut and fills not only create space for the driving surface, but when properly executed using best management practices (and the advice of a qualified engineer), balance the amount from the cut with the amount needed for the fill to reduce labor costs and preserve stability over time. Landslides and failed road cuts and fills can be a major source of sediment, result in the need for major repairs and road closures and greatly increase road maintenance costs. Vertical cut slopes should not be used unless the cut is in rock or very well cemented soil. Long-term stable cut slopes in most soils and geographic areas are typically made with about a 1:1 or 他:1 (horizontal : vertical) slope. Ideally, both cut and fill slopes should be constructed so that they can be vegetated, but cut slopes in dense, sterile soils or rocky material are often difficult to vegetate. Construction of fill slopes with a 1 1/2:1 or flatter slope promotes vegetation growth and stabilizes the fill slope surface. Benches (terraces) on large fill slopes intercept any flow of surface water and slow it down.


- 73 If fill is used, it must be retained appropriately on the downhill-side since the natural slope will become steeper and unstable if the fill is simply thrown over the edge. A retaining wall will more than likely be needed (designed by an engineer) to contain the fill. The same applies when cutting a house foundation. Do not build your house on the fill directly, (however well you feel it is compacted) or throw it over the edge to fall down the hill and create an unstable slope below the house. Slope failures, or landslides, typically occur where a slope is steep, where fill material is not compacted, or where cuts in natural soils encounter zones of weak material. Failures that occur typically impact road operations and can be costly to repair. Failures near ghuts and water crossings have an added risk of impact to water quality. Good road location can often avoid landslide areas and reduce slope failures. When failures do occur, the slide area should be stabilized as soon as possible by removing the slide material, flattening the slope, adding drainage, or using structures such as retaining walls. It is important to note however that local conditions can vary greatly, so determination of stable slopes should be based upon local experience engiand judgment. Designs are typically site specific and may require input from geotechnical engineers and engineering geologists. Local engi neers will be able to recommend suitable slope stabilization measures. COMMON STABLE SLOPE RATIOS FOR VARYING SOIL/ROCK CONDITIONS Soil/Rock Condition Slope Ratio (Hor:Vert) Most Unfractured Rock ¼ : 1 to ½ : 1 Very Fractured Rock 1 : 1 to 1 ½ : 1 Loose Coarse Granular Soils 1 ½ : 1 to 2:1 Heavy Clay Soils 2 : 1 to 3 : 1 Soft Clay Rich Zones or Wet Seepage Areas 3 : 1 to 4 : 1 Fills of Most Soils consult an engineer If in doubt, ask an engineer!


- 74 4.2.1.2.

Road Drainage

In the BVI, the three most important factors affecting the life of any roadway are “drainage, drainage, drainage”. This is certainly true of unpaved roads. Without good drainage, even the best of construction methods and materials will be wasted. The importance of providing good drainage should be obvious. Too much surface water can weaken a roadbed resulting in rutting, potholes, shoulder erosion, ditch washouts, and clogged culverts. Water flowing too slowly deposits sediments and clogs channels and culverts. Standing water can weaken the sub-base and lead to surface failure. More important, erosion of unpaved roads can degrade coastal water quality and harm coastal and marine environments. There are a number of practices that can be used to divert runoff from the surface of dirt roads to a stabilized area to minimize erosion. o

Ditches • For unpaved roadways, a well-designed ditch is essential and can be cleaned with either a backhoe or by hand. • Inspect ditches regularly and schedule cleaning every few years or more frequently after prolonged periods of heavy rain. The bottom of the ditch should remain compact and rounded. • Clean ditches when they become clogged with sediments or debris to prevent overflows and washouts. • Check ditches after major storm events as fast moving water may have developed obstructions, erosion, or bank collapse. • Re-grade ditches only when absolutely necessary and line with grass (or stone) as soon as possible.

o

Cross Drains/Water Bars • Water Bars are an inexpensive way to control and divert water from a road surface at selected intervals. These narrow bermed structures are constructed by forming a ridge or a ridge and channel diagonally across the sloping roadway, and may be shallow or deep depending on the need and anticipated runoff volumes. They can be used to divert water and prevent erosion on long, sloping roads.

o

Turn-outs • Turnouts are extensions of ditches that direct water to filtering areas. There must be adequate outlet protection at the end of the turnout area, either a structural (rock) or vegetative filtering area. (See also Sec. 4.3.2.2. Slope Drains / Storm Drain Diversion for details on the construction of proper outlet areas). • Follow culvert requirements for spacing (see next section.) • Use only in areas where the water will flow into a filtering area well away from the road and adjacent surface waters.

o

Culverts • A culvert is a closed or semi-enclosed conduit used to convey water from one area to another, usually from one side of a road to the other side. • Culverts preserve the road base by draining water from ditches along the road, keeping the sub-base dry. • Culvert installation is a simple operation, yet it is a process that is notorious for being done incorrectly and haphazardly. • Proper installation and routine maintenance are necessary to ensure the safety of the roadway. • Significant erosion problems can develop at the outlets of culverts if they have not been properly designed or installed. • Placing culverts and other outlets in relation to road slope will control volume and velocity of discharges, reducing erosion and pre venting sediment from entering surface waters.


- 75 -


- 76 4.2.1.3.

Paving

Paved surfaces are increasingly common throughout the BVI. While convenient, paved surfaces have a significant impact on water quality and the health of the environment. As more available land area gets paved over, a larger amount of rainwater ends up falling on impervious surfaces such as parking lots, driveways, sidewalks, and streets rather than soaking into the soil. This creates an imbalance in the natural ecosystem and leads to a host of problems including erosion, flash floods, water table depletion, and pollution of ghuts, waterways and coastal waters as rainwater rushing across pavement surfaces picks up everything from oil and grease spills to chemical fertilizers and other pollutants. One way to avoid these problems is to install pervious concrete or porous pavement, a material that offers the inherent durability and low life-cycle costs of a typical concrete pavement while retaining stormwater runoff and replenishing local watershed systems. Instead of preventing infiltration of water into the soil, pervious pavement captures rainwater in a network of voids in order for it to percolate into the underlying soil. In many cases, pervious concrete roadways and parking lots can double as water retention structures, reducing or eliminating the need for traditional stormwater management systems such as retention ponds and sewer tie-ins. Paving roads within two weeks of cutting it is a good practice. Although paving roads may not allow water to infiltrate soils, when implemented with proper drainage, water is controlled and can be directed to areas such as sediment basins or filters prior to transportation to a ghut which can further filter out sediments. Leaving roads unpaved greatly increases sedimentation in coastal waters. Paving ghuts on the other hand is a poor practice as a ghut will lose its function of filtering water instead. A paved ghut acts as a conduit in which water flows at a higher rate (with sediments) into coastal waters. It also eliminates important habitat for local wildlife and plants.


- 77 4.2.2.

Stabilization

Construction activities can increase erosion by removing vegetation, disturbing soil and exposing sediment to the elements. Eroded soil quickly becomes a sedimentation problem when wind and rain carry the soil off the construction site and sediment is deposited in our surface waters. Through proper slope and site stabilization, the use of conservation practices, and temporary and permanent cover, erosion and sedimentation problems can be managed. To effectively stabilize disturbed soil areas on construction sites, proper planning, selection, and implementation of soil stabilization BMPs is required. This section sets forth a few commonly accepted best management stabilization practices. 4.2.2.1.

Construction Site Entrance

One of the first measures that will need to be in place is to stabilize the construction site entrance / exit. Stabilized entrances are installed at every site entrance and exit to prevent soil from being tracked or washed off-site onto public roadways and should be used at any unpaved entrance/exit location where there is risk of transporting mud or sediment onto paved roads. The width should be at least 10ft (3m) to 12ft (4m) or as wide as the entire width of the access. At sites where traffic volume is high, the entrance should be wide enough for two vehicles to pass safely. The entrance should be flared where it joins the existing road to provide a turning radius. Runoff from a stabilized construction entrance should drain to a sediment trap or sediment basin and any pipes placed under the entrance to handle runoff should be protected with a berm. Construction entrance stabilization measures should be inspected regularly and especially after there has been a high volume of traffic or storm event. It may be necessary to add stone periodically and when repair is required. Sediments and other debris should be removed and properly disposed of so it does not end up in a ghut or along the coastline, and all associated sediment control measures should be in working condition at all times.


- 78 4.2.2.2.

Clearing the Site

Conventional land development frequently results in extensive site clearing, where existing vegetation is destroyed, and the existing soil is disturbed, manipulated, and compacted. All of this activity significantly affects stormwater quantity and quality. These conventional land development practices often fail to recognize that the natural vegetative cover, the soil mantle, and the topographic form of the land are integral parts of the water resource system that need to be conserved and kept in balance, even as land development continues to occur. This section covers techniques that preserve natural systems and hydrologic functions on a site through the use of Non-Structural BMPs. Non-Structural BMPs are intended to be used with other practices resulting in a variety of environmental and financial benefits and facilitate the treatment, infiltration and evaporation of precipitation close to where it falls while helping to maintain a more natural and functional landscape. The BMPs described in this section protect natural systems, and incorporate existing site features such as wetlands and ghuts. From a developer’s perspective, these practices can reduce land clearing and grading costs, reduce infrastructure costs, reduce stormwater management costs, and increase community marketability and property values. Blending these BMPs into development plans can contribute to the desirability of a community, environmental health and quality of life for its residents. Longer term, sites where BMPs were employed during land clearing and construction sustain their stormwater management capacity with reduced operation and maintenance demands during the operational lifetime of the project.


- 79 4.2.2.2.1.

Land Grading

Grading reshapes or alters the land surface for better use, drainage improvement, and erosion control. When preparing your grading plan, try to make slopes as gradual as possible without modifying the existing site conditions significantly. Steeper slopes result in faster moving runoff, which results in greater erosion. Erosion can occur on even the gentlest of slopes depending on soil and climate conditions. Generally speaking, slopes of 1 to 8 % (0.57⁰ – 4.57⁰) are categorized as gently sloping; 4-16 % (2.29⁰ 9.09⁰) are considered strongly sloping; slopes of 10 to 30 % (5.71⁰ - 16.70⁰) are considered moderately steep; slopes of 20 to 45 % (11.31⁰ - 24.23⁰) are considered to be steep slopes; and slopes greater than 45 % (24.23⁰) are considered very steep slopes. The site plan must show pre- and post-construction location and slope elevation of surface to be graded. • Minimal Clearing • Side Slopes 2:1 • Reverse Benches • Temporarily Stabilize with Vegetation

4.2.2.2.2.

Gradient Terracing

Gradient terraces are earth ridges and channels constructed along the face of a slope at regular intervals. Gradient terraces are constructed at a positive grade. They reduce erosion damage by capturing surface runoff and directing it to a stable outlet at a speed that minimizes erosion. Gradient terraces are usually limited to use on long, steep slopes with a water erosion problem, or where it is anticipated that water erosion will be a problem. Gradient terraces should not be constructed on slopes with sandy or rocky soils. They will be effective only where suitable runoff outlets are or will be made available. It is important that gradient terraces are designed with adequate outlets, such as a vegetated area, or proper outlet. In all cases, the outlet should direct the runoff from the terrace system to a point where the outflow will not cause erosion or other damage. Vegetative cover should be used in the outlet where possible. Terraces should be inspected regularly at least once a year and after major storms. Proper vegetation/stabilization practices should be followed while constructing these features.


- 80 4.2.2.3.

Holding the Soil in Place

As previously mentioned, erosion is the process which moves soil from one location to another by wind, water, or other natural action. Large open areas like construction sites are particularly susceptible to the forces of wind and water erosion and, when left unprotected, erosion from these areas strips the land of vital topsoil which is used to grow trees, grasses and even crops. The eroded soils then leave these areas and go into our streets, wash into storm drains and travel into our ghuts and coastal waters. This sedimentation of our ghuts and nearshore waters causes flooding, reduces water quality, and affects fish and marine life in our coastal waters. The impacts from erosion have even greater effects in the BVI where the layer of top soil is very thin (26in on average) and importing soil to erode sites significantly increases construction costs over the life of the project. A few commonly accepted best management practices designed to minimize soil erosion are set forth below. 4.2.2.3.1.

Mats, Nets & Blankets

Erosion control mats, nets or blankets are simply coverings that are placed over exposed soil to protect it from erosion. Some coverings also help facilitate the growth of vegetation. When selected and applied properly, they are one of the most effective ways to control erosion and promote water permeability on disturbed land prior to vegetation establishment, particularly on steep slopes. Numerous companies provide a wide range of different types of erosion control products but all serve the same purpose. However, it is important to understand if the fabric is not properly selected, designed, or installed, the effectiveness may be reduced drastically. Coverings require firm, continuous contact between the materials and the soil. If there is no contact, the material will not hold the soil and erosion will occur underneath. Also, covering selection depends on site conditions (slope, runoff speed, project duration, and location of installation). Be sure to read and understand the manufacturer’s installation requirements prior to purchasing the material to make sure it is suitable to the conditions at the site. Many companies will do the work for you in terms of what materials will work best as long as information on slopes and volumes are correct. Look for biodegradable products since some plastic netting has been found to entangle wildlife including reptiles, amphibians, birds and small mammals.


- 81 The following are some examples of different types of soil erosion coverings: Rolled erosion control products These flexible nets, blankets or mats are unrolled to cover exposed soil surfaces. Most of these products contain netting, either by itself or binding loose fiber materials to form a blanket or mat. Netting There are numerous types of erosion control nettings but they all are woven with various sized open spaces called apertures. Netting products that have a more tightly woven construction provide erosion control without having to use an underlying layer of mulch (See also Sec. 4.2.2.3.2. Mulching). Geogrids Geogrids are extremely durable woven materials with a polymer coating that can be used for soil reinforcement. Geogrids have a high tensile strength and are ideal for use on steep slopes or where finished slopes will be steeper than 2:1. Advantages of using geogrids include: • • •

Can be used as an alternative to riprap or a concrete retaining wall. Can be planted over with vegetation for additional strength and aesthetics. Resists degradation by water and chemicals normally found in soils.

Geotextiles Geotextiles are porous fabrics known in the construction industry as filter fabrics, road rugs, synthetic fabrics, construction fabrics, or simply fabrics. As a synthetic or biodegradable construction material, geotextiles are used for a variety of purposes including erosion control. They are also used as separators. An example of such a use is between riprap and soil. This “sandwiching” prevents the soil from being eroded from beneath the riprap, maintaining the riprap’s base.


- 82 4.2.2.3.2.

Mulching

Mulching or matting may be used during the dry season when it is hard to establish grasses. In addition to stabilizing soils, mulching can reduce the speed of storm water runoff over an area. On steep slopes or near critical areas like ghuts, mulch matting is used with netting or anchoring to hold it in place. Mulch netting can be made with excelsior, straw, coconut fiber, nylon, or paper woven into it. Used for waterways, slopes that are difficult to vegetate, areas subject to wind, or areas where other mulches are not available and anchor with staples spaced at the manufacturers’ recommendation, based on the steepness of the slope. The incinerator has a wood chipper capable of chipping trees up to 12in in diameter. For more information contact the Department of Waste Management. $ Cost Savings: Mulching provides an inexpensive yet immediate protection to soils that are exposed and that are subject to heavy erosion ! Warning: Mulch can be easily blown or washed away by runoff if not properly secured!


- 83 4.2.2.3.3.

Temporary Seeding

Temporary seeding means growing short-term vegetative cover plants on disturbed site areas that may be in danger of erosion and should be used if work on the site ceases for more than fourteen days and on areas which have been disturbed by construction and which are likely to be re-disturbed, but not for several weeks or more. This practice uses fast-growing grasses whose root systems hold down the soils so that they are less apt to be carried offsite by stormwater runoff or wind. Proper seed bed preparation and the use of high-quality seed are needed to grow plants for effective erosion control. Watering may also be necessary when seeds are first placed to ensure they begin to grow. Soil that has been compacted by heavy traffic or machinery may need to be loosened. The type of ground cover chosen is also important; do not use exotics since native vegetation will most likely grow much faster. Successful growth usually requires that the soil be tilled before the seed is applied. Seeded areas should be covered with mulch to provide protection from the weather. Seeding on slopes of 2:1 or more, in adverse soil conditions, during excessively hot or dry weather, or where heavy rain is expected should be followed by spreading mulch or reducing slopes to 1 to1.5 if at all possible. Frequent inspections are necessary to check that conditions for growth are good. If the plants do not grow quickly or thick enough to prevent erosion, the area should be reseeded as soon as possible. Seeded areas should be kept adequately moist. If normal rainfall will not be enough, mulching, matting, and controlled watering should be done. Temporary seeding also reduces the problems associated with mud and dust from bare soil surfaces during construction. $ Cost Savings: Seeding is generally inexpensive and easy to do, it establishes plant cover fast when conditions are good, stabilizes soils well, is aesthetic, and can provide sedimentation controls for other site areas and reduces costs of maintenance on other erosion controls


- 84 4.2.2.4.

Slope Protection

Slope protection is a vital component of erosion control. As many construction sites are in the grading phase, slopes become exposed requiring temporary stabilization protection before homes, other structures and permanent landscaping or other enhancements are established. Protecting hillsides and steep slopes from improper development practices helps to preserve the unique environmental qualities that we value. Furthermore, poor development practices on steep slopes can have an adverse effect on water quality as a result of increased erosion and sedimentation. 4.2.2.4.1.

Soil Retention Walls

Soil retaining walls are used to hold loose or unstable soil firmly in place. For example: Vegetated Rock Wall: Vegetated rock walls use rock and live plant cuttings to stabilize and protect the toe of steep slopes. Vegetated rock walls differ from retaining walls in that they cannot resist large lateral earth pressures so limit the wall to 2ft high. Try to use rocks from the site clearing to cut costs. Slope Face Plantings: A low retaining wall (up to 2 ft) at the foot of a slope makes it possible to flatten the slope and establish vegetation. Vegetation on the face of the slope protects it from surface erosion and landslides. Use stones from the site clearing in the design of the retaining wall. Live Stakes: Live stakes are cuttings of live branches, usually ½ in to 1 ½ in (12.7mm – 38mm) diameter and to 2-3ft (0.7m – 1m) in length, taken from living, woody plants capable of quickly and easily taking root. This is an inexpensive method that can be used when time is limited and the site is relatively uncomplicated. Live stakes are usually used on moderate slopes (4H:1V or less) of original bank soil (not fill) and where there is little active erosion or chance of bank washout Brush-layering: Brush-layering is a technique whereby live branches, ½ to 2in (12.7 mm – 50.8mm) diameter and 3-4ft (1m – 1.2m) in length, are placed perpendicular to the slope with growing tips outward. Brush-layering is used to break up slopes into a series of shorter slopes. ! Warning: Soil Retaining Wall design involves complex systems. Walls higher than 4ft (2ft if in stone) should be designed by a licensed engineer!


- 85 4.3.

sediment control

It is important to note that the effective use of erosion control mechanisms to keep soil on site is preferred to sediment control practices. This is particularly true in the Virgin Islands since most of our soil types have high clay content. Clays are particularly difficult to remove from storm water because of their very small particle size and tendency to stay suspended in storm water for long time periods. That said, in the event of sudden rain storms prior to the activation of erosion controls, sediment should be removed from runoff occurring onsite before it leaves the property. As a result, sediment control measures should be in place. As sediments are transported by water downhill, the sediment particles will settle (drop) out of the flow. This is called ‘sedimentation’. This process of “settling” can occur very slowly depending on the grain size of the sediment. The grain size of the sediment determines how long it takes for the sediment to drop to the sea floor and the water will appear clear again. Larger grain sizes (rocks or boulders) settle more quickly than finer grained sediments (clay and silt).

Simplified diagram to show the lenght of time it takes for the same amount of different types of sediment to fall to the bottom of the seabed.


- 86 -

4.3.1.

Stormwater Diversion

Stormwater is rain or any other form of precipitation that has come into contact with the ground or any other surface. This water seeps into the ground, is absorbed by vegetation, evaporates or runs off the land into storm sewers, ghuts and coastal waters. Stormwater can come from any type of land including those used for residential, commercial and industrial purposes. It is important to divert and manage stormwater for two reasons. First, as the illustration of the hydrologic cycle (in Sec. 2.4. Where Does Water Go?) demonstrates, our atmosphere absorbs water from the earth, it falls back down as precipitation where it is absorbed by the soil and used by vegetation to grow. The water eventually evaporates back into the atmosphere and the cycle continues. But our land development practices have interfered with this cycle. Precipitation is unable to seep into the soil through the hard surfaces we build such as roads and buildings and our storm sewers drain that water away too quickly. Second, as stormwater flows toward sewer systems, ghuts and coastal waters, it picks up toxic debris and chemicals such as fertilizers, oil and grease, pesticides, dirt, animal and bird faecal matter, other pollutants and litter. Stormwater diversions support environmental sustainability by minimizing or avoiding the downhill transport of polluted stormwater and reducing environmental impacts on the watersheds, ghuts and coastal waters thus working toward the goal of a healthy and functional watershed. Stormwater diversions also contribute to community safety and financial risk management by reducing the risk of flooding and erosion.


- 87 4.3.1.1.

Perimeter/Interceptor Dike & Swales

$ SAVINGS: Materials and equipment needed to construct can probably be found on the construction site; can handle large drainage areas Perimeter or interceptor dikes (ridges of compacted soil) and swales (excavated trenches or depressions) are used together to prevent stormwater runoff generated offsite from entering the construction area where there is a high risk of erosion. They reduce the amount and speed of flow and then guide it to a stabilized outfall (point of discharge) or sediment trapping area (see also 4.3.3. On-Site Detention Systems). Interceptor dikes and swales divert runoff preferably from drainage areas using a combination of earth dike and vegetated swale. Dikes and swales are generally built around the perimeter of a construction site before any major soil disturbing activity takes place and should be kept in place until disturbed areas are permanently stabilized. For a short slope, runoff can also be channeled away from locations where there is a high risk of erosion by placing a diversion dike or swale at the top of a sloping disturbed area. Temporary dikes or swales may also be used to protect existing buildings; areas, such as stockpiles; or other small areas that have not yet been fully stabilized. When constructed on the down slope side of the disturbed or high-risk area, dikes and swales will prevent runoff that contains sediment from leaving the site before sediment is removed.

Stabilization: Swales in place longer than 10 days must be stabilized with vegetation, erosion control mats, stone or other material (see also 4.3.2.1. Lined Channels/Drainage Swales). Inspect and repair swales after each heavy rain event. Temporary interceptor dikes and swales may remain in place as long as 12 to 18 months (with proper stabilization) or be rebuilt at the end of each day’s activities. Interceptor dikes and swales can be permanent controls. However, permanent controls should be designed to handle runoff after construction is complete; should be permanently stabilized; and should be inspected and maintained on a regular basis. Temporary and permanent control measures should be inspected once each week on a regular schedule and after every storm. Repairs necessary to the dike and flow channel should be made promptly.


- 88 4.3.1.2.

Check Dams & Berms

Check dams are small, temporary or permanent structures built across a drainage ditch, swale, or channel to lower the speed of concentrated flows. Reduced runoff speed reduces erosion and gullying in the channel and allows sediments to settle out. A check dam should be installed in steeply sloped swales, or in swales where adequate vegetation cannot be established. A check dam may be built from stone, or pea gravel-filled sandbags. Check dams should be used only in small open channels which will not be overtopped by flow once the dams are constructed. After each significant rainfall, check dams should be inspected for sediment and debris accumulation. Sediment should be removed when it reaches one half the original dam’s height and properly disposed of so that it does not end up in ghuts and nearshore waters. Check for erosion at edges and repair promptly as required. Check dams are installed in man-made swales, channels and ditches to slow runoff, allow soil to settle out and minimize erosion potential. The maximum drainage area above a check dam must not be greater than two acres. $ SAVINGS: Material and equipment needed to construct these practices are probably already found on the construction site; are easy to install; allow a high proportion of sediment to settle out; reduces the velocity of water 4.3.2.

Stormwater Conveyance

Stormwater conveyance is simply a mechanism to guide stormwater in a way that reduces flooding or sedimentation in receiving waters. There are a number of simple designs that can be implemented but in larger scale projects, flow capacity will need to be calculated and stormwater conveyance design will need to be developed by an engineer. The key point to remember here is that if stormwater can be controlled, it will be cheaper than mitigating the impacts caused by uncontrolled water flow. 4.3.2.1.

Lined Channels (Drainage Swales)

A drainage swale is an excavated lined channel that directs runoff to a desired location such as a sediment trapping device. These channels are lined with grass, sod, mats, or geotextiles. In order to determine the best type of lining, calculations of the volume and velocity of stormwater runoff to be conveyed will have to be identified by a qualified engineer. This type of sediment control device is only effective on flatter slopes (< 8% / 4.57â ° for most designs).


- 89 4.3.2.2.

Drainage Protection

Inlet Protection: Storm drain inlet protection places a permeable barrier, like filter fabric, excavated gravel with wire mesh or concrete block and gravel, (for areas of one acre or less), around an inlet or drain to filter sediment out of storm water. Inlet protection prevents the silting-in of inlets, storm drainage systems, or receiving channels but must be inspected after every rain and storm event, regularly cleared of sediment, and should remain in place and operational until the drainage area is completely stabilized or up to thirty days after the permanent site stabilization is achieved. Outlet Protection: Outlet protection reduces the speed of concentrated storm water flows and therefore it reduces erosion or scouring at storm water outlets and paved channel sections. In addition, outlet protection lowers the potential for downstream erosion. This type of protection can be achieved through a variety of techniques. Outlet protection should be installed at all pipe, interceptor dike, swale, or channel section outlets where the velocity of flow may cause erosion at the pipe outlet and in the receiving channel. Outlet protection should be installed early during construction activities, but may be added at any time, as necessary. The exit velocity of the runoff as it leaves the outlet protection structure should be reduced to levels that minimize erosion. Outlet protection should be designed and monitored to ensure that pipes are never blocked or restricted by debris and inspected any time that inlet protection measures are compromised and for signs of erosion and scouring.


- 90 4.3.3.

On-Site Detention Systems

Detention systems are for stormwater control and, for the most part, are dry. During heavy rainfall, the detention system (or the basin) will fill with sediment laden water and empties out at a controlled rate. Retention systems on the other hand, also called “wet ponds” are regularly filled with water that remains within its basin. If the detention basin is intended for sediment control, the outfall point should be located away from the bottom of the basin to minimize transport of sediments out of the basin. If the detention basin is intended to control water flow, the outfall should be located near the bottom of the basin, thus making it relatively ineffective at controlling sediments.

4.3.3.1.

Temporary Sediment Basin

If your project is located where runoff flows to a common location, a temporary sediment basin should be installed. Only install other types of sediment control measures if sediment basins are not possible. If any of the following are present, a sediment basin may not be appropriate. • • • • •

Shallow bedrock prevents excavation of a basin Topography in the common drainage location prohibits the construction of a basin of adequate storage volume There is not enough room available at the common drainage location to construct a basin, due to the presence of existing structures, pavement, or utilities which cannot be relocated The only common drainage location is beyond the property line or “right of way” of the construction activity and a temporary construc tion easement cannot be obtained. Where applicable BVI Laws and Regulations prohibit a basin or the construction of a basin in the common drainage locations.

NOTE: There are portable sediment basins for small areas if the site does not lend itself to construction of a basin via excavation. Temporary sediment basins can be converted into a permanent detention system for the long-term, such as an extended detention pond or constructed wetland, both of which create wildlife habitat and the propagation of threatened or endangered wetland species.


- 91 The selection among these measures depends upon a number of criteria. The following questions should help you determine which is the most appropriate. 1. Does runoff leave the area as surface flow? a. If the answer is yes, then CHECK DAMS & BERMS and SILT FENCES can be used. (See Sec. 4.3.1.2. Check Dams & Berms; Sec. 4.3.5.1. Silt Fencing) 2. Is flow concentrated in channels when it leaves the property? a. A SEDIMENT BASIN is the first option but if that is not possible due to the above factors, a SEDIMENT TRAP should be used. (See also Sec. 4.3.3.2. Sediment Traps)

3. Are structural controls located along the entire downhill perimeter of all disturbed areas? a. The entire downslope and side slope borders of the disturbed area should be lined with filtration devices, such as SILT FENCE, or with a diversion or conveyance device which will carry the runoff to a sediment basin or sediment trap prior to discharging it off site. 4. Is there a piped storm drain system with inlets in a disturbed area? a. If the answer is yes, then a SEDIMENT BASIN, SEDIMENT TRAP, or DRAINAGE PROTECTION (see also Sec. 4.3.2.2. Drainage Protection) should be constructed to remove the sediment from the runoff before it flows into the inlet. 5. Do the sediment control measures satisfy applicable BVI laws and regulations? a. Consult any design manuals or guidance provided by local authorities to assist in preparing a plan which meets their requirements. b. These requirements should be incorporated into the â&#x20AC;&#x153;Erosion, Sediment & Pollution Prevention Planâ&#x20AC;?.


- 92 4.3.3.2.

Sediment Traps

A sediment trap is formed by excavating a pond or by placing an earthen embankment across a low area or drainage swale. An outlet or spillway is constructed using large stones or aggregate to slow the release of runoff. The trap retains the runoff long enough to allow most of the silt to settle out. Sediment traps are used at the outlet of any structure that carries sediment-laden runoff (diversions, channels, slope drains, etc.). Sediment traps can handle runoff from drainage areas between two and five acres, depending upon the type of sediment trap used. The trap should be large enough to allow the sediments to settle and should have a capacity to store the collected sediment until it is removed. The volume of storage required depends upon the amount and intensity of expected rainfall and on estimated quantities of sediment in the storm water runoff. Traps should be inspected after each rainfall and cleaned when no more than half the design volume has been filled with collected sediment. All sediment and debris should be properly disposed of so as not to end up in ghuts and nearshore waters. They are temporary practices and should not remain in place longer than eighteen to twenty-four months and are not recommended to filter out super fine silts or clays. $ Cost Savings: Protects downstream areas from clogging or damage due to sediment deposits; is inexpensive and simple to install; can simplify the design process and thus reduce costs by trapping sediment at specific spots onsite


- 93 4.3.4.

Bioretention Systems

Bioretention systems must be designed by a team of engineers, hydrologists and wetland specialists with a complete understanding of the watershed in which it is being developed. These systems are most effective if they are as close as possible to the source of the runoff. They have five basic features: • • • • •

Filter/buffer strips capture and remove course sediments prior to entering the treatment area The treatment area includes a sand/soil filter bed, Conveyance of stormwater is directed in and out of the treatment area to reduce erosion. Maintenance reduction is based on the fact that all parts of the system are easily accessible for repairs and upgrades. Landscaping provides for a higher aesthetic quality for the area.

4.3.5.

Filters & Barriers

Construction stormwater best management practices are actions taken before, during and shortly after construction that control erosion and sedimentation and protect water quality. Effective erosion and sedimentation control can be achieved by careful attention to the protection of the land surface from erosion, management of runoff and slowing water velocity, capturing sediment near the source, integrating sediment control with the construction schedule and inspecting and maintaining the erosion and sediment control system.


- 94 4.3.5.1.

Silt Fencing

This method is common throughout the Territory and is too often used as the only measure for erosion and sediment control. However, this is for sediment control only and should be used in tandem with erosion control measures as a second line of defence, not the first and only method! Silt fences are temporary and for sediment control on small (one acre or less) construction sites. For larger sites, the area contributing runoff to each silt fence should not be greater than one acre. Silt fences consist of permeable filter fabric anchored by steel posts. They require: • • • • • • • • • •

proper installation before earth change activities begin placement away from the slope base trenching into the soil with the bottom of fencing covered with backfill rebar for anchoring because wood stakes often break when hammered into stony or clay-like soils and are favoured by termites reinforcement with wire mesh and placed in double rows, depending upon the steepness of the slope posts to be located on the down-stream side of fence ends of a silt fence to be curved uphill to prevent re-routing of stormwater around the fence longer slope lengths to have multiple rows of fencing never to be placed across natural ghuts regular maintenance and inspection, before and especially after each rain event

Bottom of silt fence must be trenched.

Undisturbed vegetated area between distrubed ground and silt fence.


- 95 4.3.5.2.

Brush Barriers

Brush barriers are constructed of vegetation that has been cleared for the development. Used as a barrier around the perimeter of the disturbed area, these barriers help to slow runoff and filter out sediment. Brush barriers work best if the cut vegetation is piled in rows and a filter cloth is fastened over the brush and buried in a trench on the uphill side of the barrier. If a filter cloth is not used, a berm will need to be constructed. Utilize brush cut on-site to reduce costs. Brush barriers are not effective on slopes exceeding 40% (21.8â °). They should not be used in channels, swales or any other drainage path. Sediments may need to be removed periodically. 4.3.5.3.

Filters/Buffer Strips

Filter strips are existing or planted vegetated land areas that remove sediment from storm water by slowing runoff speeds, filtering out sediment and other pollutants, and providing some infiltration. A properly designed and operating filter strip provides water-quality protection by reducing the amount of sediment, organic matter, and pollution before the runoff enters the water paths, ghuts, salt ponds, wetlands or coastal waters. Filter strips also provide localized erosion protection since the vegetation covers an area of soil that otherwise might have a high erosion potential. Proper application of a filter strip includes accounting for the type and quantity of the potential pollutant (sediment, nutrient, chemical, organic matter, etc.), soil characteristics (clay and organic matter content, infiltration rate, permeability, etc.), slope steepness, shape and size of the property draining into the filter. Other considerations include the type of vegetation applicable to the climatic conditions and the best time of year to properly establish that vegetation. Note: A filter strip is not a stand-alone solution and should be used in conjunction with other best management practices that are designed to reduce erosion. Vetiver grass is used in several Caribbean cousntries as a soft bioengineering technique and alternative to costly hard structures. It is not affected by pests and diseases, nor does it act as a host for pests or diseases that might attack crop or garden plants. It has been a successful way to stabilize soils and acts as a buffer for down slope stormwater flow, and a filter to sediment. It does require regular mowing and replanting of dead spots.


- 96 4.3.5.4.

Curtains

Turbidity curtains are flexible, impenetrable barriers in the water that help contain sediments from escaping into larger coastal water bodies. Curtains are weighted at the bottom to ensure that sediment does not travel under the curtain, which is supported at the top through a flotation system. Staked curtains are available for applications with very limited exposure to water flow or wave action. Turbidity curtains prevent the migration of sediment from a work site in a water environment into the larger body of water. The practice is also sometimes referred to as ‘turbidity barrier’ or ‘silt curtain’ which allows for containment of sediment-laden water within a work area and protects contained water from turbulence, allowing particles to fall out of suspension. Very few silt curtain applications are alike. Each is unique and requires site-specific application and adaptation. Silt curtains should be designed to pass water either under or through their walls. Curtains are designed to confine suspended sediment and to allow it to settle or be filtered, not to impede the movement of water. It is important to ensure that they do not result in damage to important resources such as corals and seagrass. Silt fencing used for terrestrial application will not work in coastal waters. “Curtains” are more suitable for projects next to the shoreline or within coastal waters.


- 97 -

4.4.

shoreline Developments & erosion

The following sections are for developments directly along the coast. While developments upland can have an indirect impact on coastal habitats and processes, developments in the coastal zone can have the most direct and adverse impacts on our coastal and marine resources. Like any development, planning is critical to avoid unsuspected costs and environmental damage, not only to your development but to those adjacent or even further down- or up-shore from your development.


- 98 4.4.1.

Shoreline Stabilization

The phenomenon of building along the shoreline in order to have a better view of the sea has one major problem; if you can see the sea, the sea can see you. When it comes to shoreline stabilization, people forget there is an inherent inability to control the highly dynamic nature of beaches. The brute force of nature, and the ability of winds, waves, sand, and storms to act in multiple directions at once, ensures that nature will win over time, every time. The underlying causes of natural shoreline erosion include sea level rise, loss of a natural sediment supply, and storms. Inventors, patent holders and distributors of coastal engineering devices can easily sell their products, especially to those in desperate need of protecting and preserving their buildings and infrastructure. Developments are often located along a shoreline because of our desire to be near the beach but when it begins to erode, “quick fixes” are needed to save the structures. The question that needs to be answered is whether or not you want to protect the beach or the buildings on coastal beach property. If you choose to protect the building, you will likely lose the beach and eventually the building, ultimately losing both in the long run. Setbacks and shoreline stabilization projects cannot follow a one-method-fits-all mentality. This is because each beach is a unique feature that is created by the energy, energy direction, natural sediment, shoreline features, reefs, and seabed features in that specific location. What seems to work on one beach likely will not work on the neighbouring beach. Each coastline in which a development is proposed requires a complete understanding of its: • current physical characteristics; • historical changes; • role within the broader sedimentary system and; • potential impacts of sea level rise from climate change. Failure to understand these important factors will result in developments that are unsustainable, far exceed initial costs and are environmentally damaging. Additionally, properties down the coast can be severely impacted by poor practices up the coast. When people build too close to the waterline on a beach, sediments are obstructed and unable to move inland. Eventually the beach will become increasingly narrow throughout the year until there is no beach left.


- 99 4.4.1.1.

Beach Nourishment

Beach nourishment is considered a “soft-engineering” technique that, if absolutely necessary, is the preferred method of stabilization. Beach nourishment or beach filling can be a non-intrusive technique when it is designed correctly. It adds sand to the system, offers storm protection, and can increase the usable beachfront. However, done incorrectly, it can be a short lived, expensive project that creates erosion and smothers nearby reefs and vegetation. Beach nourishment is not a long-term fix. No matter how much sand you add to the beach, the wave energy will continue to remove sand from the beach at the same rate, and to return the beach to the natural form. Most beaches that “need” sand are already eroding or facing the problems from man-made structures up the coast trapping their natural supply of sand. There are some best practices that can extend the lifetime of a beach nourishment or beach fill project. • Use suitable fill material. The original sand on the beach is referred to as the native material, and its presence there indicates that it is, in some measure, the stable sand size and composition for that beach. Any sand that differs from this native material will be removed from the beach more quickly than sand that has the same characteristics as the native material (the composition of the sand, the average grain size of the sand, the average shape of the sand grains and how they fit together, and how easily the sand grains are moved by the waves). Sand that is finer than the native material will be more easily lost from the beach as it is moved offshore. • Understand the natural profile of the beach. To do this correctly, you would have to survey the beach in a number of locations from the vegetation line down to the depth of closure. The more of this profile that is known, the better. The more that the added sand fits the natural profile, the better. If the filled area has a beach profile that is different from the natural profile, the fill material will adjust quickly as the beach system seeks to restore the natural profile. It is possible to increase local and adjacent erosion rates by using the wrong profile. • Spread the fill material over as large an area as possible. The natural desire to place all of the sand in front of a specific site will result in shorter term benefits. The wave energy will quickly work to smooth out the shoreline and to return it to its pre-filled shape. The same volume of sand spread over a longer shoreline, essentially spreading and smoothing out the planform of the added sand, will provide additional beach front longer, since the beach system is not as different in form from its pre-filled shape. The immediate benefit of significant added beach front will be less, but there will be many additional years of added beach front before the pre-filled waterline returns. • If a beach has never been in a site naturally, then it is unlikely beach nourishment will work without continuous, expensive methods to maintain the beach and with significant long-terms impacts to the ecosystem. • If the shoreline is rock, beach nourishment projects should not include removal of rock areas as these are part of what help stabilize the shoreline. • Any nourishment project for a turtle nesting beach is not recommended. It is estimated that it takes at least 4 years for nesting levels to return to normal on nourished beaches, assuming there are no problems with the nourishment project. • Nature will win. Beach nourishment adds sand to the beach without adverse effects to downstream beaches, but it does not prevent natural movement of sand from the beach. The perfect beach nourishment project can be wiped away during an energetic hurricane season. Preserving beachfront through beach nourishment is an ongoing process, and the most successful projects monitor what happens over time and adjust accordingly with additional future fill.


- 100 -


- 101 4.4.1.2.

Shoreline Stabilization Implications

There are over a hundred types of ‘alternative’ or ‘innovative’ technologies found throughout the world that have been patented since the 1970’s as an approach to resolve shoreline erosion[77]. In addition to traditional stabilization methods, such as armouring, common implications over the long-term include continued or accelerated erosion of fronting beaches, erosion of down-drift beaches, adverse impacts on beach flora and fauna, impacts on turtle nesting, loss of beach access, potential hazards to water-based recreational activities, impacts on water quality, and lowered aesthetic value of the beach. The following list identifies some of the common practices and why they have been unsuccessful. • Shore-parallel armouring, such as sea walls, physically cuts off local sediment supply on the beach inland or within the dune system. Waves and currents, particularly those during storms, may interact with the wall, causing waves to reflect downward, scouring sand at the bottom of the wall and pulling the sand out to sea. With the beach unable to naturally protect itself by adjusting to waves (adopting a steep storm profile) or move inland due to sea level rise, the beach will narrow until there is no beach left in front of the wall at which point the seawall collapses and fails. • Groins and breakwaters interrupt longshore sediment transport and trap sand that results in loss of a sediment supply for beaches down-drift. • Gabions are low-cost structures made of wire cages or baskets filled with rocks and stacked on top of one another in order to create a shoreline stabilization structure. According to the US Army Corps of Engineers [78], they are not to be used in open-ocean coasts or high energy environments and where they have been used, have failed. In Puerto Rico where gabions were used (because of limited resources) the following problems have been observed [79]: • Failure from wire degradation and rupturing of the basket • Failure during storms from toppling or undercutting • Hazards for beach users from exposure of leaking rocks • Protruding wire from the baskets • Loss of the recreational value of the beach because of hazards or narrowing of the beach • Offshore breakwaters are intended to modify incoming waves by creating a ‘wave shadow’ on the beach causing sand deposition. However, these structures scour the vicinity in which they are placed and can block littoral drift of sediments. Additionally, they can block water circulation, and degrade water quality as well as pose a potential hazard to swimmers or boaters.


- 102 4.4.2.

Land Reclamation

Land reclamation is the process of creating new dry land over an area covered by water. (Land reclamation can also be defined as the process of recovering land that is unusable or abandoned and making it usable again but for this manual, we provide BMPs for the first definition). In many cases, material removed from a development gets piled up in various locations around the islands or in the past, used to fill in wetland areas. First of all, it is a poor practice to just throw away soil as it is a non-renewable resource in which the Virgin Islands have a small, limited amount. Secondly, excavated material from a development should either be used in the development or a place should have already been identified and approved by the Planning Authority as to where the material should be stored prior to excavation. Creating land reclamation as a result of excess material is an unsustainable practice and should never be the reason why land is being reclaimed. If reclamation is necessary (such as to improve coastal access), an EIA may be required (depending on its purpose) since it is considered a ‘coastal zone development’ under Schedule 3 of the Virgin Islands Planning Act, 2004. An Environmental Management Plan (EMP), whether or not an EIA is required by the Planning Authority, is a best practice since it will guide the development to ensure sensitive coastal habitats outside the reclamation area are not impacted. Within the EMP, the following information must be addressed for reclamation developments: •

• •

Methodology for reclamation (to be included but not limited to): o Erosion and sediment control measures (methodology for use of turbidity curtains; use of geotextile or matting, construction site entrance/exit; drainage, etc.) o Type and amount of fill o Number of vehicles / trips for land filling and operational hours o Equipment failure mitigation measures o Timeline of construction Environmental quality objectives (tolerance limits such as water quality during the construction phase) o Tolerance limits (such as water quality) and mitigation measures o Protection or transplanting of hard corals and/or seagrasses Impacts and mitigation for changes in oceanographic conditions and processes at the development site as well as up and down-drift (at least 1km) of the project (e.g. wave heights, wave reflection and refraction, littoral sediment transport, current changes) Hazard vulnerability assessment for storm surge (height of reclamation must take into con sideration sea level rise and should be a minimum height of 8.2ft/2.5m above the high water level)


- 103 4.4.3.

Marina Construction BMPs

All marinas are different based on a number of factors such as their size, services they provide, location and operating characteristics. Consequently, BMPs that work at one marina may not work for other marinas. However, like other development sites, managing stormwater by capturing it or diverting it prior to flowing into coastal waters is a top priority, particularly if boat maintenance areas are part of the marina. Additionally, good flushing is also critical to ensure water quality is not seriously degraded. Materials and compounds used to repair boats, control fouling and corrosion, and the wastes generated by sanding, scraping, painting, varnishing and fiberglassing can contain metals, solvents, hydrocarbons and other contaminants. Paint chips, dust and other particles may contain metals such as copper, zinc and lead which are all toxic to marine life. Materials washed into the water from maintenance areas can also contaminate sediments in the marina basin, posing problems for dredging and the disposal of d material. Finally, allowing pollutants to seep into the ground can eventually contaminate the site itself; posing problems in the future if the marina is ever sold. Additionally, long term exposure to these contaminates can cause health issues for workers at the marina. Best practices for marinas fall into two categories commonly known as source-control BMPs and stormwater treatment BMPs. Source-control BMPs focus on keeping stormwater from coming into contact with pollutants while stormwater treatment BMPs involve building structures or installing devices to treat or manage runoff. Source-control practices are less expensive and can keep pollutants out of coastal waters. Some of these practices include: • •

• • • •

Building indoor maintenance areas or temporary enclosures. These will require special ventilation equipment, protective clothing, respirators, etc. Locating outdoor maintenance areas away from the water’s edge and clearly marking where work is allowed to take place. It is also a best prac tice for these areas to have an impermeable surface that can be vacu umed or swept to remove contaminants. One example is concrete work pads that are raised and surrounded by permeable gravel to control runoff. Using berms or curbs to divert runoff into stormwater treatment devices Using dustless vacuum sanders Using environmentally sensitive chemical paint strippers Enforcing good housekeeping practices


- 104 There are numerous stormwater treatment practices available but many may not be applicable for marinas because of space or site conditions. When in doubt, ask an engineer what would be most suitable for your marina. The practices listed below are common and will work in most marinas and are suitable for retrofitting existing facilities. •

• • • •

Vegetated filter strips are made of local trees and shrubs along the water’s edge to filter runoff and remove contaminants before reaching the surface waters. They must be a minimum of 5ft (1.5m) wide but the wider the strip, the more effective it will be for filtering contaminants. They are most effective on slopes less than 5% and will not function on slopes greater than 15%. As a general rule, for every one percent of slope, add 4ft (1.2m) width. Filter strips also add aesthetic value and added recreational amenities to a marina. Infiltration trenches are shallow trenches filled with clean stone (1.5”-2.5”) to create an underground reservoir that holds runoff and allows it to percolate through the bottom of the trench into the surrounding soil. Filter fabric placed 6” below the surface helps trap sedi ment before it clogs the entire trench, reducing maintenance costs. Vegetated swales (also called biofilters) are commonly used as a substitute for curb and gutter systems. Surface water is directed into a heavily vegetated channel (usually with grass). Rain gardens (also called bioretention areas) are shallow, heavily vegetated depressions that collect water. For planning and technical considerations see: http://www.bae.ncsu.edu/topic/raingarden/ Permeable pavers allow water to pass through its surface and enter the soil below. They are best used in areas with low traffic volume, roughly 30-50 vehicles per day.

4.4.3.1.

Dredging BMPs

Similar to land reclamation, dredging is not a type of development that should ever be encouraged as it results in a direct loss of coastal (e.g. salt ponds) and marine habitats as well as alterations in wave and current dynamics that will affect nearby beaches. Dredging changes the seafloor and nature will attempt to return it to its pre-dredged state. For nearshore dredging, nature will use the sediment along the shoreline for this purpose, and localized shoreline erosion may increase. However, in cases such as improving deepwater access, dredging may be required. Coastal locations where sediments have filled from poor sediment control upland may also require dredging for navigation, safety and access (e.g. marinas, ports, etc). In these cases, the cause of sediment must be identified and mitigated to reduce future costs. In any case, the location and/or use of dredged material must be identified and approved by the Planning Authority. •

• • •

Dredging methodology (to be included but not limited to): o Erosion and sediment control measures (use of turbidity curtains; storage site erosion control measures; construction site entrance/exit); o Type and amount of fill; characterization of material (e.g. identification of any contaminants); o Number of vehicles / trips for moving dredged material; operational hours; o Equipment failure mitigation measures; o Timeline of dredging. Environmental quality objectives (tolerance limits such as water quality during the dredging process) o Tolerance limits (such as water quality) and mitigation measures Impacts and mitigation for changes in oceanographic conditions and processes at the dredged site as well as up and down-drift (at least 1km) of the project (e.g. wave heights, littoral sediment transport, current changes) Hazard vulnerability assessment for coastline near the dredged area based on changes in bathymetry, wave climate and storm surge


- 105 -


- 106 -


- 107 -

5.

POst cOnstrUctiOn

Sometimes when you innovate, you make mistakes. It is best to admit them quickly, and get on with improving your other innovation. -Steve Jobs


- 108 5.1.

introduction

Due to strong economic growth in the Territory over the last two decades, land development has occurred at a rapid rate. Although positive overall, if development is left unchecked, the increased site disturbances associated with such development will increase island erosion, stormwater volume and significantly degrade water quality, which can harm coastal areas and marine life. As previously discussed throughout this Guide, the best way to mitigate impacts from new developments is to use best management practices to treat, store, and infiltrate runoff onsite before it can affect water bodies downstream. Innovative site designs that reduce imperviousness and best management practices covered in this Guide set forth proven and cost effective ways to achieve the goals of reducing erosion and improving water quality whether for a new development or when retrofitting an existing site. It is never too late to employ best practices. The following chapter sets forth practices that can help continue efforts to reduce erosion on the development site.


- 109 5.2.

Post-construction review Plan

Development can alter landscapes by changing drainage patterns, thereby increasing the volume and velocity of runoff from the site. Increased volume leads to degradation of receiving waters and increases in the occurrence of flooding. Stormwater from developed impervious areas (roofs, parking lots, driveways) can also contain a variety of pollutants that are detrimental to water quality, such as sediment, nutrients, road salts, heavy metals, pathogenic bacteria, and petroleum hydrocarbons. Therefore, it is important to monitor stormwater runoff after construction is complete. If best practices were integrated into the pre-planning and construction phases, this is the time to determine their effectiveness and if not, to determine what modifications are required. If the development is pre-existing, this is the time to determine what practices can be implemented now to make improvements for erosion control. A review plan should be developed early in the process and ideally, concurrent with the pre-development plan. This allows all stakeholders to examine all the plans simultaneously. This is useful regardless of whether the plan pertains to a new development or a redevelopment project. An effective post-construction (or retro-fit) plan will: • include a pre-and post-development hydrologic analysis; • identify stormwater reduction opportunities; • identify pollutants of concern; • identify pollution prevention measures; • identify controls that provide treatment and reduce stormwater volume and velocity; • identify stormwater treatment and controls.


- 110 5.2.1.

Pre- & Post-Development Hydrologic Analysis

The BMPs selected for each site should attempt to maintain pre-development runoff conditions. A hydrologic analysis or drainage report that considers both pre- and post-development runoff is conducted to address the following storm sizes: • • •

the 1-year or 2-year storm, also known as the “water quality storm,” to protect natural channels from erosion; the 10-year or 25-year storm to size storm drainage infra structure; the 100-year storm to address flooding.

It is important to note that storm sizes refer to size of the storm rather than the years between each storm event. Therefore, a 100-year storm means that, on average, there will be ten such storms every one thousand years. However, there may be two to three 100-year storms within a 2- year period, or within the time frame of any construction project. 5.2.2.

Stormwater Reduction Opportunities

Project planners should attempt to mimic a site’s natural hydrology after development by following better site design principles including minimizing the project’s impervious footprint, conserving natural areas, and minimizing directly connected impervious areas. These types of practices encourage infiltration and reduce the amount of runoff discharged from the site. See Chapters Three and Four for practices that adhere to these principles.


- 111 5.2.3.

Pollutants of Concern

All pollutants of concern expected at the site after development should be identified so that the most appropriate BMPs to address those pollutants are selected. The following includes potential pollutants for various land uses: Potential Pollutants for Various Land Uses Category Sediments Nutrients Heavy Metals Residential Development X X Commercial Development X X Auto Repair Shops X Restaurants Parking Lots X X Streets and Highways X X X = pollutant can potentially be expected at that project type.

Trash & Debris X X X X X X

Oil & Grease Bacteria & Viruses Pesticides X X X X X X X X X X X X

(Table adapted from San Diego Co-permittees, 2002, cited by EPA, at: http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=factsheet_results&view=specific&bmp=123


- 112 5.2.4.

Pollution Prevention Measures

Pollution Prevention Hierachy

Designs should include practices to minimize and control the sources of pollutants (see also Sec. 4.1.3. Housekeeping BMPs ). These pollution prevention measures are usually the most cost-effective methods of controlling runoff. Some examples of pollution prevention measures include: • designing outdoor material storage areas to minimize exposure to erosion; • designing trash storage areas to minimize exposure to erosion; • using efficient irrigation systems and landscape design; • designing vehicle and equipment wash areas to minimize discharges to the storm drain; • designing fuelling areas to prevent spills and exposure to erosion. All of these measures must be easily accessible to encourage use and maintenance.

then

now


- 113 5.2.5.

Stormwater Treatment & Controls

Treatment controls may need to be installed where site design and source controls are not adequate to minimize pollutants. Treatment controls should be designed and sized to control runoff from a specific storm size appropriate for the area. Treatment controls can fall into several categories: • •

Biofilters: Pollution control technique using living material to capture and biologically degrade pollutants. Common uses include processing waste water, capturing harmful chemicals or silt from surface runoff, and micro-biotic oxidation of contaminants in air. Detention basins: Excavated areas installed on, or adjacent to ghuts and bays to protect against flooding and, in some cases, downstream erosion by storing water for a limited period of a time. These basins are also called “dry ponds”, “holding ponds” or “dry detention basins” if no permanent pool of water exists. Some detention ponds are also “wet ponds” in that they are designed to permanently retain some volume of water at all times. In its basic form, a detention basin is used to manage water quantity while having a limited effectiveness in protecting water quality. Infiltration basins: An infiltration basin (also known as a recharge basin or in some areas, a sump) is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent ghut or bay. It is essentially a shallow artificial pond that is designed to infiltrate storm water though permeable soils into the groundwater aquifer. Infiltration basins do not discharge to a surface water body under most storm conditions. It is distinguished from a detention basin, sometimes called a dry pond, which is designed to discharge to a downstream water body (although it may incidentally infiltrate some of its volume to groundwater); and from a retention basin, which is designed to include a permanent pool of water. Wet ponds or wetlands: Wet ponds (a.k.a. stormwater ponds, wet retention ponds, wet extended detention ponds) are constructed basins that have a permanent pool of water throughout the year (or at least throughout the wet season). Ponds treat incoming storm water runoff by allowing particles to settle and algae to take up nutrients. The primary removal mechanism is settling as stormwater runoff resides in this pool, and pollutant uptake, particularly of nutrients, also occurs through biological activity in the pond. Filtration: The process used to treat polluted stormwater runoff by filtering the runoff through sand or other media. Filtration systems can be used to treat runoff from new and existing developments. Filtration systems provide water quality benefits by removing pollutants such as sediments, nutrients (nitrogen and phosphorus), organic material, and heavy metals. Filters, however, do not control the volume or peak flow rate of runoff. Their main benefit is in removing pollutants from stormwater and protecting the water quality of receiving ghuts, bays and other coastal waters. Hydrodynamic separation devices (HDS): Are devices that use cyclonic separation to control water pollution. They are designed as flow through structures with a settling or separation unit to remove sediment and other pollutants. HDS are used to treat and pre-treat runoff.


- 114 5.2.6.

Proof of On-Going Maintenance

Best Management Practices are not effective unless properly maintained. The plan should address who will be responsible for on-going maintenance. The proof of maintenance should be contained in a maintenance agreement that is recorded with the property. This maintenance agreement should contain the following information: • • • • • •

A description of the routine maintenance that will need to be performed Schedules for maintenance Inspection requirements Provisions for TCP to access BMPs Penalties for failure to maintain BMPs A provision to legally record the maintenance agreement.

Maintenance of these BMPs will need to be periodically assessed by Town & Country Planning Department and/or Department of Disaster Management.

5.3.

Permanent Seeding & Planting

$ Cost Savings Inexpensively: Improves the property’s aesthetics; Provides excellent stabilization; Provides filtering of sediments, Provides wildlife habitat Permanent seeding of grass and planting trees and brush provides stabilization to the soil by holding soil particles in place where long-term plant cover is desired and/or necessary. Installation specifications for permanent seeding and planting are similar to those for temporary seeding (see also Sec. 4.2.2.3.3. Temporary Seeding). Some areas where permanent seeding is especially important are filter strips, buffer areas, vegetated swales, steep slopes, and stream banks. See Chapter 4 for more information about these best management practices. Permanent seeding is effective on areas where soils are unstable because of their texture, structure, a high water table, high winds, or steep slope. o

For permanent seeding to work, it is important to select appropriate vegetation, prepare a good seedbed, properly time planting, and to condition the soil.


- 115 o

o o o o

To minimize erosion and sedimentation, remove as little existing topsoil as possible. All site controls should be in place before the topsoil is removed. If topsoils are brought in from another site, it is important that its texture is compatible with the subsoils onsite; for example, sandy topsoils are not compatible with clay subsoils. Establish permanent grass or other vegetation by seeding or planting immediately after seedbed preparation is completed. See Sec. 3.5.1.3. Vegetation Sypes for a list of native plants and shrubs or contact the Agricultural Department or National Parks Trust for information on native plants and other suitable vegetation. Apply grass seed uniformly by hand, seeder, or hydroseeder. If seeding on steep slopes greater than 15% or during the rainy season, protect the grass seed, plants and soil with mulch or erosion control matting (see also Sec. 4.2.2.3.2. Mulching). Maintain grasses and landscaping after planting by: • repairing bare spots • mowing frequently to keep weeds down • fertilize new vegetation for first 2-3 years • use environmentally friendly herbicides • check seeded areas frequently for proper watering and growth conditions

5.3.1.

Tamarind Tree

Acceptable Vegetation

Disclaimer: This introductory list comprises common native, naturalized, and/or preferred plants to be used in the British Virgin Islands for erosion control, bank stabilization and landscaping. There are many other plant options (such as those in Sec. 3.5.1.3.2. Locally important species) that have not been included here. For more information on these and other native, naturalized or preferred species, contact the Department of Agriculture or National Parks Trust. Please consult a physician prior to using any of the flora listed below for medicinal purposes. PALMS “Puerto Rican Royal Palm” (Roystonea boringuena) is able to grow in a variety of soil types, and the fact that its roots do not damage sidewalks, increase its utility for landscaping and street planting. The fruit are fed to pigs, and other livestock and the flowers are visited by honeybees. TREES “Tamarind Tree” (Tamarindus indica) can grow to 90 feet and has a large umbrella shaped crown with fine, fern like compound leaves that emerge bright reddish orange and change to light green. The bark of a mature Tamarind is furrowed. The Tamarind is not drought tolerant. Regular watering is necessary for best results. “West Indian White Cedar” (Cedrela odorata) is not a conifer but related to the mahogany tree and produces a beautiful flower that carpets the ground below when they fall. The hard wood of this tree has been used througout the British Virgin Islands for the construction of native boats and sloops.

Puerto Rican Royal Palm


- 116 “Jamaica Caper” (Capparis cynophallophora) is a large shrub or small upright tree with a slender crown composed of short branches. Foliage dense in sun, becoming open in shade. Trunks 2-6 inches in diameter. Bark is dark red brown and rough. Leaves are smooth and shiny above and rusty beneath, 2-3 inches long and is used as an accent or specimen shrub or small tree. Also useful in buffer plantings and informal hedges. Growth rate is moderate and reaches approximately 6-12 feet in height.

Jamaica Caper “Frangipani” (Plumeria alba) is native to the Caribbean and related to Oleander. It may be prop-

agated easily from cuttings of leafless stem tips in spring. Cuttings are allowed to dry at the base before planting in well-drained soil. Cuttings are particularly susceptible to rot in moist soil. In its element when it can have as much sun as is possible, however, it must quickly be noted that along with a long day of sun, an equal amount of water must be maintained in the soil. Contact with the sap can irritate the skin.

Fountain Grass

GROUND COVER “Local Bromeliad” (Pitcairnia augustifolia) is often an epiphyte, a plant that grows on other plants but is not parasitic. It can also be terrestrial and is native to the British Virgin Islands. It is highly evolved with special adaptations for survival in very dry conditions.

Frangipani

GRASSES “Hilograss” (Paspalum conjugatum) is a creeping perennial grass that grows 7.5 – 16 in. (20-40 cm) long. It is prominent in humid tropics but is drought-resistant, remaining green long into the dry season and can be used for lawns and soil conservation. “Fountain Grass” (Pennisetum setaceum) is a densely tufted perennial grass that grows ¾ - 3 ft (0.23 m – 0.9 m) high. It is commonly grown in warm climates and produces beautiful silky purple inflorescences.

Local Bromeliad Hilograss

Sand Cordgrass

Salt Marsh Cordgrass

“Sand Cordgrass” (Spartina bakeri) is arobust ornamental grass that can form clumps that are 18 to 20 feet (5.4 m – 6 m) in diameter This grass may grow from 3 to 4 (.9 m – 1.2 m) feet tall, and its fine-textured, wiry leaves form a fountain spray pattern. It grows in full dun but tolerates extended flooding; acidic; slightly alkaline; sand; loam; clay soils and drought. “Salt Marsh Cordgrass” (Spartina patens) is a hay-like grass found in the upper areas of brackish coastal salt marshes. It is a slender and wiry plant that grows in thick mats 11 – 24 in. (30-60 cm) high. Cordgrass marshes serve as pollution filters and as buffers against flooding and shoreline erosion. “Seashore Rush Grass” (Sporobolus virginicus) is an upright, spreading, perennial grass with many pointed, thin spikes (leaves) and grows in the salt spray and loose sand of beaches and the moist lowland slopes of volcanoes. They flourish in poor soils and under very harsh climatic conditions.

Seashore Rush Grass


Barbas de Indio

- 117 “Barbas de Indio” (Andropogon bicornis) is a perennial with culms slim or medium-thick that grows 3.2 – 4.1 feet (1-2.5 m) tall. “Vetiver Grass” (Vetiveria zizanioides) can grow up to 4.9 feet (1.5 m) high and form clumps as wide. The stems are tall and the leaves are long, thin, and rather rigid; the flowers are brownish-purple. Its roots bind to the soil making it highly drought tolerant and able to help to protect soil against erosion. It can survive heavy water flow and submersion for up to two months in clear water.

Sea purslane

HERBACEOUS PLANTS “Beach morning-glory” (Ipomoea pes-caprae) is a plant that helps to stabilize coastal sands, creating a habitat into which other species move. It can endure low nutrient levels, high soil temperatures, abrasion and burial by blown sand, and occasional frosts, but not hurricanes. It also grows occasionally on disturbed ground inland.

Vetiver Grass

“Beach bean” (Canavalia rosea) is a mostly herbaceous vine that trails along beach dunes and coastal strand. The thick, fleshy stem can grow to 20 ft (6.1 m) or more in length and more than 1 in (2.5 cm) in diameter. The stem is rather woody near the base and several branches radiate outward, forming mats of light green semi-succulent foliage. The sturdy, fast growing beach bean thrives in almost any well drained soil. It is highly salt, sun and drought tolerant. It will have to be pruned to be controlled. “Sea purslane” (Sesuvium portulacastrum) is a sprawling perennial herb up to 30 centimetres (12 in) high, with thick, smooth stems up to 1 metre (3.3 ft) long. It has smooth, fleshy, glossy green leaves. Flowers are pink or purple. It grows in sandy, clay, coastal soils, tidal flats and salt marshes, throughout much of the world. “Sea lavender” (Argusia gnaphalodes) is an excellent stabilizing shrub on dunes and is a pioneer species on Anegada.

Beach morning-glory

Beach bean

Sea lavender


- 118 5.4.

Permanent Retaining Walls

Retaining walls are structures that are constructed to support almost vertical (steeper than 70 degrees) or vertical slopes of earth masses. They serve to stabilize sites located on steep slopes and prevent slope failure. Additionally, permanent retaining walls reduce soil erosion and the negative impacts to receiving ghuts, bays and other coastal waters resulting from erosion and stormwater runoff. NOTE: Permanent retaining walls can be costly as any wall over four feet in height should be engineered and as a result, require site-specific design. Significant pressure can be exerted against a retaining wall, both from the weight of the soil retained and from trapped water not correctly drained from behind the wall. Wall heights, drainage requirements and material selection must be based upon on-site investigations, especially if the wrong fill material is used which can create more issues (i.e. fine grain material soil doesnâ&#x20AC;&#x2122;t allow water to go through and ends up putting added pressure on the wall in a rain event). As a result, their use may be limited to situations where other stabilization measures would be ineffective or aesthetically unacceptable.


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Gravity wall

Earth pressure vector Gravity vector (of wall) Reactive force vector (not all shown)

Piling wall

Earth pressure vector Gravity vector (of wall) Reactive force vector (not all shown)

Earth pressure vector

Cantilever wall Gravity vector (of wall)

Reactive force vector (not all shown)

Earth pressure vector

Anchored wall Gravity vector (of wall)

Reactive force vector (not all shown)

Common types of permanent retaining walls include: Rigid Gravity and Semi-Gravity Walls: These walls are often constructed of reinforced concrete, un-reinforced concrete, or stone masonry. The rigid gravity walls develop their soil retaining capacity from their dead weights. The semi-gravity walls, such as cast-in-place concrete cantilever walls, develop resistance to overturning and sliding from self-weight and weight of soil above the wall footing. Prefabricated Modular Gravity Walls: These walls include crib walls, bin walls, and gabion walls. A crib wall, concrete or timber, is a gravity retaining structure that consists of interlocking concrete or timber elements. Each crib unit is filled with compacted granular soil. A bin wall, concrete or metal, is constructed of adjoining closed-face or open-face bins. Each bin unit is filled with compacted granular soil. Gabion walls consist of baskets made of galvanized steel mesh or PVC coated wire mesh. The baskets are filled with durable rock ranging in size from 4 to 8 inches. Non-Gravity Cantilevered Walls: These walls develop lateral resistance through the embedment of vertical wall elements and support retained soil with wall-facing elements. Vertical wall elements are normally extended deep in the ground to provide lateral and vertical support. The vertical wall elements can be piles, drilled shafts, steel sheet piles, etc. Wall faces can be reinforced concrete, metal, or timber. Cantilevered walls are generally limited to a maximum height of about 20 feet. Anchored Walls: These walls typically consist of the same elements as the non-gravity cantilevered walls but derive additional lateral resistance from one or more tiers of anchors. The anchored walls are typically used in the cut situation, in which the construction proceeds from the top to the base of the wall.


- 120 5.5.

Permeable Pavers

Permeable interlocking concrete pavement (PICP) consists of manufactured concrete units that reduce stormwater runoff volume, rate, and pollutants. The impervious units are designed with small openings between permeable joints. The openings typically comprise five to fifteen percent of the paver surface area and are filled with highly permeable, small-sized aggregates. The joints allow stormwater to enter a crushed stone aggregate bedding layer and base that supports the pavers while providing storage and runoff treatment. PICPs are highly attractive, durable, easily repaired, require low maintenance, and can withstand heavy vehicle loads. Permeable paving can replace traditional impervious pavement and has performed successfully in pedestrian walkways, sidewalks, driveways, parking lots, and low-volume roadways. It is not suitable for high volume/high speed roadways. PICP should not be confused with concrete grid pavements (i.e., concrete units with cells that typically contain topsoil and grass). These paving units can infiltrate water, but at rates lower than PICP. Unlike PICP, concrete grid pavements are generally not designed with an open-graded, crushed stone base for water storage. Moreover, grids are for intermittently trafficked areas such as overflow parking areas and emergency fire lanes. The concrete pavers with permeable joint material comprise the surface layer of PICP. Pavers are typically 80 mm (3 1/8 in.) thick for vehicular areas. Pedestrian areas may use 60 mm (2 3/8 in.) thick units. Additional subsurface components of this treatment practice include the following:

• • •

Open-graded bedding course - This permeable layer is typically 50 mm (2 in.) thick and provides a level bed for the pavers. It consists of small-sized, open-graded aggregate. Open-graded base reservoir - An aggregate layer immediately beneath the bedding layer. The base is typically 75 to 100 mm (3 - 4 in.) thick and consists of crushed stones typically 20 mm down to 5 mm (3/4 in. to 3/16 in.). Besides storing water, this high infiltration rate layer provides a transition between the bedding and sub-base layers. Open-graded sub-base reservoir - The stone sizes are larger than the base, typically 65 mm down to 20 mm (2½ in. to ¾ in.) stone. Like the base layer, water is stored in the spaces among the stones. The sub-base layer thickness depends on water storage requirements and traffic loads. A sub-base layer may not be required in pedestrian or residential driveway applications. In such instances, the base layer is increased to provide water storage and support. Under-drain (optional) - In instances where PICP is installed over low-infiltration rate soils, an under-drain facilitates water removal from the base and sub-base. The under-drain is perforated pipe that ties into an outlet structure. Supplemental storage can be achieved by


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• •

using a system of pipes in the aggregate layers. The pipes are typically perforated and provide some additional storage volume beyond the stone base. Geotextile (optional) - This can be used to separate the sub-base from the sub-grade and prevent the migration of soil into the aggregate sub-base or base. Subgrade - The layer of soil immediately beneath the aggregate base or sub-base. The infiltration capacity of the subgrade determines how much water can exfiltrate from the aggregate into the surrounding soils. The subgrade soil is generally not compacted.

To compensate for the lower structural support capacity of clay soils, additional sub-base depth is often required. The increased depth also provides additional storage volume to compensate for the lower infiltration rate of the clay subgrade. In addition to installation of an under-drain, an impermeable liner may be installed between the sub-base and the sub-grade to limit water infiltration when clay soils have a high shrink-swell potential or there is a high depth to bedrock or water table. Measures should be taken to protect PICP from high sediment loads, particularly fine sediment. Appropriate pretreatment BMPs for run-on to pavers include filter strips and swales. Preventing sediment from entering the base or permeable pavement during construction is critical. Runoff from disturbed areas should be diverted away from the PICP until they are stabilized. NOTE: Several factors limit PICP use. It is not appropriate for stormwater hotspots where hazardous materials are loaded, unloaded, or stored or where there is a potential for spills and fuel leakage. For slopes greater than 2% / 1.15⁰, terracing of the soil subgrade base may likely be needed to slow runoff from flowing through the pavement structure.

The most prevalent maintenance concern is the potential clogging of the openings and joints between the pavers. Fine particles that can clog the openings are deposited on the surface from vehicles, the atmosphere, and runoff from adjacent land surfaces. !Warning: Permeable pavements may not be appropriate when land surrounding or draining into the pavement exceeds a 20 % (11.31⁰ ) slope, where pavement is down slope from buildings or where foundations have piped drainage at their footers. The key is to ensure that drainage from other parts of a site is intercepted and dealt with separately rather than being directed onto permeable surfaces!


- 122 5.6.

Rain Gardens

Rain gardens, or bioretention areas, are landscaping features adapted to provide on-site treatment of stormwater runoff. They are commonly located in parking lots or within small pockets of residential land uses. Surface runoff is directed into shallow, landscaped depressions. Rain gardens can be used for flood control, channel protection and removal of pollutants from stormwater and are generally on-line or off-line. â&#x20AC;˘ On-Line: A rain garden in a swale upstream from a check dam. â&#x20AC;˘ Off-Line: A more complex system, having six components: a grass filter strip or energy dissipation area, a ponding or treatment area, planting soil, sand bed (optional), mulch layer, and plant material. A rain garden is not a water garden, a pond or a wetland. A rain garden is actually dry most of the time. It typically holds water only during and following a rainfall event. Because rain gardens will drain within 12-48 hours, they prevent the breeding of mosquitoes. Some considerations when deciding to install a rain garden are the drainage area, slopes both at the location of the rain garden and the drainage area, soil and subsurface conditions. Rain gardens can be used at a variety of locations, but operate best when used on small sites. Slope Rain gardens are best applied to relatively shallow slopes (usually about 5 % / 2.86â °). However, sufficient slope is needed at the site to ensure that water that enters the rain garden and can be connected with the storm drain system. These stormwater management practices are most often applied to parking lots or residential landscaped areas, which generally have shallow slopes. Soils/Topography Rain gardens can be applied in almost any soils or topography, since runoff percolates through a man-made soil bed and is returned to the stormwater system. Design Considerations Specific designs may vary considerably, depending on site constraints or preferences of the designer or community. There are some features, however, that should be incorporated into most rain garden designs. These design features can be divided into five basic categories: pretreatment, treatment, conveyance, maintenance reduction, and landscaping. Pretreatment Pretreatment is a practice that causes coarse sediment particles and their associated pollutants to settle. Incorporating pretreatment helps to reduce the maintenance burden of the rain garden and reduces the likelihood that the soil bed will clog over time. Several different mechanisms can be used to provide pretreatment. For instance, runoff can be directed to a grass channel or filter strip to filter out coarse materials before the runoff flows into the filter bed of the rain garden. Other features may include a pea gravel area, which acts to spread flow evenly and drop out larger particles.


- 123 Treatment Treatment removes pollutants. The rain garden should be sized between 5 and 10 % of the impervious area draining to it and should be designed with a soil bed that is a sand/soil matrix, with a mulch layer above the soil bed and include a pond for a small amount of water (6-9 inches / 152mm â&#x20AC;&#x201C; 228mm) above the filter bed. Conveyance Stormwater should be conveyed to and from the rain garden in a manner that minimizes erosion potential. If properly designed and constructed, some stormwater treatment can even occur during conveyance to and from the rain garden. Rain gardens can be designed with an under-drain system to collect filtered runoff at the bottom of the filter bed and direct it to the storm drain system. An under-drain is a perforated pipe system in a gravel bed, installed on the bottom of the filter bed. Designers should provide an overflow structure to convey flow from storms that are not treated by the rain garden to the storm drain. Maintenance Reduction In addition to regular maintenance activities needed to maintain the function of stormwater practices, some design features can be incorporated to reduce the required maintenance of a practice. Designers should ensure that the rain garden is easily accessible for maintenance. Landscaping Landscaping is critical to the rain gardenâ&#x20AC;&#x2122;s function and aesthetic value. It is preferable to plant the area with native vegetation, or plants that provide habitat value where possible. Another important design feature is to select species that can withstand the hydrologic regime they will experience. For instance, at the bottom of the rain garden, plants that tolerate both wet and dry conditions are preferable. At the edges, which will receive less water, upland species will be the most resilient. Finally, it is best to select a combination of trees, shrubs, and herbaceous materials. NOTE: Rain gardens cannot be used to treat a large drainage area. In addition, although the practice does not consume a large amount of space, building a rain garden into a parking lot design may reduce the number of parking spaces available. Maintenance Rain gardens require landscaping maintenance, including measures to ensure that the area is functioning properly. Initially rain gardens can require intense maintenance, but less maintenance is needed over time and can be less resource intensive than traditional landscaping practices. Rain gardens should be inspected monthly until plants are established, then inspected annually thereafter. Sediment should be removed from behind check dams when accumulations reach one-half the dam depth. $ Cost Savings: Rain gardens reduce the need for other BMPs that require large tracts of contiguous land. Rain gardens can require less watering than similarly landscaped areas. Rain gardens can improve upon existing landscaping and are often an aesthetic benefit.


- 124 5.7.

Maintenance of Best Practices

The effectiveness of post-construction runoff control BMPs requires routine inspections of the control measures. Generally, BMP inspection and maintenance falls into two categories: expected routine maintenance and non-routine (repair) maintenance. Routine maintenance is performed regularly to maintain both the appearance of the BMPs and their good working order. Routine inspection and maintenance helps prevent potential nuisances (odors, mosquitoes, weeds, etc.), reduces the need for repair maintenance, and reduces the chance of polluting runoff by finding and fixing problems before the next rain. In addition to maintaining the effectiveness of BMPs and reducing the incidence of pests, proper inspection and maintenance is essential to avoid the health and safety threats inherent in BMP neglect. The failure of structural BMPs can lead to downstream flooding, which can cause property damage, injury, and even death. Inspection checklists should be developed. Checklists could include each BMPâ&#x20AC;&#x2122;s minimum performance expectations, design criteria, structural specifications, date of implementation, and expected life span. In addition, the maintenance requirements for each BMP should be listed on the inspection checklist. This will help the inspector determine if a BMPâ&#x20AC;&#x2122;s maintenance schedule is adequate or in need of revision. Also, a checklist will help the inspector determine renovation or repair needs. Routine maintenance materials like shovels and weed eaters may be easily obtained on short notice with little effort. Unfortunately, not all materials that may be needed for emergency structural repairs are obtained so easily. Thought should be given to stockpiling essential materials in case immediate repairs must be made to safeguard against property loss and to protect human health.


- 125 It is important that routine maintenance and non-routine repair of erosion BMPs be done according to a schedule or as soon as a problem is discovered. Because many BMPs are rendered ineffective for runoff control if not installed and maintained properly, it is essential that maintenance schedules are maintained and repairs made promptly in order to identify and address maintenance issues quickly in order to reduce costs. A low cost fix to repair a BMP can quickly become an expensive replacement if the BMP fails. In fact, some cases of BMP neglect can have detrimental effects on the landscape and increase the potential for erosion. However, routine maintenance, such as cutting grasses, should be flexible enough to accommodate the fluctuations in need based on relative weather conditions. For example, more harm than good may be caused by cutting during an extremely dry period or immediately following a storm. The effectiveness of BMP inspection will be a function of the inspectorâ&#x20AC;&#x2122;s familiarity with each BMPâ&#x20AC;&#x2122;s location, design specifications, maintenance procedures, and performance expectations. Documentation should be kept of the dates of inspection, findings, and maintenance and repairs that result from the findings of an inspector. Such records help maintain an efficient inspection and maintenance schedule and provide evidence of ongoing inspection and maintenance. Because stormwater BMP maintenance work is usually not technically complicated (cutting, removal of sediment, etc.), workers can be drawn from a large labor pool. As structural BMPs increase in their sophistication, however, more specialized maintenance training might be needed to sustain BMP effectiveness. $ COST SAVINGS $: Management practices using materials that break down fairly easily (such as filter fabric) may mean more frequent replacement and, therefore, increased costs. The use of more sturdy materials (such as geotextiles) where applicable may increase the life of certain BMPs and reduce replacement costs.


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5.8.

Conclusion

The management of erosion and stormwater runoff from sites after the construction phase is vital to controlling the impacts of development on water quality. The increase in soil erosion as a result of earth moving activities for home sites and roads and the increase in the amount of impervious surfaces such as rooftops, roads, driveways, patios, and parking lots due to land development can have a detrimental effect on aquatic systems. Runoff can also contain a variety of pollutants that are detrimental to water quality, including sediment, nutrients, heavy metals, pathogenic bacteria, and petroleum hydrocarbons and has been associated with loss of aquatic biodiversity.


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6.

aPPenDiX 1: elements & Use of environmental impact assessment (eia)


- 129 Most people see the environmental impact assessment (EIA) as an obstacle on a long checklist of “things to do” in order to get planning approval. Think of it more as a tool that guides the design and construction of a development into a more cost effective and sustainable project. It is obvious developments will have an impact on the environment, but the EIA process will provide a clear picture of what impacts could occur and how those impacts can be mitigated. Not all projects will require an EIA. The Virgin Islands Planning Act, 2004, Sec. 26 states: (1) Unless the Authority otherwise determines, environmental impact assessment shall be required in respect of any application for development permission to which Schedule 3 applies. (2) The Authority may require environmental impact assessment of any development, other than a development set out in Schedule 3, where it is of the opinion that significant adverse environmental impact could result. Schedule 3 - Matters for which environmental impact assessment shall be required. • • • • • • • • • • • • • • •

Hotels of more than twelve rooms; any industrial plant which in the opinion of the Authority is likely to cause significant adverse environmental impact; quarrying and other mining activities; marinas; airports, ports and harbours; dams and reservoirs; hydro-electric projects and power plants; desalination plants; water purification plants; sanitary land fill operations, solid waste disposal sites, toxic waste disposal sites and other similar sites; gas pipeline installations; any development projects generating or potentially generating emissions, aqueous effluent, solid waste, noise vibration or radioactive discharges; any development involving the storage and use of hazardous materials. coastal zone developments; development in wetlands, marine parks, national parks, conservation areas, environmental protection areas or other sensitive environ mental areas.

The Physical Planning (Environmental Impact Assessment) Regulations, 2012 provides the requirements for screening, procedures concerning applications for planning permission, the preparation of an EIA, procedures on the environmental impact assessment and procedures for a hazard vulnerability assessment. All this information is available through the Town & Country Planning Department.


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7.

aPPenDiX 2: elements & Use of Hazard Vulnerability assessment (HVa)


- 131 The Virgin Islands are geographically located in an area susceptible to a number of natural hazards such as earthquakes, tsunamis, storms, hurricanes, and oceanic swells. A ‘sustainable development’ requires building in a way that is resilient to (can easily recover or be able to withstand) these natural hazards. Understanding the physical characteristics of a proposed development and potential impacts from natural hazards is a high priority in the early stages of planning in order to reduce short and long-term economic, social and environmental impacts and costs. The Department of Disaster Management provides the service of producing a Hazard Vulnerability Assessment (HVA) for anyone interested in purchasing a piece of property, sub-dividing or developing land. It is a valuable tool towards ensuring the appropriate design and location of a building, construction quality, and maintenance are incorporated in a development. For the low cost of $75.00 for a residential development and $250.00 for a commercial or large scale development, a report can be produced in about 3 weeks and is based on 3 major elements: • • •

The susceptibility of an area to a specific hazard or hazards; The likely strength or intensity of an event when it occurs (i.e. what is the potential for damage); and The likelihood or chance of such an event occurring.

The easy-to-read report includes (but is not limited to) surface deposits, underlying bedrock, slope, landslide risk, earthquake shaking intensity, inland and/or coastal flooding risk, wind speeds, storm surge, and tsunami hazards for the property being assessed. The report also includes the issues and recommendations to mitigate potential problems and why you should do so. This work, however, does not replace the work of a certified professional that may be required to conduct engineering analysis or design specific to the property. For more information contact the Department of Disaster Management (284-468-4200) or visit the website at www.bviddm.com


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8.

aPPenDiX 3 Developerâ&#x20AC;&#x2122;s checklist for Planning


- 133 This checklist is for developer’s to review before ground breaking. Even if you didn’t have to do an EIA, or and EMP, these are basic questions for any size of development that if you can’t answer the question or answer it as “yes”, you risk running into problems that will cost you a lot of time and money.

• • • • • • • • • • • • • • • • • • • • • • •

Do you fully understand the application & approval process? Have you had a topographic survey completed for your property? Have you met with TCP for a “pre-planning” meeting? Has an HVA been completed (if required)? Have all the natural characteristics of the property been identified (underlying geology, land contours, soils, vegetation types, and/or coastal and marine features)? Have any species (flora and/or fauna) of importance (endangered, threatened, locally important, invasive) been identified on the property? Do the development plans/architectural designs take into consideration these natural characteristics or species of importance and how? Have all the hydrological processes on the property been identified (e.g. location of wet/dry ghuts, wetlands, potential stormwater impacts on the property resulting from adjacent or upland developments, receiving waters) Do the development plans/architectural designs take into consideration hydrological processes?How? Has the development been phased and has the construction schedule/timeline been developed? Have protective measures for the preservation of features/vegetation, footprint boundaries, setbacks and buffers been identified (or clearly marked) prior to ground-breaking? Have good housekeeping practices been identified? If a road has to be cut, does the design have drainage plans included? Is the road going to be paved within 30 days of being cut? Have the plans been developed for erosion control at the construction site entrance? Do you know where excess excavation materials are going to be stored? Once the site has been cleared, what erosion control measures will be in place to control exposed soils from blowing or washing away? If the hillside is going to be cut, are there slope protection measures? Have sediment controls been identified around the perimeter of the property? Are there sediment controls for storm water conveyance (drainage)? Do you have sediment controls other than silt fencing? Do you have your erosion, sediment and pollution prevention plan documented? Have you met with your construction team to explain to them what measures you have in place to reduce erosion and control sediment?

Additional questions for developments in the coastal zone: For beachfront developments, are setbacks based on the historical behaviour of the beach (rate of erosion)? For beachfront developments, are setbacks measured from the vegetation line? For shoreline developments have the oceanographic processes (wave climate, currents, storm vulnerability) been identified? Is the development on a turtle nesting beach? How will the development ensure the nesting habitat is not disturbed?

• • • • •


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9.

aPPenDiX 4: erosion, sediment & Pollution Prevention Plan


- 135 This outline or “Table of Contents” is a guide to help you develop the “Erosion, Sediment and Pollution Prevention Plan” (ESAPPP) for your development and can be tailored to suite the scale of your development. Make sure all subcontractors and workers have access to and know the plan. If it cannot be easily reviewed and referred to it is likely it will not be followed. Remember, this is not the environmental management plan but may be a part of it. For more information, see: http://cfpub.epa.gov/npdes/stormwater/swppp.cfm#template 1. SITE EVALUATION, ASSESSMENT & PLANNING 1.1. 1.2. 1.3. 1.4. 1.5. 1.6. 1.7. 1.8. 1.9. 1.10. 1.11.

Project/Site Information Contact Information/Responsible Parties (e.g. operators, subcon tractors, surveyors, architects, engineers, etc.) Applicable laws and regulations, permits Topography, hydrology and coastal features Construction site estimates Receiving waters Site features (Physical characteristics that are sensitive or will be preserved) Potential sources of pollution Historic preservation (Identify any historic buildings or artifacts on the site that may require adjustments to the stormwater controls plan to ensure the preservation of the historic site). Nature & sequence of construction activities Maps

2. EROSION AND SEDIMENT CONTROL BMPS 2.1. 2.2. 2.3. 2.4. 2.5. 2.6. 2.7. 2.8. 2.9. 2.10. 2.11.

Phasing of construction activity Pre-construction protective measures Road development controls Construction entrances/exits Site clearing controls Soil stabilization Slope protection Stormwater controls flowing onto and through project Perimeter controls & barriers On-site sediment retention / detention measures Maps

3. GOOD HOUSEKEEPING BMPS 3.1. 3.2. 3.3. 3.4. 3.5. 3.6.

Material handling and waste management Building material storage and staging areas Washout areas Equipment / vehicle fuelling, and maintenance areas Equipment / vehicle washing Spill prevention and response plan

4. SELECTING POST-CONSTRUCTION BMPS 5. INSPECTIONS 5.1. 5.2. 5.3.

Inspectors & inspection schedule Delegation of authority (who does what and when) Corrective action log

6. RECORD KEEPING AND TRAINING 6.1. 6.2. 6.3.

Recordkeeping (who keeps what records) Log of changes to the SWPPP Training (who has been trained for what)

7. APPENDICES

Appendix A – Permits for development Appendix B - Inspection reports Appendix C- Corrective Action Log Appendix D – SWPPP Amendment log Appendix E – Training log Appendix F – Delegation of Authority


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10.

aPPenDiX 5: the environmental Management Plan


- 137 Approved developments which have gone through the EIA process may require an environmental management plan (EMP). An EMP is a framework that describes the means of complying with all applicable laws and regulations and achieving specific environmental objectives and targets (usually set out in the impact assessment) for the construction and post construction (operational) phases of a development. The EMP is not the erosion, sediment and pollution prevention plan, but the EMP may include it. Two types of EMPs exist; one is for the constructional phase of a project while the other is for the operational phase of a development. An Effective EMP shall: • • • • • •

project/site specific; Ensure compliance with recommendations in the EIA and terms/conditions of approval; Ensure compliance with all applicable laws and regulations including but not limited to any relevant environmental legislation/stan dards; Ensure that environmental risks associated with project are properly managed; Ensure that project-specific management protocols are in place; Be explained and made available for future reference to all subcontractors and workers. If it cannot be easily reviewed and referred to it is likely it will not be followed.

The format of the EMP will be site-specific and based on the size of the project. For small projects, most information could be in a template, checklist, or matrix format based on the potential issues. For large complex projects, the impacts and controls can be broken down into the different phases of the project in addition to the various forms and checklists that might be required. No matter what the size of the project, the EMP will include the following sections: (1) background information; (2) the environmental management strategy; (3) the implementation strategy; and (4) monitoring and reviewing strategies. I.

BACKGROUND INFORMATION

This section of the EMP includes: • •

An introduction of the project A description of the project that includes but is not limited to: 0 Location (including description) and expected construction activities

List of various processes involved in constructing the project 0 Work/operating hours including details of any work to be undertaken outside working hours 0 Employment numbers and type 0 Equipment to be used • EMP context and objectives 0 Explanation of how the EMP fits into the overall planning process and how the document will be used 0 List of all the approvals and conditions of approvals and how and when these conditions will be satisfied 0 Listing of all the studies completed thus far and any future studies • Listing of all relevant existing environmental policy, legislation, regulations, etc.


- 138 II.

ENVIRONMENTAL MANAGEMENT STRATEGY

This section of the EMP includes: • •

III. •

Management structure (roles and responsibilities) including names, contact information and positions of personnel responsible for environmental management and emergency contingency planning and response (can be in a matrix format) Reporting mechanisms that includes personnel responsible for producing the reports and when they would be prepared for: 0 What types of construction monitoring will occur 0 How non-compliance will be handled 0 Corrective actions that will be taken 0 How complaints will be managed Environmental training of staff 0 Contractors and sub-contractors working on the project shall be given environmental awareness and emergency response training concerning their roles under the EMP. 0 Description of specific types of training for various personnel should be documented, including the names of the trainee and trainer IMPLEMENTATION STRATEGY Construction risk assessment matrix with the following headings: List of project activities Actual and potential impacts associated with each activity 0 Indication as to the significance of each impact using an appropriate method of risk assessment 0 Site/project appropriate environmental controls, guidelines or targets 0 Indication of when and how often risk assessment will be carried out Relevant plans and maps such as (but not limited to): 0 Environmental sensitive areas onsite or in vicinity 0 Existing drainage and mitigation plans for all alterations to existing drainage 0 Vegetation to be preserved and/or habitat requiring protection (if any) 0 Specific locations to be monitored (such as for water quality) 0 Environmental Schedule that includes forms and reports used during day to day environmental management, including site inspection checklists, monitoring checklists, environmental incident report etc. Emergency contingency plans and response 0 0

• IV. •

MONITORING & REVIEWING STRATEGY Environmental Monitoring matrix with the following headings: 0 0 0

Environmental monitoring activity objective EIA recommendations Methodology (how monitoring will be carried out)


- 139 Schedule of monitoring (frequency) Responsible party (who will carry out the monitoring) 0 Controls, guidelines or targets Corrective actions that define the procedures for dealing with non-compliance of various environmental controls, guidelines or targets put in place for project EMP Review 0 Describes when / how often review of the document will be carried out 0 Once construction is completed, the operational aspect of the development may require continual monitoring 0 Changes in roles & responsibilities 0 Cycle of continuous improvement (adaptive management) and revision to the EMP 0 0

â&#x20AC;˘ â&#x20AC;˘


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- 141 -

11.

citatiOns, WeBsites, iMage creDits


- 142 Literature Cited [within brackets] 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31.

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Coral record of increased sediment flux to the inner Great Barrier Reef since European settlement. Nature 421, 727–730. Wolanski, E., Duke, N., (2002). Mud threat to the Great Barrier Reef of Australia. In: Healy, T., Wang, Y., and Healy, J. A., (Eds), Muddy Coasts of the World: Processes, Deposits and Function. Amsterdam, Netherlands. P 533-542. Roff, G., Clark T. R., Reymond, C.E., Zhao, J.,Feng, Y., McCook, L.J., Done, T. J.,Pandolfi, J.M., (2012). Palaeoecological evidence of a historical collapse of corals at Pelorus Island, inshore Great Barrier Reef, following European settlement. Proceedings of the Royal Society B. De’ath, G., Fabricius, K.E., Sweatman, H., Puotinen, M., (2012). The 27-year decline of coral cover on the Great Barrier Reef and its causes. Proceedings of the National Academy of Science, 109:44. P 17995-17999. Lewis, J.B., (1984). The Acropora inheritance-a reinterpretation of the development of fringing reefs in Barbados, West Indies. Coral reefs, 3. P117-122. 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An integrated stormwater management approach for small islands in tropical climates. Urban Water Journal, 4. P 211-231. Gore, S., (2012). Beach Geomorphology and Management in the British Virgin Islands. PhD Thesis. University of Ulster, Coleraine. 243pp. Alam, A., (circa 1990). A survey of watersheds in the British Virgin Islands. BVI Department of Agriculture. Tortola, British Virgin Islands. 135pp. Island Resource Foundation, (2012). An Environmental Profile of the Island of Virgin Gorda, British Virgin Islands, including Eustatia, Mosquito, Necker, Prickly Pear, Saba Rock, The Dog Islands, Broken Jerusalem, Fallen Jerusalem, and Round Rock. Island Resources Foundation. Tortola, British Virgin Islands and Washington, DC. 255 pp. Island Resource Foundation and Jost Van Dyke’s (BVI) Preservation Society, (2009). An Environmental Profile of the Island of Jost Van Dyke, British Virgin Islands including Little Jost Van Dyke, Sandy Cay, Green Cay and Sandy Spit. JVDPS. Jost Van Dyke, British Virgin Islands. 135pp. Island Resource Foundation, (2013). An Environmental Profile of the Island of Anegada, British Virgin Islands. Island Resources Foundation. Tortola, British Virgin Islands and Washington, DC. 255 pp. NOT PUBLISHED YET


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Castelle, A.J., Conolly, C., Emers, M., Metz E.D., Meyer, S., Witter, M., Mauermann, S., Erickson, T., Cooke, S.S., (1992). Wetland Buffers: Use and Effectiveness. Adolfson Associates, Inc., Shorelands and Coastal Zone Management Program, Washington Department of Ecology, Olympia, Pub. No. 92-10. 39. Rogers, C., (1979) The effect of shading on coral reef structure and function. Journal of experimental Marine Biology Ecology, 41. PP 269-288. 40. Hemminga, M. A., and Duarte, C. M., (2000). Seagrass Ecology, Cambridge, Great Britain: Cambridge University Press. 298pp. 41. Spencer, T. and Viles, H., (2002). Bioconstruction, bioerosion and disturbance on tropical coasts: coral reefs and rocky limestone shores. Geomorphology, 48. P 23–50. 42. King, C. A. M., (1972). Beaches and Coast. Second Edition. Arnold, London, 570pp. 43. Mimura, N., Nurse, L., McLean, R.F., Agard, J., Briguglio, L., Lefale, P., Payet, R., Sem, G. (2007). Small islands. 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Website sources Chapter 2 2.1. In a “Perfect Watershed” World:

www.naturalstep.org www.greenvi.org www.irf.org

2.2. What is a Watershed? :

http://ga.water.usgs.gov/edu/watershed.html

2.3. Watershed Anatomy:

http://www.watershedatlas.org/fs_indexwater.html http://water.epa.gov/type/oceb/fact1.cfm http://www.uvi.edu/sites/uvi/Publications/watercourses_landscapes.pdf http://www.uvi.edu/sites/uvi/Publications/strategy_management.pdf http://water.epa.gov/type/rsl/monitoring/upload/2002_08_13_volunteer_stream_stream.pdf http://www.thegef.org/gef/sites/thegef.org/files/publication/GEF_RidgetoReef_CRA_lores.pdf

Chapter 3 3.5.1.2. Soils:

http://www.coralreef.gov/transportation/sederosuvi.pdf

3.5.1.3. Vegetation Types:

http://www.irf.org/documents/VG%20Profile%20Final/VG_Environmental_Profile_May_2012.pdf

3.5.1.3.2. Invasive Species:

http://www.issg.org/database/species/search.asp?sts=sss&st=sss&fr=1&sn=&rn=British+Virgin+Islands&h ci=-1&ei=-1&lang=EN http://www.seaturtle.org/mtrg/projects/anegada/Anegada%20BAP.pdf

3.5.2.1. Ghuts:

http://www.for.gov.bc.ca/tasb/legsregs/fpc/fpcguide/soilreha/rehab2.htm http://www.uvi.edu/sites/uvi/Publications/strategy_management.pdf http://www.uvi.edu/sites/uvi/Publications/FTGU_News_June_10.pdf

3.5.2.2. Wetlands:

http://wetlandinfo.derm.qld.gov.au/resources/static/pdf/buffer-guide/wetland-buffer-guideline-final-221111.pdf

3.5.3.1. Beaches: (BMPs turtle nesting beaches)

http://www.barbadosseaturtles.org/documents/manual.of.best.practices.safeguarding.nesting.beaches.pdf

3.5.3.2. Mangroves:

http://manatee.ifas.ufl.edu/seagrant/pdfs/Mangrove_Trimming_Guidelines.pdf

3.5.3.4. Coral Reefs: (Species of importance)

http://www.iucnredlist.org/

3.5.4.1. Dune Systems

http://www.cep.unep.org/issues/sanddunes.PDF


- 146 Chapter 4 4.1.1. Phasing & Scheduling

http://www.nova.edu/ncri/research/a21/caribbean_coral_spawning_table.pdf

4.1.2.1. Preserving Natural Vegetation

https://edis.ifas.ufl.edu/pdffiles/FR/FR23900.pdf http://www.coralreef.gov/transportation/sederosuvi.pdf http://www.uvi.edu/sites/uvi/Publications/FTGU_News_June_10.pdf

4.1.2.2. Footprints

http://www.leeduser.com/glossary/term/4695

4.1.2.3. Setbacks/Buffers

http://www.unesco.org/csi/pub/info/info49.htm http://www.unesco.org/csi/act/cosalc/cosalc1.pdf http://www.epa.gov/region6/6en/w/sw/sediment.pdf http://www.unesco.org/csi/pub/info/info49.htm

4.1.3. Housekeeping BMPs

http://cfpub.epa.gov/npdes/stormwater/swppp.cfm

4.1.3.1. Feral Animals

http://faculty.jsd.claremont.edu/emorhardt/159/pdfs/2006/Campbell.pdf http://caribjsci.org/July08/44_199-205.pdf http://ntl.bts.gov/lib/24000/24600/24650/Chapters/M_Ch11_Slope_Stabilization.pdf

4.2.1.1. Cut & Fill 4.2.1.2. Dirt Road Drainage 4.2.1.3. Paving

http://www.mass.gov/dep/water/resources/dirtroad.pdf http://www.coralreef.gov/transportation/sederosuvi.pdf http://pdf.usaid.gov/pdf_docs/PNADB595.pdf http://perviouspavement.org http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=browse&Rbutton=detail&bmp=135

4.2.2.1. Construction Site Entrance

http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=factsheet_results&view=specific&bmp=35 http://www.epa.gov/region6/6en/w/sw/sediment.pdf

4.2.2.2.1. Land Grading

http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=browse&Rbutton=detail&bmp=32 http://www.dec.ny.gov/docs/water_pdf/sec5bperm10.pdf http://www.mde.maryland.gov/programs/Water/StormwaterManagementProgram/SoilErosionandSediment Control/Pages/2011_ESC_details.aspx http://www.coralreef.gov/transportation/sederosuvi.pdf http://www.epa.gov/region6/6en/w/sw/sediment.pdf http://soils.usda.gov/technical/manual/contents/chapter3.html

4.2.2.2.3. Surface Roughening 4.2.2.3.1. Mats, Nets & Blankets

http://www.epa.gov/region6/6en/w/sw/sediment.pdf http://depts.washington.edu/propplnt/Chapters/erosioncontrolchapter%5B1%5D.pdf http://www.mass.gov/dep/water/resources/dirtroad.pdf


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4.2.2.3.2. Mulching

http://www.nvtrcd.org/custom-2/2009%20Better%20Backroads%20Manual.pdf http://www.mass.gov/dep/water/resources/dirtroad.pdf http://depts.washington.edu/propplnt/Chapters/erosioncontrolchapter%5B1%5D.pdf http://www.epa.gov/region6/6en/w/sw/sediment.pdf

4.2.2.3.3. Temporary Seeding

http://www.epa.gov/region6/6en/w/sw/sediment.pdf

4.2.2.4.1. Soil Retaining Walls

http://www.mass.gov/dep/water/resources/dirtroad.pdf http://www.nae.usace.army.mil/reg/nrrbs/TECHNICAL-SUPPLEMENTS/TS14M.pdf

4.3.1.2. Check Dams & Berms

http://www.dec.ny.gov/docs/water_pdf/sec5atemp1.pdf http://www.epa.gov/region6/6en/w/sw/sediment.pdf

4.3.2.2. Drainage Protection

http://www.coralreef.gov/transportation/sederosuvi.pdf http://www.epa.gov/region6/6en/w/sw/sediment.pdf http://www.dec.ny.gov/docs/water_pdf/sec5bperm5.pdf http://www.mde.maryland.gov/programs/Water/StormwaterManagementProgram/SoilErosionandSediment Control/ Pages/2011_ESC_details.aspx

4.3.3.2. Sediment Ttraps

http://www.epa.gov/region6/6en/w/sw/sediment.pdf http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=factsheet_results&view=specific&b mp=59 http://www.cabmphandbooks.com/Documents/Construction/SE-3.pdf http://www.coralreef.gov/transportation/sederosuvi.pdf http://www.epa.gov/region6/6en/w/sw/sediment.pdf http://www.dec.ny.gov/docs/water_pdf/sec5atemp1.pdf

4.3.5.1. Silt Fencing

4.3.5.3. Filters/Buffer Strips 4.3.5.4. Turbidity Curtains

http://www.sera17.ext.vt.edu/Documents/BMP_Filter_Strips.pdf http://ohioline.osu.edu/aex-fact/0467.html http://el.erdc.usace.army.mil/elpubs/pdf/doere21.pdf

Chapter 5 5.2.3. Pollutants of Concern 5.2.4. Pollution Prevention Measures 5.2.5. Stormwater Treatment & Controls

http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=factsheet_results&view=specific&bmp=123) https://fortress.wa.gov/ecy/publications/summarypages/0510032.html (under the Stormwater Management Manual) http://en.wikipedia.org/wiki/Biofilter http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=browse&Rbutton=detail&bmp=67 http://water.epa.gov/scitech/wastetech/guide/stormwater/index.cfm http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=factsheet_results&view=specific&bmp=68


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5.2.6. Proof of On-Going Maintenance

http://www.cabmphandbooks.com/Documents/Development/MP-52.pdf http://www.tentowns.org/10t/docs_etc/filtsys.pdf http://en.wikipedia.org/wiki/Hydrodynamic_separator http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=factsheet_results&view=specific&b mp=123

5.3. Permanent Seeding & Planting

http://www.epa.gov/region6/6en/w/sw/sediment.pdf

5.4. Permanent Retaining Walls

http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=browse&Rbutton=detail&bmp=47 http://itd.idaho.gov/enviro/Stormwater/BMP/PDF%20Files%20for%20BMP/Chapter%205/PC-17%20%20Retain ing%20Walls.pdf

5.5 Permeable Pavers

http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=browse&Rbutton=detail&bmp=136 http://www.icpi.org/sustainable

5.6 Rain Gardens

http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=factsheet_results&view=specific&bmp=72 http://www.groundwater.org/ta/raingardens.html http://www.lowimpactdevelopment.org/raingarden_design/whatisaraingarden.htm

5.7. Best Practices Revisited

http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm?action=factsheet_results&view=specific&bmp=91

APPENDIX 2: Summarized from Rolli, 2011; can be accessed from www.bviddm.com under the “Publications” section, Disaster Digest 2011 APPENDIX 5: http://www.environment.gov.za/sites/default/files/docs/series12_environmental_managementplans.pdf And Penn, 2013 – Town & Country Planning Department)


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image credits PAGE 2 4-5 8-9 10 11 12-13 15 15 15 15 18-19 22 22 24 27 28-29 31 32 34 36 37 37 37 37 37 37 38 38 38 39 39 39 39 39 39 40 40 40

CREDITS Drawing: Form 1G students from St. George’s Secondary School Google Earth Google Earth Form 1G students from St. George’s Secondary School Form 1G students from St. George’s Secondary School L. Hiesinger (GBR aerial photo) www.fanpop.com (Sedimentation off Australia) Robert Packett ( Healthy corals of the Great Barrier Reef ) Pete Faulkner, Mission:awareness/Marine Photobank (Bleached corals) A. Jenik (Beef Island 1946) BVI Survey Department Drawing: T. Downing M. Jennings NASA Goddard Space Flight Center BVI National Parks Trust (Road Town 1953) BVI Survey Department Adapted from “Landscape Planning Environmental Applications, Second Edition (Marsh, 1991) Town & Country Planning Department Image adapted from Department of Disaster Management (6) J. Scheiner (1) Royal Botanic Gardens, Kew (2) ©Pedro Acevedo-Rodriguez. Courtesy of Smithsonian Institution, Plant Image Collection (3) ©Pedro Acevedo-Rodriguez. Courtesy of Smithsonian Institution, Plant Image Collection (4) ©Pedro Acevedo-Rodriguez. Courtesy of Smithsonian Institution, Plant Image Collection (6) Royal Botanic Gardens, Kew (7) Royal Botanic Gardens, Kew (8) ©Pedro Acevedo-Rodriguez. Courtesy of Smithsonian Institution, Plant Image Collection (9) Royal Botanic Gardens, Kew (10) Carlos Pacheco, USFWS (4) Forest & Kim Starr (6) Steven Paton, ©Smithsonian Institution (8) www. orchidboard.com (9) Pedro Acevedo-Rodriguez. Courtesy of Smithsonian Institution, Plant Image Collection . (10) USDA (11) ©Pedro Acevedo-Rodriguez. Courtesy of Smithsonian Institution, Plant Image Collection . (1) ©G.A. Cooper. Courtesy of Smithsonian Institution, Department of Systematic Biology-Botany. (2) ©Pedro Acevedo-Rodriguez. Courtesy of Smithsonian Institution, Plant Image Collection. (4) ©G.A. Cooper. Courtesy of Smithsonian Institution, Department of Systematic Biology-Botany.


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(5) Forest & Kim Starr (6) R.A. Howard. ©Smithsonian Institution. Courtesy of Smithsonian Institution, Richard A. Howard Photograph Collection Watercolour image: Venus Bay Observation Project - Australia Josiah’s Bay 1953, 1991, 2002) BVI Survey Dept. Image Science and Analysis Laboratory (Star coral) NOAA Center for Coastal Monitoring and Assessment Biogeography Team (Rough cactus coral) Photo credit: NOAA (Mountainous star coral) NOAA Center for Coastal Monitoring and Assessment Biogeography Team (Lamark’s sheet coral) NOAA Center for Coastal Monitoring and Assessment Biogeography Team (Elliptical star coral) NOAA Center for Coastal Monitoring and Assessment Biogeography Team (Anegada 1991, 2002) BVI Survey Department (Anegada 1953) BVI Survey Department (Cane Garden Bay 1953, 2002) Garden Bay) BVI Survey Department (2002 Aerial photo of Cane Garden Bay) BVI Survey Department B. Potter www.redorbit.com (Humpback whales) J. Scheiner (Coral spawning) A. Jenick (Protective barrier) C. Petrovic S. Fox Montana Audubon BVI National Parks Trust Cate School Bank Stabilization Project, CA Drawing: T. Downing Diagrams: Department of Disaster Management Drawing credit: T. Downing Labarca Bro Services, Texas ( Vendura™ retaining wall blocks ) C. Petrovic EcoMatting™, EcoDepot, LLC (Geotextiles) http://teachertomsblog.blogspot.com www.selbysoil.com (Brush layering) USDA Drawing: T. Downing U.S. Environmental Protection Agency, Washington, D.C. “Protecting Water Quality from Urban Runoff.” Drawing: T. Downing Drawing: T. Downing (Top photo) Konjian Yu, American Society of Landscape Architects 2010 Award of Excellence (Proper silt fencing) www.wayneswcd.org Drawing: T. Downing C. Titley-O’Neal


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Diagram adapted from: Speybroeck, J., et al., (2006). Beach nourishment: an ecologically sound coastal defence alternative? A review. Aquatic Conservation: Marine and Freshwater Ecosystems, 16: 419-435. C. Titley-O’Neal (Bottom photo) www.sustainable-chicago.com/ www.causes.com www. hydroston.com.au (Center) www.jcpw.org Photo credit: Hinkson Creek Urban Retrofit Project, Boone County Stormwater Program, MO Steve Spring / Marine Photobank (Top photo) Kongjian Yu, American Society of Landscape Architects, Award of Excellence, 2012 (Biofiltration) www.waterfrontoronto.ca Mike Breedlove, photo in Erosion Control Magazine; July 2010 (West Indian Cedar) Forest & Kim Starr (Jamaica Caper) Photo courtesy of GroundWorks (Local Bromeliad )Photo courtesy of GroundWorks (Hilograss) Forest & Kim Starr (Fountain grass) Forest & Kim Starr (Sand Cordgrass) www.floridagrasses.org (Salt Marsh Cordgrass) www.floridagrasses.org (Seashore Rush Grass) Forest & Kim Starr (Barbas de Indio) J. Gonzales, Darwin Initiative (Beach Morning Glory) Tauolunga Drawing: T. Downing Drawing: Form 1G students from St. George’s Secondary School Drawing: Form 1G students from St. George’s Secondary School Drawing: Form 1G students from St. George’s Secondary School Drawing: Form 1G students from St. George’s Secondary School Drawing: Form 1G students from St. George’s Secondary School


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Reducing Erosion  
Reducing Erosion