Slope Instability Assessment using a weighted overlay mapping method, A case study of Khorramabad- Doroud railway track, W Iran

Every year, a considerable portion of the national budget specifies to reconstruct the properties which have been destroyed during natural disasters in Iran. Recognition of vulnerable sites to natural disasters can reduce the probable damages. The most important point in designing railway tracks is to join stations in the least possible time. So, the railway track is meant to cross lots of valleys, mountains and hilly areas. In order to insure the safety of lives and properties that are going to use the railway track, a supplementary study of landslide and rock fall susceptible areas is vitally important. Six factors of slope angle, morphology, material's fabric (lithology), vegetation cover, hydrological condition and faults and fractures activities, were recognized as major factors in occurrence of a landslides in the Khorramabad - Doroud railway track. Spatial data of these factors were collected from satellite remote sensing imageries, 1:100,000 geological maps and 1:100,000 topographical map sheets and also field investigations. After production of thematic data layers, they were resampled by the cell size of 250 meters. In this GIS based overlay mapping approach, According to the influence to landslides, the Data layers were arranged in a hierarchy order from 1 to 6, where the bigger number, shows higher susceptibility to mass movements. Based on computed Landslide indexes, the area was classified into five different classes of instability including, critical, highly unstable, moderately unstable, moderately stable and stable zone. To facilitate the validation, statistical analyses and field investigations were performed. Results showed a significant relationship between susceptibility classes and recorded mass movements.