The Zoning of Arasbaran Forests Flood Hazard Based on Analytic Hierarchy Process and GIS (Study Area: Sotanchai-Asheghloo Watershed)

To prevent the occurrence of floods, it is necessary to identify areas having high potential for this phenomenon. The aim of this research was to estimate runoff coefficient, understanding the effective factors in flooding, and the flood hazard of Arasbaran forests (Sotanchai basin). For this purpose, first, the required data, including the maximum daily precipitation, soil, slope, land use, vegetation density and drainage density layers, were prepared in geographic information system (GIS) environment. In the following using the analytic hierarchy process (AHP) method, an effective weight was assigned to each of the six factors influencing the flood hazard of the basin. Through applying the weight of each layer and combining it, the flood hazard zonation map of the basin was prepared with different return periods (10, 25, 50, and 100 years). The results showed that 15 - 19% of the basin area had a medium flood potential during the period of 10 to 100 years and 1-13% had a high flood hazard. During the 10- and 25-year return periods, no area of the basin was in the flood hazard category, but in the 50- and 100-year return periods, 0.32 and 0.96% of the basin area were in the very high flood hazard category, respectively. Generally, it can be concluded that due to good forest density and vegetation, flood hazard was low in the region, instead areas with high flood hazard were located in areas, where forests have been destroyed.