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View Full Version : Flooding in the Philippines. Two potential solutions.



lastlid
30th August 2012, 21:58
Two potential solutions for Metro Manila. Currently being looked at. Which do they go for? Anybody got any better solutions?

"A system of water collection ponds in flood-prone areas has been offered as a cheap and quick alternative to the Department of Public Works and Highways (DPWH) flood-control system that is estimated to cost P352 billion.

Antonio Oposa, an environment lawyer and a Ramon Magsaysay awardee in 2009, made the suggestion before a congressional oversight committee weeks after Metro Manila and nearby provinces suffered widespread flooding as a result of heavier-than-usual rains caused by an enhanced southwest monsoon.

“Let’s do it the natural way…. [the] cheaper and the more effective way in urban areas. Let’s not build everything in concrete,” Oposa said.

At the hearing of the Joint Congressional Oversight Committee on the Clean Water Act, Senator Pia Cayetano and Laguna Representative Dan Fernandez supported the proposal to make putting up water catchment facilities a requirement for business establishments before they are given permits.

Cayetano and Fernandez, cochairs of the joint committee, welcomed the proposal amid government’s noncompliance with Republic Act No. 6716, which calls for the construction of rainwater ponds in all barangays in the country.

“I quiver when I hear the amount of money that would be spent. Hundreds of billions of pesos. Can’t we just buy property worth a million pesos or two million pesos? Buy land and dig 1,000 square meters and around it the poor could plant vegetables for food,” Oposa told the panel.

“That will arrest subsidence or reverse it,” he added. Subsidence refers to a land mass sinking due to depleted aquifers.

Massive flooding has been blamed on subsidence and on the rise of the sea level due to global warming.

The oversight panel heard Oposa and representatives of the DPWH, Metro Manila Development Authority (MMDA) and other agencies involved in the Aquino administration’s flood-control programs.

Up to 2035

A DPWH master plan for a comprehensive flood-control management in Metro Manila involves the construction of a ring-road dike on the rim of Laguna de Bay, embankments and catch basins in the Marikina River watershed and an 8-kilometer dike and pumping station in Camanava (Caloocan, Malabon, Navotas and Valenzuela) area. The program is slated to be completed by 2035.

Asked later in an interview if he was offering the water collection pond system as an alternative to the DPWH master plan, Oposa said the DPWH plan was too expensive.

“The situation is quite simple. Bring back the water to the ground,” he said.

Solution is not in billions

Oposa said P100 million would be enough to expropriate pieces of property in Metro Manila for water catchment ponds and to build retaining walls around them.

“The solution is not in billions. The solution is in common sense. Find a place for the water to go,” he said.

The water catchment ponds would have porous bottoms—lined with pebbles instead of being overlaid with concrete—so that the rain water would seep through the ground and restore aquifers.

“The water would be soaked in by the soil because it is quite dry,” he said.

The only portions of the ponds that would be made of concrete would be the walls to keep the sides from sliding.

He said the ponds, one-meter to three-meter deep, would be located in low-lying areas prone to flooding.

Vegetables, fish

Oposa said vegetable gardens could be put up around the ponds.

He also proposed that the ponds be stocked with fish so that they could provide recreational fishing.

Fernandez noted the local governments’ lack of compliance with the law requiring rainwater catchments to be put up in every barangay.

He asked the MMDA if it could compel local government units in Metro Manila to require establishments to put up water catchment facilities before they are given business permits.

Environment officer

Cayetano said there was a need to make the position of environment officer an item in the employment list of local government units.

“May I now instruct the secretariat [to study] two resolutions. One is on the environmental officer and one is on the parking and also the requirements that catchments be included [in the prerequisites] in securing business permits,” Cayetano said.

“Whether we do this by way of a recommendation to the MMDA or by bill, we’ll ask our secretariat to advise the committee,” she said.

Oposa also suggested that homes be equipped with their own small water catchment ponds.

To promote rainwater ponds, he said a property used for the catchment pond could be exempt from real estate tax."

http://newsinfo.inquirer.net/259680/eco-lawyer-common-sense-will-solve-floods

Terpe
31st August 2012, 11:09
It's an interesting subject and apparantly quite complex.

There was a recent TV report on the potential impacts of Hurricane Isaac on New Orleans considering the billions of dollars spent on flood defences.
Interestingly, there was quite some concern about the volumes of rain expected as the surface drainage and run-off had not been upgraded to cope with the projected amount of rain expected.

The flood and sea-intrusion defences were confidently expected to give protection.

So it seems that solutions would need to be considered for all potential root causes. :Erm:

lastlid
31st August 2012, 11:13
It's an interesting subject and apparantly quite complex.

There was a recent TV report on the potential impacts of Hurricane Isaac on New Orleans considering the billions of dollars spent on flood defences.
Interestingly, there was quite some concern about the volumes of rain expected as the surface drainage and run-off had not been upgraded to cope with the projected amount of rain expected.

The flood and sea-intrusion defences were confidently expected to give protection.

So it seems that solutions would need to be considered for all potential root causes. :Erm:
Yes. Holes in the ground wouldn't deal with all kinds of root causes. Net rising sea levels would need to be dealt with in other ways. I think this author's focus is on runoff from rain which he sees as one of a group of key root causes.

Avoidance of land reclamation would need to be addressed too as a futile exercise and some areas affected by sea level rises might need to be deemed lost causes.

Not all holes in the ground would work in the desired way. Permeability would be key to this.

As you say, a combination of solutions is required.

Having said that, cheap holes in the ground ought to be an easy and cheap start to runoff related flooding if funding is an issue.