Integrated GIS‐Hydrologic‐Hydraulic Modeling to Assess Natural Flood Management Strategies on Flood Risk in Alluvial Fans

ABSTRACT

This study investigates the effect of natural measures on flood risk reduction in alluvial fans using hybrid hydraulic‐hydrological models by implementing different natural flood management (NFM) scenarios. NFM methods are considered as sustainable flood management methods that lead to flood risk reduction. Implementing effective NFM methods leads to reducing flood velocity, increasing water storage, and increasing infiltration and soil water storage. The study area is the Abbakhsha river reach located in Bardsir City, Kerman Province, Iran, with a catchment area of 1136 km ² . Numerous floods have occurred in the past in the study river section, which is located on the alluvial fan. The hydrological, topographical, and geological data are used in this analysis. HEC‐HMS hydrological model, HEC‐RAS 2D hydraulic model, and ArcMap software are used to examine the NFM scenarios. In this study, three scenarios consist of changing a straight river reach to a meandering form, creating an offline storage area, and planting on the floodplain of the river. The result showed that the use of NFM methods in this river reach has reduced flood risk with a 100‐year return period; furthermore, the scenarios of meandering, offline storage area, and planting led to expected annual damage (EAD) reduced by 15.5%, 14%, and 13.5%, respectively. The results of this research can assist planners and decision makers in making informed decisions and policies regarding flood management using NFM in the study area.