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Mayon Volcano (INQUIRER file photo by Ed Lustan)
MANILA, Philippines – State volcanologists warned of possible lahar and mudflow from three active volcanoes as Typhoon Rolly threatens Luzon, and is expected to bring its high volume of rain.
In a lahar advisory issued on Friday, the Philippine Institute of Volcanology and Seismology (Phivolcs) said heavy rains from the typhoon can trigger lahar and mudflows in rivers and drainage areas of the Mayon, Pinatubo and Taal volcanoes.
According to the monitoring of the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa), “Rolly” is expected to make landfall over the province of Quezon, and may even reach the category of super typhoon.
Currently, the wind signal for tropical cyclone No. 2 is hoisted over the eastern part of Camarines Sur, Catanduanes, Albay and Sorsogon.
Mayon State
Phivolcs warned that heavy rains can generate lahar in the main channels that drain the Mayon volcano by incorporating loose material from remnant pyroclastic density current (PDC) deposits from the volcano’s eruption from January to March 2018.
“Most of the erodible PDC deposits occupy the watershed areas of the Miisi, Mabinit, Buyuan and Basud channels,” said Phivolcs.
“In addition, the oldest and erodible eruption deposits occupy the watershed areas on the east and west slopes of the building and can be remobilized as non-eruptive lahars by erosion of the banks and channel beds.”
Thus, sediment-laden streams and lahar currents can occur in the Miisi, Binaan, Anoling, Quirangay, Maninila, Masarawag, Muladbucad, Nasisi, Mabinit, Matan-ag and Basud channels.
Pinatubo situation
“Intense and prolonged rains can generate lahars without eruption in the main rivers that drain the western Pinatubo Volcano, where significant deposits of the 1991 PDCs remain in the basin,” Phivolcs said of Mount Pinatubo.
“The Pinatubo lahars are likely to be confined to channels and found in the upper-middle reaches of the Sto. The systems of the Tomas-Marella and Bucao rivers, but they can pass into muddy streams and floods in the lower reaches and affect the adjacent communities of San Marcelino, San Narciso, San Felipe and Botolan, province of Zambales ”, he added.
Language perspective
Likewise, the typhoon’s heavy rains can generate a muddy flow around Taal Volcano, particularly on the slopes west of Lake Taal, where “the remaining thin ash can be remobilized in streams and roads and overland from the slopes to the lake”.
Taal Volcano (taken October 26, 2020). Photo by Mike Frialde / INQUIRER.net
Muddy flow and runoff may reappear in previously affected communities of Agoncillo and Laurel, Batangas province, Phivolcs said.
“DOST-Phivolcs strongly recommends that communities and local government units in the risk areas identified above continually monitor typhoon conditions and take preventive response measures for their safety from Rolly,” the agency warned.
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