417 / 2024-03-15 09:23:29

Impact of land use and land cover changes on flood - A Case study of Bagmati River Basin, Nepal

land use land cover, flood, HEC-RAS, inundation, Nepal

Subtheme 1: Water-related Hazard and Risk Reduction > Topic 1: Water Hazard Under Climate Change

Flood disasters result in significant losses worldwide, impacting both tangible and intangible aspects. Floods triggered by monsoonal rainfall in Nepal, particularly along the Bagmati River and its tributaries, lead to erosion, sediment deposition, and channel migration. One critical factor influencing hydrological processes is land use and land cover (LULC). Therefore, it is essential to assess the impact of LULC on the floods. These changes significantly influence flooding dynamics in Nepal, affecting the nation prone to seasonal inundations and flash floods. The purpose of this study is to analyze the impact of changes in land use and land cover on flooding in the Bagmati River Basin, Nepal. The study, covering the period from 2000 to 2019, reveals significant changes in LULC in the Bagmati watershed. During this period, there was a decrease of 196.144 km² in agricultural land, while built-up areas increased by 86.2 km². The forest area, however, increased at an average rate of 4 %. The HEC-RAS is applied to the study by modeling to assess the extent of inundation caused by flooding. The study's findings reveal that the area affected by inundation in 2000 and 2019 was 495.8 km² and 543.4 km² respectively Notably, the built-up areas that underwent inundation witnessed an increase of 15.4% during this period. This outcome demonstrates that the expansion of inundated built-up areas poses higher risks to people living in flood-prone regions. Furthermore, it highlights the significant influence of LULC changes on flood events. The findings indicate that human activities that replace natural environments with altered areas disrupt the water cycle, increase impervious surfaces, reduce natural drainage, and decrease water retention capacities, which ultimately lead to flooding.