The government is preparing to build water cisterns and detention ponds at 39 sites across Metro Manila as part of a longer-term strategy to mitigate flooding, Metropolitan Manila Development Authority (MMDA) General Manager Nicolas Torre III said Tuesday.

Torre said the projects are among additional flood-control interventions being prepared by the MMDA and the Department of Public Works and Highways (DPWH) as existing drainage, dredging and clearing operations have yet to fully prevent flooding in the capital.

“In the next few days, may-announce si Chairman Don Artes ... ng iba pang mga gagawin natin gaya halimbawa itong water cistern, mga detention pond na gagawin sa iba-ibang lugar, around 39 ito lahat,” Torre said in a television interview.

The proposed structures are intended to temporarily hold excess rainwater during heavy downpours, reducing pressure on Metro Manila’s drainage systems and waterways.

The 39 potential sites were identified following a preliminary study by Dutch engineering consultancy Haskoning. The locations include areas in Caloocan, Las Piñas, Malabon, Makati, Manila, Mandaluyong, Marikina, Muntinlupa, Navotas and Parañaque, among others.

The push for additional interventions follows repeated flooding across Metro Manila despite ongoing dredging, desilting, drainage clearing and pumping operations.

“Obviously dahil hindi talaga kompleto na nawala ang baha, mayroon pa rin mga pagbaha,” Torre said. “Dapat obviously kailangan natin ang panibagong mga intervention operations.”

Aging drainage system

Torre said the government also needs to address Metro Manila’s aging drainage infrastructure, particularly in older parts of Manila.

He said Public Works Secretary Vince Dizon had acknowledged that some drainage systems in the capital are already old and need to be modernized, expanded or rehabilitated.

“Dahil siyempre noon pa ang mga yan at nag-iba na ... dahil sa climate change, urbanization, nag-iba na ang behavior ng tubig,” Torre said.

The government is increasingly looking at measures that can temporarily retain rainwater rather than relying solely on drainage systems to immediately carry runoff away.

A detention basin is also being eyed to address recurring flooding along EDSA-Balintawak in Quezon City, which has been hit by heavy flooding in recent weeks.

Meanwhile, Torre said the MMDA would continue dredging and desilting major and smaller waterways, including rivers, esteros and lateral canals.

The agency is also using mapping equipment to measure changes in the depth of waterways and determine whether dredging operations are producing results.

According to Torre, the MMDA assesses flood-control efforts using three indicators: the extent of flooding, the maximum depth of floodwater and the time it takes for floods to recede after rainfall stops.