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  Straits Times 23 Dec 06
Hillview landslide one of the largest here
It's also complex as debris spots are difficult to access, says consultant
By Tracy Sua

Today Online 23 Dec 06
Why waters overran Thomson
Taking lessons from flood, PUB installs sensor, hopes to raise ground, build bigger drains Leong Wee Keat

Channel NewsAsia 23 Dec 06
Efforts to control floods in Singapore on track, but more needs to be done

Channel NewsAsia 22 Dec 06
PUB looks at new measures to beat the floods
By Valarie Tan

SINGAPORE: Public Utilities Board (PUB) is looking at new measures to help those in low-lying areas beat the floods.

The first step has already started at Joan Road which was badly hit by the recent heavy downpour. A water sensor has been installed at the canal by PUB to trigger an electronic signal once water levels go above a certain level. An SMS message will then be sent to a PUB officer who will then send a flash flood alert to residents and shopowners.

Yap Kheng Gan, Drainage Director, PUB, says they would like to look at the flooding issue seriously.

PUB let excess water out of the MacRitchie Reservoir on Monday when heavy rain warnings were first sounded. It was stopped the next day when drains were full. But the move was too late as water had already started spilling from the reservoir. Heavy rainfall then caused excess water to overflow into Joan Road.

PUB says there are now long-term plans to develop the area, including raising the low-lying floor area up to ground level once the three-year lease of the shopowners runs out.

PUB says building good drainage systems and flood prevention are long-term projects which also require coordination from other government agencies, like the URA and HDB. For now, PUB's more immediate plans include closely monitoring the areas which were badly hit by the floods to see where PUB can lend its help.

Referring to the drain at Joan Road, Mr Yap says: "For that kind of rainfall obviously that drain was not capable of coping with so much water thus the flood took place. That place will get priority from our people to make sure the drains are cleared, that there are no debris."

PUB says there are currently six sensors like the one installed at Joan Road and these are placed in areas known for localised flash floods such as Commonwealth Ave.

But as the hydrodynamics of different areas can vary greatly, PUB will move these sensors around to better test them. - CNA/so

Today Online 23 Dec 06
Why waters overran Thomson
Taking lessons from flood, PUB installs sensor, hopes to raise ground, build bigger drains Leong Wee Keat weekeat@mediacorp.com.sg

IT may have seemed to be the worst flood in recent memory, causing damage and plenty of inconvenience.

But to look at it in context — if Dec 19's flooding had taken place in the 1970s and 1980s, more people would be affected and displaced, said the Public Utilities Board (PUB) on Friday.

Unlike the floods of December 1978, which affected 1,000 people and left seven dead, last Tuesday's heavy downpour affected just 100 people and there were no casualties. It was also a "localised" flood, affecting the Thomson and Mandai areas where 15ha was submerged in water, unlike the 3,200ha in 1978, said PUB drainage director Yap Kheng Guan.

Low-lying areas Chinatown and Little India were also not affected.

Giving a blow-by-blow account of the conditions that led to this week's flood, the PUB and National Environmental Agency (NEA) blamed it on a confluence of two factors: Intense rainfall and high tide. In fact, the rainfall within the first 16 hours of that wet Tuesday was 313mm — higher than the average of 284mm for the whole of previous December months.

A storm surge of 35 to 40 knots — an increase from the normal 10 to 20 knots — drove rain clouds near and over Singapore. This caused a build-up of rain clouds over the island, said the NEA's chief meteorological officer Lam Keng Gaik.

The PUB had let excess water out of MacRitchie Reservoir last Monday when heavy rain warnings were first sounded. It was stopped the next day when drains were full. But it was too late as water had already started spilling from the reservoir.

In particular, three short bursts of intense rainfall — after a prolonged period of rain — coincided with the high tides, resulting in floods. About 100 PUB staffers were activated.

The flood waters left a devastating trail among the nurseries based in Thomson Road, with estimated damage of up to $1 million.

Asked if the PUB had warned them of the impending flood, Mr Yap said monsoon advisories were sent to residents and shop-owners in all low-lying areas in October — as with previous years.

Just a day before Dec 19, the PUB had also advised of high tides and heavy rainfall through the media, he said. But despite these early warnings, Mother Nature still wreaked havoc.

Still, the PUB is not taking any chances in a repeat of the floods in the two areas. Besides close monitoring and investigations at the two areas, the PUB has installed an electronic water-level sensor in a canal at Joan Road on Friday.

This sensor — among the six being deployed island-wide in canals here — would alert PUB officials immediately if a threshold of the water level is breached. A flash flood alert will then be sent to residents and shopowners.

In the long term, Mr Yap said the plan is to bring up the ground level there and build bigger drains. But such big-scale projects also require coordination from other government agencies, such as the URA and HDB.

"We take this flood very seriously," said Mr Yap. "We will look at measures: Whether we should expand the drains, fill up the ground, and so forth."

While the north-east monsoon winds are weakening, the weather for the next few days is likely to stay wet, said the NEA. According to the weatherman, prolonged heavy rain like the Dec 19 one is unlikely.

Straits Times 23 Dec 06
Hillview landslide one of the largest here
It's also complex as debris spots are difficult to access, says consultant
By Tracy Sua

THIS week's landslide at Hillview Gardens estate is one of the largest yet seen in Singapore, said the geotechnical and civil engineering expert brought in by the slope's land owner, the Ministry of Defence (Mindef), as a consultant to oversee slope stabilising works.

It is also a very complex one to tackle, said Professor Wong Ing Hieng, because it is difficult to access the debris spots on Gombak Hill to conduct repair or strengthening works.

The continuing wet spell also hampers the process. Heavy rains caused the landslide on Tuesday morning, sending tonnes of soil, shrubs and trees in a 50m stretch cascading down to Jalan Dermawan, smashing into a playground, blocking the road, and affecting two cars and three homes.

Mindef has advised the three families to stay away from their houses for the next four to six weeks so that the slope can be made safe again.

Mindef brought in Prof Wong to advise its contractors, who have been hard at work since Tuesday, digging a trench at the top to redirect the flow of water to prevent further slides.

The 62-year-old specialist said a mound of debris that had slid down the slope and pushed against a 30m high water tank was unstable and poses a danger to the three houses nearest the site.

Residents feared the water tank, which has a concrete base, would collapse. The Public Utilities Board said the tank is stable but it was emptied as a precaution.

On Thursday, sensors were attached to the tank to monitor any movements. Meanwhile, over 100 truck-loads of soil and debris that had piled up as high as 1.5m on the road have been removed. This cleared the path to the homes, allowing residents to return to retrieve essentials or to rescue their pets.

This is not the first landshifting incident affecting Jalan Dermawan. In 1984, torrential rains caused the land a street away from the current site to move. Six hillside bungalows were affected and one was so badly damaged that it had to be demolished.

Prof Wong said the last comparable landslide happened about four to five years ago in central Singapore.

He explained how the Jalan Dermawan landslide occurred: 'The material within an underlying slope consists of residual soil and completely weathered material of Bukit Timah granite. During the heavy rain, water seeped into the slope and the ground immediately behind the slope, increasing the water pressure in the slope. The rain-induced high water pressures caused the landslides.'

Prof Wong said his assessment will take some time and it will determine what methods will be used to shore up the land.

Channel NewsAsia 23 Dec 06
Efforts to control floods in Singapore on track, but more needs to be done

SINGAPORE : Environment and Water Resources Minister Yaacob Ibrahim says efforts to control floods in Singapore are on track, but more needs to be done. And this will require coordination from other government agencies.

Heavy downpours on Tuesday saw flooding in at least four locations, including nurseries near the junction of Olive Road and Joan Road.

This prompted the PUB to put install water sensors at Joan Road and five other spots to help low-lying areas beat the floods. The sensor will trigger an electronic signal once water levels hit above certain levels.

But more can be done and Dr Yaacob says there are plans to work with relevant government agencies to widen the canal at Joan Road.

Dr Yaacob adds that there'll be fewer areas prone to flooding once the Marina Barrage dam at Marina Bay is ready next year. - CNA /ls
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