| Estuaries are coastal regions characterised by complex hydrodynamics, involving mixing of fresh and saline water, tidal motion and river flow. This results in transport and entrapment of sediments. Trapping locations (estuarine turbidity maxima, ETM) are sensitive to variations in external forcing (storms, sea level rise, river flooding), site-specific bathymetry (islands, navigation channels, shoals) and sediment characteristics. Striking examples of ETM featuring such variations (of both natural and anthropogenic origin) are the Pearl River Estuary (PRE), China, and the Ems Estuary, Netherlands/Germany. Understanding ETM dynamics and the sensitivity to changing conditions is important for estuarine management (maintenance of navigational channels, water quality and ecology). The complex bathymetry of PRE, a two-channel system with several islands and four tributaries, makes ETM dynamics inherently three-dimensional. As previous research primarily focused on variability in either the longitudinal or transverse direction, current modelling expertise is unable to unravel the interwoven longitudinal and transverse turbidity structure. Our goal is to investigate/understand the formation of ETM and its sensitivity to forcing, bathymetry and sediment characteristics in estuaries. The innovation is twofold: (1) a detailed understanding of the combined influence of lateral and longitudinal trapping, (2) application to site-specific problems in PRE. We adopt an integrated approach, involving three key aspects: idealized modelling, numerical modelling and field data. Idealized models, including the essential physical processes and large-scale geometrical/bathymetrical features in a simplified way, are specifically geared to unravel trapping mechanisms. Numerical models, including state-of-the-art process formulations, extend these results to transient forcing conditions and aspects specific for PRE. Field data serve as input and validation for both models. Since detailed data in the PRE are lacking, new field measurements will be conducted. This joint Chinese/Dutch project helps to gain insight in ETM dynamics in the Pearl River Estuary and other estuaries in the world. |
