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Lingdingyang Bay, Pearl River Estuary (China): geomorphological evolution and hydrodynamics

Abstract The Pearl River is the largest river in southern China; it has eight outlets flowing into the South China Sea, four of which (Humen, Jiaomen, Hongqili and Hengmen) empty via Lingdingyang Bay. Tides, discharge strength and the presence of islands control sediments within these four outlets. Sediments are deposited, and form three shoals and two channels. The shoreline and its seabed topography have changed dramatically with increasing human impact. In order to understand the geomorphological evolution of Lingdingyang Bay and its hydrodynamics, we integrated data obtained from two marine environment investigations conducted by the Guangzhou Marine Geological Survey (GMGS) in 2003 and in 2012, together with remote sensing multi-temporal images and historical materials, and analysed them using a geographical information system (GIS). The results obtained show that the outlets are becoming narrower; the surface water area of Lingdingyang Bay is diminishing. Meanwhile, the sediment flux is reducing and becoming finer grained because the currents are being blocked by shoals and islands. Some parts of the bay are becoming deeper (27–37 m in the Chuanbi Channel). Correspondingly, the hydrodynamics in the bay are becoming weaker and sediments easier to deposit. Water exchange between the inner and outer sea is decreasing under the influence of unrestricted anthropogenic activities. Lingdingyang Bay should be managed and protected continuously based on a scientific framework: otherwise, it will become narrower and, perhaps, even evolving eventually into a river, which may result in serious futures disasters through flooding and tides.