Zoning the Landslide Hazard in Jahan Watershed in the North Khorasan Province

Landslide zoning is one of the methods which can help to determine the critical areas from slope stability point of view and the obtained zoning maps can be used in planning for sustainable development. In land slide zoning of Jahan watershed, six factors were used as slope, direction, rainfall, geology, distance from fault and distance from streams. In this study, statistical index (SI) method was used for landslide zoning. In this method, according to the extent of the slip zones in each classes of the different under study parameters, weighted value for each cell was considered and finally the sum of weighted values for each cell was studied with several overlaying layers. Then the landslide hazard classes using Histogram analysis and using Jenks optimization method was developed. Analysis indicated that among the factors, geology and rainfall factor have more important role in causing landslides in the study area. From the view point of land sliding hazard, J1 is at the first priority and J13، J'24، J'14، J17، J'22، J20، J21، J19، at the last one. Under the northern watersheds, due to the risk of land sliding, they are placed at high and very high risk area. The best way to reduce landslide risk in Jahan watershed is to increase vegetation cover through revival, modification and managerial operations in pastures.