Determining the potential of flooding using Topsis method, case study mazandaran province, Galandrud catchment

Various factors such as morphometric of the basin, rainfall, soil type and vegetation have an important role in the potential of flooding. Flood hazard mapping is very important for catchment Management. Catchment morphometric parameters control its hydrologic response. Understanding a basin’s response to high rainfall based on geomorphological indices can be valuable when studying flood hazard in ungauged catchments. The study area, Galandrud catchment is located in the northeastern Alborz, Mazandaran province and south of Royan city. In this research, Galandrud catchment divided to 12 sub- catchment. Twelve criteria were chosen; including catchment area, drainage density, compactness coefficient, circularity ratio, confluence ratio, area ratio, length ratio, basin slope, river gradient, concentration time, mean annual precipitation and curve number. To quantify potential of flood these parameters are integrated with a technique for order of preference by similarity to ideal solution (TOPSIS). The TOPSIS technique is one of the multi criteria decision making method, which, it is defined as the alternative that is simultaneously farthest from the negative ideal and closest to the ideal alternative. The weight for each indicator is determined based on Shannon’s entropy. The results of the TOPSIS analyses indicated that sub-catchments 12, 10 and 3 with closeness coefficient 0.548, 0.486 and 0.462 have ranking 1, 2 and 3 respectively.