Exposure of public and private infrastructure to flood hazards in the Mohana-Khutiya River Basin, Nepal

Flooding in Nepal's Terai region poses significant threats to public infrastructure, yet the exposure of facilities to flood hazards remains underexplored. Using a two-dimensional hydrodynamic model, this study simulated flood extents for 20, 50, 100-year return period (YRP) and assessed the exposure of buildings and transportation networks in Mohana-Khutiya River Basin, Nepal. Chure Rural Municipality and Godawari Municipality experienced the highest flood depths of 17.6 and 17.5 m, respectively, for all YRPs. Building exposure increased by 40% in 50 YRP and by 43% in 100 YRP, compared to 20 YRP. Dhangadhi Sub-metropolitan City was identified as the most exposed in terms of building exposure. Health facilities' exposure was limited, with two buildings affected in 20 YRP, and three affected in 50 and 100 YRPs. Dhangadhi's exposure to school increased across all return periods. Godawari Municipality had the highest bridge exposure. 223 km of roads were exposed in 20 YRP, rising to 296 km in 100 YRP. Critical infrastructure in Dhangadhi Sub-metropolitan City, Godawari, and Krishnapur Municipalities was increasingly exposed to higher return periods. The findings underscore the importance of integrating flood hazard assessments into urban planning for effective disaster risk management.