TEMPO.CO, Jakarta - Executive Director of Rujak Center for Urban Studies Elisa Sutanudjaja, provided a scientific explanation about what caused the flood that devastated a vast area in Jakarta's Greater Area on New Year's Day.

Elisa pointed out that it is no wonder that the 180 million cubic-meter rainfall on that fateful night caused flash floods which led to colossal damages.

Quoting a statement by Gadjah Mada University's Professor of hydrology Joko Sujono, Elisa asserted that Jakarta's mostly concrete-covered surface could not absorb the large quantity of rainwater on New Year's Eve.

"As a comparison, an olympic-sized swimming pool is able to hold 2,500 cubic-meter water. So the rain over Jakarta that night is comparable to 72 thousand Olympic swimming pool water [dropped over the city]," said Elisa at the Jakarta Legal Aid Institute (LBH Jakarta) on Monday, January 6, 2020.

This situation, Elisa added, is made worse by the fact that 85 percent of the Capital City is covered in concrete, leaving the city with only 5 percent of open green spaces, reservoirs to accommodate water, and private-owned open spaces.

According to Elisa, Jakarta's administration had even claimed 90 percent of Jakarta's land area is covered in concrete.

"The 180 million cubic-meter rainwater fell over land space that is 90 percent made of concrete, which is then diverted to rivers and canals that constitutes a mere 3 percent of the city's size. That amount of water will automatically overflow," said Elisa.

Furthermore, Jakarta's flat topography with barely any high grounds, combined with the sinking grounds in the city's northern area only made the flood worse. "The water is trapped before it reaches the sea," said Elisa.

Not only did the city experience heavy rainfall, the flood was also caused by the amount of water channeled through rivers from satellite cities such as Depok that flows to Jakarta's Ciliwung.

M YUSUF MANURUNG