Cascading Erosion in the Tide‐Dominated Changjiang Delta: A Novel Radionuclide Approach

Abstract Nearshore erosion is well‐documented in sediment‐deficit river deltas but remains less understood beyond their delta front (DF), particularly its extension to the deeper prodelta (PD) and distal mud (DM). This study investigates the response of Changjiang subaqueous delta and its DM to sediment decline following the 2003 closure of the Three Gorges Dam. By analyzing temporal and spatial variations in 210 Pb ex profile styles, discrepancies between 210 Pb and 137 Cs sediment accumulation rates, and surface sediment grain sizes, we identified the onset of erosion at the DF shortly after 2003, which spread to the PD by 2009 and reached the northern DM by 2015. By tracking the burial depths of the 1963 137 Cs peak, we found progressively lower erosion rates in newly eroded subzones primarily due to sediment redistribution. This study, leveraging historical radionuclides data, offers a valuable approach for monitoring erosion in areas lacking remote sensing detection and historical bathymetric data.