Flood hazard and Risk maps using two-dimensional hydraulic model LISFLOOD-FP (Case Study: Araz Kooseh region)

Predicting the hydraulic behavior of the river in the face of possible floods is of particular importance to reduce the risk and damage to urban areas, facilities under construction, farms and other uses around the river. Hydraulic models are the most efficient tool for planning and developing structural and non-structural methods of flood management and reduction. Simulation of river hydraulic behavior is necessary to predict hazardous points and determine flood damage in different conditions as well as flood insurance. The purpose of this study was to use the LISFLOOD-FP two-dimensional hydraulic model and a 5m high digital elevation model to provide a flood zone with a return period of 500 years and then hazard and damage maps for the Araz Kooseh area on the southwest side of Gonbad city.

In this study, the area of Chehel Chay River located at Araz Kooseh was studied. The LISFLOOD-FP two-dimensional hydraulic model outputs were used to calculate the risks associated with flooding, including the risks of water flooding, its severity, and the depth of water flooding that affects people or the environment. After collecting the data and using a series of equations, the risk was calculated and the data were graphically represented as hazard maps. The calculated risk included flood risk to people, buildings, infrastructure, and a building damage map.

In this study, for floods with a return period of 500 years, the highest probability of mortality was 10.08% and the highest probability of bodily injury was 34.81% and the highest amount of damage to buildings was estimated at 8300 million Rials.

Based on theoretical experiences, one of the appropriate methods for flood management is to determine the extent of flood progress and its height relative to the ground and also to determine the characteristics of floods. These characteristics include the speed and direction of flood progress in different return periods, which are called hazard maps. Determining these criteria can lead to a reduction in flood damage in different areas. All four hazard maps including Risk of fatality, Risk of injury to people and Physical Risk Assessment for buildings as well as Economic flood risk to buildings maps showed that the northeast side of the river is the most vulnerable part of the study area. Due to high density construction in those areas, weakness in the strength of buildings and the antiquity of some buildings, awareness of the people and municipalities about the severity of flood risk and understanding the hydraulic behavior of the river is important.