Assessing Flood Susceptibility by Adopting Remote Sensing Techniques and Fuzzy-AHP Method (Case Study: Zoshk Watershed, Shandiz)

This study sets out to assess flood susceptibility in the Zoshk watershed, Razavi Khorasan, using the coupled fuzzy-AHP method, which incorporated different stages including rate assignment to criteria and sub-criteria based on expertise, fuzzification of rates, fuzzified weight assignment, and ultimately superimposing the layers. To this end, fifteen thematic maps of different characteristics were generated and used as inputs to the modeling process, including morphometric (DEM, slope, aspect, planar and profile curvatures, RSP, TRI), topo-hydrologic (flow accumulation, proximity to streams, HAND, TWI, SPI), edaphic (curve number), vegetation (NDVI), and climatic (precipitation) factors. Results revealed that among the adopted flood controlling factors, the factor of proximity to streams as the mainstream and a key driver to flood events plays the most critical role in the study area, followed by flow accumulation, curve number, and normalized difference vegetation index (NDVI) (topo-hydrologic, edaphic, and botanic, accordingly) with the respective fuzzified weights of 0.072, 0.071, 0.07, 0.068, and 0.067. The results of flood susceptibility zonation attest that 27.5% (1873 ha) of the entire study area falls within the very high and high susceptibility classes. The spatial distribution of high flood susceptibility classes in upstream and downstream sectors indicates that soft engineering techniques (biologic and biomechanical measures) in upstream and hard mechanical engineering measures in downstream areas should be concurrently considered. Additionally, educating the local communities about the concepts of flood hazard and risk should be considered across the entire area, from the lowest to the highest susceptible parts of the study area.