A World Bank expert and neophyte lawyer on Wednesday proposed the construction of a dam at the Marikina River as one of the long-term solutions to prevent flooding in Metro Manila.
In an interview with reporters, WB lead irrigation engineer Joop Stoutjesdijk said his WB-funded team would submit next year “an antiflooding road map for the next 25 years” which would include the proposed construction of an upriver dam that could cost “billions of dollars.”
At the hearing of the House committee on Metro Manila development, Marikina City Representative Miro Quimbo said that building a dam in the Montalban side of the Marikina River would provide the “quickest relief” to flooding in the metropolis.
“It will greatly help in slowing down the flow of rain falling in the denuded areas above Marikina, including San Mateo, Antipolo and [Rodriguez]. There should also be an energy component to allow the government a certain degree of recovery. It should be underscored, however, that the dam must be placed in a safe environment taking into consideration the location of the West Valley fault line,” said Quimbo.
According to him, Marikina’s experience at the height of Tropical Storm “Ondoy” showed that water levels rise quickly in the city despite the lower amount of rainfall.
“The river swells after two hours. It used to take at least six to seven hours of continuous rainfall for that to happen,” Quimbo said. “Owing to the siltation of the Marikina River … the river’s containment capacity is down by 60 percent from eight years ago,” he said.
According to Stoutjesdijk, Metro Manila was more prone to flooding than other Southeast Asian cities because it has only one major river spillway (Pasig River) unlike, for example, Jakarta and Bangkok, which has several rivers to bring water out of the city and into the sea.
Part of the WB’s flood management proposal calls for the creation of a single, central agency which will have full authority to carry out flood control projects and disaster impact programs. The WB is also proposing the resettlement of people living near waterways or the implementation of onsite development to clear the limited number of waterways and ease the flow of water out of the urban areas.
Meanwhile, the Department of Public Works and Highways (DPWH) said Wednesday it was planning to construct several huge, underground basins in low-lying areas in Metro Manila to control flooding.
Retarding or catchment basins, also called retention tanks, are manmade underground caverns which can temporarily store floodwater in case of heavy rains. The stored water can then be gradually released as the weather improves.
“We want to do a permanent solution to flooding and the permanent solution is, to put at the height of heavy rains, excess water underneath. Our cities’ drainage systems cannot quickly remove rainwater spilling from all drainage pipes,” Public Works Secretary Rogelio Singson told reporters.
The underground basins and tanks will be useful, especially with the La Niña phenomenon, and amid predictions that climate change will result in a heavier than usual amount of rainfall.
“We have to retard the peak flow. We have to reduce that peak flow and this should not be done during heavy rainfall,” he said.
According to him, there are two retarding basins in the metropolis. One is in Fort Bonifacio in Taguig City underneath the restaurant area on Burgos Circle while the other is located beneath the Magallanes interchange in Makati City, he said.
Singson added that the DPWH plans to construct retarding basins in nine or 10 flood-prone areas identified by the Metropolitan Manila Development Authority. These include España Boulevard in Manila and Araneta Avenue and Mother Ignacia Street in Quezon City.