Sustained increase in suspended sediments near global river deltas over the past two decades

River sediments sustain deltaic wetlands, yet many rivers have reduced sediment supply due to damming. The dynamics and drivers of coastal suspended sediment concentration (SSC) and its response to river sediment changes have not been comprehensively assessed. Using satellite images (MODIS) from 2000 to 2020 for 349 global deltas, the study quantifies coastal SSC and river sediment plume area (RPA). Globally, SSC and RPA increased on average by +0.46% and +0.48% yr−1, respectively; over 59% of deltas show increases in both. Increases are widespread across all continents except Asia. The relationship between river sediment supply and coastal SSC varies among deltas; up to 45.2% exhibit opposing trends between river sediment supply and coastal SSC, likely due to tides, waves, salinity, and delta morphology. The observed SSC increase near river deltas suggests potential resilience of wetlands to sea-level rise, although the persistence of these trends is uncertain.

Xuejiao Hou, Danghan Xie, Lian Feng, Fang Shen, Jaap H. Nienhuis