Floods are common to many parts of Ethiopia causing a lot of losses to human lives as well as damage to property. This thesis was conducted to know the extent of flood inundation area for Azuari River. Different models used for this study such as, hydraulic model HEC-RAS, hydrological model HEC-HMS with integration of ArcGIS, HECGeoHMS and Ras Mapper tools. Primary data, surveyed river cross section and secondary data‟s such as rainfall, stream flow, DEM, Land use / land cover and Soil type data‟s collected and used for the study. Totally around 30 years of observed flow data 20 years (1985-2004) for calibration and 10 years (2005-2014) for validation used. After the analysis of the data it was find that HEC-HMS calibration and validation result was good and the performance of the model. This performance is checked with coefficient of determination, Nash-Sutcliffe Efficiency, Root mean square error(RSR) and present of bias (PBIAS) with good result of 0.73,0.73,0.49 and -1.5% for calibration, 0.81, 0.8, 0.45 and-1.3% for validation respectively. The result of hydrologic model by HEC-HMS shows a flow value of 52.80m 3 /s, 121.00 m 3 /s,181.00m 3 /s and 223.00m 3 /s for return periods of 2, 10, 50 and 100 year respectively. Due to the unavailability of observed water level and rating curves in the study area the HEC-RAS model calibration and validation result compared information gathered from elderly person. These flooded areas along the side of the Azuari River are 0. 92 km 2 , 0.72km 2 , 0.59km 2 and 0.42km 2 for 100, 50, 10 and 2years return periods, respectively. Therefore in order to mitigate this damage structural and nonstructural measures recommended depending upon the severe of damage at each station. Key words: ArcGIS, HEC-HMS, HEC-RAS, TIN, DEM, Flood map