Application of Google earth to investigate the change of flood inundation area due to flood detention dam

This paper is intended to investigate the effect of Narmab storage dam on downstream inundated area for three reservoir operation scenarios. ArcView GIS was coupled with HEC-RAS to produce a flood map for flood discharge of different return periods. Google-Earth software was applied to depict the extent of floodplain in actual landscape. The inflow hydrographs for 4 return periods (50-, 100-, 500- and 1,000-year) were routed through Puls method in order to obtain the outflow hydrographs passing through dam spillway. Results show that, through the operation of reservoir, the downstream inundated area can be reduced up to 75.1 % as a function of reservoir available storage. Furthermore, calculations showed that the reduction rate of inundated area for 50-year floods is largely more than 1,000-year floods, implies the high ability of Narmab dam on flood control especially for floods with shorter return period.