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) 50 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Month 9 Amount of Rainfall (mm) 100 200 300 400 500 600 0 1931 1932 1933 ha 2540 floodedTotal = area 1934 1935 peopleaffected 50,000 1936 1937 = 3.2m level Tide 1938 died people 5 1939 1954 Dec 1940 1941 1942 1943 1944 Major Floods in Singapore Past 1945 1946 ha 2750 floodedTotal = area 1947 1948 peopleaffected 3,000 1949 1950 = 3.2m level Tide 1951 died people 5 Dec 1969 Dec 1952 to 2009) (1931 Rainfall Hour 24 Maximum 1953 1954 326 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 Year 1968 1969 467 1970 1971 1972 1973 1974 1975 1976 512 1977 1978 1979 1980 1981 1982 1983 1984 Total flooded area = 3178 ha 3178 floodedTotal = area 1985 & house shophouses 4 club Total flooded area = 12 ha 12 floodedTotal = area 1986 1 families, 29 nurseries, 8 1987 1931 peopleaffected 1,000 Tide level = = 3.2m level Tide 1988 = 3.0m level Tide 1989 died people 7 1990 1978 Dec 1991 2006 Dec 1992 1993 1994 1995 1996 1940 1997 1998 1999 Record 2000 No 2001 10 Amount of Rainfall (mm) 2002 2003 2004 2005 2006 366 2007 2008 2009 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 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 Pumping stations & tidal gates Station 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