Rains may trigger lahar from Pinatubo, Taal volcanoes, Phivolcs warns

MANILA – The Philippine Institute of Volcanology and Seismology (Phivolcs) on Saturday warned of lahar flows from Pinatubo and Taal volcanoes amid heavy rains brought by the southwest monsoon.

In an advisory, Phivolcs said heavy rains could generate volcanic sediment flows or lahars, muddy streamflows or muddy run-off in rivers and drainage areas.

“Prolonged and intense rainfall may generate non-eruption lahars on major rivers draining western Pinatubo Volcano where significant deposits of the 1991 pyroclastic density currents (PDCs) remain on the watershed,” it said.

According to Phivolcs, Pinatubo lahar flows are likely to be channel-confined and occur on the upper to middle reaches of the Sto. Tomas- Marella and Bucao River systems but may transition to muddy streamflows and floods on the lower reaches and affect adjacent communities of San Marcelino, San Narciso, San Felipe and Botolan in Zambales province.

Muddy streamflows may likewise be generated along the O’Donnell and Pasig-Potrero River systems draining the Pinatubo edifice to the north and southeast, respectively and affect downstream communities in Tarlac and Pampanga provinces.

“Prolonged and heavy rainfall may also generate muddy streamflow, muddy runoff and even volcanic debris flows around Taal Volcano, particularly on the slopes west and north of Taal Lake,” Phivolcs said.

It said old and loose volcanic deposits, already saturated from previous rains, may be remobilized in streams, roads and across the lakeward slopes.

In particular, muddy and debris flows can recur on previously affected communities of Agoncillo, Laurel and Talisay in Batangas province.

Phivolcs advises communities and local government units of the identified areas to continually monitor storm conditions and take preemptive response measures for their safety. (PNA)