Landslide hazard zonation using Fuzzy logic (A case study: ChamSangar watershed)

Landslides are one of the most destructive phenomena of nature that cause damage to both property and life every year، therefore، landslide susceptibility zonation (LSZ) is necessary for planning future developmental activities. In this study، the operator of fuzzy logic in landslide hazard zonation has been used in the Chamsangar watershed. For study the stability of slopes in the Chamsang field، in first step the sliding point and subsequent distribution maps of landslide were prepared using satellite images and field excursions (recording the sliding points by GPS). The correlation level between sliding points and each effective factor in landslide occurrence including slope، aspect، landuse، elevation، lithology، rainfall، drainage and distance to road determined using frequency ratio model. The fuzzy values prepared by expert view and the membership functions appointed for all effective factors in ArcGIS®10. 1environment. The Sum of Quality (QS) index used for evaluation and deviation of operators outputs which applied in estimation of sliding risk. Results show that Gama operator 0. 9 with QS=0. 554 is the more suitable than Fuzzy Algebraic Sum with QS=0. 042 and Fuzzy Algebraic Product with QS=0. 008 for prepare the landslide risk maps in Chamsangr field. According the zoning based on the gamma operator 0. 9، the 13. 39، 47. 58، 32. 7، 5. 44، and 0. 884 percent of the area is located in very low، low، medium، high and very high risk classes، respectively.