Estuarine morphology and depositional processes in front of lateral river-dominated outlets in a tide-dominated estuary: A case study of the Lingding Bay, South China Sea

Abstract This study examined estuarine morphology and depositional processes in front of lateral river-dominated outlets in a tide-dominated estuary, such as the Lingding Bay in South China Sea. The estuary receives sediments from four deltaic distributary outlets of the Pearl River Delta, of which three outlets (in the western part of the estuary) are river-dominated and one at the head is a tide-dominated inlet. The results obtained from an analysis of historical bathymetric maps and numerical experiments of the sediment dynamics are consistent and indicate that tides predominate the morphological shaping of the lateral river mouth shoals. Accordingly, the eastward progradation of the shoal areas decreased from the upper to lower estuary. The resultant estuarine morphology could be characterised by exponentially decreasing cross-sectional bathymetric areas from the lower to upper estuary. This morphological evolution occurred despite intensive human disturbances. Reduced tidal influences may enhance the southeastwardly deposition of riverine sediments, while increased influences would enhance the erosion of the lateral river mouth shoals. Furthermore, increased tidal influences enhance sediment resuspension and their eastward transportation towards the west trough of the bay, such that lesser sediments are deposited at the river mouth shoals. Hence, it can be concluded that lateral river-dominated outlets in a tide-dominated estuary like the Lingding Bay induce unique estuarine geomorphic features and sedimentary processes that are strongly influenced by tidal action.