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Scientists clueless on cause of Southern Leyte landslide

May 6, 2008 2:09am

SOUTHERN LEYTE, Philippines - It has been more than two years since a massive landslide buried the village of Guinsaugon in this town, but scientists are still clueless as to what triggered to catastrophe that claimed thousands of lives.

"Was the landslide caused by ground shaking or excessive rain? This is one of the things that is not yet resolved," said Mark Albert Zarco, a professor at the Department of Engineering Sciences at the University of the Philippines in Diliman, Quezon City.

He and other scientists from the Philippines, Canada, United States, Japan and Sri Lanka gathered here last week for a workshop to determine the cause of the landslide, develop a research plan for identifying hazard hot spots and mitigating the impact of catastrophic landslides, and help integrate scientific findings in the rehabilitation of Saint Bernard.

Richard Guthrie, a landslide expert from the University of Waterloo in Canada, said in a separate interview that they still have to determine what activated the rockslide-debris avalanche.

"We have not completely sorted out the earthquake portion of it but we have had very large rains and we have had very large earthquakes in the past," he said.

Mr. Guthrie, who visited Guinsaugon a month after the landslide, said ground movement occurs in the area at an estimated 2.5 centimeters a year due to the weakening of the rock mass.

"The rocks have been stretched and strained. As time moves on, the rock begins to age and die and finally it collapses. The important thing is that we’re able to know the preconditioning of the slopes," he told reporters.

Mr. Zarco said there were signs that the village was prone to landslides. But the residents were not aware of the cracks in the ground, muddy water coming out of holes in the ground, and irregular water flow from the mountain.

Saint Bernard Mayor Rico Rentuza said the residents were not trained to notice the warning signs.

The landslide claimed 1,119 men, women and children on Feb. 17, 2006.

Mr. Rentuza said the Guinsaugon experience showed the importance of setting up an early warning system.

"There have to be ways to get people to report signs of a landslide to authorities. For landslide, we don’t have a warning system. We can only warn people by way of monitoring," Mr. Zarco said.

Mr. Rentuza said they will incorporate the scientists’ findings in their disaster management plans.

The workshop discussed studies on landslide and debris avalanches based on experiences in New Zealand, geologic evidences, and eyewitness accounts. - Sarwell Q. Meniano, BusinessWorld