Inventory Survey of Slope Failures in Sri Lanka

The most common type of landslides in Sri Lanka is shallow, rapid-moving slope failures, particularly in response to an intense, short-duration storm. Different from reactivated landslides, the slope failures frequently occur on steep natural and artificial slopes without indications, thus posing a significant risk to population and property. An inventory survey of slope failures showed that the slope failures were related largely to slope steepness and slope height, and more than 80% of the slope failures occurred on slopes with a slope angle of 25–45° and a slope height of more than 5 m. A simple topographical model was developed based on the inventory survey results. The topographical model can be used to predict slope failure hazard areas and to prepare site-specific slope failure hazard maps for residential developments and land use planning decisions in sloping area.