Tuesday, 9:00 AM in 556 AB (RICC)
(subject to change)
The Dee is a macrotidal estuary in the eastern Irish Sea. High levels of accretion have made the Dee a shallow system with vast areas of saltmarsh and low water exposure of sand and mud banks. This study aims to explain morphological changes seen in the estuary and identify the processes responsible. Recent LIDAR surveys have provided unprecedented high resolution bathymetric data of the Dee. LIDAR data provides high quality input for numerical modelling and also facilitates volumetric calculations whereby morphological behaviour can be inferred. Asymmetry in the vertical tide is a controlling factor of morphological changes. An ebb or flood dominant tide will induce residual sediment transport whereas an equilibrium estuary will have a long-term sediment flux of zero. Tidal dominance is predominantly governed by the basin shape (hypsometry), a relationship which is further investigated here by idealised modelling. The concept of basin evolution towards ‘morphological equilibrium’ is also considered. The nature of tidal propagation in the Dee has been examined by numerical modelling (POLCOMS – Proudman Oceanographic Laboratory Coastal Ocean Modelling System) and the results presented here. Recent results of sediment modelling in the estuary are also shown and future research in this area discussed.