Dredging rivers' estuaries is a must: Expert

The Jakarta Post, Jakarta

An expert from the Netherlands Engineering Consultants (Nedeco) said that floods in the capital could be eased by up to 80 percent next year if the city administration dredged at least five of its river's estuaries.

"The estuaries' sediment that has reached a depth of three meters significantly contributed to the flood in January and February. Therefore, dredging them is a very important action," Nedeco hydrologist Gerard Pichel said.

Pichel was speaking at a workshop on Thursday on the results of the Nedeco's quick reconnaissance flood study.

"Dredging the rivers up to 10 kilometers or more from their estuaries should become the first priority for the city administration," Pichel said.

The rivers and their estuaries that should be dredged include Cengkareng Drain, Western Flood Canal, Ciliwung River, Sunter River, and Cakung Drain.

Dredging 10 kilometers of the rivers' estuaries would smooth the rivers' water flow as sediments in their upper parts would be eroded and taken away down the stream, he said.

Nedeco estimates that the government should spend Rp 510 billion on dredging the five estuaries and 65 kilometers of waterways as well as cleaning up the other parts.

According to Nedeco's study, 10,000 hectares of Jakarta were flooded in February at a cost of around Rp 10 trillion.

"If the city completed the dredging project before the next rainy season (December), I can guarantee that some 8,000 hectares of the area would not be inundated," said Pichel.

Other Nedeco's recommendations included widening the Manggarai gates, improving the structure bottlenecks, minor detention measures, retention reservoirs, and full maintenance and rehabilitation of the drainage system.

Nedeco, which recommended the construction of the Eastern Flood Canal in 1973, also said that the Indonesian government should also start long term programs, like river improvements and the development of the Eastern Flood Canal. It estimates that this project will cost Rp 5.7 trillion.

"If we implement the short-term program, it does not mean that we stop the long-term program like development of the Eastern Flood Canal," Pichel said.

The construction of the West Canal, 17 kilometers long, was completed by the Dutch in 1918. But the width of the channel has been narrowed considerably, disrupting the flow of water through it.

Meanwhile, Koss Wieriks, an official of the Netherlands' Ministry of Transport Public Work and Water management said that the changes in land use and changes in the rivers significantly contributed to the flooding.

"The rain (in Jakarta) is falling in more or less the same intensity as hundreds of years ago. But changes in the land use and changes in the rivers have caused higher levels of the run- off of the rainwater," he added.