Flood hazard assessment is vital for managing risks from extreme hydrological events. However, Indonesia's national assessments often overlook the direct hazards of floods to people. This study evaluates hydrodynamic characteristics and flood risks in the Pemali River Basin using a 2D HEC-RAS combined with DEFRA's 'Flood Hazard to People' method. Simulations for Q10, Q100, Q1000, and QPMF scenarios revealed an escalating trend in flood depth, velocity, and inundated area as flood intensity increased. Although flood depths were typically below 1 meter and velocities were generally less than 0.5 m/s, localized high velocities up to 1.8 m/s near the upstream riverbanks and depths up to 2 meters were observed in the coastal and densely populated areas during severe events. Spatial analysis identified Brebes and Wanasari as the most affected regions, with cultivated crops being the most frequently inundated. Hazard maps revealed four categories: low, moderate, significant, and extreme hazard zones, with moderate and significant zones dominated the landscape. Moderate hazard zones pose risks to vulnerable people, with significant to extreme zones endangers most individuals, regardless of demographic factors. These insights highlight the need for integrating hydrodynamic modeling into flood risk assessments and implementing adequate mitigation measures.
Ghifari et al. (Thu,) studied this question.