Investigation the relationship between frequency of landslide with active tectonic, based on morphotectonic indices in Fahlian River Watershed

Landslide is one of the natural hazards in watersheds that cause a lot of damage every year. Neotectonic activity plays an important role in increasing the occurrence of landslides. The purpose of this study is to investigate the relationship between active tectonics and landslide inventory using morphotectonic indices in the ​​Fahlian River Basin. For this purpose, landslides distribution in the region were first mapped out and stored with the help of Google Earth images, LANDSAT-8 images, aerial photographs and field visits. Next to the extraction and calculation of four morphotectonic indices; volume to basin surface index (V/A), bifurcation index (BR), surface canal density index (P) and relative relief index (Bh). Morphotectonic indices were measured in each sub-basin. Preparation of these indicators has been done using topographic and geological maps, satellite images, field visits and using geometric and mathematical principles with the help of the features available in ArcGIS10/4. Each index was divided into three categories in terms of tectonic activity, and finally, based on the segmentation of each index, the level of tectonic activity of the region was determined on the basis of the index of relative tectonic activity index (Iat). Finally, by cross ovrlaying of the landslide inventory map to the relatively active tectonic zonation map, the percentage of landslides occurred in each tectonic zone was determined. The results showed that 67.34% (428.34 ha) of landslides occurred in the area with high tectonic activity, which covers only 45.73% of the total area of ​​the study basin. This result indicates the role of active tectonics in increasing landslide occurrence.