The Philippine Institute of Volcanology and Seismology (Phivolcs) issued a lahar advisory for Kanlaon Volcano at 11 p.m. on Wednesday, June 5, citing the ongoing threat of “lahars, muddy streamflows, or muddy run-off” downstream of the active volcano in Negros Island.
Citing the Philippine Atmospheric, Geophysical, and Astronomical Services Administration’s forecast for June 6 and 7, Phivolcs said heavy rainfall, with estimates of 100 and 200 millimeters (mm), is expected to affect Negros Island in the next two days.
It warned that the rains could lead to an increased volume of lahars, muddy streamflows, or muddy run-off in several downstream communities and rivers draining into the southern slopes of Kanlaon, the same areas affected by lahars on Wednesday afternoon.
Phivolcs said the lahars on Wednesday have deposited grey cohesive mud, plant debris, and gravel in at least four waterways: Tamburong Creek, flowing through Biak-na-bato and Calapnagan, La Castellana; Intiguiwan River in Guinpanaan and upstream Baji-Baji Falls in Cabacungan, La Castellana; Padudusan Falls, Masulog, Canlaon City; and the Binalbagan River, which drains the southern flank of Kanlaon Volcano.
It added that they were generally channel-confined, but flows along Tamburong Creek overflowed and deposited a few centimeters of sediment on a stretch of the main road in Biak-na-Bato, rendering it impassable to motorists.
“These lahars began approximately around 1 p.m. and lasted 25 minutes based on the seismic record. A total of 23.75 mm of rain over a two-hour period was also recorded by the All-Weather Station of the Manghumay, Mailum, Bago City Observation Station (VKMH) of the KVN. Higher rainfall volumes may have likely occurred around the summit area of the volcano,” Phivolcs said.
Due to the anticipated rainfall in the next two days, Phivolcs warned that lahars could threaten communities along the middle and lower slopes with inundation, burial, and washout.
It recommended increased vigilance and readiness among communities along rivers draining southern Kanlaon.
These communities and local government units are advised to continually monitor weather conditions and take preemptive response measures for their safety from potential lahars.