Science-based approach

These days the prospect of a mere thunderstorm and the sight of dark clouds can trigger panic among residents of flood-prone areas.

One of our colleagues, whose house was inundated by floodwaters nearly up to the second floor earlier this year, was stunned the other weekend by that cataclysmic flood that rose rapidly within just one hour of torrential rain, again submerging their home in about three feet of water.

Their sofa set, newly re-upholstered in white, was sent to the cleaners, whose fee was nearly as much as the cost of the furniture, probably because of strong demand amid the floods. The cabinets became warped.

Looking on the bright side, they reported that they managed to save one of their refrigerators, using a hair dryer to clean the machine. The other one, however, probably was not dried enough. When plugged in, its control board sparked and the appliance was kaput.

The flash flood caught motorists on the road, who watched helplessly in horror, some trapped inside their vehicles, as the water rose rapidly up to the window. In some areas, cars were submerged nearly up to the roof.

Former public works secretary Rogelio Singson, an industrial engineering graduate of University of the Philippines in Diliman, echoed what many people noticed: it was the first time ever, he said, that the UP Diliman campus became flooded. It was also a first for the Ateneo campus.

That was just an hourlong thunderstorm, which scientists said dumped more rain per hour than storm Ondoy.

The bad news is that such extreme rainfall and destructive flash floods are emerging as the new normal. The worse news is that our decades-old drainage systems are not equipped to deal with it.

And of course the worst news is that, thanks to gargantuan corruption, it will take time before engineering interventions that can mitigate the flooding can be completed, even under fast-tracked work schedules.

*      *      *

Both Singson and the executive director of Project NOAH, UP professor Mahar Lagmay, say the drainage system in Metro Manila was built for an urban environment many decades ago, when the concrete jungle and the population were much smaller.

That drainage system, built for street runoffs, used to be complemented by natural water catchments, mainly soil and greenery that could absorb rainfall or direct the water to creeks and rivers, and on to Manila Bay.

Today most of those catchments, and even creeks, have disappeared, with high-rises and mixed-use property complexes built over them. We can see this in the UP-Ateneo area in Diliman. These concrete structures all dump their used water and runoffs into the aging drainage system that has not expanded commensurately.

The result, which both Lagmay and Singson say is inevitable, is extreme flooding. It used to hit only once in a lifetime, but now it occurs at distressingly close intervals. In some areas where the thieves behind flood control projects have effectively made creeks narrower by turning even the bottom into concrete, the intervals are now just a matter of days.

NOAH, set up in 2012, stands for Nationwide Operational Assessment of Hazards. It has a detailed flood hazard map accessible online that the public can consult to avoid getting trapped in severe flooding during thunderstorms.

Lagmay, a geologist, told The STAR’s online show “Truth on the Line” last week that apart from overly relying on concreting for flood control (probably because it offers more opportunities for kickbacks), many engineering interventions tend to fight the natural geological features of waterways.

“We must build with nature,” he said.

Singson also told “Storycon” on One News last Friday that flood control must be integrated with overall water resource management designed around the major river systems nationwide.

He confirmed that an integrated water management master plan was completed under his watch as public works secretary, but it was buried and forgotten when the Duterte administration took over. The plan is there but was never implemented, Singson insists: “Hindi ko naman inuwi yun.”  He didn’t take it home with him.

Singson noted that piecemeal and uncoordinated flood control projects, often with little or no feasibility studies, were instead implemented even along major rivers that run through various “political divisions” or districts. Project NOAH was defunded under Rodrigo Duterte, so it moved from the Department of Science and Technology to UP.

Now we know the reasons for these developments.

Perhaps new DPWH Secretary Vince Dizon should try to find that master plan first before spending precious public funds for yet another flood control master plan. These studies are expensive.

*      *      *

It will take time before proper flood control infrastructure can be completed. In the meantime, both Singson and Lagmay are proposing the provision of water impounding facilities or cisterns in buildings and even at home, if possible supported by water recycling fixtures.

Singson cites the use of basement areas in buildings in Japan for rainfall impounding. He thinks this can be tested in at least one shopping mall in Metro Manila.

The basements in Japan are connected to a massive underground system that impounds excess water in reservoirs during heavy rainfall. When the storm is over, the water is pumped at controlled rates into the sea or rivers. The water retention facilities run under both private and public infrastructure.

In our plundered country, the trillions that have been lost to corruption in the past decades could have been used to develop even a limited version of this flood control system.

Lagmay has a cheaper approach, but it will work best with widespread public participation. During rains, he says, households especially in flood-prone areas can bring out drums or other containers to catch rainwater.

If much of the community will do this, he says it will reduce the amount of water accumulating in the streets and prevent the drains from becoming quickly overwhelmed. The impounded water can be used for watering plants or cleaning the driveway.

Such households habits, combined with the cisterns in high-rises, offices and commercial buildings, can ease flooding, says Lagmay. Toss in better solid waste management so the drains don’t get clogged, and there could be some relief while waiting for corruption-free flood control infrastructure to be completed.

Perhaps his suggestion can be tested in a pilot community. If people see that it works, water impounding can also become the new normal.

Instead of relying on politicians to deal with flooding, we should pay heed to the scientists.