A Simplistic Approach for Evaluating Urban Flood Risk through the Integration of HEC-RAS 2D and GIS

Recent research in flood risk management has predominantly focused on employing hydrodynamic models to assess unpredictable flow changes resulting from uncontrolled urban development. Hydrodynamic models are part of the nascent drivers enhancing flood risk identification zones. In this research, flood risk in the region of a varying terrain of Sheffield City, located in South Yorkshire, England, was assessed through the integration of HEC-RAS 2D and GIS. For this study, terrain data (LiDAR data) and hydrological data (river flow) for the River Don in the case study area were acquired from the Department for Environment Food and Rural Affairs (DEFRA). These data were utilized to develop 2D hydrodynamic models using HEC-RAS-v6.2. The daily mean flow time series (flow hydrograph) from River Don during the flood event scenarios considered was used as the upstream boundary condition (input point), while the normal depth was considered the downstream boundary condition to simulate the unsteady flow condition. The simulated flood demonstrated satisfactory performance when compared to historical records of extreme flood events reported by the Sheffield City Council and the Environment Agency. Data produced from the simulation includes flow (floodwater) depth, flow velocity, and water surface elevation (WSE). The analyzed results indicated that more than 35% of the case study area will be underwater in the event of flooding of great magnitude. Also, it was observed that the northeastern portion of the study area displays a wide range of topographical features, including varying elevations, and is more susceptible to severe inundation. It was evident from the simulation that a 100% increase in river flow (discharge) would result in approximately 45% of the city becoming flooded. The results of this study offer decision-makers productive input to make informed choices promptly, minimizing casualties and property damage. This study aids in mitigating flood risk within vulnerable areas through the hydrodynamic models and execution of appropriate flood control measures. River flooding (fluvial flooding) is denoted as urban flood risk in the context of this study.