Managing Stormwater in Urbanised Singapore for Flood Control

Flood and Storm Surge Control Training Tokyo, Japan 25 – 27 Jan 2011 Singapore Representatives: Dorinda Hua / Senior Engineer1 Loh Yee Wen / Engineer Introduction

2 Singapore: Our Unique Circumstances

Singapore

Land Area ~710 km 2 Population 4.99 mil Average Annual Rainfall 2,400 mm Average Water Demand 1.6 mil m 3/day

3 PUB Manages The Complete Water Cycle From sourcing, collection, purification and supply of drinking water, to treatment of used water and turning it into NEWater, drainage of stormwater

Rain Sea Treatment ofof Used Water

Direct Non- Potable Use Collection ofof Used Water in Sewers

4 Catchment & Waterways Department

To plan, develop & manage our reservoirs & waterways for water supply & flood control and integrate them with the surrounding environment in a sustainable manner.

– optimise collection & storage of rainwater – reduce flood-prone areas – maintain good raw water quality in our reservoirs & waterways – create value through integration of waterways & reservoirs with surrounding developments – foster closer relationship between people & water

5 Floods – Past and Now

6 The Blue Map of Singapore

• Some 7,000 km of roadside drains • 32 major rivers

7 Types of Drains / Canals

Outlet drain

Open roadside drain Closed roadside drain

Canal River 8 Physical Conditions Affecting Drainage in Singapore

• island generally flat with pockets of low lying areas • affected by high tides • increased stormwater runoff from urbanisation

AVERAGE MONTHLY RAINFALL • annual rainfall of around (FROM 1869 TO 2009) 350 2400mm 300 288.9 • 2 main seasons dictated by 255.5 244 250 monsoons

194.3 200 184.5 178.7 – northeast monsoon 171.9 176.2 170.2 161.7 162.2 158.3 (Nov to Mar) 150 – southwest monsoon Amount of Rainfall (mm) AmountRainfall of 100 (May to Sep)

0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Month

9 Past Major Floods in Singapore

Maximum 24 Hour Rainfall (1931 to 2009) 600 Dec 1978 Dec 1969 1,000 people affected 3,000 people affected 7 people died 512 5 people died Tide level = 3.2m 500 Tide level = 3.2m Total flooded area = 3178 ha Total flooded area = 2750 ha 467 Dec 2006 Dec 1954 8 nurseries, 29 families, 1 400 50,000 people affected club house & 4 shophouses 5 people died Tide level = 3.0m 366 Total flooded area = 12 ha Tide level = 3.2m No Total flooded area = 2540 ha 326 Record 300 1931 1931 1940 1940

200 Amount of of (mm) (mm) RainfallRainfallAmount Amount Amount of Rainfall (mm) (mm) RainfallRainfall of of Amount Amount

100

0 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 Year

10 Past Floods

Potong Pasir, Dec 1954 Newton Circus, Dec 1969 Braddell Road, Dec 1978

Orchard Road, Dec 1954

Bideford Road, Dec 1969 3200 ha in the 1970’s Braddell Road, Dec 1978 11 Recent Floods

Marina Station Road Syed Alwi Road (10 Mar 2010) Localised (26 Sep 2008) and short floods

Sims Ave East near Lor Marican Coronation Walk (12 Apr 2008) (19 Nov 2009)

12 Stormwater Management in Singapore

13 Stormwater Management

Objective

Provide a first-rate drainage system to :

• harness rainwater for our water needs; and

• keep Singapore flood free.

14 How Do We Manage Flood Risks?

PUB manages flood risks in three ways:

15 Reducing Flood Prone Areas

16 Approach to Managing Flood Risk (1) Provide adequate drainage ahead of new developments • Plan and implement drainage systems and set aside drainage reserves based on current and projected land uses In consultation with other development agencies such as URA, HDB, LTA and JTC e.g. Sungei Punggol • Implement flood alleviation projects to tackle and reduce the size of flood prone areas e.g. Marina Barrage

17 Approach to Managing Flood Risk (1) Provide adequate drainage ahead of new developments • Plan and implement drainage systems and set aside drainage reserves based on current and projected land uses In consultation with other development agencies such as URA, HDB, LTA and JTC e.g. Sungei Punggol • Implement flood alleviation projects to tackle and reduce the size of flood prone areas e.g. Marina Barrage

Before

After 18 Approach to Managing Flood Risk (1) Provide adequate drainage ahead of new developments • Plan and implement drainage systems and set aside drainage reserves based on current and projected land uses In consultation with other development agencies such as URA, HDB, LTA and JTC e.g. Sungei Punggol • Implement flood alleviation projects to tackle and reduce the size of flood prone areas e.g. Marina Barrage

19 Approach to Managing Flood Risk (1) Provide adequate drainage ahead of new developments • Plan and implement drainage systems and set aside drainage reserves based on current and projected land uses In consultation with other development agencies such as URA, HDB, LTA and JTC e.g. Sungei Punggol • Implement flood alleviation projects to tackle and reduce the size of flood prone areas e.g. Marina Barrage

3 in 1 project :- 1) Flood alleviation − to act as a tidal barrier to control floods in the city 2) Water supply − to be a freshwater reservoir 3) Lifestyle attraction − vibrant waterfront with water based20 activities Approach to Managing Flood Risk (2) Adopting flood protection measures

• Stipulate the platform and crest levels required for new buildings and infrastructural facilities for flood protection purposes

• Raise low lying grounds / roads that were flood prone (in conjunction with redevelopment proposals)

• Advice on appropriate protection measures for older buildings

Higher platform level for wafer fabrication plants

21 Approach to Managing Flood Risk (2) Adopting flood protection measures

• Stipulate the platform and crest levels required for new buildings and Kim Seng Road infrastructural facilities for flood protection purposes BEFORE • Raise low lying grounds / roads that were flood prone (in conjunction with redevelopment proposals)

• Advice on appropriate protection AFTER measures for older buildings

BEFORE

Pan Island Expressway AFTER

22 Approach to Managing Flood Risk (2) Adopting flood protection measures

• Stipulate the platform and crest levels required for new buildings and infrastructural facilities for flood protection purposes

• Raise low lying grounds / roads that were flood prone (in conjunction with redevelopment proposals)

• Advice on appropriate protection measures for older buildings

Flood Barrier

23 Approach to Managing Flood Risk (3) Making continual drainage improvement

• Continually reviewing and improving drainage in flood prone areas

BEFORE AFTER

Drainage improvement at Joan Road Outlet Drain

24 Maintenance of Waterways

Keeping the drains and waterways free flowing and to operate drainage facilities Regular desilting of canals and rivers Cleansing of open roadside drains Trapping and removing flotsam & debris • Float booms • Mechanical debris removal facility Pumping stations & tidal gates

25 Maintenance of Waterways

Float Boom

26 Maintenance of Waterways

Tidal Gate

27 While the flood problems in Singapore are under control, we can still expect floods for two main reasons :

• low-lying areas where ground levels are barely above high tide are prone to flooding when heavy rain coincides with high tides. The only effective flood control measure is to raise the ground levels in conjunction with redevelopment

• there is a limit to which we can widen drains because of land constraints. Very intense rainfall can overwhelm the drains and cause flash floods. Such floods however will be minor and of short duration

28 Active Beautiful Clean (ABC) Waters Programme

A. ACTIVE New recreational spaces B. BEAUTIFUL Integration of waters with urban landscape C. CLEAN Improved water quality

“…Turn Singapore into a City of Gardens and Water” – PM Lee, ABC Waters Public Exhibition - Feb 2007 29 Active Beautiful Clean (ABC) Waters Programme

Long-term strategic initiative MacRitchie Reservoir – To transform our utilitarian drains, canals and reservoirs into vibrant, aesthetically pleasing and clean flowing streams, rivers and lakes

– To bring people closer to the water so that they will cherish and take ownership

– To create a seamless blue-green network well integrated with the adjacent developments

Kallang River Bishan Park 30 Active Beautiful Clean (ABC) Waters Programme

Kolam Ayer ABC Waterfront After

Before

31 Active Beautiful Clean (ABC) Waters Programme

Sengkang Floating Wetland

32 Active Beautiful Clean (ABC) Waters Programme

Lower Seletar Reservoir

Family Bay Water Activities

Family Bay Water Puppet Show

33 Flood Management in Singapore

34 Flood Management

a) Keeping the public informed • Preparing for the North East Monsoon • Getting information • Weather and Water Level Alert System

b) Response and investigation into floods • PUB’s officers and contractors will step up inspections of drains in flood prone areas in • Teams on standby when intense rain is forecasted preparation for the year end monsoon period. • Teams on sites will render quick assistance to affected residents and motorists together with Traffic Police • Flood advisories will be distributed to premises located in flood prone areas & who • Investigate flood, identify cause and take immediate action have been affected by recent floods

•c)Flood Extreme advisories event include: of widespread flooding ••Dates Activate when high national tides are response greater than plan or –equal includes to 3m (important rescue and for areas evac uation affectedoperations by floods coinciding with high tides) • Singapore Police Force – Lead agency in managing all joint operations • Informationinvolving on safety where and public security can obtain of public, information together on withweather, mult iplewater government levels, or otheragencies pertinent information • Websites, hotlines, contacts of flood board suppliers, etc. • Suggestions on how to protect their belongings/premises

35 Flood Management

a) Keeping the public informed • Preparing for the North East Monsoon • Getting information • Weather and Water Level Alert System

• Informationb) on Response how to Manage and Flash investigation Floods is into floods available at PUB’s• Website Teams on standby when intense rain is forecasted http://www.pub.gov.sg• Teams on sites will render quick assistance to affected residents and motorists together with Traffic Police • Investigate flood, identify cause and take immediate action

c) Extreme event of widespread flooding • Activate national response plan – includes rescue and evacuation operations • Singapore Police Force – Lead agency in managing all joint operations involving safety and security of public, together with multiple government agencies

36 Flood Management

a) Keeping the public informed • Preparing for the North East Monsoon • Getting information • Weather and Water Level Alert System

b) Response and investigation into floods Heavy rain warnings currently • Teams on standby when intense rain is forecasted issued on: • Teams on sites will render quick assistance to affected residents and motorists together with Traffic Police • NEA website • Investigate flood, identify cause and take immediate• Weather@SGaction • Radio • SMS (to limited no. of c) Extreme event of widespread flooding recipients) • Activate national response plan – includes rescue and evacuation • Water level alerts areoperations currently issued via SMS • Singapore Police Force – Lead agency in managing all joint operations – When sensor records water levels >75%, >90%, SMSes are sent out (to limited no. of recipients) involving safety and security of public, together with multiple government • During flood events,agencies PUB works with Mediacorp to broadcast over radio the locations of flooded areas so that public can avoid these areas.

• Water level alerts for building owners/management committees in flood prone areas

37 Flood Management a) Keeping the public informed • Preparing for the North East Monsoon • Getting information • Weather and Water Level Alert System b) Response and investigation into floods • Teams on standby when intense rain is forecast • Teams on sites will render quick assistance to affected residents and motorists together with Traffic Police • Investigate flood, identify cause and take immediate action c) Extreme event of widespread flooding • Activate national response plan – includes rescue and evacuation operations • Singapore Police Force – Lead agency in managing all joint operations involving safety and security of public, together with multiple government agencies

38 Flood Management a) Keeping the public informed • Preparing for the North East Monsoon • Getting information • Weather and Water Level Alert System b) Response and investigation into floods • Teams on standby when intense rain is forecasted • Teams on sites will render quick assistance to affected residents and motorists together with Traffic Police • Investigate flood, identify cause and take immediate action c) Extreme event of widespread flooding • Activate national response plan – includes rescue and evacuation operations • Singapore Police Force – Lead agency in managing all joint operations involving safety and security of public, together with multiple government agencies

39 The Singapore International Water Week is the global platform for water solutions that brings policymakers, industry leaders, experts and practitioners together to address challenges, showcase technologies, discover opportunities and celebrate achievements in the water world.

The event’s flagship programmes comprise: • Lee Kuan Yew Water Prize • Water Leaders Summit • Water Convention • Water Expo • Business Forums

Details & Register at: www.siww.com.sg

40 Thank you