Pampanga mayor fears new lahar flows

By Ding Cervantes, The Philippine Star

Posted at Aug 11 2012 12:08 AM | Updated as of Aug 11 2012 08:08 AM

SAN FERNANDO, Pampanga, Philippines  – A Pampanga official warned residents Friday that millions of tons of Mt. Pinatubo’s lahar along the Pasig-Potrero River could move toward heavily populated centers and two major highways here.

“The towns of Sto. Tomas and Minalin are in danger of being buried by volcanic materials, in the way that Bacolor was buried under several meters of debris in the 1990s after Mt. Pinatubo’s eruption. Portions of southeastern San Fernando are also in danger,” San Fernando Mayor Oscar Rodriguez said.

In a meeting with Gov. Lilia Pineda, other local officials and engineers of the Department of Public Works and Highways, Rodriguez appealed to the national government for “immediate engineering intervention against the serious threat we are facing.”

Asked how much lahar debris could be remobilized if the monsoon rains continue on Mt. Pinatubo slopes, Rodriguez cited the estimates of experts that it could be “in the millions of tons.”

This, after raging floodwaters shattered the so-called transverse dike and accompanying lahar materials overtopped the “tail dike” along the Pasig-Potrero River, one of the most active lahar channels after the Pinatubo eruption in 1991.

Rodriguez recalled that much of Bacolor was then buried by volcanic debris, and in 1995, a dike built across the river purportedly to protect Barangay Cabalantian and other remaining portions of Bacolor gave way, sending an avalanche in the middle of the night and burying alive scores of residents.

The following year, government engineers started construction of a U-shaped megadike along the Pasig-Potrero River to contain lahar flows and shield this city and other populated areas from lahar.

They also built within the megadike other structures, including the transverse dike across the lower reaches of the river, to soften the impact of lahar flows on the lower bend of the megadike as well as the “tail dike” which served as additional protection.

“The transverse dike has been destroyed and remobilized lahar materials have already overtopped the tail dike, creating two channels that are now flowing dangerously toward the towns of Sto. Tomas and Minalin,” Rodriguez warned.

He said that if the lahar flows finally destroy the megadike, millions of tons of lahar debris that accumulated on the riverbed of the Pasig-Potrero could bury Sto. Tomas and Minalin, which have remained heavily flooded since typhoon “Gener” last week.

“We know the danger that could face us and the threat is really serious now,” he said.