Determination of flood susceptible areas with GIS-based entropy method: Akarçay Basin (Afyonkarahisar)

Floods can cause material damage and loss of life, especially by affecting residential areas and agricultural lands. Flood risk maps enable taking pre-flood precautions and making correct decisions in areas that may be at risk by determining the possible effects of floods in advance. Therefore, the creation of flood risk maps is of critical importance in minimizing the damage caused by floods and taking pre-flood precautions. This study was conducted to determine flood risk areas and create maps for the part of the Akarçay Basin within the borders of Afyonkarahisar province using GIS. In the study, GIS-based Multi-Criteria Decision Analysis was applied and the Entropy method was used in the weighting phase. In order to perform flood analysis, flow, slope, drainage density, sub-basin size and aspect criteria were considered. In the weighting phase, the flood susceptibility map was created by calculating the weight values for each criterion with the Entropy method. The generated flood susceptibility map was compared with the flood boundaries (Q500) determined according to the 500-year flow rate that could occur according to the Rational method. According to the comparisons, within the Q500 flood boundaries, 79% of the sensitivity classes determined according to the Entropy method are Very High risk areas, 16% are High risk areas, 4% are medium risk areas, and low and very low risk areas are 1%.