Location of Dez River Flood Risk Maps with Passive Defense Approach (Case Study of Dezful City)

Today, reducing the vulnerability of urban land uses to reduce the amount of damage is one of the most important objectives that city planners and managers are trying to achieve, which is important by using new approaches to crisis management such as passive defense. It is achievable and can be effective in creating a safe environment in cities. Urban flood risk mapping is a new tool that can be used to identify development sites to reduce public risk and damage to land uses. These maps show the condition of residential areas and other uses in relation to floods and state that flood control operations and flood warning systems should be considered in areas that are highly vulnerable. In this research, flood prone areas in the return period of 2, 5, 25, 50, 100, 200 and 500 years in an interval of 5.8 km from the Dez River bed in the central area of ​​Dezful city using HEC-RAS model and ArcGIS software was prepared, for this purpose digital maps with 10 meters accuracy, discharge statistics of Dezful regulatory dam hydrometric station and river morphology features were used in the study area. Since the Dez river basin is a flood zone with a return period of 25 years, the results showed that the maximum depth and speed of water during the flood with a return period of 25 years are 19.47 m and 7.43 m/s, respectively. For the return period of 2, 5, 25, 50, 100, 200 and 500 years, 65.6, 106.3, 1.154, 1.168, 180.6, 192.4 and 208 hectares under flood cover, respectively. It is decided that due to the existence of residential areas and resort uses on the banks of the river, it is necessary to carry out flood control operations and flood warning systems in the parts where more vulnerability is predicted, and in order to Necessary measures should be taken to remove the illegal possessions that have taken place in the bed and privacy of the Dez river.