Increasing Flood Frequencies Under Warming in the West‐Central Himalayas
Somil Swarnkar, P. P. Mujumdar
Abstract
Abstract The west‐central Himalayan River basins face significant damage caused by extreme floods annually. We selected the upper Ganga basin (UGB), the west‐central Himalayan basin, to demonstrate how maximum cumulative storm and total rainfall received during monsoon control the extreme flow variability. In addition, the downscaled CMIP6 data sets were used for projections of extremes. The results suggest that historically Alaknanda basin receives a relatively higher magnitude of monsoon and storm rainfall than the other regions in the UGB, which manifested into significant extreme flow variability at the Alaknanda outlet. The extreme flows at the UGB outlet are projected to be more frequent under warming scenarios. The nonstationary flood frequency magnitudes are higher than those obtained from the stationary frequency method, implying a need for a review of return periods used in the designs of flood control structures in the region.