Years of massive urbanization has reduced the city's water retention ability, causing annual floods with massive losses, a seminar heard recently.
Officials and experts floated ideas for runoff management schemes, such as basement storage for rainwater and flood-control basins, at the seminar on urban flood management held by the Public Works Ministry and the Japan International Cooperation Agency (JICA).
"We must respond to the dynamics of change in the city... Settling the flood problem is not a static matter," said Widagdo, the ministry's director of rivers, lakes and reservoirs.
He said throughout the city's development, there had been scant attention paid to water management.
"There have been considerations *on available room for water*, but it is still lacking."
According to the National Development Planning Agency (Bappenas), the 2007 flood caused the capital losses amounting to Rp 8.8 trillion (US$924 million).
"We didn't realize areas that once had the ability to retain water, as well as open spaces, had transformed into settlements. So where should the water go?" Widagdo asked.
Over the years, many areas, which previously functioned as water catchments, had been bulldozed to make way for various commercial and housing construction projects.
Budi Santoso, told the seminar that urbanization had taken its toll on the city, causing constant floods.
"The Ciliwung river's basin areas have gone through uncontrollable urbanization, which in turn causes uncontrollable runoff *of the river's waters* that will quickly channel itself towards flood mitigating facilities. For example, the West Flood Canal has already been widened, yet still failed to prevent runoff."
Eko Djuli Sasongko, head of Building Codes Subdirectorate, said that the mistakes in construction design had caused the ongoing erosion of the city groundwater-retaining ability, in his presentation.
"The existing malls and buildings have always paved grounds without catchment areas. The biggest sins are committed during the construction of *large* buildings," he said.
"There have been many mistakes, such as with the Bumi Serpong Damai, where there are many malls that don't have catchment facilities."
The seminar explored methods to manage rainwater to prevent putting too much burden on rivers and building water catchment facilities in already urbanized areas.
Eko cited the example of storing water on top of buildings and using it to water plants, as well as storing water in a building's basement using a retention pool.
"The method is costly, however."
The 2005 government regulation No. 36 on construction, which accompanies the 2002 Law No 28 stipulates that buildings are supposed to have a rainwater management facility like absorption wells, as part of a building's feasibility conditions. (dis)
