Landslide hazard mapping and its evaluation using GIS: An investigation ofsampling schemes for a grid-cell based quantitative method

An application of Gls for landslide hazard assessment using multivariate st atistical analysis, mapping, and the evaluation of the hazard maps is prese nted. The study area is the Kulekhani watershed (124 km(2)) located in the central region of Nepal. A distribution map of landslides was produced from aerial photo interpretation and field checking. To determine the factors a nd classes influencing landsliding, layers of topographic factors derived f rom a digital elevation model, geology, and land use/land cover were analyz ed by quantification scaling type ii (discriminant) analysis, and the resul ts were used for hazard mapping. The effects of different samples of landsl ide and non-landslide groups on the critical factors and classes and subseq uently on hazard maps were evaluated. Simple random sampling was used to ob tain samples of the landslide group, and either an unaligned stratified ran dom sampling or an aligned systematic sampling method generated the non-lan dslide group. For the analysis, one set of the landslide group was combined with each of five different sets of the non-landslide groups. Combinations of different samples yielded some minor differences in the critical factor s and classes. The geology was found to be the most important factor for la ndslide hazard. The scores of the classes of the factors quantified by the five analyses were used for the hazard mapping in the Gls, with four levels of relative hazard classes: high, moderate, less, and least. The evaluatio n of five hazard maps indicated higher accuracy for the combinations in whi ch the non-landslide group was generated by the unaligned stratified random sampling method. The agreements in the hazard maps, produced from differen t sample combinations using unaligned stratified random sampling for select ing non landslide group, were within the acceptable range for the practical use of a hazard map.