National water agency PUB explained that the flash floods on Sunday morning were caused by two bouts of heavy rainfall.
It said this at a news conference on Sunday afternoon, which was also attended by Minister for the Environment and Water Resources Vivian Balakrishnan.
The first bout of rainfall started slightly past 6am, and second downpour, which was more intense, occurred at about 10.30am.
About 65mm of rainfall was recorded within 30 minutes.
This was worse than the one on June 16 last year, which had 100mm of rainfall within two hours.
PUB said it had mobilised staff and contractors to the flooded sites once it received alerts of heavy rain.
PUB also deployed tankers to affected areas to pump out the water from carparks located in basements of buildings.
PUB chief executive Khoo Teng Chye said he is studying some possible solutions to prevent future occurrences.
"These include, possibly, building a big retention pond near where we can then trap some of the peak flows," Mr Khoo said.
"The other alternative is to really create a diversion canal from where this pond is to the Singapore River.
"But given Singapore's built-up situation, these are very, very expensive schemes."
Meanwhile, Dr Balakrishnan outlined five key areas that he would focus on, in dealing with floods in Singapore.
Speaking after inspecting the flood areas at Tanglin Mall, Dr Balakrishnan said one of his priorities now is to ensure safety is maintained along drains.
Dr Balakrishnan stressed there's no compromising safety.
He said railings will be installed where needed, and drains covered in the short term so that no one gets hurt.
On Wednesday, a 15-year-old teenager died when he fell into an uncovered drain swollen with rainwater.
"Personally, I think our weather has changed. I'm actually psychologically prepared for it to get worse," Dr Balakrishnan said.
"You're dealing with nature, and you're dealing with the weather; you have to be prepared that there is a limit to human engineering and what we can deliver.
"But having said that, let us make sure we have done the best we can and within those limits, then cope with whatever else that nature throws at us."
Dr Balakrishnan said because of the changing weather conditions, his ministry will need to review planning norms, which includes designing of drainage systems.
He added another priority is to ensure roads are passable even during heavy rainfall.
He said he intends to ensure buildings are better prepared to cope with the occurrence of floods.
During heavy rainfall last year, the basement of Tessarina condominium was flooded.
The management there has since made improvements such as installing a flood barrier.
When the Bukit Timah canal flooded its banks on Sunday morning, the siren was activated and residents were alerted to drive their cars out of the basement, and the flood barrier was closed.
Tessarina Condominium management committee chairman Leonard Yip said: "The primary strategy for us was to lobby for improvements to the Bukit Timah canal and also for raising of Wilby Road.
"So, we believe that most of the problems will be solved".
At Bukit Timah Road, flash floods occurred at the stretch from Blackmore to Maplewood Road, making some lanes impassable to traffic earlier Sunday morning.
PUB is currently making drainage improvement works to the Bukit Timah canal.
Works to deepen the canal will start by the end of this year.
The project is expected to be fully completed by November 2012.
It said this at a news conference on Sunday afternoon, which was also attended by Minister for the Environment and Water Resources Vivian Balakrishnan.
The first bout of rainfall started slightly past 6am, and second downpour, which was more intense, occurred at about 10.30am.
About 65mm of rainfall was recorded within 30 minutes.
This was worse than the one on June 16 last year, which had 100mm of rainfall within two hours.
PUB said it had mobilised staff and contractors to the flooded sites once it received alerts of heavy rain.
PUB also deployed tankers to affected areas to pump out the water from carparks located in basements of buildings.
PUB chief executive Khoo Teng Chye said he is studying some possible solutions to prevent future occurrences.
"These include, possibly, building a big retention pond near where we can then trap some of the peak flows," Mr Khoo said.
"The other alternative is to really create a diversion canal from where this pond is to the Singapore River.
"But given Singapore's built-up situation, these are very, very expensive schemes."
Meanwhile, Dr Balakrishnan outlined five key areas that he would focus on, in dealing with floods in Singapore.
Speaking after inspecting the flood areas at Tanglin Mall, Dr Balakrishnan said one of his priorities now is to ensure safety is maintained along drains.
Dr Balakrishnan stressed there's no compromising safety.
He said railings will be installed where needed, and drains covered in the short term so that no one gets hurt.
On Wednesday, a 15-year-old teenager died when he fell into an uncovered drain swollen with rainwater.
"Personally, I think our weather has changed. I'm actually psychologically prepared for it to get worse," Dr Balakrishnan said.
"You're dealing with nature, and you're dealing with the weather; you have to be prepared that there is a limit to human engineering and what we can deliver.
"But having said that, let us make sure we have done the best we can and within those limits, then cope with whatever else that nature throws at us."
Dr Balakrishnan said because of the changing weather conditions, his ministry will need to review planning norms, which includes designing of drainage systems.
He added another priority is to ensure roads are passable even during heavy rainfall.
He said he intends to ensure buildings are better prepared to cope with the occurrence of floods.
During heavy rainfall last year, the basement of Tessarina condominium was flooded.
The management there has since made improvements such as installing a flood barrier.
When the Bukit Timah canal flooded its banks on Sunday morning, the siren was activated and residents were alerted to drive their cars out of the basement, and the flood barrier was closed.
Tessarina Condominium management committee chairman Leonard Yip said: "The primary strategy for us was to lobby for improvements to the Bukit Timah canal and also for raising of Wilby Road.
"So, we believe that most of the problems will be solved".
At Bukit Timah Road, flash floods occurred at the stretch from Blackmore to Maplewood Road, making some lanes impassable to traffic earlier Sunday morning.
PUB is currently making drainage improvement works to the Bukit Timah canal.
Works to deepen the canal will start by the end of this year.
The project is expected to be fully completed by November 2012.
