The Impact of Gravity‐Driven Sedimentation on Reshaping the Huanghe (Yellow River) Delta Front
Shihao Liu, John A. Goff, Shu Gao, Aiping Feng, Ya Ping Wang, Jianjun Jia, Weifen Hu, Wei Feng, Yonggui Yu
Abstract
Abstract Many of the world's mega‐river deltas are currently degrading due to a shortage of sediment supply feeding their construction. Here, using bathymetric and seismic data, the geomorphological/sedimentary evolution on and near a recently abandoned (1976 CE) Huanghe delta lobe is investigated. The delta front (DF) exhibits a lobe switching‐controlled pattern of progradation followed by mass wasting on the upper front, and redeposition at the seaward toe of the front; the latter process appears to be associated with sediment failure and contributes to delta degradation. During degradation, mass wasting‐driven deepening of the upper DF was initially up to ∼0.86 m/yr from 1978 to 1985 CE, slowed to ∼0.12 m/yr from 1985 to 2000 CE, and has been negligible since. In either prograding or degrading, gravity‐driven sedimentation results in a downlapping seismic unit superimposed on the bottomset of an earlier converging clinoform, with numerous buried/exposed submarine channels at its seaward terminus. These units exhibit a shore‐parallel elongated and continuous geometry, suggesting lateral spreading, which we attribute to alongshore hydrodynamic (especially tidal) remolding. Our findings underscore the significance of sediment gravity flows in the evolution of a degrading delta front, particularly as a principal mechanism of downslope mass transport that gentled (halving the gradient) and reshaped the DF over time. Gravity‐driven accumulations sourced from upper DF collapse can account for ∼1/3 of the previous DF and laterally extend over an unexpectedly large area (∼60‐km long) through hydrodynamic redistribution. Both processes should be considered for modeling other subaqueous deltas.