Mayon Volcano lahars threaten Bicol amid rains – PHIVOLCS

Metro Manila, Philippines — Lahars, or volcanic sediment flows, from Mayon Volcano threaten Bicol amid continuous rainfall, the Philippine Institute of Volcanology and Seismology (Phivolcs) said on Sunday, Dec. 1.

Based on the state weather bureau’s 11 a.m. advisory, the shear line may trigger severe intensity and possible high-volume rainfall over Albay.

Aside from lahars, the persistent rains may cause “muddy streamflows or muddy run-off in rivers and drainage areas.”

Those along the Miisi, Binaan, Anoling, Quirangay, Maninila, Masarawag, Muladbucad, Nasisi, Mabinit, Matanag, Basud, and Bulawan Channels in Albay should be on alert for possible lahars and sediment-laden streamflows.

“Prolonged and heavy rainfall may generate post-eruption lahars on major channels draining Mayon Volcano by incorporating loose material from remnant pyroclastic density current pyroclastic density current (PDC) deposits from the January-March 2018 eruption,” Phivolcs said in a separate advisory.

Most of the erodible PDC deposits are in the watershed areas of Basud, Buyuan, Miisi, and Mabinit Channels.

“Older and erodible eruption deposits that occupy the watershed areas on the eastern and western slopes of the edifice and can be remobilized as non-eruption lahars by erosion of banks and channel beds,” it added.

Phivolcs warned that Mayon lahars can threaten communities downstream of the channels with inundation, among others.