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Rehabilitate Laguna Lake to stop flooding

Republika

THE WAY I SEE IT | Susan Amoroso

This week three things pre-occupied my mind: the devastation Typhoon Ulysses brought to the farmers, loss of lives and damage to properties; the media release of Health Secretary Francisco urging us to support the anti-covid vaccination program of the government; and thirdly, how to bring back the household income to pre-covid levels.


It is very concerning that the flooding in Metro Manila could have been avoided if only the Laguna Lake was desilted and rehabilitated to its former baseline depth of 6.3 meters. The government through the Laguna Lake Development Authority (LLDA) under the Department of Environment and Natural Resources (DENR) could have rehabilitated Laguna Lake alongside the desilting of Pasig River. Why? Because 110 rivers and tributaries empty into Laguna Lake as the catch basin before these waters go to Pasig River. After which like a circuit, Pasig River empty finally into Manila Bay as their final destination.


The Department of Public Works and Highways (DPWH) estimates that around 3300 cubic meters per second goes to Pasig River during heavy rainfall. Unfortunately, the great Pasig River can only take in 900 cubic meters. In effect there is an excess of 2400 cubic meters. The inland excess water now floods the low lying areas in the cities of Caloocan, Malabon, Marikina, Navotas, Valenzuela; Tondo, Sta. Cruz, Sampaloc, San Andres, Sta. Mesa in Manila; Talayan and Tatalon in Quezon City; southern towns of Taguig, Pateros and Taytay; San Juan and Mandaluyong City; East Manggahan in Pasig City.


Considering that the country experiences some 3,000 millimeters of rainfall each year, during intense and continuous rainfall, the Pasig River, Malabon-Tullahan River, and Marikina River swell. That my dears cause the flash floods and the long-standing floods we residents in Metro Manila experience during the rainy season.


In 1999, that is 21 years ago, the reported losses due to flooding in Metro was almost P1 Billion. An estimated 10,600 hectares in Metro Manila are flood prone areas.


The open waterways and drainage structures and flood control devices of the DPWH are deemed ineffective if the main artery which is Pasig River from where waters from Laguna Lake passes through are clogged. Let us remember that Laguna Lake, the catch basin of 110 rivers and tributaries, if not desilted and rehabilitated will not be effective as a catch basin at all.
Benedicto D. Dorado, a medical doctor cum environmentalist has for years on end advocated for the dredging, desilting and rehabilitation of Laguna Lake as the most effective mitigation program to flood control.


Dorado said that desiltation and dredging of Pasig River alone is not enough because Laguna Lake, the main catch basin has not been desilted and dredged.


Years of soil erosion due to rampant deforestation from the surrounding mountains such as the Sierra Madre Mountains and other debris have accumulated under the seabed of Laguna Lake. The original depth of Laguna Lake was 6.3 meters around its 90,000 hectares total area. Now the silt is 3.5 meters leaving only 2.8 meters for the water level, Dorado explained.


Dorado said the same is true with Pasig River. It must also be desilted and dredged. But first deforestation and quarrying around the surrounding areas must be stopped to avoid siltation of Laguna Lake.


Dr. Dorado has a published research titled “Laguna Lake Flood Control and Lake Shore Park Project’’ which he wants the Duterte government to look into closely. Maybe this column can do a report on this later. Cheers. As always hope springs eternal.


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