PUB to install water level sensors at affected flood areas at Bt Timah
By Hoe Yeen Nie, Channel NewsAsia | Posted: 24 November 2009 2052 hrs

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SINGAPORE : As a result of the massive flood along Bukit Timah Road last Thursday, PUB, the national water agency will install water level sensors next week to warn of potential floods.

PUB has also started widening canals along Bukit Timah Road.

On the November 19, a freak downpour dumped 92 millimetres of rain on the Bukit Timah area in 30 minutes, about half the amount Singapore sees in the entire month alone.

On regular days, a diversion canal off the main Bukit Timah canal helps to channel water into Sungei Ulu Pandan.

But last Thursday, PUB said the intensity of the storm meant that the diversion canal could not drain water away quickly enough, resulting in massive flooding along Bukit Timah Road.

PUB stressed that the problem does not lie with the canal system as floodwaters drained away within an hour.

Due to the rainy season, PUB had increased inspections of flood-prone areas. But Bukit Timah was not one of them.

PUB said that is because two diversion canals built in the last 30 years had been effective in draining water away from the low-lying areas. However, following the flood, PUB will install a water level sensor at the main canal near Blackmore Drive.

PUB will be alerted when the canal is 50 per cent full. It will then warn residents and traffic police of potential flooding.

It said the sensor "is enough" to alert residents of further floods, and comes on top of on-the-ground monitoring when there are heavy rains in the area.

PUB added that it will soon widen the diversion canal, from its current 11 metres on average to 26 metres. This will allow the diversion canal to cope with more intense downpours.

"We noticed that over the past few years, there have been a lot of new condominiums developed. This has changed the land surface type from grass areas to concrete surfaces. Because of that, the amount of run-off has increased," explained Tan Nguan Sen, director of Catchment and Waterways, PUB.

Upgrading works also include widening the stretch of the main canal between Wilby Road and Maple Avenue. Work will begin late next year and will be completed in 2012.

PUB said there are only about 80 hectares, or 160 football fields, of flood-prone areas in Singapore. This is down from over 3,000 hectares in the 1970s, after authorities carried out extensive works to improve drainage systems. - CNA /ls