Flood is the devastating natural events as it causes massive destructive of life, economy and infrastructure. The main objective of this study was Flood Inundation mapping Using HEC-RAS and Geospatial Techniques. Different models, including the hydraulic model (HEC-RAS) and the hydrological model (HEC-HMS) integrating ArcGIS were used for conducting this study. Primary data such as river cross sections, and secondary data such as rainfall, stream flow, digital elevation model (DEM), land use, land cover, and soil type were collected and used for the study. Totally, around 19 years of observed flow data 13 years (1986–1998) for calibration and 6 years (1999–2004) for validation were used. It is observed that HEC-HMS calibration and validation results were good, and the performance of the model was checked with the Nash Sutcliffe Efficiency, root mean square error, and percent of bias. Values of 0.723, 0.57, and 10.83 for calibration and 0.753, 0.485, and 8.253 for validation were obtained for NSE, RMSE, and PBIAS, respectively. The peak flood magnitude obtained for 2, 5, 10, 25, 50, and 100 years return periods were 50.4, 76.1, 107, 151.9, 211, and 301 m 3 /s, respectively. The HEC-RAS model calibration and validation results were compared using satellite images downloaded from Landsat 7 and a relatively good result was obtained. The flood inundation map is prepared using the RAS Mapper tool and different flood inundation maps are obtained for different return periods. The flood inundation map covers 100.8, 151.5, 200, 280, 350.2, and 453 ha for 2, 5, 10, 25, 50, and 100 year return periods, respectively. Therefore, in order to mitigate these damages, both structural and nonstructural measures are recommended, depending on the severity of the damage at each station. Key words: flood inundation mapping, HEC-RAS, Suha River, RAS Mapper, HECHMS