Preparing the Risk Map of Flood Occurrence in the Ghomnab Chai Basin Using ANP model and GIS Technique

The mountainous areas of northwest of the country are susceptible to flood risk due to their topography and relatively good rainfall throughout the year, especially in spring. The aim of this study was to prepare map of the risk of flooding in the Gomanab Chai catchment, which located in the East Azerbaijan province. 10 effective factors in the occurrence of this phenomenon, such as Precipitation, Lithology, Land use, Slope, Vegetation density, Stream Power Index, Topographic wetness index, Drainage density, Sediment Transport Index, Gravelius coefficient were used to prepare the zoning map. Network Analysis Method (ANP) and Super Decisions software were used to weighting the criteria in this study. The final results obtained from the present study showed that the weight of the 10 criteria were 0.271, 0.201, 0.150, 0.118, 0.081, 0.056, 0.043, 0.032, 0.025 and 0.018 respectively. Precipitation, lithology, land use and slope had the highest weights, respectively. Finally, by combining these layers according to their weight in GIS, the zoning map was obtained. The results showed that 210 km2 (50%) of the area is at risk of flooding. Therefore, the necessity of managing surface water in the area seems necessary in order to prevent flooding as well as proper exploitation of the waters of the area.