Flood susceptibility analysis of dereli district in giresun province with multi-criteria decision analysis based on geographical information systems

Many cities around the world have to cope with floods due to various reasons such as rapid and unplanned urbanization, opening of stream beds for construction, and construction of bridges and culverts with insufficient cross-sections on streams. Floods usually leave behind great material damage and cause loss of life and property. In order to reduce the damages caused by floods, flood-susceptible areas should be determined and various engineering measures should be taken in these areas. One of the most important data produced for this purpose is flood susceptibility maps. These maps show areas prone to flooding or areas that may be affected by a flood event in the future. In this thesis, a flood susceptibility map of Dereli district of Giresun was produced by using the Analytical Hierarchy Process (AHP) method, which is one of the Multi-Criteria Decision Analysis (MCDA) methods. Ten factors (precipitation, slope, elevation, distance to the river network, land cover, flow accumulation, drainage density, topographic wetness index (TWI), geology/lithology and aspect) widely utilized in the literature were also used in this study to produce the flood susceptibility map with the AHP method. The generated flood susceptibility map includes 5 classes showing "very low, low, moderate, high and very high" flood-susceptible areas. According to this classification, it has been determined that approximately 1% of the study area is susceptible to high or very high flooding. Furthermore, it has been discovered that the district center of Dereli is located in a location with high or very high flood sensitivity, which is one of the major outcomes that should be highlighted here. The produced flood susceptibility map was compared with the flood inventory experienced in the district on August 22, 2020, and it was determined that the susceptibility map was 80% compatible with this inventory. Therefore, it was concluded that the produced flood susceptibility map can guide decision makers to reduce flood damages.