Zoning and Management of the hazards of Floodwater in the Siminehrood River Using the HEC–RAS Hydraulic Model

Zoning flood in the rivers and watercourses within different return periods and identifying and introducing areas at risk of flooding are non-structural, important measures in the flood management discussion. The aim of this study was to identify natural areas prone to flooding in the region and to review the hazards and consequences of its occurrence in order to identify floodgate lands at the river bed. In this study, the HEC-RAS model, HEC-GEORAS appendix, and ArcGIS software were used to simulate the river flow, and to calculate and determine water surface profiles and other hydraulic characteristics of flows. According to the results of the floodgate zone, it can be said that the area of land at risk of flooding has increased at the entire study area due to the increase of return period and has also dramatically changed at different study region due to the geomorphological conditions of the area. So that, if we consider the area of the floodgate zone with a 25-year return as our basis, 3607/43 hectares are at risk of flooding in all the regions, of which 2129/69 hectares are in the region 3.The region 3 can be introduced as the most critical region of floodgate, so that the largest area of arable lands, garden areas and residential areas of this region are at the risk of flooding in the river bed. The average maximum power of the river in the returns course 1.5-100 years old has the highest value in the region 2 (573/7 watt per square meter). So this region, the harmful effects and damages are taken into consideration rather than the power of the river, which can be considered as the most critical region of erosion.