'Yolanda-like disaster in Metro Manila could affect half of GDP'

MANILA, Philippines — The country's economic output could be "significantly" affected if a destructive cyclone like "Yolanda" hits Metro Manila and surrounding areas, a Cabinet official warned on Thursday.

Public Works and Highways Secretary Rogelio Singson said if a similar super typhoon devastates the metropolis, Rizal province, Laguna and parts of Bulacan, a third or even half of the country's gross domestic product (GDP) will be affected.

"So pag hindi natin in-address in a permanent way itong flood management dito, [an] Ondoy or a Pablo or a Yolanda hitting this area could affect 50 percent of our GDP immediately," Singson said during the Flood Summit currently being held at the House of Representatives.

According to Singson, the said areas will be covered by the Metro Manila flood management master plan, which will require an estimated P350-billion budget. They will have a total area size of 4,354 square kilometers or seven times the size of the metropolis.

The whole area covers a total population of 17.1 million, 16 cities and one municipality in Metro Manila, 63 cities and towns in Calabarzon, and eight more in Bulacan.

It also encompasses several major river systems and waterways including the Pasig-Marikina river basin, the Laguna Lake river basin and the so-called "core" Metro Manila drainage basin system.

Causes of flooding and long-term solution

Singson said the flood master plan has identified and tries to address three technical causes of flooding in Metro Manila:

• there is a huge volume of water coming from the Sierra Madre Mountains that the Marikina River cannot hold
• the constrained drainage systems and waterways also cannot hold the rainfall in "core" Metro Manila
• the volume of water in the Laguna Lake basin floods the surrounding low-lying communities

"Aside from the water na hindi makalabas agad, inabutan ka pang high tide, then you have the situation where the low-lying communities really get submerged," Singson said.

He said among the long-term solutions identified is the establishment of a dam or a retarding basin in Montalban, San Mateo and Marikina to hold up the water coming from the Sierra Madre.

"You don't want all of that volume to come down at the same time while the rainfall or the typhoon is happening. So you retard it. Imbakin mo muna doon," the official said, adding that they are now finding the exact location where the retarding basin will be built.

The public works chief said they are also trying to restore the natural flood plains in Montalban and San Mateo.

Other flood management solutions eyed are the improvement and recovery of the carrying capacities of waterways by removing obstructions and informal settlements, the upgrading of pumping stations, dredging and construction of additional drainage culverts.

Singson said they hope to complete 44 projects by July.