Watch out for flash floods this weekend

High tide and heavy rain could coincide to produce deluge in low-lying places
Grace Chua Straits Times 12 Jan 13;

THERE could be localised flash floods this weekend and early next week, if the forecast heavy rain coincides with high tide levels.

The highest tides will range from 3.3m to 3.4m in the late morning and early afternoon today to next Tuesday.

Afternoon showers are also expected over the next few days, said national water agency PUB and the National Environment Agency.

If the two occur at the same time, flash floods could hit low-lying coastal areas such as Fort Road and Meyer Road which are vulnerable to tidal surges (see box).

Water levels will already be high in canals that open directly into the sea, such as the Bedok and Siglap canals, before more water is dumped into them by the rain.

January marks the middle of the north-east monsoon season, and thundery showers, mainly in the afternoon and evening, can be expected for the rest of this month.

In general, January is the third wettest month of the year, with average monthly rainfall of 243.2mm.

Tides are affected by astronomical factors such as the sun and the moon, said a Maritime and Port Authority spokesman. High tides occur when the moon and Earth are closest to each other.

Today's new moon also means the moon, sun and Earth are aligned, reinforcing the gravitational pull of both sun and moon to cause a spring tide.

At such times, maximum tides are very high and minimum ones are very low - for instance, minimum tides are expected to be about 0.3m in Changi this afternoon.

The highest recorded spring tide in Singapore since 1975 was 3.68m in December 1999. And the last time high tides and heavy rain coincided was in November 2011, causing flash floods on the Ayer Rajah Expressway and Neo Pee Teck Lane in Pasir Panjang.

Residents in affected areas can protect their properties by installing flood barriers such as aluminium panels or stop-boards with sandbags, and by storing belongings at a high level.

The PUB has staff on the ground monitoring the situation, as well as equipment such as pumps on standby, said a spokesman.

Mr Tony Tan, who runs the Betel Box hostel in Joo Chiat Road, recalled the last floods in the area some years ago: "Some of my neighbours' ground floors were flooded."

But flash floods have "not bothered us" for a couple of years, he added. "The recent infrastructure works seem to have been effective."

Since 1991, the Government has mandated that new reclaimed land be 1.25m above the highest recorded tide.

In 2011, the PUB revised its drainage code for better protection against floods. Now, new reclaimed land must be 1m above the previous requirements, while building platform levels must be 60cm above the highest recorded flood level or 30cm to 60cm above ground level.

For weather alerts, the public can visit www.nea.gov.sg or weather.nea.gov.sg, check the @NEAsg Twitter account, call the weather forecast hotline on 6542-7788, or listen to radio broadcasts.

Background story

Areas that may beaffected

LOW-LYING coastal areas, and places where canals and drains open directly into the sea, could be affected by flash floods if high tides coincide with heavy rain. These are:

IN THE EAST: Changi Lorong 101 to 106, Everitt Road North, Langsat Road, Changi Road, Meyer Road, Margate Road, Broadrick Road, Jalan Seaview, Tanjong Katong Road South and Mountbatten Road.

IN THE WEST: Wan Lee Road, First Lok Yang Road, Jalan Mat Jambol, Yew Siang Road, Jalan Pasir Ria, Neo Pee Teck Lane and Clementi Road.

HIGH TIDE TIMES

DATE TIDE (m) TIME

Jan 123.3 10.52

Jan 133.4 11.41

Jan 143.4 12.28

Jan 153.3 13.13