Urban Flood Hazard in the Context of Rapid Urban Growth in the Kathmandu Metropolitan City, Nepal

The increasing complexity of urban expansion and its impact on hydrology is significant, especially in densely populated regions. We conducted this study in the Kathmandu Metropolitan City (KMC), Nepal. It is an essential urban center with several essential amenities and opportunities compared to other cities in Nepal. Due to its abundant facilities, the City pulls thousands of people from different parts of the country, experiencing rapid urban expansion. The rapid urban expansion, which involves the widening of paved and impervious surfaces, has increased the potential impact on urban hydrology. Impervious materials partially seal the surface, significantly reducing water infiltration. Thus, it increases the speed and amount of surface runoff. As a result, the City gets inundated every monsoon, impacting thousands of people. We aimed to conduct flood hazard assessments under continuous urbanization using an Analytical Hierarchy Process integrated (AHP) with a Geographic Information System (GIS). The study revealed that land use/ land cover and distance from the river were significant factors contributing to urban flooding, while the type of soil was the least important contributing factor. The core region of the City is in the "very high" to "high" risk zone, while the fringe areas are in the "medium" to "low" risk zone.