Evaluation of the flood risk of the Bilecik province using Geographic Information Systems

This research geographically covers the territory of Bilecik province, located in the Southern Marmara Section of the Marmara Region. Bilecik province, which covers 0.56% of our country's land with a surface area of 4321 km2, consists of the Central district, Osmaneli, Gölpazarı, Yenipazar, İnhisar, Pazaryeri, Bozüyük and Söğüt districts. The lands of Bilecik province, located between the North Anatolian Fault Zone in the north and the Eskişehir-Thrace Fault Zones in the south, have been deeply split and disintegrated by the Sakarya River and its tributaries. In general, mountainous areas and plateau areas constitute the sloping and high areas in Bilecik province, while valleys and basins with bottoms observed in a limited area (such as the Sakarya River and its tributaries, Gölpazarı plain) constitute the plains and low areas. The main starting point of this study is the recent frequent floods in Bilecik province and the lack of flood risk analysis of the province. Three different analysis applications were used to reveal the flood risk of Bilecik province in order to obtain a more detailed view of the places that may be affected by a natural disaster covering a micro area such as flood. For this purpose, DEM 5m sensitivity base numerical data of the study area was prepared and the factors predisposing to flood risk were analyzed with the help of GIS software. With the help of geomorphological indices, sediment transport index, stream power index, slope analysis, aspect analysis, solar radiation analysis, topography heterogeneity analysis, slope curvature analysis and stream drainage density analysis were performed and areas that could cause floods in the region were determined. In addition to these analyses, two more map analysis methods frequently used in flood risk analyzes were applied. First, the surface analysis was completed using the topographic moisture index method, and the water-saturated topographies in the land were evaluated by taking into account the specific basin area of the basin and the slope slope. Finally, risk analysis was performed using the AHP method and the "Weighted Sum" tool. To be used in the AHP - Analytical hierarchy method, data on the road, slope, hydrology, precipitation, soil, land use and geology of the field were analyzed and potential flood surfaces were mapped. As a result, a map presenting the flood risk analysis of Bilecik province was created by evaluating three different flood risk analyses.