Following the massive flooding in the National Capital Region (NCR) and the Rizal Province, President Marcos has directed government agencies to study the building of weirs along tributaries to control the water flow from Sierra Madre down to nearby areas.

Marcos said this as he led the situation briefing on the effects of Super Typhoon Carina and the enhanced southwest monsoon in Rizal Province on Friday, July 26.

In his remarks, the President noted that the unimpeded water flow causes severe flooding during the rainy season.

"If there's a weir pinapadaan niya ang tubig pero mayroon siyang binabagalan yung takbo (it allows water to flow but slows it down as well)," he said.

"I don't see a weir here in this country which is parang bagay na bagay sa atin yun. Maybe it's applicable here in the Philippines. I think it might be because I've seen it in other places and although the water passes, mababa yung tubig dito sa baba, mas mataas yung tubig doon sa taas. Pero dumadaan yung tubig, pati isda nakakadaan (the water level is low down here but it is higher upstream. Still, the water flows, even the fish can pass through)," he said.

A weir is a small barrier built across a stream or river to control and raise the water level slightly on the upstream side, essentially a small-scale dam.

It is used to prevent flooding, measure water flow, and hold water. The impounded water can be used in towns, homes, industry, or irrigation.

A weir generally allows the water to flow over the crest (which is the top) or sometimes underneath some sections. On the other hand, dams mainly allow water flow to be regulated or controlled by gates or spillways.

During the briefing, Public Works and Highways Secretary Manuel Bonoan told President Marcos that the previous plan was to build the Marikina Dam to control floodwaters from Sierra Madre but it has been reconsidered because of the construction of Wawa Dam.

“So, our plan is to build a series of small dams sa ibaba ng (below) Wawa Dam so that itong mga floodwaters na ito (the floodwater) will be impounded,” Bonoan said.

Rizal local officials acknowledged the importance of the Wawa Dam construction, which has greatly mitigated flooding in the province during the typhoon and Habagat.

During its inauguration, officials expected the dam to be filled with water in six months. But it was almost filled with rainwater in just two days, noting the recent high precipitation level.

They said that without the dam, San Mateo, Montalban, Marikina, Pasig, and parts of Quezon City could have been flooded.