Managing Stormwater in Urbanised Singapore
for Flood Control
Flood and Storm Surge Control Training
Tokyo, Japan
25 – 27 Jan 2011
Singapore Representatives:
1Dorinda Hua / Senior Engineer
Loh Yee Wen / Engineer

Introduction

2

Singapore: Our Unique Circumstances

Singapore

Land Area~710 km2

Population

4.99 milAverage Annual Rainfall

2,400 mmAverage Water Demand

1.6 mil m3/day
3

PUB Manages The Complete Water Cycle
From sourcing, collection, purification and supply of drinking water, totreatment of used water and turning it into NEWater, drainage ofstormwater

RainSea

TreatmentofUsed Water

Direct NonPotable Use

CollectionofUsed Waterin Sewers

4Catchment & Waterways Department
To plan, develop & manage our reservoirs &waterways for water supply & flood control andintegrate 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 & water5

Floods – Past and Now6

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

Canal

Closed roadside drain

River8Physical Conditions Affecting Drainage in Singapore• island generally flat with pockets of low lying areas• affected by high tides• increased stormwater runoff from urbanisation• annual rainfall of around
2400mmAVERAGE MONTHLY RAINFALL(FROM 1869 TO 2009)

350

288.9

300
244

Amount of Rainfall (mm)

250

255.5

200

184.5

– northeast monsoon(Nov to Mar)

194.3
178.7

161.7

171.9

176.2
162.2

158.3

• 2 main seasons dictated bymonsoons

170.2150– southwest monsoon(May to Sep)

100

500JANFEB

MARAPR

MAYJUNJULMonthAUG

SEP

OCT

NOVDEC9

Past Major Floods in Singapore
Maximum 24 Hour Rainfall (1931 to 2009)600

Dec 2006
8 nurseries, 29 families, 1club house & 4 shophouses
Tide level = 3.0m
Total flooded area = 12 ha

Amount of Rainfall (mm)Dec 1954
50,000 people affected
5 people died
Tide level = 3.2m
Total flooded area = 2540 ha467

366

No
Record326
1931

3002001940

400512

Dec 19781,000 people affected
7 people died
Tide level = 3.2m
Total flooded area = 3178 ha

100

0
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
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

Amount of Rainfall (mm)500

Dec 1969
3,000 people affected
5 people died
Tide level = 3.2m
Total flooded area = 2750 ha

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 197811

Recent Floods

Marina Station Road
(10 Mar 2010)

Localisedand shortfloods

Sims Ave East near Lor Marican(12 Apr 2008)

Syed Alwi Road
(26 Sep 2008)

Coronation Walk
(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 offlood 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 offlood prone areas
 e.g. Marina Barrage

BeforeAfter18

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 offlood 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 offlood prone areas
 e.g. Marina Barrage

3 in 1 project :-1) Flood alleviation
2) Water supply
3) Lifestyle attraction− to act as a tidal barrier to control floodsin the city
− to be a freshwater reservoir− 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 andinfrastructural facilities for flood
protection purposes• Raise low lying grounds / roads thatwere flood prone (in conjunction withredevelopment 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 andinfrastructural facilities for floodprotection purposes

Kim Seng Road
BEFORE• Raise low lying grounds / roads thatwere flood prone (in conjunction withredevelopment proposals)• Advice on appropriate protection
measures for older buildings

AFTER

BEFOREPan Island Expressway

AFTER
22

Approach to Managing Flood Risk
(2) Adopting flood protection measures• Stipulate the platform and crest levelsrequired for new buildings andinfrastructural facilities for floodprotection purposes• Raise low lying grounds / roads thatwere flood prone (in conjunction withredevelopment 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 inflood prone areas

BEFORE

AFTER

Drainage improvement at
Joan Road Outlet Drain

24Maintenance of Waterways


Keeping the drains and waterways free flowing and to operatedrainage 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


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

Float Boom

26

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

Pumping
StationTidal Gate

27

While the flood problems in Singapore are under control, wecan still expect floods for two main reasons :•low-lying areas where ground levels are barely above high tide areprone 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.
B.
C.

ACTIVENew recreational spaces
BEAUTIFUL
Integration of waters with urban landscape
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 ProgrammeLong-term strategic initiative

MacRitchie Reservoir– To transform our utilitarian drains, canals and reservoirs intovibrant, 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 Park30

Active Beautiful Clean (ABC) Waters Programme
Kolam Ayer ABC Waterfront
AfterBefore31

Active Beautiful Clean (ABC) Waters Programme
Sengkang Floating Wetland

32Active Beautiful Clean (ABC) Waters ProgrammeLower Seletar Reservoir

Family Bay

Water Activities

Family Bay
Water Puppet Show33

Flood Management in Singapore

34

Flood Managementa) Keeping the public informed•••

Preparing for the North East Monsoon
Getting information
Weather and Water Level Alert Systemb) 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 andmotorists 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

Extremeeventof widespread flooding• c)Floodadvisories
include:Activate
national
response
planor –equalincludesrescue andevacuation• • Dateswhen hightides are
greater thanto 3m (importantfor areas
operations
affectedby floods coinciding with high tides)• Singapore Police Force – Lead agency in managing all joint operations• Information
whereandpublic
can obtain
information
onwithweather,waterlevels, orinvolvingon
safetysecurityof public,
togethermultiplegovernment
otherpertinent information
agencies• Websites, hotlines, contacts of flood board suppliers, etc.
• Suggestions on how to protect their belongings/premises

35

Flood Managementa) Keeping the public informed•••

Preparing for the North East Monsoon
Getting information
Weather and Water Level Alert System• Information
how to Manage
Floods is into floodsb) onResponseand Flashinvestigation
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 andmotorists together with Traffic Police• Investigate flood, identify cause and take immediate actionc) 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
agencies36

Flood Managementa) Keeping the public informed•••Preparing for the North East Monsoon
Getting information
Weather and Water Level Alert Systemb) Response and investigation into floods•••c) Extreme event of widespread flooding•••

Heavy rain warnings currently

Teams on standby when intense rain is forecasted issued on:Teams on sites will render quick assistance to affected residents andmotorists together with Traffic Police• NEA website• Weather@SG
Investigate flood, identify cause and take immediate
action• Radio• SMS (to limited no. ofrecipients)

Activate national response plan – includes rescue and evacuation
operations
Water level alerts are 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,
PUB works with Mediacorp to broadcast over radio the locations of flooded areas so that publicagencies
can avoid these areas.

•Water level alerts for building owners/management committees in flood prone areas37

Flood Managementa) Keeping the public informed•••

Preparing for the North East Monsoon
Getting information
Weather and Water Level Alert Systemb) Response and investigation into floods•••

Teams on standby when intense rain is forecast
Teams on sites will render quick assistance to affected residents andmotorists together with Traffic Police
Investigate flood, identify cause and take immediate actionc) 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
agencies38Flood Managementa) Keeping the public informed•••

Preparing for the North East Monsoon
Getting information
Weather and Water Level Alert Systemb) Response and investigation into floods•••

Teams on standby when intense rain is forecasted
Teams on sites will render quick assistance to affected residents andmotorists together with Traffic Police
Investigate flood, identify cause and take immediate actionc) 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 InternationalWater Week is the global platform
for water solutions that brings
policymakers, industry leaders,experts and practitioners together
to address challenges, showcase
technologies, discoveropportunities and celebrateachievements 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 you41