ST. BERNARD, Southern Leyte--Irenea Velasco could still vividly recall her ordeal when a massive landslide hit her village of Guinsaugon in St. Bernard in the morning of Feb. 17, 2006.

The then 58-year-old widow was at her billiard hall when she heard people shouting in Cebuano, "Landslide! landslide!" as mud and boulders came crushing into their village. A few seconds later, a second wave of landslide swallowed at great speed almost the entire village.

Velasco clung tightly to the leg of a billiard table. Minutes later she found herself covered with mud, with only her chin resting on the billiard table preventing her from falling deep into the mud--and death.

She saw a glimmer of light and started shouting for help. But it was not until five hours later that she was pulled out to safety by rescuers who heard her repeated hitting a long stick under a pile of G.I. roofing.

Only Velasco and a few other villagers survived the landslide. More than 1,100 perished that day.

Velasco was asked to give her testimony during the five-day international conference on the Guinsaugon landslide, held April 28 to May 2 in Tacloban City, in Palo, Leyte and in St. Bernard.

About 60 Filipino and foreign geoscientists from Japan, Canada, United Kingdom, New Zealand, Sri Lanka, and Nepal, engineers, urban planners and disaster management workers attended the conference aimed to be a sharing venue on landslide mitigation measures in their countries and to have a better understanding of the Guinsaugon landslide and help integrate their findings into the rehabilitation efforts of St. Bernard.

She told the experts that life was going on smoothly in their village until some people started cutting the trees on Mt. Can-abag in the early 1980s. Since then their water became murky whenever there was heavy rain, she added.

To scientists taking part in the conference, however, there could be reasons more than just the cutting of trees that caused the Guinsaugon tragedy.

Studies
For many years the people of Guinsaugon--one of the big and progressive villages in St. Bernard that lies at the foot of Mt. Can-abag--have been living normally, albeit dangerously.

When the landslide struck the village in 2006, it covered a 3.2-square kilometer area with rock and debris. It had a run out of 4.1 km and a volume of 14 to 17 million cubic meters.

Another piece of research disclosed that the topography along the Can-abag ridgeline showed signs of frequent landslides in the past due to adverse geologic conditions, high rainfall and earthquakes along the Philippine Fault Zone.

The 1,200-km Philippine Fault Zone transects the country from north to south including St. Bernard town in Southern Leyte.

On that morning of Feb. 17, 2006, just prior to the landslide in Guinsaugon, two mild earthquakes were felt in the area.

According to the Philippine Institute of Volcanology and Seismology (Phivolcs), the first was a magnitude 3.3 quake located 6 kilometers west of Guinsaugon. The second had a magnitude of 4.3 located 5 km west of the village. The second tremor happened at 10:36 a.m., about the same time when the earth started to slide down to Guinsaugon.

Southern Leyte also experienced heavy rains days prior to the landslide.

Rainfall data of the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa) taken from its Otikon station in Libagon town showed that the accumulated rainfall from Feb. 8 to 17, 2006 was 674 mm, while the average rainfall on Feb. 17 was 2.6 mm.

A different study presented during the conference noted that the saturation brought by the heavy rains might have raised the ground-water level on the slope and caused the clay on the soil spaces to expand. "Its presence as a fill material ... can act as wedge (and later lubricant) that may result to a loss of strength (and decreased viscosity)."

Other studies cited other factors that contributed to the landslide like the steep slopes and the presence of weak and strong rock layers.

Then there were the natural processes like erosion, previous landslides and past earthquakes which experts said significantly contributed to the weakening of the slope mass before its failure.

Famous question
Many of the experts, however, believed the Guinsaugon landslide was rainfall and earthquake induced.

But what really triggered the landslide?

Dr. Richard H. Guthrie, a geoscientist from the Landslide Research Program of the Department of Earth Sciences in the University of Waterloo in Ontario, Canada, said this is a "famous question" that they were still "struggling with a little bit."

"You have a landscape, which is massive ... which is moving a lot every year. And within that, the rocks have been stressed and strained and you let time and gravity move on. The rock fabric begins to age and die," he said in an interview at the Cristo Rey College in St. Bernard during the last of their 5-day conference.

Guthrie said the trigger could be the rain but he admitted they "haven't completely sorted out the earthquake portion of it."

He said what really happened could be a confluence of events "that come together to create, unfortunately, that big disaster."

Dr. Mark Albert H. Zarco of the Department of Engineering Sciences of the University of the Philippines-Diliman, a co-chairman of the conference, said many experts agreed that the trigger could be the rainfall, but he quickly added that there were many predisposing factors such as the steep slopes and the structures.

"I think the more important thing is that we all agree that this valley is highly vulnerable (to disaster)," Zarco said.

Disaster risk management
He said what is needed now is to set up early warning systems, public awareness on landslide and to teach the locals the signs of an impending disaster so they could immediately report these to the authorities and give the people time to evacuate--all of which were discussed in the conference.

St. Bernard Mayor Rico C. Rentuza said he was gratified that experts answered questions about the Guinsaugon landslide, "like why and how it happened."

Most importantly, the conference taught them about mitigation measures, including early warning systems.

"This is very helpful especially to me as chief executive who makes decisions in terms of disaster preparedness and rehabilitation," he said.

The experts also developed during the conference a research plan for identifying hazard-prone areas and mitigating the impact of catastrophic landslides in the country.

Dr. Sandra G. Catane of the UP-based National Institute of Geological Sciences (NIGS), who chaired the organizing committee, said Filipino scientists could learn much from their foreign counterparts. "Other countries are more advanced; they already now have a warning system ... for landslides."

Catane also stressed the need to accelerate the development of the country's landslide risk reduction effort.

"Our situation would worsen because of global warming. So, there would be rains ... and many landslides," the country's leading landslide expert warned.