Landslide susceptibility analyses of Gölpazari (Bilecik) and its vicinity

In this study, it is aimed to evaluate Gölpazari District (Bilecik) and its vicinity in terms of landslide susceptibility. For this purpose, based on previously recorded landslide occurred in the study area, landslide susceptibility analyses of approximately 690 km² were carried out with the aim of identifying the areas where landslides are likely to happen. Bilecik city Gölpazarı district landslide susceptibility analyses are performed by utilizing GIS (Geographic Information Systems) based program with Frequency Ratio Method (FR) known as one of the most widely used methods in the literature. A total of 200 landslides were recorded after comprehensive field and office studies and landslide inventory maps were generated. For the first analysis, only the slide zone of landslides known as split area are inventoried, and for the second analysis, all spatial distributions of the landslides are inventoried. Approximately 5% (42) of the landslides included in the inventory were selected as test data, and the remaining 158 landslides were included in the analyses. The parameters to be used in the susceptibility studies were determined as a result of literature surveys and field observations (affecting the land most). The identified parameters are dip of slopes, height, lithology, slope direction, slope curvature and distance to the river. The maps of parameters were produced by using ArcGIS PRO, ESRI2019 program. Parameters' maps and landslide inventories produced by GIS software were overlapped by using Frequency Ratio Method and frequency ratio (FR) value was calculated. After FR values were calculated, all NFR values in the parameter subgroup were calculated by a simple statistical operation, and the significance of the parameters were determined based on its importance in the literature. Landslide susceptibility maps were produced as a result of the two analyzes, and it was tried to determine the accuracy of high and very high sensitive areas and the applicability of these maps for future studies. As a result of these analyses, it was found that the accuracy levels of the first and second analyses were 88% and 78%, respectively. Keywords: Frequency Ratio, Landslide, Landslide Susceptibility, Landslide Susceptibility Map, Landslide Inventory, Slip Zone.