On the extension and deflection of bayhead river-mouth shoal within a tide-dominated embayment, pearl river estuary

Based on chart data from the 1900s to the 2020s, it is evident that the western bayhead river-mouth shoal in Lingding Bay, Pearl River Estuary, has extended and deflected. This study uses geostatistical methods and numerical simulation experiments to investigate the dynamics of western river-mouth shoals in tide-dominated estuarine embayments. The results show that these shoals extend and deflect between two channels in a clockwise pattern, with their eastward expansion constrained by the adjacent channel. The semi-variogram and anisotropic model effectively describe changes in shoal orientation. Based on numerical experiments, we found that tides contribute to eastward lateral residual sediment transport and deposition, which is the primary sedimentary process for river-mouth shoal extension. Moreover, residual sediment transport at nearby channels or troughs induces this clockwise deflection of river-mouth shoals, with secondary effects from Coriolis forces. Future studies should consider three-dimensional processes to better understand sedimentary processes under intensive human activities in Lingding Bay, Pearl River Estuary. •The river-mouth shoal extends and deflects between two channels in a clockwise pattern.•The clockwise deflection of river-mouth shoals is induced by residual sediment transport in nearby channels or troughs.•Coriolis forces serves as a secondary factor for shoal deflection.