Rains, lahar threaten lives around Mega Dike

By Franco Regala

CLARK, Pampanga — Several towns in Pampanga province particularly the towns of Porac and Bacolor, where the multibillion Mega Dike (FVR Dike) structure is situated are at risk from lahar flows if heavy rains similar to the 1972 incessant rains and Ondoy-like storm happen, said Philippine Institute of Volcanology and Seismology (Phivolcs) Director Renato Solidum.

Solidum issued the warning for consideration of authorities in low-lying areas as more rains are expected this month with the onset of the La Niña phenomenon.

Citing a 2008 study by Phivolcs, Solidum said that incessant rains may repeat the worst 1972 disaster, which submerged many areas in Central Luzon particularly Pampanga.

He added that villages living inside the megadike should understand the possible lahar-floods threat.

“Heavy rains that will be brought about by an Ondoy-like typhoon may trigger lahar flows and flooding in the province because the river gets shallower kasi nasi-silt siya. In short, hindi yan nakakamatay until na magkaroon ka ng sobrang lakas ng ulan and in a short duration iaanod muli yung napondo doon at kung hindi ma-contain ng dike ay baka lumampas (Heavy siltation in the river won’t kill you; but once heavy rains come in, the dike won’t be able to contain the weight of the and water silt deposits until an overflow occurs),” the chief volcanologist explained in a media briefing, here.

“Kapag nagkaroon ng siyam-siyam katulad nung 1972 na tuloy-tuloy ang bagyo at pag-ulan, ’yun ang kailangan nating bantayan at paghandaan para masiguro natin ang ating kaligtasan (When a tragedy like in 1972 when typhoons came one after another occurs, that’s what we need to prepare for to ensure our safety),” he said.

“For example, our modeling said if we assume 10 million cubic meters of lahar, which immediately after the eruption ay nangyari yun, so what can happen is that the flow can start depositing above doon sa SCTEX (Subic-Clark-Tarlac Expressway) point sa Delta 5 watch-point. Kung doon nagsimula banda ang deposition baka dito sa may Mancatian area ay abutin doon. So babantayan natin na ang flow at yung ilog ay hindi doon kasi ang tendency ng tubig papunta doon,” he added.

The Megadike, also known as the “‘FVR Dike” in attribution to the former president Fidel V. Ramos, has around 5,000 inhabitants, records from the Department of Social Welfare and Development (DSWD) show. The structure was built and designed U-shaped some 18 years ago to contain mudflows of lahar and to protect several towns in the province.

The 56-kilometer, U-shaped dike designed for lahar catchment structure links Angeles City, Clark Freeport and the upstream where the Pasig-Potrero River in Barangay Manibaug-Pasig in Porac and down to the traverse dike to river channel going to the City Of San Fernando, Minalin, and Pampanga River in the fourth district and exit to Manila Bay.

The PhiVolcs chief advised quarry operators to do “flood-quarrying” or an “engineered-design” quarrying along the Pasig-Potrero river and other adjacent river channels in order to prevent heavy siltation which may endanger several barangays inside the megadike in Bacolor and Porac.