S'pore's strategies to reduce the likelihood of heavy flooding

SINGAPORE – There were reports of flash floods across Singapore after heavy rain last Saturday (April 17).

Such bouts of intense rainfall are expected to become more frequent with climate change.

National water agency PUB has come up with a number of strategies to reduce the likelihood of heavy flooding.

Here are some examples.

Catchment-level detention tanks

• PUB currently manages two detention tanks, the Stamford Detention Tank and Opera Estate Pumping Station, which have a capacity of 38,000 cubic m and 15,000 cubic m respectively.

• A third such tank in Syed Alwi Road is due to be completed by 2025. It will have a capacity of 9,300 cubic m.

Detention tanks

• Detention tanks collect and store stormwater run-off during a storm.

• They then release it at controlled rates into the drainage system, reducing peak discharge rates.

Minimum platform and crest levels

Elevating the entrances of buildings and MRT stations to prevent stormwater from flowing into them.

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Rain garden

• Helps cleanse water that flows into drainage system by filtering. 

• Slows down the speed of run-off entering drainage systems

Canals and drains

• Singapore currently has about 8,000km of drains, rivers and canals.

• If necessary, they can either be widened or deepened, or new infrastructure can be built.

Workers cutting grass inside the canal of Serangoon River in December 2020. ST PHOTO: LIM YAOHUI

Flood barriers

Can be quickly deployed to protect homes and buildings in the event of a flash flood.

Green roofs

Rooftop vegetation captures rainwater, allowing evaporation and transpiration to take place, and reducing the amount of run-off entering drainage systems.

The Green Roof (right) at the Keppel Marina East Desalination Plant. PHOTO: ST FILE

Despite these efforts, why do flash floods still occur?

• Intensity of the storm can be much more than what the drainage system is able to handle.

• Options to reduce flooding may be limited in low-lying areas, as drains cannot be dug deeper than downstream levels, which will prevent water from flowing away

• Due to land scarcity, it is not practical to build bigger drains to meet every extreme rainfall event in Singapore.

• Drains can get clogged with leaves and litter.

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