Taking the load off Stamford Canal

When it rained yesterday, Mr Chik Hai Lam held his breath.

He hasn't been the same since the Orchard Road floods in 2010.

The Liat Towers supervisor is in charge of the flood gates outside the building. And if they don't work, the shop owners will give him a hard time.

But things could get better in the near future.

PUB yesterday announced its proposed solution to move the water when it gathers in the area as Stamford Canal can't handle the deluge of water when hit by intense rainfalls.

On Dec 23 last year, 152.8mm of rain fell on Orchard Road in the three hours between 2.20pm and 5.20pm, flooding parts of the shopping district.

The proposal is to build a diversion canal so that water from the upper part of the Stamford Canal Catchment will not flow into the Stamford Canal, but into the Singapore River via River Valley.

In addition, an underground storage tank the size of 15 Olympic-size pools or 38,000 cum will be built at Tyersall Avenue, opposite the Singapore Botanic Gardens.

The tank will hold excess run-off.

PUB said the diversion canal and underground tank will be able to divert 38 per cent of the water to the Singapore river.

Work is slated to start early next year and be completed by 2017, though the detention tank is expected to be completed earlier by 2015.

Tenders for the detailed study of the construction of these two structures will be carried out in the second half of this year.

How much will it cost?

PUB could not give an estimate until the detailed study is done.

But Minister for the Environment and Water Resources Vivian Balakrishnan had told Parliament in January that a diversion canal could cost between S$300 million and S$400 million.

Stamford Canal Catchment

The Stamford Canal Catchment is about 630ha or the size of 583 football fields.

It captures stormwater from Holland, Napier and Cuscaden Roads upstream; Orchard Road and Handy Road midstream, and parts of Clemenceau Avenue, Stamford and Beach Roads downstream.

Each of the new solutions targets specific flood risks on different sections of the Stamford Canal Catchment.

A catchment is an area where rainfall is collected for water supply.

Said PUB's director of catchment and waterways, Mr Tan Nguan Sen: "The diversion canal provides flood protection primarily for the middle section of the catchment, in areas like Cuscaden Road and Orchard Road.

"However, on its own, the diversion canal will not be able to provide adequate protection for the upstream areas at Holland Road and Napier Road.

"The detention tank addresses vulnerable upstream areas at Holland Road and Napier Road. To optimise flood protection over the entire catchment, we therefore opted for this complementary mix of source and pathway solutions."

The national water agency's decision comes after nine months of studying various flood protection measures proposed by a panel of experts.

The 12-member panel on drainage design and flood-protection measures was appointed by the ministry in June last year.

The panel had recommended a more complete approach from retention of water at source to improving drains that carry away the water.

After the floods in 2010, PUB raised a 1.4km stretch of Orchard Road between Orange Grove Road and Cairnhill Road, which it said prevented the road from being flooded during subsequent heavy rains.

It has also stepped up checks on canals and drains during the current north-east monsoon season to make sure they are not blocked.

WHEN IT RAINS, IT FLOODS

Dec 23, 2011

Flash floods hit Liat Towers at Orchard Road and other parts of the main shopping belt.

Some 150mm of rain fell from 2.20pm to 5.20pm.

Water ponded in the open area of Liat Towers, the underpass between Lucky Plaza and Ngee Ann City, and the basement of Lucky Plaza.

June 5, 2011

Tanglin Mall, Forum Shopping Centre and the basement carpark of Delfi Orchard were flooded.

About 65mm of rainfall was recorded on the island within 30 minutes on the Sunday morning, compared to the 100mm within three hours on June 16, 2010.

June 25, 2011

Floods occurred in Geylang, MacPherson Road, Old Airport Road, Thomson Road, Bukit Timah and Orchard Road.

The PUB said 100mm of rain fell within an hour, between 8am and 9.30am.

But no widespread damage was reported and flood waters subsided within an hour.

Around $2.4million is estimated in insurance payouts.

June 16, 2011

Orchard Road was flooded.

In just three hours, between 8am and 11am, 100mm of rainfall was recorded.

That is 60 per cent of the average rainfall for the month of June.

The deluge caused an estimated $10 million in damage.

This article was first published in The New Paper.

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