Sedimentary response of the modern Huanghe (Yellow River) delta front to water-sediment regulation schemes: Insights into hyperpycnal flow dynamics and delta stability

The modern Huanghe (Yellow River) delta front, China This study employs the forward stratigraphic model Sedflux-2D to investigate morphodynamic responses at the modern Huanghe delta front under two operating modes of the Water-Sediment Regulation Scheme (WSRS): (i) synchronous regulation (coupled peak water and sediment discharge) and (ii) asynchronous regulation (staggered flow and sediment release). Although previous studies have recognized event-scale variations in sediment transport, morphodynamic responses to different WSRS modes remain underexplored. To address this gap, water discharge and sediment supply are prescribed as independent boundary conditions to isolate the effects of regulation strategy and sediment availability. The model explicitly incorporates event-scale suspended-sediment concentration pulses capable of generating hyperpycnal flows and WSRS-induced sediment coarsening to reproduce realistic sediment-transport dynamics across event to interannual timescales. Sedflux-2D simulations show that WSRS-induced sediment coarsening enhances delta-front stability on interannual timescales. At event scales, both regulation mode and sediment supply control depositional patterns and stratigraphic partitioning. Elevated sediment concentrations trigger hyperpycnal flows that increase trapping efficiency, contributing ∼27 % of total event-scale accumulation. Synchronous regulation promotes distal transport and bottomset accretion, whereas asynchronous operation concentrates proximal deposition and steepens foreset slopes. These results highlight the coupled influence of regulation timing and sediment availability on delta stability and offer guidance for optimizing WSRS to sustain sediment-starved deltas worldwide. • Compared delta morphodynamics under synchronous vs. asynchronous regulation modes. • Delta morphodynamics versus syn- and asynchronous regulations revealed. • Hyperpycnal flow and deposition patterns were quantified under both regulations. • Asynchronous regulation aids progradation yet increases slope instability risks.