PUB says that the canal water level at the accident site rose from 0.7 m to 2.5 m in 20 mins
The body of the missing teenage girl swept away in the Sungei Pandan canal on Sunday afternoon has been found.
The police alerted the media at 1pm that Debra Koh's body had been found in the open seas near the river mouth of Sungei Pandan.
The teenager, along with three friends, had been swept away by strong currents while trying to retrieve a handphone that had fallen into the canal. The accident happened near Block 182 Bukit Batok West Avenue 8 at about 3.40pm.
One of the teenage boys managed to swim ashore 20 minutes later, while the other boy and girl were rescued 40 minutes later.
All three were taken to the National University Hospital where they were treated for minor injuries
In response to media queries, the Public Utilities Board (PUB) said, “A canal can look quite dry but as it is fed by a system of drains, heavy rain that occurs elsewhere within the catchment can bring down a rapid surge of water within minutes.”
This is especially so in Singapore, where short but intensive periods of tropical rainfall results in the rapid build-up of water in drains and canals, said PUB.
PUB added that the section of the canal where the teenagers had entered is usually dry, but it has a catchment size of 173 ha, which is about one-third the size of Bukit Batok town.
“If it rains at the furthest point of this catchment which is about 1.3 km away, it will take only 15 minutes for the water to reach that part of the canal,” PUB said.
With regards to the depth of the water, PUB said that it was 2.5m at the accident site. Based on the rainfall recorded on April 22, PUB estimates that the maximum water level was about 0.7m high and it took about 20 minutes for the water to reach that level.
During a thunderstorm, the water current at that section of the canal is the strongest, due to a steep drop in the gradient which causes a rush of water.
PUB has dismissed the tide gates as a cause of the surge in water. It said that the teens were swept away by the stormwater that had collected in the canal from the network of drains within its catchment.
“As the tide gates are located 4 km downstream from the site of the incident, it has no impact on the water flow upstream,” it added.
The PUB advises the public not to enter any canals as there may be swift currents due to a sudden surge of rapid water flow. Safety railings are put up along deep drains and canals to prevent people from falling in.