Floods usually cause many financial and human losses all over the world. National economy of Iran is negatively affected by financial losses of floods. However, human losses due to floods are not considered in economic accounts and also it is impossible to compensate most of such damages. It has been started to study about flood damage reduction for better management of floodplains in Iran during the last decades while the floods have caused many damages to different areas. A 13-Km part of Herochay- Khalkhal River was selected for estimating flood losses. Because of the lack of hydrometric stations in the desired cross-section of the River, the regional flood analysis for southern parts of Ardebil Province was done, thereafter the discharge with different return periods was estimated using the calculated model. . Cross sections of TIN map with the scale of 1:1000 were prepared using HEC-GeoRAS extension and imported to HEC-RAS. Using these data and the real flood hydrograph, steady and unsteady flows were simulated and HEC-DSS file was created and also flood zoning for different discharges with different return periods was performed. Required data about the value of buildings and their contents and also the value of agricultural products were collected using a corresponding questionnaire. All these data were entered the flood impact analysis model (HEC-FIA) and by simulating the flood which happened in 9th July 2012, damages to agriculture and buildings and also human losses were estimated. An area of about 23.71 hectares of farmlands are affected by the simulated flood and economic losses to agriculture and buildings was calculated to be 4,681.54 and 9,480.69 Million Rials, respectively. Results can be adopted for floodplains management and for adjusting the comprehensive plans of cities and villages in order to reduce flood damages and losses. Key Words : Regional analysis , HEC-RAS , Assessment, HEC-GeoRAS , Flood damage, HEC-FIA, Herochay River.