Assessing land use planning scenario impacts on flood hazard and risk in Bustan dam basin

One of the most important factors causing flood and related causalities is flood plain encroachment and inappropriate land use type. The flood zonation is one of the management tools for predicting the severity of losses caused by flood in order to control them. The main purpose for this study was impact assessment of land use planning scenario on flood inundation extent and losses caused along a 21 km reach of the Gorganroud river main channel within the Bustan dam basin. To this end, the basic data required by the model such as geometric properties and cross-sections (at 316 locations) of the river channel, roughness coefficients estimated by the Cowan method and peak discharge of hydrographs calculated by the Mod-Clark conceptual distributed method were entered to HEC-RAS hydraulic model. After calculation of the water surface profile by the HEC-RAS model, flood inundation extent for 2, 5, 10, 25, 50, 100 and 200 – year return periods and two conditions of current land use and land use planning scenario was calculated using the HEC-GeoRAS software and flood risk zonation was done for 5 classes of risk. Results of statistical test showed that the flood risk zones decreases significantly in case of scenario planning for all return periods (p