Hydrodynamic Modelling and Multi-Criteria Analysis for Flood Susceptibility Mapping in the Downstream Area of Aceh Tamiang

Abstract

Aceh Tamiang Regency is located downstream and has a low-gradient, flat topography, placing it at higher risk of fluvial flooding. Exacerbated by extreme weather events and tropical cyclones, physiographic factors commonly used for mapping often fail to capture and estimate flood magnitude, including floodwater velocity. Therefore, this study proposes a combination of MCA and one-dimensional (1D) unsteady flow hydrodynamic modeling using HEC-RAS. ArcGIS Pro was applied to perform a weighted overlay integrating rainfall, land cover, soil type, slope, and dynamic hydrodynamic outputs, including flow velocity and flood depth. These parameters were assigned weights of 30% and 20%, respectively. The results showed that the majority of the area (76%) is moderately susceptible to flooding, while the remaining 24% is highly to very highly susceptible. Comparison with published inventory data on previous floods and information from the literature showed good agreement between the modeled flood susceptibility zones and documented flood-affected areas, validating the approach. The results provide initial estimates of flood susceptibility using a novel approach and have the potential to support policy development in comparable regions, subject to future field validation.