A researcher studies geohazard maps in the Philippines

Imelda V. Abaño

Engineers from the Philippines and the United States have come up with a new system to determine an area's landslide risk, which they hope will improve building codes and mitigate against landslides in mountainous tropical regions hit by monsoons.

The research — undertaken by Artessa Saldivar-Sali at the US-based Massachusetts Institute of Technology (MIT) — was published in the May issue of Engineering Geology.

The new tool, originally developed for the mountainous Baguio City in the Philippines, classifies an area's susceptibility to landslides on a scale from very low to very high.

The system is based on factors that are easily available even in countries with poor facilities, such as bedrock geology, slope gradient and vegetation type. An overall risk rating is then obtained from adding risk-contributing factors such as population and land use.

As the researchers point out, the system will be applicable in other developing countries with landslide-prone regions.

"The system could be applied directly to any country with similar topography, geology and climate, which would be much of South-East Asia," said Herbert Einstein, from MIT and Saldivar-Sali's supervisor, in a press release.

The Philippines sits on the Pacific 'ring of fire', a geologically unstable area of South-East Asia that experiences frequent geohazards such as earthquakes — often triggering other hazardous events such as tsunamis and landslides.

Although landslides can occur anywhere in the world, they pose a particular threat in mountainous tropical regions such as the Philippines, where tropical cyclones and monsoons are common — with an average of 20 cyclones striking the Philippines every year.

According to Leoncio Amadore, a meteorologist from the Philippine Atmospheric, Geophysical and Astronomical Services Administration, climate change is one of the factors contributing to the severity of the typhoons.

Deforestation and blasting activity associated with mining and road construction are also undermining the stability of slopes in heavy rain.

"We have long been conducting geohazard mapping, but we welcome this new landslide risk assessment system. It will help hasten the updating of the country's geohazard maps to identify other landslide-prone areas and prevent more tragedies from happening," said Neoman De la Cruz, regional director of the Philippine Mines and Geosciences Bureau.

"Once geological hazards are properly identified and characterised, their effects can be mitigated, if not eliminated, by preventive engineering measures," De la Cruz told SciDev.Net.

Reference: Engineering Geology 91, 85 (2007)