The Philippine Institute of Volcanology and Seismology (Phivolcs) warned on Friday, July 21 of a potential lahar flow near Mayon Volcano in Albay due to moderate to heavy rains from tropical depression Egay.
In its advisory issued at 10 a.m., Phivolcs said there is a possibility of lahar and sediment-laden streamflows on all river channels that drain the Mayon Volcano's slopes, particularly the Mi-isi, Binaan, Anoling, Quirangay, Maninila, Masarawag, Muladbucad, Nasisi, Mabinit, Matan-ag, and Basud channels.
Local governments and communities near these drainages are urged to exercise caution and evacuate residents to higher ground in the event of heavy rainfall.
“The incoming tropical depression is expected to bring about prolonged and heavy rainfall which may generate syn-eruption lahars along major channels draining the Mayon Volcano edifice by incorporating loose material from thick pyroclastic density current (PDC) deposits and ashfall from the ongoing 2023 eruption,” Phivolcs said in its advisory.
“The bulk of erodible PDC deposits currently occupy the watershed areas of the Mi-isi, Bonga, and Basud channels. In addition, older and erodible eruption deposits 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,” Phivolcs said.
It pointed out that Mayon Volcano's lahar can inundate, bury, and wash away communities along the middle and lower slopes and downstream of these channels.