The Philippine Institute of Volcanology and Seismology (Phivolcs) on Monday. Nov. 24, warned that heavy rains caused by Tropical Depression “Verbena” could trigger lahar and sediment-laden streamflows from Kanlaon Volcano that could hit nearby communities.
Kanlaon lahars, which were shown by Typhoon “Tino” to be strong enough to transport enormous volumes of gravel and boulders, could threaten communities by “their force of impact, inundation, burial and wash out”, Phivolcs said.
Kanlaon Volcano on Monday emitted ash at 5:54 a.m. for six minutes and 6:54 a.m. for 30 minutes, Phivolcs reported.
Pagasa has warned that “Verbena” and the shear line will potentially bring heavy to intense rainfall over several areas of Central Philippines, including Negros Island, in the coming days, Phivolcs said.
This can generate volcanic sediment flows or lahars, sediment-laden streamflows or muddy run-off and related siltation in rivers and drainage areas on Kanlaon Volcano, which is currently at Alert Level 2, Phivolcs said.
Phivolcs said it strongly recommends increased vigilance and readiness of communities in pre-determined zones of lahar and related hazards from Kanlaon.
Prolonged heavy to intense rainfall may generate life-threatening lahars and sediment-laden streamflows on major channels draining the southern, western and eastern slopes of Kanlaon Volcano, it said.
Post-eruption lahars can be generated by intense rainfall eroding loose material from remnant pyroclastic density current (PDC) deposits of Kanlaon’s October 24 explosive eruption and loose ashfall from recent ash emission events.
In addition, non-eruption lahars can be generated when areas on the upper slopes that have been recently exposed by landslides or weakened during the passage of Typhoon “Tino” earlier this month become susceptible to failure and feed debris to rivers that have already delivered destructive flows to downstream communities, Phivolcs said.
Communities in Bago City, La Carlota City, La Castellana, Moises Padilla and San Carlos City, Negros Occidental and Canlaon City, Negros Oriental may be affected by lahars and sediment-laden streamflows and related flooding and siltation at:
• Ibid River
• Cotcot River
• Talaptapan River
• Malaiba River
• Panubigan Creek
• Buhangin – Indurayan River
• Najalin River
• Inyawan River
• Maragandang River o Panun-an Creek
• Intiguiwan River
• Camansi River
• Maao River
• Tokon-tokon River
• Masulog River
• Binalbagan River
• Taco Creek
• Linothangan River
• Binalbagan River
These communities as well as those further downstream of the channels are advised to be prepared in case evacuation becomes necessary and to avoid traversing affected streams even those farther downslope of the volcano, Phivolcs said.
Phivolcs strongly advised the communities and local government units of the identified areas of risk to continually monitor the rainfall conditions and to take pre-emptive response measures for their safety.*