Tai Po: From a Flood-prone to a Water-resilient Town by S7_H

Transforming Tai Po From A Flood-prone Into A Water-resilient Town CHEN Yongxin HUANG Suqi KWOK Ying Yuet LIN Zhewei LIU Ye SHANG Rui

TABLE OF CONTENTS Understanding the Water Issues & Problem Scoping

Introducing the Technical Flow & Baseline Assessmet

Proposing Design Intervention

Demonstration with A Selected Site

Project Background

Urban Typology Reclassiﬁcation

Key Concepts & Problem Statement

Surface Permeability Assessment

Flood Risk Assessment

Introduction of Diﬀerent Types of Catchment

Urban Typology Reclassifcation

Project Brief

Design Toolbox

Water Management Capacity Assessment

Design Principles

Design Plan & Section View

Overseas Case Studies

Survey & Interviews

Integrated Design Strategy for Diﬀerent Zones

Evaluation

1. BACKGROUND

GEOGRAPHICAL CHARACTERISTICS OF HONG KONG A coastal city with a phenomenal amount of coastline compared to its size

● ●

Southern China Eastern Pearl River Delta

●

A phenomenal amount of coastline → Main area of Hong Kong: 456km → The other 263 islands in Hong Kong waters: 722km

URBAN DEVELOPMENT HISTORY OF HONG KONG The ratio of built-up area to non-built-up area has siginiﬁcantly increased in the past 50 years New Town

Land Area

Planned Population

1st Generation New Town (1970s) Tuen Mun

3,259 ha

649,000

Tsuen Wan

3,285 ha

845,000

Sha Tin

3,591 ha

735,000

2nd Generation New Town (Late 1970s) Yuen Long

561 ha

196,000

Fanling/Sheung Shui

667 ha

326,000

Tai Po

2,898 ha

347,000

3rd Generation New Town (1980s & 1990s)

(Source: Jacqueline Hung / geo3241.wordpress.com)

Tung Chung

Nil

Tin Shui Wai

430 ha

306,000

Tseung Kwan O

1,738 ha

450,000 5

BUILT-UP AREA & SURFACE PEAMEABILITY OF HONG KONG

Tai Po

●

A coastal town

●

Highly urbanised town

●

Large area / high ratio of impermeable surface

●

Signifcant change of coastline and landscape

THE STUDY SITE : TAI PO

Site Boundary Identiﬁcation: Small street blocks of Tai Po town centre

Area of Site:

10.67 km² 7

URBAN CHARACTERISTICS OF THE STUDY SITE (TAI PO)

●

Built-up Area: 70.3%

●

High concentration of old residential buildings and small number of commercial buildings

●

Concentrated in the centre and east of the plot 8

URBAN DEVELOPMENT HISTORY OF TAI PO 1

(Source: uwants.com)

(Source: Cheng Po-hung / HULU Culture)

(Source: Pang Yuk-man / Orange News)

(Source: Pang Yuk-man / Orange News / powered by Centamap)

(Source: Public Records oﬃce)

(Source: HULU Culture)

1&2

1950 - 60s

Home of ﬁshery and agricultural communities

3&4

1960s - 70s

Reclamation for the Tai Po Industrial Estate

Before 1970s

2010s

Map and coastal line before and after land reclamation 9

GEOGRAPHICAL CHARACTERISTICS OF TAI PO East

West

Lower Stream

Upper Stream

3D Map of Lam Tsuen Valley

Located in the lower basin of Lam Tsuen Valley, Tai Po town centre is highly susceptible to ﬂood

(Source: JC-WISE Water Initiative on Sustainability & Engagement)

(Source: Bastille Post)

(Source: Topick)

CLIMATE CHANGE IN HONG KONG Observed & Projected Increasing Intensity & Frequency of Precipitation

Challenge Higher Frequency & Risk of Flooding

(Source: Hong Kong Observatory)

Average Annual Rainfall Distribution in Hong Kong (1991-2020)

Areas Vulnerable to Storm Surge

(Source: Hong Kong Observatory)

FLOOD PREVENTION STRATEGY OF HONG KONG 12 Fortiﬁcation

● ● ●

Upstream: build drainage tunnels to intercept stormwater from the mid-levels and discharge it directly into the sea or to other channels and drains Midstream: build storage tanks in the midstream for temporary stormwater storage to relieve the discharge load of the downstream drainage system Downstream: carry out river drainage improvement works or build new drainage channels to upgrade the capacity of drainage system

SERIOUSNESS OF FLOODING IN TAI PO Existing Flooding Blackspots

(Source: Drainage Services Department)

Pesdestrian Tunnel in Kwong Fuk Road

Normal Days

During Typhoons 13

2. KEY CONCEPT & PROBLEM STATEMENT

RELATIONSHIPS OF SURFACE WATER FLOODING & RUNOFF CONTROL A site that heavily relies on fortiﬁcation with imprevious urban surface and high ratio of surface runoff to rainfall

Impervious Urban Surface

Heavy Precipitation

Limited Capacity of Drainage System (i.e. overload)

High Ratio of Surface Runoff to Rainfall

Surface Water Flooding (Source: ABC Waters Design Guidelines by PUB Singapore’s National Water Agency)

RELATIONSHIPS OF SURFACE WATER FLOODING & RUNOFF CONTROL Evaporation

Rainfall

Drainage System

Total Annual Precipitation

Inﬁltration

Storage 16

3. PROJECT BRIEF

VISION OF OUR STUDY MULTIPURPOSE

An aspirational future state for

urban water resilience

where servicing strategies deliver

long-term

liveability, sustainability and prosperity.

GOALS OF OUR PROJECT MULTIPURPOSE

Assessing rainwater management capacity of Tai Po

Enhancing water management capacity in Tai Po

Providing resilient and vibrant river edge

Improving the quality of the living environment

OVERSEAS CASE STUDIES SPONGE CITY: WUHAN Sponge cities aim at absorbing and reusing rainwater instead of funnelling it away

According to Technical Guidelines for Sponge City Construction by the Chinese Government, the annual runoff control rate target of Hong Kong is around 75%

(Source: https://focus.cbbc.org/sponge-citiies)

(Source: Technical Guidelines for Sponge City Construction) 20

OVERSEAS CASE STUDIES SINGAPORE ABC PROGRAMME Storm hydrograph showing the relationship between surface runoff control and the level & time of peak discharge

(Source: ABC Waters Design Guidelines)

Utilising diverse natural-development approaches to achieve rainwater collection and ﬂood mitigation

(Source: ABC Waters Design Guidelines) 21

PROJECT TARGETS

Scenario

Return period 50 & 200 years

Rainfall Intensity 135.2 mm/h

Rainfall Evaporation

Rainwater Runoff Control Target:

75%

Target

Drainage System

Total Annual Precipitation

30mm hourly

Increase the area of

Permeable surface to 50% in the toal surface coverage (m2)

increase the rainwater

storage capacity

Inﬁltration

Storage

(m3)

METHODOLOGY ELEMENT, SYSTEM & URBAN TYPOLOGY Different Elements

Four Systems

Various Typologies

Diagram describing varying inﬁltration rates of different natural and built solutions (Source: Singapore ABC Programme) 23

4. URBAN TYPOLOGY RECLASSIFICATION

ANALYTICAL FRAMEWORK Assess Each Typology

Assess Each System

Classify the Site into Diﬀerent Typologies

Identify Four Systems

Assess Water Management & Runoﬀ Control Capabilities

Map Each Element in Respective System

Introduce Design Toolbox

(Green, Blue, Road, Building)

Identify Which Element(s) Should Be Redesigned

Propose An Integrated Design 25

URBAN RECLASSFICATION 12 TYPOLOGIES

Woodland/Grassland

Agriculture

Waterbody

Open Space

Industrial Site

Roads

Highway

Railway

Rural Settlement

High-rise Building

Mid-rise Building

Low-rise Building

7 - 11 storeys

≤6 storeys

≥ 12 storeys

GEOGRAPICAL INFORMATION SYSTEM: ArcGIS PRO Reclassiﬁcation Know-why

Reclassiﬁcation Process

Input: Land Utilisation + Building Information

Output: 12 Typologies

GEOGRAPICAL INFORMATION SYSTEM: ArcGIS PRO Map showing the segmentation result with the 12 typologies

ANALYSING TYPOLOGY USING ARTIFICIAL INTELLIGENCE (AI)

AI and Programming for Future Cities

Design network as a bunch of layers with Downsampling and Upsampling inside

AI TECHNIQUE: U-Net (Python) U-Net Model Process Downsampling

Upsampling

Aerial/Satellite image Tiles

INPUT

OUTPUT

Result: Segmentation map

Label Tiles Corresponding ground truth masks

Predicted Segmentation Masks

U-Net is a deep learning method for fast and precise segmentation of images, which can enhance the reproducibiliy of the project. 30

LIMITATION OF U-Net IN THIS STUDY

Sample of Prediction

Limitation

High-rise buildings create obstruction on the images which would lower the accuracy Use satellite images with higher resolution and more information

Recommendation

Try out other alternatives to label the images Get more training data 31

5. BASELINE ASSESSMENT OF FLOOD SUSCEPTIBILITY

FLOOD RISK ASSESSMENT: ArcGIS PRO Factors and steps taken in ArcGIS Pro to asess the ﬂood risk of the site

Inputs

Factors

Layers

FLOOD RISK ASSESSMENT: ArcGIS PRO

High risk area:

21.15% are in places with high ﬂood risk

Lam Tsuen River (Near Tai Po Tai Wo Road) & Tai Po River Fung Yuen Lo Tsuen Tolo Harbour

SURFACE PERMEABILITY ASSESSMENT: ArcGIS PRO Reclassﬁcation of land use for assessing surface permeability of the site using ArcGIS Pro

Impervious Surface

Agriculture Woodland / Shrubland / Grassland / Wetland Water Bodies

SURFACE PERMEABILITY ASSESSMENT: ArcGIS PRO Map of impermeable / permeable surface

Current Permeable Ratio:

30.74%

WATER MANAGEMENT CAPACITY ASSESSMENT

Identifying Return Periods for Our Design

Calculating Intensity-Duration-Frequency (IDF) Relationship

Getting Runoff Coeffecients

WATER MANAGEMENT CAPACITY ASSESSMENT Step 01

What is Return Periods?

Return period (T) of an event is the average time (recurrence interval) between events greater than or equal to a particular magnitude.

WATER MANAGEMENT CAPACITY ASSESSMENT Step 01

What is Return Periods?

Identify return period for our design: 50 year, 200 years

Drainage Services Department (DSD) recommends using rainfall return periods of

50 years for main rural catchment drainage channels and urban drainage branch systems, and 200 years for urban trunk drainage systems (DSD, 1994).

WATER MANAGEMENT CAPACITY ASSESSMENT PART Step 2 02

Intensity-Duration-Frequency (IDF) Relationship

(Source: HKSAR Geotechnical Engineering oOﬃce)

Wisner’s constants a, b, c for the N09 Raingauges Duration (min)

Extreme Intensity x (mm/h) for various Return Periods T (year) 50-yr

100-yr

200-yr

114.5

122.1

135.2

WATER MANAGEMENT CAPACITY ASSESSMENT Step 03

RUNOFF COEFFECIENTS (DSD2013) ● ●

Place: Hong Kong Methods commonly used in estimating surface runoff: Rational Method

Range of Runoff Coeﬃcients (C) Recommended for Rational Method Suface Characteristic

Asphalt

0.7-0.95

Concrete

0.8-0.95

Brick

0.7-0.85 Flat (stilty/clayey soil)

0.13-0.25

Steep (stilty/clayey soil)

0.25-0.35

Flat (sandy soil)

0.05-0.15

Steep (sandy soil)

0.15-0.20

Grassland

Steep natural slopes or shallow soil underlain by impervious rock layers, C may be taken as 0.4-0.9.

QUESTIONNAIRE SURVEY: ArcGIS Survey123 + Tableau (1)

People’s Perception of Flooding Issues in Tai Po

Do you think that the ﬂooding situation in Tai Po has become more serious than before?

To what extent the ﬂood water negatively impacted the followimg type of land use in Tai Po?

QUESTIONNAIRE SURVEY: ArcGIS Survey123 + Tableau (2) People’s Understanding & Preference of Flood Prevention Strategy Which ﬂood mitgitation strategy you prefer the most? (1st = most perferred; 3rd = least preferred)

QUESTIONNAIRE SURVEY: ArcGIS Survey123 + Tableau (3) Priority Setting Which of the following are your priorities of water-friendly and -resilient culture in Tai Po? (Please select no more than 5 answers)

STAKEHOLDERS ENGAGEMENT: INTERVIEWS STAGE 1

Water quality is the prerequisite for promoting water-friendly culture and water recreational activities. To achieve this by: Flood prevention by surface runoff control Prohibition against illegal wastewater discharge

Monday

Tuesday

Wednesday

Thursday

Friday

Saturday

Sunday

Nullah ecotour / leisure

Evacuation of crowd from sunken park

Nullah ecotour / leisure

Floating/ riverside Market

Ferry services to Tai Mei Tuk

STAGE 2

Silt / garbage removal Ferry services to Ma On Shan

STAGE 3

1. 2. 3.

Ferry services to Ma On Shan

River and water ecology monitoring, conversation and public education Removal of silt and garbage from the river when needed Increase of the ratio of permeable pavement & green & public space with rainwater storage functions 45

6. DESIGN INTERVENTION

DESIGN FRAMEWORK

Rezone the site

Identify the four systems

STEP 1

● Conservation & Eco-agricultural Zone ● Transition Zone ● Sponge Urban Zone ● Coastal Zone

STEP 2

● ● ● ●

Green system Blue system Road system Building system

Use natural development approaches to tackle the water issues

STEP 3

● Store ○ ○ ● Adapt ○ ○ ○ ○

Adopt the integrated approaches in treating stormwater runoff

STEP 4

Retention Reuse Puriﬁcation Detention Inﬁlitration Conveyance 47

INTEGRTED CATCHMENT AFTER REZONING

Conversation & Eco-agricultural Zone

Woodland / Shrubland / Grassland / Wetland > 50%

Transition Zone

Low-rise Building + Rural Settlement + Woodland > 50%

Sponge Urban Zone

High-rise Building + Industry Park + Road > 50%

Coastal Zone

Within 1km of the coast

DESIGN TOOLBOX System

Element

Rainfall Runoff Coefﬁcient

Storage Retention

Reuse

Adaptation Puriﬁcation

Detention

Inﬁltration

Conveyance

CONSERVATION & ECO-AGRICULTURAL ZONE INTEGRATED STRATEGY Key Functions:

Store, Delay & Adapt

Greenspace Urban forest can be employed along upperstream to restore richness of ecosystem, including biodiversity and habitat. Dense vegetation in forest also encourage water storage both in canopy and ground.

Waterbody Wetponds can be created near urban forest delay ﬂoodﬂow, collect and purify rainwater during rainy season. It also provides entertain landscape for local citizens.

Road Permeable design on road network to increase inﬁltration to reduce surface runoff and preserve ground water for local ecosystem.

Building Using planter box and water tanks for rainwater harvesting and puriﬁcation, to meet the needs of daily water usage and minimize the impact on river upperstream. 50

CONSERVATION & ECO-AGRICULTURAL ZONE SECTION VIEW

TRANSITION ZONE INTEGRATED STRATEGY Key Functions:

Store, Delay & Adapt

Greenspace Revegetation in local creeks and riparian area helps increase water quality through inﬁltration and sedimentation. More vegetation also assist with ﬂood detention.

Waterbody Agriculture field and rainwater wetland can be designed on upper stream to delay flood flow and purify rainwater for downstream management.

Road Permeable pavers along the street and over the tree trench help increases the permeability of local infrastructure, increasing its resilience against flooding by reducing ground runoff. Moreover, water is naturally filtered and pollutants are removed during infiltration

Building Multi-level water treatment systems can be applied to local buildings to increase water utilization and flood resilience. Green and blue roof helps collect and filter rainwater, which is then channeled and cleansed through greenwall and finally stored in water tanks and planter boxes. Green and blue designs not only reduce urban heat island effect but also create a pleasing and eco-friendly environment.

TRANSITION ZONE SECTION VIEW

SPONGE URBAN ZONE INTEGRATED STRATEGY Key Functions:

Store, Inﬁltrate & Adapt

Greenspace Public green space including park and sunken plaza will detent rainwater ﬂow and reduce ﬂood risk. Public green space also provide amenity and recreational facilities for citizens, which can be a potential for future local development.

Waterbody River banks will be rejuvenated with bioswales to delay ﬂood, improve water quality and preserve local ecosystem. Water friendly facilities will also be equipped to attract local citizens to visit riverside.

Road Permeanble green blue street with pervious concrete and vegetated swale along the street will effectively facilitate inﬁltration, to encourage groundwater storage and recharge.Flow pathways will be established between detention basin to slow down water ﬂow.

Building Green and blue roof, water tank, green wall will be applied to redesign buildings, to ﬁlter and store rainwater. 54

SPONGE URBAN ZONE SECTION VIEW

COASTAL ZONE INTEGRATED STRATEGY Key Functions:

Recreation, Education, Delay & Adaptation

Greenspace Revegetate along coastline with natural waterfront buffer, such as mangrove to mitigate the the impact of astronomical tide and sea level rise.

Waterbody Vegetated swale will be applied along waterfront as natural buffer to reduce erosion and increase biodiversity. Aquacultural area will also be deployed to increase water quality and attract tourists. The watergate infrastructure will be upgraded to prevent sea water from backﬂow. Water transit will be developed to facilitate transport connection between Tai Po and Sha Tin.

Road Redesign roads with permeable surface and vegetated swales to promote inﬁltration rate and reduce surface runoff. New path will be designed to increase accessibility to waterfronts.

Building Revitalization of the Tai Po island house conservation studies center, to emphasize climate change, prompt cultural heritage conservation and environmental protection, as well as to rise the public awareness on water resilience. Sewage plant will also be redesigned as a public tour site for an overview of water treatment process.

COASTAL ZONE SECTION VIEW

DESIGN PRINCIPLE GREEN SYSTEM

STREET SYSTEM

BLUE SYSTEM

BUILDING SYSTEM

User

USER MANUAL Satellite Image ArcGIS Pro / U-Net

Typology Conserve & Eco-agriculture Zone

Transition Zone

Sponge Urban Zone

Coastal Zone

Four Zones Four Systems Typical Strategy Toolbox

Tool Selection

Urban Design Comparison • Rainfall Runoff Coefﬁcient • Impervious Surface

7. DEMONSTRATION

SELECTED SITE

Area of Site:

0.28 km²

Site boundary 61

SITE RECLASSIFICATION & REZONING

Sponge Urban Zone

DESIGN PLAN

SECTION VIEW

EVALUATION SURFACE PERMEABILITY Before: 19.51%

After: 50.45%

EVALUATION RUNOFF COEFFICIENT

TOTAL RUNOFF COEFFICIENT:

0.45-0.67 66

8. DISCUSSION & WAY FORWARD

CONTRIBUTION OF OUR STUDY

Assessment of Flood Susceptibility

●

Promotes urban water resilience using permeable surface rate and rainwater runoff coeﬃcient as metrics

User Manual for Water-resilient Town Design

● ●

Integrated natural development approaches for surface runoff control Proved effective in Tai Po and can be applied to other towns and communities in Hong Kong

LIMITATION OF OUR STUDY

U-NET Model

Hydraulic Modelling

● ●

Insuﬃcient training data Obstruction caused by the large number of high-rise buildings in Hong Kong

●

Lack of hydraulic modelling

WAY FORWARD Interdepartmental Communications & Coordination for Better Management

Regular Climate Forecast & Flood Mitigation Strategy Review

Assessment of the Actual Inﬁltration Capacity of Different Element & Tools

Territorial-wide & district-based strategy 4

Studies of the Impact of Sea Level Rise & Astronomical Tide on Flooding

3 Water Quality Improvement Through Holistic Approach of Flood Control, Ecology Protection & Conservation 70

Thank You for Listening

9. GLOSSARY

GLOSSARY Volume capture ratio of annual rainfall

Runoff

Based on the analysis and calculation of multi-year daily rainfall statistical data, the cumulative annual rainfall controlled (not discharged through drainage system) in the site through natural that enhanced inﬁltration, storage, evaporation, etc., as a percentage of the total annual rainfall.

Water that ﬂows away from high areas to low areas

Stormwater runoff

Stormwater runoff is generated from rain and snowmelt that ﬂows over land or impervious surfaces, such as paved streets, parking lots, and building rooftops, and does not soak into the ground.

Typology (w.r.t. permeability)

Identification and classification of land cover rather than land use to determine and evaluate how well water filters through different substances in a particular area.

Permeable & impermeable surface

Runoff coeﬃcient

Permeable surfaces (also known as porous or pervious surfaces) allow water to percolate into the soil to filter out pollutants and recharge the water table. Impermeable/impervious surfaces are solid surfaces that don’t allow water to penetrate, forcing it to run off. A dimensionless coefficient relating the amount of runoff to the amount of precipitation received. It is a larger value for areas with low infiltration and high runoff (pavement, steep gradient), and lower for permeable, well vegetated areas (forest, flat land).

Groundwater & Inﬁltration

Groundwater is derived from rain and melting snow that percolate downward from the surface; it collects in the open pore spaces between soil particles or in cracks and ﬁssures in bedrock. The process of percolation is called inﬁltration.

Volume of LID facilities for catchment runoff control

With total runoff control as the goal, the effective storage area of low impact development facilities required per unit catchment area (excluding rainwater regulation volume).

Storm Water

Stormwater is water from rain — or melting snow — that does not quickly soak into the ground. Stormwater flows from rooftops, over paved areas and bare soil, and through sloped lawns and fields. As it flows, this runoff collects and transports soil, pet waste, pesticides, fertilizer, oil and grease, leaves, litter, and other potential pollutants that ultimately wind up in local bodies of water. Stormwater is important because it can lead to pollution, erosion, flooding and many other environmental and health issues if not properly understood and maintained.

GLOSSARY Water Sensitive City (WSC)

Water sensitive urban design (WSUD)

Water Urbanism

Sponge city

Low Impact Development (LID) Catchment

The term “Water Sensitive City” (WSC) is widely used in literature to describe this new ideal to aim for, where cities will successfully deliver safe and reliable water services to all, now and in the future, in an eco-friendly manner.

Water sensitive urban design is a component of nature-based solutions that use the natural environment (e.g. soil, water, plants) to respond to diverse environmental, economic, social, and climate challenges. Water sensitive urban design involves the integration of water cycle management with the built environment through urban planning and design. Water Urbanism is an innovative approach to design practice and pedagogy that holistically joins the study of social and physical infrastructures, public health, and hydrological systems. A sponge city is a new urban construction model for ﬂood management, strengthening ecological infrastructure and drainage systems, proposed by Chinese researchers in early 2000 and accepted by the Chinese Communist Party and the State Council as urbanism policy in 2014. Low Impact Development (LID) is a term used in Canada and the United States to describe a land planning and engineering design approach to manage stormwater runoff as part of green infrastructure. LID emphasizes conservation and use of on-site natural features to protect water quality. Catchment refers to the area which drains into a stormwater drainage system.

Catchment Area (w.r.t. passive water harvesting)

Areas of a site where water is harvested, including where rain falls directly on plant canopies and pervious water harvesting inﬁltration areas, and where rain falls on impervious rooftops, sidewalks, parking lots, driveways and other surfaces from which stormwate is directed toward water harvesting inﬁltration areas.

Catchment Ratio (w.r.t. passive water harvesting)

The ratio of the water harvesting catchment area to the canopy area of the plants that use water harvested from that catchment area.

Design rainfall depth

Design rain indicates to what depth liquid precipitation would cover a horizontal surface in an observation period if nothing could drain, evaporate or percolate from this surface. The precipitation depth of 1 mm corresponds to a liquid quantity of 1 litre to 1 m² of ground area

10. REFERENCE

Choy, C., Wu, M., & Lee, T. (2020). Assessment of the damages and direct economic loss in Hong Kong due to Super Typhoon Mangkhut in 2018. Tropical Cyclone Research and Review, 9(4), 193–205. https://doi.org/10.1016/j.tcrr.2020.11.001 Collet, L., Beevers, L., & Stewart, M. D. (2018). Decision-Making and Flood Risk Uncertainty: Statistical Data Set Analysis for Flood Risk Assessment. Water Resources Research, 54(10), 7291–7308. https://doi.org/10.1029/2017WR022024 Imhoff, M. L., Zhang, P., Wolfe, R. E., & Bounoua, L. (2010). Remote sensing of the urban heat island effect across biomes in the continental USA. Remote Sensing of Environment, 114(3), 504–513. https://doi.org/10.1016/j.rse.2009.10.008 Neal, J., Keef, C., Bates, P., Beven, K., & Leedal, D. (2013). Probabilistic ﬂood risk mapping including spatial dependence. Hydrological Processes, 27(9), 1349–1363. https:// doi.org/10.1002/hyp.9572

Xu, H., Shi, T., Wang, M., Fang, C., & Lin, Z. (2018). Predicting effect of forthcoming population growth–induced impervious surface increase on regional thermal environment: Xiong’an New Area, North China. Building and Environment, 136, 98–106. https://doi.org/10.1016/j.buildenv.2018.03.035 Yang, K., Pan, M., Luo, Y., Chen, K., Zhao, Y., & Zhou, X. (2019). A time-series analysis of urbanization-induced impervious surface area extent in the Dianchi Lake watershed from 1988–2017. International Journal of Remote Sensing, 40(2), 573–592. https:// doi.org/10.1080/01431161.2018.1516312 Columbia GSAPP. (2019). Water Urbanism: Can Tho. Retrieved March 15, 2022, from https://www.arch.columbia.edu/books/reader/419-water-urbanism-can-tho Environmental Protection Department. (2020). River water quality in Hong Kong in 2020 - epd.gov.hk. Retrieved March 15, 2022, from https://www.epd.gov.hk/epd/sites/ default/ﬁles/epd/english/environmentinhk/water/hkwqrc/ﬁles/waterquality/ annual-report/riverreport2020.pdf ARUP. Shanghai urban drainage masterplanning. (n.d.). Retrieved 15 March 2022, from https://www.arup.com/en/projects/shanghai-drainage-masterplan NYCEDC. (n.d.). Lower Manhattan Coastal resiliency. Retrieved March 15, 2022, from https://edc.nyc/project/lower-manhattan-coastal-resiliency ABC Waters Design Guidelines 4th Edition. (2018). Retrieved 15 March 2022, from https:// www.pub.gov.sg/Documents/ABC_Waters_Design_Guidelines.pdf Drainage Services Department Sustainability Report 2017-18. (2018). Retrieved 15 March 2022, from https://www.dsd.gov.hk/Documents/SustainabilityReports/1718/en/ index.html

11. APPENDIX

QUESTIONNAIRE SURVEY Part (2b) Understanding how ﬂooding affects people’s daily lives

QUESTIONNAIRE SURVEY Part (2a) People’s Perception of Flooding Issues in Tai Po Has ﬂooding problem in Tai Po become more serious than before?

Which of the following (s) is/are the major ﬂooding backspot(s) in Tai Po?

What is/are the major reason(s) of ﬂooding in Tai PO?

system: Greenspace number: 1 element: Conventional Raingarden source: NRCS USDA, ABC waters

system: Greenspace number: 2 element: Soakaway Raingarden source: ABC waters, Water Sensitive Cities

system: Greenspace number: 3 element: Agriculture Field source: Finland’s ERDF-funded CircularHoodFood project

system: Greenspace number: 4 element: Cleansing Biotypes source: ABC Waters

system: Greenspace number: 5 element: Dry Swales source: NCSU

system: Greenspace number: 6 element: Wet Swales source: ABC Waters

system: Waterbody number: 7 element: Wet Pond source: ABC Waters, Hai Mian Cheng Shi Jian She Ji Shu ZHi Nan(海绵城市建设技术指南）

system: Waterbody number: 8 element: Aquaculture source: 孙传致，斯特芬·奈豪斯，格雷戈里·布拉肯 . 基于基塘系统的珠江三角洲多尺度水敏设计研究 [J]. 风景园林，2019，26（9）：31-44.

system: Waterbody number: 9 element: Rainwater Wetland source: ABC Waters, Hai Mian Cheng Shi Jian She Ji Shu ZHi Nan（海绵城市建设技术指南）

system: Street number: 10 element: Pervious Asphalt source: https://www.js888.com.tw/product-1-5.html

system: Street number: 11 element: Pervious Concrete source: American Concrete Institute (ACI)

system: Street number: 12 element: Porous Asphalt source: CAHILL Associates 2003

system: Street number: 13 element: Permeable Pave source: https://salmonfallsnurseryandlandscaping.com/permeable-pavers/

system: Street number: 14 element: Permeable Pavement over Tree Trench source: https://www.deeproot.com/blog/blog-entries/stormwater-quantity-and-rate-control-beneﬁts -of-trees-in-uncompacted-soil-2/

system: Street number: 15 element: Bioretention swale within roadside drain source: ABC Waters

system: Building number: 16 element: Green Roof source: ABC Waters

system: Building number: 17 element: Balcony source: ABC Waters

system: Building number: 18 element: Planter Box source: ABC Waters,Vo Trong Nghia Architects

system: Building number: 19 element: Green Wall source: ABC Waters

system: Building number: 20 element: Downspout Planters source: Stormwater Management Manual. Eugene

system: Building number: 21 element: Water Tank source: Stormwater Sydney, Tredje Natur

100

system: Building number: 22 element: Ground covered green space for underground buildings source: Seksan design

101

system: Building number: 23 element: Sunken Plaza source: Zhengtong Construction

102