Asymmetric Evolution of the Yellow River Delta Under the Influence of Seasonal Sediment Dynamics: Long‐Term Deposition Versus Transient Transport

Morphological evolution of river deltas exhibits significant spatiotemporal heterogeneity driven by the coupled anthropogenic and hydrodynamic forcing. The present Yellow River Delta (YRD) presents an abnormal behavior of asymmetric evolution against the seasonally varying longshore currents, for which the mechanisms remain elusive. Based on bathymetric data and field observations in combination with numerical modeling, we investigated the role of seasonal sediment dynamics in shaping the morphology of YRD. Results show that during summer, high river‐laden sediment supply and weak estuarine hydrodynamic forcing promote rapid deposition, with ∼50% of sediment retained adjacent to the river mouth, another 10%–25% at the downdrift (right) side of the river mouth and ∼10% at the updrift (left) side. Despite receiving less sediment supply, the updrift side exhibits net accretion, while the downdrift side undergoes erosion on a multi‐year scale. The counterintuitive accretion on the sediment‐starved side arises from winter storm–induced sediment redistribution across the delta. While storms enhance sediment resuspension, the subsequent transport and re‐deposition are modulated by topo‐hydrodynamic feedback. Under strong seasonal forcing, delta progradation alters the regime of local hydrodynamics, generating vortices that trap sediment on the updrift side while enhancing the downdrift erosion. These internally generated feedback ultimately lead to the asymmetric progradation of YRD opposite to the prevailing longshore current. Furthermore, the obtuse‐angle channel configuration relative to the longshore current intensifies this asymmetric evolution. Our findings demonstrate that river‐dominated deltas can exhibit feedback‐driven asymmetric evolution as shaped jointly by seasonal forcing and morphological adjustment, with broad implications for deltaic evolution worldwide.