Heavy rain, flash floods expected in December and January

SINGAPORE — With the North-east Monsoon season expected to start later this month, there may be localised flash floods in low-lying areas on some days come December and January, the Meteorological Service Singapore (MSS) said on Thursday (Nov 24) in a joint statement with national water agency PUB.

This will occur if heavy rain coincides with high tides, which are expected to reach 2.9m to 3.3m from Dec 14 to 17 and Jan 13 to 15, both agencies said.

Between December and January, short-duration moderate to heavy thundery showers are also expected mostly in the afternoons, extending into the evening on some days.

During this period, there may also be two to four episodes of monsoon surges, which bring about prolonged periods of widespread moderate to heavy rain lasting between two and five days, along with occasional windy conditions and cooler temperatures.

To prepare for the rainy season, officers from the PUB have distributed advisories to around 600 residents and shopowners in low-lying and flood-prone areas, instructing them on how to protect belongings and premises in case of flash floods.

The water agency also has a network of 170 closed-circuit television (CCTV) cameras to monitor road conditions in low-lying areas and hot spots, as well as 205 sensors installed in major drains and canals to provide real-time data on water levels. 

To keep tabs on flash floods during heavy rain, members of the public may view some of these CCTV images online and get information on the water-level sensors via PUB’s website (under drainage and flood management) or its free mobile app, MyWater. They may also go to PUB’s Facebook or Twitter accounts for the latest updates.

Ahead of the monsoon season, PUB said that it has inspected about 100 major construction worksites to ensure that the drains around the areas are free-flowing. It is working with agencies and town councils to ensure drains and canals are clean and functioning effectively. 

The National Environment Agency (NEA), for instance, has increased the frequency of checks and cleaning of drains and drop-inlet chambers, which channel rainwater from the roads into drains. Drainage improvement projects are ongoing at 76 locations islandwide. 

Works at the Sunset Way outlet drain are expected to be completed in the second quarter of next year, while works at Kallang River (between Bishan Road and Braddell Road) are scheduled to be done by the fourth quarter of 2018. 

PUB also has plans to begin drainage upgrading works at 26 locations by the end of the year.

On average, Singapore sees 18 rain days in December and 13 rain days in January, based on a 30-year climatological reference period from 1981 to 2010. Come February and March, the North-east Monsoon season will enter a dry phase — with less rainfall, drier weather conditions and occasional windy conditions.