MANILA, Philippines — Many speculations surfaced as to the massive flooding that submerged portions of Marikina and Pasig during the onslaught of Typhoon Ulysses.
Department of Science and Technology (DOST) Undersecretary Renato Solidum explained in an interview with UNTV on Friday (November 29) what could have caused the deluge in Marikina and Pasig despite the fact that the volume of rains brought by Typhoon Ulysses was lesser than that of Typhoon Ondoy in 2009.
“Ang source ng tubig pagdating sa baha sa Marikina-Pasig river ay iyong ulan mismo na tatama sa Sierra Madre [The source of floodwater in Marikina-Pasig river would have been the rainfall that will hit the Sierra Madre],” said Solidum, who is also the Director of the Philippine Institute of Volcanology and Seismology (PHIVOLCS).
“Talagang hiwalay po ang rivers na nag-de-drain sa Marikina River at sa Angat. In fact, usapin na rin ito noong panahon ni Ondoy. Kung matatandaan ninyo, ganoon din ang mga usapin pero hiwalay po talaga sila,” he added.
[Marikina River and Angat drain into two separate directions. In fact, this was the same issue during Ondoy. If you recall, this was the same issue but they are separate.]
Solidum explained that the water that is being released from Angat Dam usually flows towards Bulacan specifically the towns of Norzagaray, Angat, Bustos, San Rafael, Baliwag, Plaridel, Calumpit, Hagonoy, and Paombong; not, and never will reach, Marikina City.
National Power Corporation (NAPOCOR) Dam Manager Engr. Conrado Sison Jr said they always make sure that the process of releasing excess water in dams is under careful control because they have to maintain a sufficient water supply for irrigation in view of the dry season.
“Hindi tayo basta-basta nagpapakawala ng tubig dahil iyan po ay mahalaga din po sa atin [We do not just release water considering its value],” he said.
“Kung nagkaroon tayo ng premature spilling din tapos wala ng darating na ulan parang tinapon lang natin yung tubig which is alam naman natin lalong lalo na dito sa area na ito eh kailangan din naman para sa domestic water supply at irrigation [If we there was premature spilling without expecting another rainfall, it’s like wasting water that could have been used for domestic supply and irrigation],” he added.
USec. Solidum believes that man-made activities could have worsened the situation like deforestation, uprooting of trees and quarrying that resulted in landslides and flash floods.
“Madami na pong mga subdivision o settlement sa taas ng Marikina for example sa Rodriguez Rizal, San Mateo na ang epekto po nito imbes na yung tubig ulan pumasok sa baba sa lupa. Ito po ay gagapang ng mabilis kasi sementado na, aspaltado na at didiretso nang mas mabilis sa ilog,” Solidum said.
[There are a lot of subdivisions or settlement areas right above Marikina. For example, in Rodriguez and San Mateo in Rizal, the soil could no longer absorb the rainwater because the roads are already cemented. The water would tend to rapidly flow to the river.]
“Ngayon iyong mga ilog hindi rin nababawasan ang lalim. Nagsi-silt po iyan dahil sa mga baha previously at mga basura. Sa mga factors pong iyan talagang bibilis po ang pagdating ng tubig sa ilog at biglang tataas ang tubig,” he added.
[Also, the depth of rivers do not change. The rivers silted up because of the previous floods and waste deposits. So from those factors, water will rapidly flow downstream and will cause a sudden increase in river water.]
Solidum added that the onslaught of Typhoon Ulysses also coincided with the high tide conditions.
The experts said it is still important at present to work on restoring the rivers into their original carrying capacity and encourage tree planting to help prevent much worse incidents associated with the overflowing of rivers. –MNP (with reports from Val Villaflor)
MANILA, Philippines – Dam Safety Expert Roderick dela Cruz suggests that the Philippines must formulate a program that will focus on the aspect of dam safety in consideration of the communities near the downstream.
With 30 years of experience, dela Cruz who is based in the United States currently works as Senior Engineering Manager at SoCal Edison, one of the largest energy companies in the US and manages over 80 dams across Southern California.
In an interview via Zoom, dela Cruz recalled that, following the onslaught of Typhoon Ondoy that devastated his hometown Hagonoy, Bulacan ten years ago, he proposed to the government to establish a national dam safety program that would regulate and facilitate the dams in the country.
“When I was writing this paper, what I noticed really was one, a lack of program in the Philippines. We do not have a standard on how we monitor, how we design and how we improve the performance of an existing dam,” he said of his article published in 2012 in The Journal of Dam Safety.
He explained that dam management is crucial and needs a high level of expertise as he compares the extent of damage a broken dam could cause which is more massive that of a nuclear plant.
“I compared the risk noong dam kumpara sa risk nung Bataan Nuclear Power Plant. Sa aking pananaw mas malaki ang risk ng dam kesa sa nuclear plant [I compared the risk pose by a dam to that of the Bataan Nuclear Power Plant. I believe a dam poses higher risk than a nuclear (power) plant],” he said noting that the extent of the devastation of a broken dam could reach a larger number of communities than that of the nuclear plant.
“Ang question nga is bakit pinayagang hindi operate yung [My question is: Why not allow the operation of a] nuclear plant because of our concern and yet you continue to operate a lot of these major dams na hindi natin naiintindihan talaga kung ano ang magiging consequences kung saka-sakaling bumigay ang dam [without understanding the consequences when they break]?” he added.
He stressed that in the US, dams can be classified as high hazard structures when they pose a great danger to the community. Thus, a specific agency or a private firm is being tapped to manage them.
Such is the case with his company in Southern California which, despite being a private firm, operates under the regulation of the Federal Energy Regulatory Commission.
He also stressed that strict requirements and regulations for the safety and continuous operations of the dams are given utmost importance in the US.
Dela Cruz reiterated that having a dam safety program, the risk of dam breakage and destructive release of water will be prevented. It will also help protect dam structures from breaking in the event of an earthquake.
The dam safety expert also underscored that regular assessment and maintenance of dams must be conducted to prevent damage especially in consideration of the years that the dams have been operating.
“Ang isa ko ngang concern, maaari kasing ang protocol na na-establish long time ago, maaaring hindi na ngayon applicable dahil ang downstream impact mo ay nabago na [Also one of my concerns would be the protocols that have been established a long time ago may no longer be applicable due to the changes in downstream impact],” he explained.
“So those are areas that need to be evaluated para matingnan natin kung dapat ba natin baguhin ang [to determine if there is a need to change the] protocol, for what reason or for what purpose. So there needs to be a holistic approach ng [of the] assessment and evaluation of our dam based on risk,” he added.
In the Philippines, the La Mesa dam in Quezon City is the oldest (1929) followed by Ipo Dam in Bulacan (1938); Caliraya Dam in Laguna (1942); Ambuclao Dam in Benguet province (1956); Binga Dam in Itogon, Benguet (1960); Angat Dam in Bulacan (1967); Pantabangan Dam in Nueva Ecija (1974); Magat Dam in Cagayan Valley (1982); and San Roque Dam in Pangasinan (2008).
For its part, the National Irrigation Administration (NIA) has assured that it is conducting regular maintenance and structural assessment in all of the dams in the country.
MANILA, Philippines — Water level in Angat Dam increased significantly throughout the traverse of Typhoon Ulysses in Luzon and Bulacan where the facility is located.
According to the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), Typhoon Ulysses added around 9 meters of water to Angat’s reserve. From 205.50 meters on November 11 to it rose to 214.15 meters on November 13, at 6:00 AM — only about three meters short of reaching its maximum capacity of 217 meters.
The highest volume added was from Wednesday to Thursday which reached 5.8 meters.
Meanwhile, National Water Resources Board (NWRB) Executive Director Sevillo David said that currently the spillage is being done gradually in consideration of the communities that may be affected and to avoid aggravating the situation downstream.
“May spilling na ginagawa ang NPC but mina-manage ang releases considering safety of the dam and likewise the situation of the downstream communities in Bulacan which are already flooded to minimize its effect,” he explained.
Angat Dam is the main source of domestic water supply in Metro Manila and nearby provinces. MNP (with inputs from Rey Pelayo)
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