Identify areas susceptible to flooding and assess the damage using software HEC-FIA (Case study: Ghamsar watershed)

Importance of predicting flood contingency to reduce damages in urban areas, farms and etc. around the river, studding hydraulic and hydrologic behavior of river such as flood forecasting is critical. The simulation of the hydraulic behavior of the river is important to predict the damage caused by floods in different situations, river engineering projects, economic and social studies, control plans and flood inhibition and other related studies to the river system. Floods threat people's lives and properties all over the world. Development of cities and villages in riversides and floodplains without any considerations about hydrologic and dynamic conditions of rivers and upstream areas increases flood risk and respective infrastructural, financial and life losses. Flood is the second natural disaster that will damage to human societies all over the world. The cities and residential areas have the highest risk and are susceptible to physical damages of flood events. Anticipating and the flood control can be taken a big step in the management of water resources. For planning and decreasing the damages of this natural phenomenon, identification of the regions with flood risk, awareness about flood probability with different return periods and flood damage assessment that includes human and financial damage can help for effective management flooded areas. HEC-FIA model, as one of the most recent models (2012) for flood damages and effects assessment, was used in this study to evaluate the human, structural and agricultural damages of flood in Ghamsar watershed. For achieving this goal and increasing the accuracy in identification of hazardous areas, steady and unsteady flow was simulated in different return periods using HEC-GEO RAS and HEC-RAS software. For preparation of inundation maps, the river channel and its morphology must be simulated to extract 3-dimencial cross-section and flow hydraulic parameters. The purpose of this research is to integrate HEC-RAS hydraulic model with ArcGIS software through HEC-GEO RAS extension in order to simulate the hydraulic parameters of the mainstream of Ghamsar watershed basin and estimate steady and unsteady flows. The data required for HEC-RAS such as cross sections was prepared using DEM, which is provided in HEC-Geo RAS software. These data with the data of discharge in different return periods and also real flood hydrograph were transferred to HEC-RAS software for simulating steady and unsteady flows. The discharge in different return periods was calculated by flood frequency analysis on maximum instantaneous discharges. HEC-DSS file and flooding height are the outputs of HEC-RAS software. Flooding height data was transferred to HEC-GEO RAS for preparing inundation height map. The results of unsteady flow simulation are discharge time series in HEC-DSS format files, with economic, agricultural, structural and population data which was obtained from questionnaire-based methods, were entered to HEC-FIA software for agricultural and structural damage assessment. In this study Ghamsar watershed was selected that is one of sub watershed of Daryache Namak sub-basins and has experienced flood damages during recent years (for example 2007). Due to the fact that hydrometric data is based on flood studies, flood frequency analysis done for moment maximum discharge because that is the most important parameter in preparation of flood map with different return periods. The preliminary results of this research are flood inundation maps around Bonrood River and discharge time series (HEC-DSS format files). Applying these results in HEC-RAS model, the agricultural, structural and human damages of flood were calculated. These maps showed that inundation measures were increased by increasing return periods. Considering the results, these models could be applied to provide logical measures in order to study flow's hydraulic properties. The results showed that the model can be used to study the hydraulic properties of flow provide acceptable value. Based on the results, 3.23 ha of the area is damaged (12.8 billion Rials). In the structural part, 36 structures around Bonrood River were at risk of flooding and also people are damaged. HEC-FIA can be a tool for flood risk management used by managers and relevant stakeholders to plan for dealing with potential floods. HEC-FIA estimates damages caused by dam failure that the relevant organizations can use this function to assess the risk of damaging. The crisis management team can use the warning systems defined in the HEC-FIA model. According to the results of estimating human damages, it is better to use a warning system other than a siren (for example, an automatic telephone call) in areas where buildings are dispersed.