In its 11 AM bulletin today, the Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) forecasted Typhoon Ruby to make landfall in Samar area before noon of December 6. The typhoon is estimated to bring heavy to intense amount of rainfall within its 700 km diameter, thus posing grave threat of extreme rainfall-induced landslides and lahars in volcanic edifices, particularly in Albay and Sorsogon Provinces. In Albay Province, extreme rainfall may trigger landslides and excessive erosion of old pyroclastic deposits in the upper to middle slopes of Mayon Volcano, generating lahars in all river drainages. Potentially large-magnitude lahars can threaten downstream communities along river channels with inundation, burial and washout. The greatest lahar hazard can consequently be faced by communities along the Masarawag (Guinobatan), Maninila (Guinobatan), Buyuan-Padang (Legaspi City), Lidong (Sto. Domingo), Mabinit (Legaspi City), Basud (Sto. Domingo), Miisi (Daraga), Anoling (Daraga) and Nabonton (Ligao City) Channels. Furthermore, lahar-related flooding, washout and siltation can subsequently occur along the Yawa River, threatening adjacent and low-lying areas of Legaspi City. In Sorsogon Province, extreme rainfall may cause excessive erosion of existing pyroclastic deposits in the upper slopes of Bulusan Volcano, triggering lahars in rivers draining the southeastern, southwestern and northwestern flanks. Potential moderate-volume lahars can threaten downstream communities along the Malunoy (Patag), Mapaso, Cadac-an, Tinampo and Cogon Rivers in Irosin and the Añog-Rangas River in Juban. In view of the above, PHIVOLCS strongly recommends vigilance and readiness of communities in pre-determined zones of lahar hazards in the above volcanoes. Preparedness on clearing and rehabilitation operations is also recommended in the event of debris deposition on roads and bridges that traverse lahar channels. PHIVOLCS reiterates that strict avoidance of the Permanent Danger Zones in both Mayon and Bulusan Volcanoes must be observed due to the potentially amplified dangers of rockfalls, avalanches, landslides and steam-driven explosions at the summit area. -The Philippine Institute of Volcanology and Seismology (PHIVOLCS)
Posted on: Fri, 05 Dec 2014 08:47:57 +0000