The consequences of flooding are complex and far-reaching. These consequences includerndirect damage to property and structures, as well as disruption of economic activity andrndisplacement of affected population, with the attendant costs of evacuation and temporaryrnaccommodation. They include loss of agricultural productivity, including both opportunity asrnwell as direct damage to crops in various stages of cultivation. They include direct damage torninfrastructure, in addition to disruption of transportation and services, potentially affectingrnpopulations not directly touched by flood waters, and for extended periods of time, notrnlimited to the period of inundation.rnFlood is causing economical, social and environmental damage and lives loss in Ethiopia. Inrnrecent year, the August 2006, flooding is one of the worst flooding events. Understanding ofrnflood risk is the first step for Flood risk management. Dembia floodplain is a frequentlyrnflooded catchment with Megech River. Flood risk management strategies have not beenrndeveloped for this region and there is no spatial planning approach for regional development.rnThis study focuses on studying the flooding characteristics in the flood plain of the catchmentrnusing two-dimensional (2D) hydrodynamic modelling.rnFlood risk mapping is an important aid to a community to take action in the present for thernreduction of future damages, to plane for flood preparedness and response, to developrninfrastructure for reducing flood severity and flood damage, and to guiding development tornavoid increased risk where hazard is frequent. An important aspect of this study is therndevelopment of models and procedures that could be used in generation of flood risk map.rnThis research was based on four major steps. The first step was to prepare input data for thernmodelling, such as topographic mesh, upstream boundary and surface roughness.rnTopographic mesh was generated using SMS11.0 based on 53238 x-y-z survey points.rnUpstream boundary condition was generated by flood frequency analysis methods.rnThe second step involves the calibration of the model based on field measured data. Therncalibration is performed by manually changing surface roughness coefficient until the goodrnfit between simulated and measure surface water level is obtained.rnThe third steps concern simulation and mapping of flood hazard parameters based on modelrnresults respectively. The model results consist of flood depth, flow velocity and surface waterrnelevation.rniirnThe final step is flood risk mapping. Flood risk map was generated by weighting flood depth,rnflow velocity and flood duration. Flood hazard and flood risk maps are important tools torncommunicate flood risk to different target groups.