FLASH FLOOD HAZARD ASSESSMENT OF SWAT RIVER CATCHMENT USING REMOTE SENSING AND GIS TECHNIQUES

Abstract

Flash floods are natural disasters and are short time events, which are very often within first few hours after starting of heavy rainfall in an area with steep hill slope, such as the Swat River valley in Khyber Pakhtunkhwa province of Pakistan. This study deals with the use of TRMM 3B42 version 7, daily precipitation estimates, satellite based surface soil moisture, topographic wetness index, slope, Normalized difference wetness index, land use and in situ soil types to estimate the flash flood potential. Based on the contribution, the data layers were given a relative Flash Flood Potential (FFP) index ranging from 1 to 5 respectively, representing lowest to highest potential. The layers were assigned weights using analytic hierarchy process model and then overlaid in GIS environment to get the final output as FFP map. The FFP map showed that runoff generating physiographic factors contributed more in the south of the study area, i.e. the southern part is at highly hazardous. The FFP areas identified were cross validated with the 2010 flood damage reports supporting the results, hence the adopted methodology. It is concluded that the near-real-time satellite remote sensing rain estimates and GIS techniques can help to analyse and assist in flash floods hazard assessment of Swat basin and geomorphologically similar areas.