Marikina River dam readied

To avoid a repeat of the massive flooding in eastern Metro Manila similar to that caused by Tropical Storm “Ondoy” in 2009, the government will build a massive dam in Marikina River with the help of the World Bank.

The Washington-based multilateral lender will extend by next year a $400-million loan for the $700-million Pasig-Marikina River Basin Flood Management Project, documents showed.

Besides the World Bank’s investment project financing, the Philippine government will shell out $35 million, which will still leave a financing gap of $265 million for the project to be implemented by the Department of Public Works and Highways (DPWH) over a 6.5-year period.

The World Bank noted that the World Risk Index report for 2019 showed that the Philippines was the third-riskiest natural hazard-prone country in the world, with 74 percent of Filipinos seen vulnerable to natural disasters.

In Metro Manila alone, “migrants who typically have low-paying jobs are unable to afford decent housing and often end up as informal-settler families living in hazards-prone zones,” the World Bank said.

Citing the experience when “Ondoy” hit the country 11 years ago, the World Bank pointed out that “there were over 700 fatalities, many in the Pasig-Marikina River Basin due to severe flash floods, and it caused substantial damage and losses, equivalent to about 2.7 percent of GDP [gross domestic product].”

Post-“Ondoy,” the World Bank supported the crafting of a flood management master plan for Metro Manila and surrounding areas, whose implementation over a 25-year period has been estimated to cost P352 billion.

The World Bank and the Beijing-based Asian Infrastructure Investment Bank (AIIB) already jointly funded the master plan’s ongoing urban drainage improvement component.

Specifically for the Pasig-Marikina River Basin, the DPWH plans to build an 81-meter high, 350-meter long Marikina Multi-Purpose Dam across a Marikina River gorge.

“The spillway capacity of the dam is designed for the probable maximum flood of around 6,300 cubic meters per second. The dam would be constructed within the Valley Fault System containing two active faults close to the dam—West Valley Fault and East Valley Fault with distance of 5.4 kilometers and 9.5 kilometers, respectively, to the dam site with the estimated earthquake magnitude of 6.2-7.2. The design has considered the required strength and stability of the maximum earthquake as the consequences of a dam failure would be extreme due to the large population and infrastructure value concentrated downstream,” the World Bank said.

Besides floodwater management, the project will also develop early warning and flood forecasting systems as well as emergency-response planning and inundation mapping.

The World Bank said the indigenous peoples and small farmers to be displaced by the project will be provided not only with new housing but also sustainable livelihood. INQ