FLOODING INCIDENTS

FLOODING INCIDENTS:

(Assistance to affected residents): 5.

Mr Christopher de Souza asked the Minister for the Environment and Water Resources (a) what measures are taken to alleviate the incidence and severity of flooding; and (b) what help was provided to residents affected by the flooding incident on 19th November 2009.

The Minister for the Environment and Water Resources (Assoc. Prof. Dr Yaacob Ibrahim): Sir, over the years, Singapore's flood-prone areas have been reduced from more than 3,000 hectares in the 1970s to 79 hectares today, or about 0.1% of Singapore’s total land area. By 2011, PUB targets to further reduce flood-prone areas to 56 hectares.

To continually improve our flood management infrastructure and keep pace with increasing developments, PUB has an ongoing drainage improvement programme. This involves a dynamic review of rainfall patterns and their impact on flood prone areas, as well as areas where surface runoff is expected to increase in tandem with plans for greater urbanisation. For example, as part of the programme to cater for new developments in the Upper Bukit Timah area in 10

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to 15 years' time, PUB has plans to deepen and widen the first stage of the Bukit Timah Phase 1 Diversion Canal.

Notwithstanding this, flooding incidents may still occur due to extreme storms such as the one on 19th November last year. To further mitigate the risk of flash floods, PUB carries out regular site surveillance and maintenance to ensure that our drains are kept free of chokage. PUB has installed water level sensors to monitor water levels in drains and canals within flood-prone areas and plans to expand the network of water level sensors to include other major waterways. This will provide early warning of impending floods and facilitate prompt deployment of officers to the potentially affected sites to clear any debris that may have accumulated and put up traffic warning signboards if necessary. PUB also taps on LTA's 24-hour CCTV system to monitor road conditions at over 500 locations. When flooding occurs, PUB alerts the public through the media of the situation and mitigation measures that are being taken.

The flooding incident on 19th November last year in the Bukit Timah area was caused by an exceptionally intense storm. In just two hours, 110 mm of rain fell, of which 92 mm fell between 1.20 pm and 1.50 pm. This was equivalent to about 40% of the typical rainfall for the entire month of November falling within half an hour. The high intensity of the rain that day caused the Bukit Timah Phase 1 Diversion Canal to overflow. This caused localised flooding along two stretches of Bukit Timah Road: from Coronation Road to Third Avenue and from Wilby Road to Blackmore Road. The junction of Sixth Avenue with Bukit Timah Road was also flooded.

To assist affected residents, PUB deployed its staff and contractors to pump out floodwaters from the premises and clear the debris at affected roads.

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PUB also met up with the management of affected premises to advise them on implementing measures to better safeguard against floods such as building physical crests to prevent water from flowing into their basement car parks.

It would not be cost-effective to build a large and extensive drainage system that caters for all extremities. A balance is needed between setting aside more land and resources for drainage infrastructure and for other development requirements. But PUB will continue to regularly review its flood alleviation measures and continue to invest in drainage infrastructure so as to ensure an effective drainage network.

Mr Christopher de Souza (Holland-Bukit Timah): Thank you, Minister, for the comprehensive reply. The areas that the Minister discussed were all in my constituency. I was told that PUB worked overtime to drain and pump out, I think, about 30 hours worth of water and for that, thank you on behalf of the residents. However, I would like to seek two clarifications. The first is in relation to crest protection. Is there any way that PUB or the Ministry of the Environment and Water Resources can work with developers before the development is T.O.P-ed to have mandatory crest protection for basement carparks? Secondly, the drainage system that the Minister talked about – and I understand that it comes from the Bukit Timah Canal and goes through Wilby Road as a tributary into Sungei Ulu Pandan and then to the Pandan Reservoir – how will all of these have no bottlenecks in order that drainage actually does go to the Pandan Reservoir?

Assoc. Prof. Dr Yaacob Ibrahim: Sir, to the first question, I have been told by PUB that we work very closely with the developers and, if my memory serves me right, I think this is part of the Building Code that whenever you have basements,

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there are certain requirements that you have to put in place against flash floods. I will clarify this and inform the Member what are the stipulations. I have been told that it has already been in place and therefore we will continue to review if that is adequate or not. In some of the basements that were flooded, they did not have such requirements because they were built before the requirements came into effect in the Code.

Sir, on the second point, I agree with the Member that drainage reliability and robustness is very important for us. The work that PUB will start in the third quarter of this year to widen the canal and the diversion canal will help the water to be drained off quickly. But, at the end of the day, it is about clearing up the litter as much as possible because our canals do pick up a lot of litter. Going forward, what the PUB will do is to continue to work with our contractors to ensure that whenever there is a reported blockage, we will clear it immediately. And when the rainy season is coming, we will step up our manpower to check at those places located in low-lying areas.

As I mentioned in my reply, we will put in place these measures to ensure that we have some form of early warning system. We cannot prevent the kind of extreme event that occurred on 19th November last year, but if it does happen, I think the most important thing is our response. So, this is the assurance that I can give to the Member – that we will do our very best to ensure that we can reduce the impact as much as possible – but it will be impossible to design for such extremities.