The proposed 50-year drainage masterplan for Metro Manila is still in the works, Metropolitan Manila Development Authority said.

MMDA general manager Procopio Lipana said on Friday that the agency has submitted the masterplan's terms of reference to the Department of Public Works and Highways (DPWH) that could help create and implement it.

The masterplan would determine the 'detailed engineering design' of drainage systems in the entire Metro Manila, according to MMDA Acting Chairman Romando Artes in previous interviews late last year.

He added it would seek to prevent unstable flow of excess water due to varying sizes of drainages.

The proposed 50-year drainage masterplan would be funded by World Bank.

During the torrential rains from the southwest monsoon carried by Typhoon Carina, the MMDA reported existing drainage systems in Metro Manila carried 74 mm per hour for more than 10 hours.

The figure was more than twice the carrying capacity of drainages at 30 mm per hour, it noted.

Lipana said that with rainfall from the southwest monsoon that allegedly exceeded that of Typhoon Ondoy in 2009, both drainages and pumping stations operated by the MMDA could have been overwhelmed by such a volume that was 'beyond their capacity.'

However, except for the Libertad pumping station that caught fire, the rest of the 71 pumping stations remained operational during the incessant rainfall, he added.

He also blamed garbage for the widespread flooding in the metropolis, as well as the lack of discipline of residents - particularly those living near waterways - in disposing their trash. He mentioned the incident wherein flooding along EDSA near the old MMDA building in Makati City subsided after the agency's personnel performed declogging and retrieved waste from nearby drainage.

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