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18 February 2009

Rain pattern reassuring, but flood risk remains

Rain pattern reassuring, but flood risk remains

The Jakarta Post , Jakarta | Thu, 01/18/2007 3:21 PM | Jakarta

Adianto P. Simamora, The Jakarta Post, Jakarta

Scientists have predicted the city will see a rainy conclusion to January.

But while rainfall is expected to be within the normal range, floods are still inevitable because the soil has lost its ability to absorb water.

The forecast was made by a join team comprising experts from the Bandung Institute of Technology (ITB) and the Agency for the Assessment and Application of Technology (BPPT).

Team member The Houw Liong of the ITB's School of Physics said rainfall rates would average 15 millimeters an hour, similar to rates in the wet season of 2005.

""We are particularly worried about the ability of the soil to absorb runoff water. If the rain continues for more than two hours, a number of areas will flood. But the floods won't be as serious as those of 2002,"" he said.

Thirty-one people died in the 2002 floods and 300,000 residents were forced to evacuate their homes.

The team applies the Adaptive Neuro-Fuzzy Inference System (ANFIS) model to calculate weather risks, using data from the last 40 years, including on river levels and rainfall rates.

For Jakarta's weather, the team uses data from the city's three largest rivers: the Ciliwung, the Pasanggrahan and the Sunter.

Liong said the model was also applied in countries like Japan and the United States.

Flooding has become an annual occurrence in the city, with 40 percent of Jakarta at or below sea level and an outdated, ineffective drainage system.

The Jakarta administration has identified 78 flood-prone areas in the city.

The Meteorology and Geophysics Agency (BMG) earlier predicted higher rainfall rates in early January.

The prediction was then revised due to last week's record-high temperatures.

The agency then warned that a drought could hit the city this year.

Asep Karsis of the BPPT said the floods in Jakarta might start in the upland areas of Puncak, Bogor and Depok.

""We can't guarantee that Jakarta will be free from floods this year if garbage continues to clog its waterways.""

Thirteen rivers run through the city.

The Jakarta administration has allocated Rp 500 billion for the provision of food, shelter and medicines for flood victims.

It has also spent hundreds of billions of rupiah on upgrading the city's drainage system, dredging rivers and completing the construction of the East Flood Canal.

However, experts have said the construction of flood canals is only a temporary solution.

""Flood canals channel rainfall and water runoff into the sea. Jakarta will then face water shortages in the dry season,"" Liong said.

The construction of the 23.5-kilometer East Flood Canal is expected to reduce the flood risk in East and North Jakarta.

The canal will accommodate water from the Cipinang, Sunter, Buaran, Jati Kramat and Cakung rivers.

The central government is also involved in flood prevention and control methods this year.

The Public Works Ministry recently installed an early warning system that provides realtime water level information for the Cisadane and Ciliwung rivers.

Commentary :

This writing was based on the interview in January 18, 2007 before the severe floods.

For 2009, the peak of rainfall in Jabodetabek (Jakarta, Bogor, Depok ,Tanggerang and Bekasi) acoording to ANFIS will be in February.

(HouwLiong)

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