Catchment-scale flood hazard mapping and flood vulnerability analysis of residential buildings: The case of Khando River in eastern Nepal

This study considers the Khando River (a tributary of Koshi River) in eastern Nepal. It is focused on quantify the hazard and vulnerabilities across one of the frequently flooding catchments, i.e. Khando River, we conducted flood hazard assessment for 20, 50, 100, and 200 years return periods. We coupled flood hazard analysis with vulnerability analysis of the most dominant construction system along the river channel, i.e. wattle and daub houses. Based on the measured inundation depths, we created vulnerability and fragility functions. The flood hazard maps, damage mechanisms due to the 2017 flood, and vulnerability, as well as fragility, curves are reported in this paper. The flood hazard analysis highlighted that the 2017 flood was equivalent to 20 years return period flood. Flood hazard analysis shows that the variation in the maximum inundation depth is not so wide between 20 and 200 years return periods for the Khando River catchment. Flood vulnerability analysis of residential houses along the riverbank highlighted that the wattle and daub construction system is highly vulnerable even for 20 years return period flood. Thus, the floods equivalent to 50, 100, and 200 years may have detrimental consequences in the future.