Expected rain fuels risk for sediment-laden stream flows

MANILA -- Communities in Mayon and Bulusan volcanoes' lower fringes face possible sediment-laden stream flows triggered by rain expected until next week.

Philippine Institute of Volcanology and Seismology (Phivolcs) warned about such possibility after Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) forecast until around Monday (Jan. 23) light to moderate rain showers and thunderstorms over Bicol Region hosting Mayon and Bulusan and over Central Visayas, Eastern Visayas and Mindanao.

"Such rain can erode the volcanoes' loose, sandy deposits which eventually mix with water in arteries there to become sediment-laden stream flows," said Phivolcs geologist Mabel Abigania.

She said communities concerned must prepare for such possibility.

Abigania urged preparation, noting sediment-laden stream flows can strike like flash floods that rapidly inundate low-lying areas.

"People must be alert to such occurrence," she said.

In its bulletin released Thursday, Phivolcs reminded the public to avoid Mayon Volcano's active streams, river channels and lahar-prone areas "especially during extreme weather conditions when there's heavy and prolonged rainfall."

Phivolcs also cautioned people within Bulusan Volcano's valleys and along its river/stream channels about possible sediment-laden stream flows there.

Heavy and prolonged rainfall can trigger lahar in Bulusan, Phivolcs warned.

Lahar is flowing mixture of volcanic debris and water, said Phivolcs.

Abigania, however, said the possibility for lahar in Mayon and Bulusan volcanoes at present is still "low".

She said PAGASA's expected light to moderate rainfall until Monday will unlikely trigger onslaught of lahar there.

"Prolonged heavy rainfall can cause lahar flows," she added.

In its weather advisory 1 released Thursday, PAGASA said the tail-end of a cold front may bring cloudy skies with moderate to occasionally heavy rain and isolated thunderstorms over Central Visayas, Northern Mindanao, Caraga, as well as Leyte and Southern Leyte provinces.

"Residents in such areas are alerted against possible flash floods and landslides," said PAGASA.

PAGASA forecaster Jun Galang said the tail-end of a cold front may already gradually dissipate in two to three days.

He said another tail-end of a cold front may develop, however, bringing light to moderate rain and thunderstorms to Bicol, Eastern Visayas, Central Visayas and Mindanao.

Those thunderstorms will likely occur during afternoons, he added.

National Disaster Risk Reduction and Management Council (NDRRMC) said rain from tail-end of a cold front and low-pressure area earlier this month resulted in landslides and flooding in parts of the Visayas and Mindanao.

Government suspended classes in some areas of regions VI, VII, VIII, X, Negros Island Region and Caraga Region due to continuous rain and flooding there, NDRRMC said in it situation report 4 released Thursday.

Flooding and landslides rendered several roads impassable, NDRMC continued.

A total 48 houses in Misamis Oriental and Leyte provinces sustained damages due to the inclement weather, NDRRMC added. (PNA)

Source: Philippines News Agency

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