Zero absorption equals floods

Last Monday, I passed by the San Francisco del Monte district in Quezon City, and I was surprised that the Grab driver took a different route, avoiding the road along a creek. He explained that the road was unpassable because illegal settlers along the creek had placed their belongings on the road to dry them. For nearly a kilometer, I saw so many cars being stripped of interiors and engines being flushed out after being sunk in the recent flash flood.

Last week, DPWH Secretary Manny Bonoan said that they were ready to meet up with legislators to explain or air their side on the recent flooding and the complaints that the government’s flood control program had failed. Even the President spoke up and said that the flooding was as much due to climate change as well as sheer volume of rain that cannot be predicted.

Imagine how much worse the situation would have been if San Miguel Corporation had not voluntarily undertaken the river dredging and clean-up of the Pasig River system, Tullahan River, Bulacan River system, San Juan River, as well as the San Isidro River in San Pedro, Laguna. And still, no one is joining in to help in the clean-up.

According to published data of SMC, the Pasig River clean-up was 26 kilometers long and produced 1,185,207 metric tons of waste and silt. The Bulacan River system was 70.36 kilometers in length and had 4,041,523 metric tons of waste and silt removed by SMC.

The perennial headache Tullahan River is 10.9 kilometers with 1,124,183 million metric tons. San Juan River is 7.61 kilometers with 322,739 metric tons of silt and waste, and the shortest San Isidro River at 5.3 kilometers long had more silt and waste than San Juan River, producing 413,972 metric tons of silt and waste.

In total, the more than two years of voluntary clean up done by San Miguel Corporation covered 120.16 kilometers of rivers and cleared 7,087,624 metric tons of silt and dirt.

According to testimonies of barangay captains in historically flood prone areas, there has been substantial reduction of flooding or lowering of flood levels and quicker drainage compared to the time before the river clean up was undertaken by SMC in their area.

That is good to know, but the question is – why was there major flooding in many parts of Metro Manila? The first reason goes back to what the Grab driver pointed out and was also shown in many news reports during the storm. Many illegal settlers and illegal structures still stand along the creeks, rivers and waterways, as well as the shoreline in Tondo and Cavite.

Many local government units have a hands-off or blind side when it comes to illegal settlers, garbage disposal and waste being dumped or piled on sidewalks, streets, canals and open spaces. Almost every barangay in every urban area has this characteristic.

Even if companies like San Miguel Corporation willingly take on the clean up of waterways, they can’t win the war if the LGUs don’t have the political will to clear and protect riverbanks, embankments and tributaries. If I remember correctly, SMC chief Ramon Ang once pointed out that after they finish their voluntary clean up, it will only take two years for waste and silt to pile up again if other problems are not addressed.

Aside from illegal settlers and structures, the second and bigger contributor to flooding has to do with urban planning, water and environmental engineering designs and management.

When I wrote the title “Zero absorption equals flooding,” I was referring to the fact that if we surveyed or audited the entire ground area or footprint of Metro Manila and other urbanized areas, people will be shocked to learn that there are far more cemented or concrete covered areas than open or porous ground.

We have adopted engineering designs from the West that were used 50 or 60 years ago for countries that did not have urban concentration and population and lots of open space, fields and prairies. In those days and places, rainfall would be absorbed by the ground immediately.

With urbanization, engineers changed the plans and adopted the design that would collect as much water as possible on concrete surfaces and direct them to canals, sewers and finally to waterways. But as PBBM pointed out, climate change was a game changer, so we have far more rain directed and concentrated in volume, resulting to flooding.

Filipinos already knew what was coming many years before. Remember the time when the MMDA and the DPWH suggested the construction of a gigantic cistern under the football field and parade grounds of UST that could take in a big volume of rainwater and slowly release it as needed? Unfortunately, the idea was shot down on the UST side.

The same was suggested to the developers of the Bonifacio Global City, who welcomed the suggestion and implemented the cistern design. While flooding continues to happen around UST, I picked up social media chatter last week that praised the BGC developers for their progressive view because flooding does not occur in BGC as it does in other areas.

While many countries have adopted the use of pavers or those jigsaw puzzle style concrete blocks that allow water to be absorbed into the ground, the Philippines does not have a law requiring this environmentally friendly anti-flooding engineering solution. We also do not require ground cover plants on slopes and embankments where water washes out soil and dirt into rivers.

We need to open up the ground surface so water can be absorbed, not wasted. Let us not forget the twin of floods named drought. Let the earth drink the rains as God designed.

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