GIS based susceptibility mapping of karst depression in gypsum: A case study from Sivas basin (Turkey)

A method is presented for mapping of collapse susceptibility using Geographical Information System (GIS). Collapses in karst terrains are very serious geological hazards and can damage engineering structures and cause groundwater contamination. Preparation of collapse susceptibility maps will serve to successful urban planning in karst terrains. Susceptibility of collapses and the effects of collapse-related factors, such as geological and hydrological (lithology, tectonic activity, drainage systems, springs), topographical (slope angle, slope aspect, elevation), land-use (distance from roads and settlement areas) and vegetation cover were evaluated using GIS, field observations and remote sensing data of Landsat Thematic Mapper (TM) satellite images. A susceptibility map was constructed using the frequency ratio techniques. As a result, all factors had a relatively positive effect on the susceptibility map in the study area. The validation of the susceptibility map was checked by considering actual collapses. For this purpose, degree of fit (DF) was calculated, and the values obtained indicated the high quality of map.