Flood hazard assessment using hydro-dynamic model and GIS/RS tools: A case study of Babuzai-Kabal tehsil Swat Basin, Pakistan

Flooding is the most recurrent and devastating phenomenon around the globe. Heavy precipitation in the monsoon season especially in south Asian countries like, Pakistan, Bangladesh and India coupling with snow melting, generates, overflow in the river channels. This overflow in the river channel ravages the downstream areas and cause damages to both life and property. Due to the frequent flooding and its destruction, the demand for flood hazard assessment using GIS and RS, has tremendously increased. In the present study the river channel in the district Swat, northern Pakistan was modeled through the integration of field data, HECRAS, ASTER DEM and GIS. GIS and HEC-GeoRAS were used for the geospatial analysis of the study using ASTER DEM (30 m). The river geometry data was obtained through the field survey using Total Station (Sokkia, Model No= CX105). HEC-RAS has been used for the simulation of the hydrological data. The HECRAS model was calibrated by known water discharge (4971 m3/s) for the peak flood of 2010 with the support of Manning's 'n' values and contraction and expansion of the river channel. The overall model results show an average difference of 0.36 m, which is in the acceptable limits. To validate the results against known water surface (HFL) for the year 2010, a correlation curve was developed. The curve indicated best correlation (R2= 0.99) between known and computed water surfaces. However, due to the relatively coarse resolution of the ASTER DEM, the development of flood hazard map was limited. Further, the study suggested that the integration of GIS, RS and HEC-RAS play a vital role in the prediction of future floods and its spatial inundation in the nearby floodplains.