Wave modulation of flood‐driven jet dynamics, suspended‐sediment dispersion and event‐scale morphodynamics in the Modaomen Estuary

Abstract As a river–wave‐dominated estuary, the morphological evolution of the Modaomen Estuary is jointly controlled by river discharge and wave forcing. Using measured bathymetry, we developed a two‐dimensional coupled wave–current–sediment model within the TELEMAC‐MASCARET system to quantify how waves, under floods of different magnitudes, modulate the flood‐driven jet, suspended‐sediment dispersion and event‐scale morphodynamics. The results show that (1) waves do not change the fundamental jet structure, but constrain its seaward spreading and systematically reduce its spatial extent and intensity; the modulation depends on tidal phase (flood/ebb) and flood magnitude, and waves also induce a northeastward deflection of the jet. (2) Waves limit offshore sediment export, producing a more concentrated and spatially uniform sediment distribution within the jet zone, with suppressed southwestward diffusion and enhanced northeastward (landward) transport; this directional redistribution strengthens with increasing flood magnitude. (3) Although the wave‐driven redistribution does not fundamentally alter the overall erosion–deposition pattern among flood scenarios, it causes two persistent modifications: greater mean siltation thickness within the zone of established flow, with enhanced accumulation near the termini of the eastern and western channels, and a stronger erosional tendency on the southwestern flank, accompanied by increased deposition on the northeastern flank.