Watershed prioritization for the identification of spatial hotspots of flood risk using the combined TOPSIS-GIS based approach: a case study of the Jarahi-Zohre catchment in Southwest Iran

Flash flooding caused by excessive rainfall in a short period of time is one of the worst environmental hazards, especially in arid and semi-arid regions. Watershed prioritisation identifies and ranks the different watersheds in a catchment based on multiple parameters, which play a role in the land and water degradation. This article deals with the prioritization of 24 sub-catchments in the Jarahi-Zohre catchment in southwest Iran by applying the mixed multivariate linear model of TOPSIS. Morphometric parameters, such as the constant of channel maintenance, drainage density, ruggedness number, infiltration index, stream power index, stream frequency, slope, drainage texture rate, relief rate, form factor, bifurcation ratio, as well as the topographic wetness index, were used as TOPSIS input data, along with precipitation information. The results obtained from the weighting analysis show that ruggedness number, slope and rainfall information have the largest impact on flood events. The sub-catchments Seidyon, Emamzadeh Jafar, and Takht Deraza have a high flood risk and should be given the highest priority for soil and water conservation measures. To validate the results, the prioritization scheme was compared to the flood events in recent years.