Flood Zoning Using HEC-RAS and GIS (Chardavol River, Ilam)

Flood is one of the phenomena in different regions of the world and our country that cause financial losses each year. In Programs to deal with floods، flood zoning are one of the non-structural prevention solutions that the economic justification is higher. In this study، parts of the flood areas in Chardavol River (Chenare reach) at different return periods are evaluated. First، statistics and information hydrological such as discharge was collected from Regional Water Organization of Ilam. Then after testing a run test and Kendal test، uniformity and randomness of the data was confirmed. Then using the average daily discharges at hydrometric station، by using SMADA software، the different distributions of the observed and been completed data was fitted and 3 Parameter log normal as the best distribution of data was determined. Then after making the field operations، river reach with 1. 5 km length was selected. Then preparation of river TIN From digital mode، by using the extension HEC-GeoRAS، 50 cross section created on the TIN and introduced to the model. Finally، performing a series of procedures and specific operations، maps flood zoning in the 5، 25، 50، 100 and 200 returns period is provided. The results of this study showed that flood risk marginal lands because of the wide channel bed in most areas are relatively low. This event in floods with high return periods is observed