PENENTUAN ZONA KERAWANAN GERAKAN TANAH DENGAN METODE HEURISTIK DAS SERANG KABUPATEN KULON PROGO (Determination of mass movement vulnerability zone using heuristic methods in Serang watershed Kulon Progo District)

Landslide, one of the physical environmental disasters, can be defined as the movement of rock mass, soil, or shredded material that forms a slope down the slope Kulon Progo Regency has always been a landslide-prone area that most often occurs in the Special Region of Yogyakarta in the last three years. One way to reduce the risk of hazards is by mapping the hazard assessment of mass movement disasters. The purpose of this study is to determine the zone of vulnerability to landslides in the Serang watershed, Kulon Progo. The method used is heuristic, where the assessment of the potential for ground motion is based on a geomorphological approach with a weighting analysis of each parameter. The parameters used are slope, rock type, geological structure (distance to fault), land use, and landslide event distribution. Each parameter is assigned a value and a weight variable based on the factors that most influence slope safety. They are then calculated in a linear variable manner, resulting in an index value for soil movement vulnerability. The index value is grouped spatially into four (4) hazards with equal interval class division, very low hazard with an area of 95.93 km2 (46%); low hazard with an area of 72.02 km2 (34%); moderate hazard with an area of 38.56 km2 (18%); and very high hazard with an area of 1.96 km2 (0.01%). Based on the spatial analysis, the distribution of the existing landslide events are increasing correlatively with the higher the hazard zone.