Delineation of flash flood hazard zones based on morphometric parameters using GIS technique in upper Lematang sub-watershed

Abstract

The hilly and mountainous topography with high annual rainfall triggered a flash flood in the upper Lematang sub-watershed. The impact caused not only damaged infrastructure, agriculture land, and even fatalities. This research aimed to conduct flash flood hazard zoning based on morphometric parameters using the GIS technique. By extracting the DEM data, it is generated to a slope map, flow direction, flow accumulation, stream order, and watershed boundary. The data were then evaluated to obtain the morphometric parameters. Parameters analyzed using the PCA approach to get the correlation between parameters related to flash flood hazards. Of the 12 parameters, the KMO value is 0.66, and a significant level is 0.001 <0.05 with a sufficient level of intercorrelation. The result of PCA analysis, two factors were obtained with an eigenvalue > 1, and the cumulative percentage of the two factors was able to explain data variations of 87.49%. Finally, using 12 parameters, the upper Lematang sub-watershed area had 48.79% very-high hazard zones of a flash flood, 16.48% high zones, 20.28% moderate zones, and 0.97% low zones, and 13.48% very-low zones. The results of this study can be used in mitigation activities as well as for integrated watershed management.