Ranking System Determines Landslide Risk

Author:  Emma Wear

Institution:  Indiana Wesleyan University
Date:  July 2007

Landslides in the tropics can kill thousands and cause catastrophic loss of property. Now, engineers at MIT have developed a ranking system that quantifies a slope's susceptibility to landslides caused by tropical storms, a tool they hope will be used to guide future construction and current mitigation measures in at-risk areas.

The ranking system, developed by professor Herbert Einstein and graduate student Artessa Saldivar-Sali, was designed for Baguio City in the Philippines, but could easily be adapted to apply to much of Southeast Asia, according to their paper published in the May issue of Engineering Geology.

"The uncertainty of natural threats and their consequences have to be--and can be--treated in a systematic manner using hazard and risk analysis, assessment and management," said Einstein. "The problem of typhoon-induced landslides is a good example of the sort of natural threat we can address in this way."

Under the system, an area's hazard ranking is determined from its history of landslides, the type of bedrock and vegetation, and the angle of its slope; land use and population data are incorporated to calculate the overall risk ranking. Because all of this information can be obtained in the field or from existing records, the ranking system can easily be used in developing countries.

The model the engineers developed for the ranking system revealed some unexpected factors for landslide risk. For example, the steepness of the slope was not the most crucial component. Rather, the slope interacted with the type of bedrock, so that very steep areas could still be stable if they consisted of very hard rock such as limestone.

The researchers hope that the ranking system will enable flexible building codes, for example, by requiring increased structural support in the most susceptible areas. It could also be used to determine which areas should be targets of current mitigation measures such as reforestation and the installation of piles on the slope.

Written by Emma Wear