The Jakarta administration is working on new solutions to cope with flooding during the capital’s increasingly unpredictable rainy season that could force private entities to play a more active role.

Governor Joko “Jokowi” Widodo said on Wednesday that in the long run, his administration would make it an obligation for developers to build water catchment fixtures, including percolation pits, in residential areas, at shopping malls and near office buildings.

The administration plans to dig a total of 10,000 pits between 100 and 200 meters deep in 13 areas across the city.

“Percolation pits can be effective in alleviating flooding problems because they can hold rainwater and directly channel it to the ground. At the same time, we improve groundwater quality,” he said, adding that the administration would start construction next year.

The long-term plans will go together with the existing plans to dredge and expand 13 city rivers under the Jakarta Emergency Dredging Initiative (JEDI).

Officials and experts argued that dredging was not effective in dealing with the floods caused by intense rains that inundated the city’s main thoroughfares and paralyzed traffic over the weekend.

Urban planner Elisa Sutanudjaja said on Wednesday that every building should be built with a rainwater catchment facilities. “Inundation will not happen if buildings have pits to accommodate runoff. Moreover, those buildings are built with basements in which the pits should be installed.”

Elisa said that the 2-meter-deep drainage system along Jl. Jendral Sudirman and the pumps on Jl. MH Thamrin that could move 30 cubic meters of water per second should be enough to channel the water to the rivers.

However, sediment in the rivers had made it hard to directly channel the water into the sea.

“That’s why we need to build pits at locations where most of the ground is covered by construction — so it can absorb the water,” she said, adding that the number of skyscrapers in the area had decreased the ability of the land to absorb rainwater.

Flooding along Jl. Jendral Sudirman also affected UOB Plaza, filling three out of its four basement levels. The management of the building, assisted by the Jakarta Fire Agency, was still trying to clear the water out of the floors on Wednesday.

“We are bit overwhelmed as this kind of incident has never happened before. Rainwater has actually seeped in several times but not as severe as this time, when our water pumps could not handle it,” Vaniza Andika Dewi, of the UOB Plaza tenant relations department, told The Jakarta Post.

Vaniza said that the building’s management was currently discussing measures to prevent flooding from reoccurring.

Jokowi said that in the short term, the administration would add more pumps at four locations along major thoroughfares such as South Jakarta’s Senayan and Jl. Gatot Subroto, the Hotel Indonesia traffic circle and near Trisakti University in West Jakarta.

Besides adding pumps, Jokowi also planned to enlarge the size of the culverts on Jl. MH Thamrin.

“The size of the culvert is too small; the diameter is only 60 centimeters. It will work well if the rain intensity is normal, but if it is more than 120 millimeters per hour like yesterday, the culvert won’t be able to handle it,” he said.

Ery Basworo, the Jakarta Public Works Agency chief, said that the culvert near Hotel Indonesia traffic circle had not been repaired since it was built in the 1970s.

“We will propose this project in next year’s budget. If it is approved by the governor, then we will start working on it.” (aml)

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