Author : Beatriz Cuevas Jadina

Summary : This study was conducted in the watersheds of St. Bernard, Southern Leyte to determine and identify the major factors influencing landslide occurrences and make recommendations for suitable land use. The major attributes of the watersheds that were mapped using geospatial (Geographic Information System (GIS)), Global Positioning System (GPS) and remote sensing (RS) technologies were; rock formations and fault lines, seismic occurrences, slope, Digital Elevation Model (DEM) and vegetation and land use. Slope Stability Index Mapping (SINMAP) in GIS environment was used to locate ares in the watershed that are prone to landslide. The data inputs to run the model are DEM, location of actual landslide initiation points (7 points; identified using SPOT image-5m resolution taken in 2008, and ASTER image-10 m resolution taken in 2006 which were used as reference in the model) and geotechnical parameters (ex. soil density). Important output from SINMAP is a digital slope stability index (SI) map showing areas that are less prone to landslides (SI values>1) and areas that are susceptible to landslides (SI values <1) or the unstable zones. The unstable zones constitute 33% of the total land area of the watersheds. These are found at the ridges near the fault and at higher elevation with slope angles >50. It is strongly recommended that the unstable zones of the watershed should remain as protected zone and should be planted with tress to enhance slope stability. The research site is mapped as having moderately suitable (38%) to suitable (59%) for abaca and moderately suitable (44%) to suitable (53%) for coconut production. Moderately suitable areas are found at lower elevations and gentle slopes. Human settlement is strongly discourages in the unstable zones and its immediate surrounding vicinity (approximately > the 4 km run-out distance).