Dynamics and drivers of tidal flat morphology in China

Abstract

Abstract Recent remote sensing analysis has revealed extensive loss of tidal flats, yet the mechanisms driving these large-scale changes remain enigmatic. This study traces the spatiotemporal variations of 2538 tidal flat transects across China to elucidate how their morphological features vary with external factors, including suspended sediment concentration (SSC), tidal range, and wave height. We observe a correlation between flat width and SSC distribution, and between flat slope and tidal range. A national-wide decline in flat width is observed together with SSC reduction between 2002 and 2016. Intriguingly, sediment-rich flats exhibit a more rapid response to SSC reduction compared to sediment-starving areas, but the converse is observed with SSC increase. These conditional responses stem from the morphodynamic tendency towards equilibrium, which is well explained by synthetical modeling. This finding suggests that tidal flats are resilient to sediment supply reduction, and nation-scale sediment allocation can assist in preserving valuable intertidal areas.