Flash flood risk modeling of swat river sub-watershed: a comparative analysis of morphometric ranking approach and El-Shamy approach

Abstract

Globally, flash floods are the most damaging natural hazards, because of its sudden nature and difficulty in forecasting that restrains emergency responses. Flash floods triggered by thunderstorms are frequent in the high mountainous area of Hindukush Himalaya in the north of Pakistan. The current study employed two widely used approaches for flash flood risk modeling, i.e., morphometric ranking approaches (MRAs) and El-Shamy’s approach to analyzing their effectiveness for flash flood susceptibility modeling in Swat river watershed, district Swat, Pakistan. The digital elevation model was utilized to delineate the watershed and drainage network using the ArcHydro tool of ArcGIS. A total of 15 morphometric parameters have been used for flash flood modeling. The analysis suggests that the Swat river watershed consists of 17 sub-basins. The MRA-based flash flood risk assessment suggests that sub-basins B1 and B2 (12% of total sub-basins) are highly susceptible to flash flooding. While sub-basins B4, B6, B11, B13, and B17 (59% of the total sub-basin) are moderately susceptible to flash flood risk. El-Shamy-based modeling suggests that sub-basins B12, B14, and B16 (18% of total sub-basins) have high flood susceptibility while sub-basin B5 has the lowest. The field observation and 2010 flood reports by WHO and NDMA suggest that the flash flood susceptibility modeling results by the MRA are more accurate as compared with El-Shamy’s approach. The results of the study perceived to help execute appropriate remedial measures to extenuate the potential flash floods in the study area.