MORE than three decades after its devastating eruption, Mt. Pinatubo remains a serious threat to communities around it, mainly because of lahars, the Philippine Institute of Volcanology and Seismology (Phivolcs) reported.
Information released by Phivolcs revealed that Mt. Pinatubo, once believed to be a dormant volcano until its eruption in June 1991, released large amounts of volcanic materials. The heavy rains that followed the eruption triggered lahars along the rivers draining from the volcano.
Phivolcs said repeated lahar flow events have altered the landscape, changing river channels, burying areas, damaging roads and bridges, and affecting communities.
Phivolcs said that almost all of the debris spit out by the volcano’s crater have been transported downstream over the years; substantial deposits remain on the slopes and in river channels, which pose serious risks in the event of heavy downpour.
‘These materials may still be remobilized during periods of heavy rainfall, making lahars and flooding a continuing hazard in areas downstream of the volcano,’ it said.
In the last quarter of August this year, Phivolcs said heavy and continuous rainfall attributed to the southwest monsoon or habagat triggered lahar flowss and associated flooding along the major river systems draining Pinatubo volcano-the Sto. Tomas Bucao, Pasig-Potrero, Sacobia, and Abacan rivers.
The DOST immediately deployed a quick response team to assess the impacts using robotic process automation (RPA) and aerial surveys, as well as ground validation, documenting 82 impact areas, 30 of which had damaged structures, 16 with new lahar deposits, 10 showing erosion, seven with channel widening, and seven affected by flooding.
During typhoons and heavy rainfall, especially brought about by habagat, Phivolcs issue lahar warnings from time to time to alert communities of the potential danger.
Phivolcs recommended that damaged structures be assessed and referred to the engineers or mandated agencies for further evaluation and measures to mitigate further damage.
Phivolcs also called on local governments to update their disaster risk reduction and management, evacuation, contingency and land-use plans using relevant hazard information and recent observations from affected areas, and to integrate updated hazard information into local planning.