Projecting Socio-Economic Exposure due to Future Hydro-Meteorological Extremes in Large Transboundary River Basin under Global Warming Targets

The present study analyses the projected hydroclimatic extremes, flood risks, and socio-economic exposure in a transboundary, flood-prone river basin using downscaled CMIP6 projections. The study uses a novel multifaceted evaluation of socio-economic vulnerability by assessing variability in precipitation extremes and flood wave characteristics based on global warming levels (GWL) of 1.5, 2, and 3 °C, as well as the EF (2021–2050) and FF (2071–2100) periods. The expected changes in flood wave characteristics under worst scenario were assessed using a multi-model ensemble approach, selecting the best-ranked models through decision-making. By 2100, peak floods were projected to increase by 10–14% in prominent cities during the pre-monsoon and monsoon seasons. Annual precipitation extremes and average annual runoff were projected to increase significantly under various SSP scenarios. However, reducing the GWL to 1.5 °C could result in a 15% reduction in annual precipitation and a 9000 m³/s reduction in peak flood discharge. Increased flood discharges would lead to larger inundations, causing significant disruptions to agricultural areas (+ 1,200 km²) and urban areas (+ 38 km²). This analysis also quantified substantial displacement risks under SSP370 and SSP585, driven by rapid population growth and intensified hydroclimatic extremes. The study reveals that climate change has increased the basin’s overall flood vulnerability, which may have a significant impact on socioeconomic well-being.