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  Today Online 29 Dec 06
Fact that most of Singapore unaffected by floods a testament to drainage works but unexpected can happen
Letter from Yap Kheng Guan Director, Drainage Public Utilities Board (PUB)

Today Online 29 Dec 06
Rain warnings given out based on satellite and ships' data
Letter from Lam Keng Gaik Chief Meteorological Officer Meteorological Services Division National Environment Agency (NEA)

Straits Times Forum 28 Dec 06
Flood-prone areas cut from 3,200ha to 130ha
Letter from Yap Kheng Guan Director, Drainage PUB

PUB, the national water agency, thanks Mr Thomas Lee Zhi Zhi for his letter, 'Civil Service should be more proactive' (ST, Dec 27).

On Dec 19, Singapore was hit by the third-highest rainfall recorded since 1931. The 24-hour rainfall recorded was 366mm. This exceeds the average amount of 284 mm recorded for the month of December in previous years. The highest rainfall recorded in one day was 512 mm in 1978, while the second-highest rainfall recorded was 467mm in 1969.

The floods took several days to subside and thousands of people were affected.

Since then, the drainage system in Singapore has been improved and the flood-prone areas were effectively reduced from 3,200ha to 130ha.

New projects, such as the Marina Barrage, are some of the proactive steps that we have been taking to further decrease the flood-prone areas.

Although heavy rainfall was expected this period, the rainfall on Dec 19 was exceptionally high.

Only two locations, Olive/Joan Road and Upper Thomson/Mandai Road, had prolonged flooding for about a day as they are both low-lying areas. The junction of Olive Road and Joan Road lies in the Caldecott Valley, which is between 1.5m and 3m below the level of the main road.

While these low-lying areas flood occasionally, this is the first time that the waters overflowed onto the roads and affected traffic on Upper Thomson Road and the junction of Olive Road and Joan Road.

The Thomson nurseries are slated for redevelopment in the long term, which will include raising the ground level and building bigger drains. Meanwhile, PUB will continue to monitor the area and take action to help alleviate flooding.

PUB works closely with other agencies - the National Environment Agency on weather and Traffic Police on road conditions.

The public is welcome to give feedback to our 24-hour call centre, PUB- One, on 1800-284 6600.

Today Online 29 Dec 06
Rain warnings given out based on satellite and ships' data
Letter from Lam Keng Gaik Chief Meteorological Officer Meteorological Services Division National Environment Agency (NEA)

We refer to the letters, "Why no warning on floods" (Dec 22).

Prolonged heavy monsoon rain usually affects Singapore in the months of December and January. The prolonged monsoon rain is caused by a sudden increase of north-eastern winds (monsoon surges), which usually converges on Malaysia, Singapore and Indonesia. This wind convergence gives rise to large cloud clusters and heavy rain that may last between two and seven days.

The NEA uses computer simulation models and observation data from satellites and ships in the South China Sea to predict a prolonged heavy monsoon rain spell.

On Dec 18 at 9.22pm, the NEA issued a warning of prolonged heavy monsoon rain. The warning was disseminated to the media in addition to various agencies such as the Public Utilities Board, Singapore Civil Defence Force and Singapore Police Force.

The warning indicated moderate to heavy rain expected until mid-day on Dec 19 and the warning was reviewed and further extended to Dec 20 at 9am.

We would like to thank your reader for the feedback and would like to assure the public that NEA will continue to update the public (through media and on our website) should we detect any prolonged heavy monsoon rain.

The public may also obtain the latest weather reports by calling the NEA's weather forecast hotline at 6542 7788 or visiting our website www.nea.gov.sg, "Weather Outlook".

Today Online 29 Dec 06
Fact that most of Singapore unaffected by floods a testament to drainage works but unexpected can happen
Letter from Yap Kheng Guan Director, Drainage Public Utilities Board (PUB)

The PUB, the national water agency, thanks Khoo Lih-Han and Henry Lim Li Shun for their letters, "Plan for floods the way we plan for terror attacks" and "Meteorological Services seem unable to anticipate rains" (both Dec 22).

On Dec 19, Singapore was hit by the third-highest rainfall recorded in 75 years. The 24-hour rainfall recorded was 366mm. This amount of rainfall recorded in one day exceeds even the average amount of 284mm recorded for the month of December in previous years.

Despite the exceptional rainfall over the northern and central parts of Singapore, flooding occurred in two low-lying areas. Olive/Joan Roads and Upper Thomson/Mandai Roads had prolonged flooding for about a day as they are both low-lying areas. The junction of Olive Road and Joan Road lies in the Caldecott Valley, which is between 1.5m and 3m below the level of the main road.

In 1978, the highest rainfall recorded in one day was 512mm while the second highest rainfall recorded was 467mm in 1969. The 1978 floods took several days to subside and thousands of people were affected.

Since then, the drainage system in Singapore has substantially improved and the flood-prone areas effectively reduced from 3,200ha to 130ha. New projects such as the Marina Barrage are some of the drainage improvement works undertaken proactively to decrease the flood-prone areas in Singapore.

However, during exceptionally intense storms, there is still the possibility that storm water in some drains and canals can overflow and cause localised flash floods, especially when the area is low-lying and the heavy rain coincides with an incoming high tide.

The PUB strives to put in place the best possible drainage system but the reality is that we sometimes cannot predict Mother Nature.

The fact that most parts of Singapore remain unaffected despite abnormal rainfall on Dec 19 is proof that our drainage system has served us well. While these low-lying areas flood occasionally, this is the first time that the waters overflowed onto the roads and affected traffic at Upper Thomson Road and the junction of Olive and Joan Roads.

The Thomson nurseries are slated for redevelopment in the long term, which will include raising the ground level and building bigger drains. Meanwhile, the PUB will continue to monitor the area and take action to help alleviate flooding in that area.

The PUB works closely with the Singapore Police Force and other agencies to render assistance in such occurrences. During the intense storm on Dec 19, the PUB worked closely with the Traffic Police on-site to divert traffic.

The PUB's field teams and contractors also helped to clear debris from the drains caused by the flooding. The PUB and the NEA have also been sending out warnings of heavy rain and the possibility of flash floods in low-lying areas.

Prior to the onset of the north-east monsoon, flood advisories were also distributed door-to-door to 600 residents and shop owners in these areas.

The public can also take precautionary measures such as storing their belongings on higher levels or placing sandbags at entrances to block floodwaters.

In the event of heavy rain, the PUB and the NEA will alert the public when necessary. The public can obtain the latest weather reports, including heavy rain warnings, by calling the NEA's weather forecast hotline at 6542 7788 or visiting "Weather Outlook" at www.nea.gov.sg. They can also call PUB-One at 1800-284 6600 to report any floods.
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