Flood zoning using HEC-RAS and GIS software(Case study of Silakhor plain river, Lorestan province)

Among the natural disasters, floods are recognized as the most common natural disaster worldwide. Every year, floods cause extensive damage to farms, farmland, dams, bridges and roads, and in addition to financial losses, sometimes cause casualties. The most important action in flood control and management is estimating and determining the flood zone. Lorestan province is one of the water-rich provinces of the country, about 59% of which is located in Karkheh catchment and the remaining 41% in Karun catchment. This province suffers a lot of financial and human losses due to the flood. Due to the importance of the issue in this project, the main rivers of Lorestan province, including the main rivers of the Silakhor basin, were flooded. For this purpose, HEC-RAS software was used as a solver for flow equations in the river and GIS software was used as a tool to show the flood zone. The inlet flow rate to the rivers was determined based on the measured values ​​and different return periods, and in order to determine and estimate the roughness coefficient, in addition to local visits along the rivers, reliable sources were used in this field. The results showed that if the HEC-RAS model is properly calibrated, it has a very good ability to model the flow characteristics such as water surface width (flood zone), depth and flow velocity along the studied rivers. In addition, it was found that the GIS model has a very good ability to display the results of the HEC-RAS model to determine flood zones. In general, the use of these two softwares together can determine the depth and area of ​​the flood with appropriate accuracy.