Future Floods in Bangladesh under 1.5°C, 2°C, and 4°C Global Warming Scenarios

Abstract

This is the first study to assess the possible changes in floods in the Bangladesh part of the densely populated Ganges–Brahmaputra–Meghna (GBM) delta at 1.5°C, 2°C, and 4°C global warming levels. This study was undertaken with the aim of joining the efforts of the global scientific community to assist in the preparation of the upcoming Special Report on 1.5 Degrees by the Intergovernmental Panel on Climate Change. The future changes in the possibilities of peak synchronization of nearby large rivers were assessed for the first time. Peak synchronization is critical for flood assessment in low-lying delta regions like Bangladesh. Results indicate that the flood peaks of the GBM rivers are more likely to synchronize in the future. Results also indicate that the flood magnitudes may become more severe in the future. At global warming levels of 1.5°C, 2°C, and 4°C, flood flows with a 100-year return period are projected to increase by about 27%, 29%, and 54% for the Ganges; 8%, 24%, and 63% for the Brahmaputra; and 15%, 38%, and 81% for the Meghna, respectively, compared with a baseline of 1986–2005.