Sediment Delivery to Sustain the Ganges-Brahmaputra Delta Under Climate Change and Anthropogenic Impacts

The principal nature-based solution for offsetting relative sea-level rise in the Ganges-Brahmaputra delta is the unabated delivery, dispersal, and deposition of the rivers’ ~1 billion-tonne annual sediment load. Recent hydrological transport modeling suggests that strengthening monsoon precipitation in the 21st century could increase this sediment delivery 34-60%; yet other studies demonstrate that sediment could decline 15-80% if planned dams and river diversions are fully implemented. We validate these modeled ranges by developing a comprehensive field-based sediment budget that quantifies the supply of Ganges-Brahmaputra river sediment under varying Holocene climate conditions. Our data reveal natural responses in sediment supply comparable to previously modeled results and suggest that increased sediment delivery may be capable of offsetting accelerated sea-level rise. This prospect for a naturally sustained Ganges-Brahmaputra delta presents possibilities beyond the dystopian future often posed for this system, but the implementation of currently proposed dams and diversions would preclude such opportunities

Etude du champ de gravité et du géoïde dans le Delta du Bengale au Bangladesh

International audienceUne connaissance précise du géoïde dans les zones littorales et au niveau du continuum Terre-Océan est indispensable pour contraindre notamment les aléas de submersion associées à la remontée des eaux ou à des événements extrêmes (tempêtes, cyclones, tsunamis). Des erreurs sur le géoïde peuvent aboutir à des erreurs d'élévation des terres relativement aux océans. Ces erreurs sont de plusieurs mètres comme dans le delta du Bengale où plus de 200 millions de personnes habitent. La campagne FRES au Banglasdesh (mars 2022) a permis l'acquisition de plus de 170 mesures de gravité et a occupé 55 stations de mesure