High-frequency observations reveal cross-shore variability in storm-driven sediment dynamics and tidal flat recovery

Intertidal flats are vital coastal ecosystems that provide critical services including shoreline buffering, carbon sequestration, and habitat provision. Their response to increasingly frequent or intense storms under climate change is a pressing concern, especially on intertidal flats in weakly tidal coastal environments, where weak tidal currents and storm-modified inundation can produce complex sediment dynamics. This study characterizes the spatial heterogeneity of short-term storm response and post-storm adjustment on an intertidal flat in Laizhou Bay, China, by integrating high-frequency hydrodynamic measurements, sediment transport analysis, and profile-scale geomorphic surveys during and after a storm event. Results show that the storm modified inundation and wave conditions, reshaped near-bed wave-current interaction, and altered combined wave-current shear stress. These near-bed stress changes promoted sediment resuspension and event-scale sediment redistribution. RTK-GPS surveys and surface sediment samples further indicated storm-related bed lowering and surface coarsening along the surveyed cross-shore profile. During the observation period, a three-part short-term adjustment pattern emerged along the cross-shore profile, indicating that local geomorphic setting conditioned how storm disturbance was translated into post-storm adjustment. The landward sector showed rapid post-storm stabilization as wave and current forcing weakened. The central sector showed delayed adjustment associated with tidal-advective sediment redistribution, indicating a prolonged transport influenced post-storm adjustment process. The seaward sector showed comparatively muted fixed-point bed-level variability and weaker local transport activity, although RTK-GPS surveys still indicated profile-scale bed lowering near this sector. Empirical Orthogonal Function analysis summarized the shift from storm-driven disturbance to tidal-modulated post-storm adjustment. These differences indicate that short-term storm response was not uniform along the surveyed cross-shore profile, but varied with local geomorphic setting. Replicated profiles and longer observations are needed to test whether similar response patterns occur more widely in weakly tidal coastal environments.