An investigation on Ardesen (Rize) region on the basis of landslide susceptibility

SUMMARY An Investigation on Ardeşen (Rize) Region on the Basis of Landslide Susceptibility In this study, the Ardeşen (Rize) area located in the north-eastern part of the Black Sea region, where frequently-occurring landslides loss of human lives and goods, are investigated with respect to landslide susceptibility. 1/10.000 scaled geological map of the Ardeşen area has been prepared, and, from bottom to the top of the sequence, the Hemşindere Formation (Upper Cretaceous), Granitic rocks (Upper Maastrichtien), the Hamidiye Formation (Plio-Quateraary) and alluvium (Quaternary) have been defined in the area. As a result of literature and field studies, lithology- weathering-, slope-, aspect-, land cover-, shear strength-, proximity to stream-, drainage density- and proximity to road parameters were found to be effective during the production of the landslide susceptibility map. The layer maps have been produced based on field, laboratory and office studies, geographical information system and digital photogrammetry techniques. In addition, the landslide inventory map needed to define the relations between these layer maps and the previous landslides, has been produced by digital photogrammetry techniques. Analytical Hierarchy Process has been used to determine the effect (weight) of each data layers and subgroups of the layers on the occurrence of landslides the obtained layers were evaluated according to their weights and analyzed, and then the landslide susceptibility map was produced. This map was divided into five zones based on the degree of susceptibility to landslides, identified as very low-, low-, medium-, high- and very high- risk zones. The field and percentage distributions have been calculated, and about 28% of the study area was found to be under the landslide risk. Furthermore, a comparison of the landslide susceptibility map and landslide inventory map carried out in order to check the validity of the finalized model, showed on overlap of about 84%. In addition, residences in the study area were determined by air photos and about 30% of them were found to be in the areas highly and very highly susceptible to landslide indicating that about 2300 persons living in these residences are under the landslide risk. Key Words: Landslide susceptibility map, Landslide inventory map, Geographical information system, Digital photogrammetry, Analytical hierarchy process VI