Assessment of landslide hazard, risk in Chehel - Chay Watershed, Golestan Province, Iran

In this study applicability of three landslide hazard zonation models including weighted density area bivariate statistical model (semi-quantitative model)، multivariate stepwise regression model and logistic multivariate regression model (quantitative models) have been compared for the Chehel_Chai watershed in Golestan province to prepare risk map based on the hazard map of superior model. Landslide distribution map of the study area was prepared using air photos interoperation and field studies. Then nine parameters including elevation، slope، aspect، lithology، distances from fault، stream and road، land use، and annual precipitation were chosen as landslide effective factors. Potential landslide hazard maps were provided using three models. Chi-square test was used to analyze difference between hazard classes of models. Kappa index was used to compare the conformity rate of the hazard maps. Qs index was also used for evaluation of models accuracy. Hazard map، elements at risk map and vulnerability map were used in the preparation of risk map Results show that measured Chi-square statistics is statistically significant at 99% of confidence interval، and there is an appropriate differentiation among landslide hazard classes. Kappa index between hazard maps of models vary between 0 to 0. 2، indicating that there is a slight conformity between them. Weighted bivariate statistical model has been identified as the superior model for Chehel_Chai watershed with Qs equal to 3. 622. According to the risk map 7. 67% of the study area is in high class and 5. 37% of the area placed in very high Class.