SINGAPORE - The flash floods that occurred in nine locations in eastern Singapore on Monday morning (Jan 8) occurred in low-lying grounds with drainage works in progress except for one location, PUB said at a media briefing on Monday night.

The drains were working and managed to drain the floods when the rain stopped, PUB's director of catchment and waterways Yeo Keng Soon told the media.

The floods arose because rain developed too quickly in the area, a spokesman for the Meteorological Services Singapore said.

Within just four hours, 118.8mm of rain was recorded at the Kim Chuan Road rain gauge. That amount is about half of Singapore's average monthly rainfall in January.

All the reported flood areas are low-lying grounds with drainage works in progress except Tampines Avenue 12.

Investigations are still ongoing for the area, and should be completed within the next two days. Preliminary investigations did not show any obstruction.

The ongoing drainage works in the affected areas will be completed by March 2019 and the revamped drains will discharge water faster.

Investigations will also be conducted to find out if there were any other contributing factors to the flood.

Heavy rain paired with a Sumatra squall that developed over the Strait of Malacca and moved eastwards, affecting Singapore, led to flash flooding in areas including Tampines, Bedok and Changi from 8.30am on Monday.

Videos and photos showed people wading in deep water, cars stranded on flooded roads and traffic slowing on waterlogged lanes.

PUB advised motorists and pedestrians to avoid all flooded areas and not to push their stalled vehicles or wade through the flood because it is unclear where the open drains are.

Thundery showers are expected over the next few days. Depending on their severity, flood contingency plans may be activated.