Interaction of suspended cohesive sediment and turbulence

This paper describes the work done in the COSINUS project, carried out within the framework of the European MAST3 research programme, on the interaction between suspended (cohesive) sediment and turbulence, with particular emphasis on its modelling. Specific attention is given to the modelling of buoyancy damping effects and turbulence production due to internal waves. Finally, some experimental results are presented on the effect of advected turbulence to the entrainment of fluid mud

Aquaculture induced erosion of tropical coastlines throws coastal communities back into poverty

Shallow tropical coastlines harbour unique mangrove ecosystems, which support livelihoods and provide a natural barrier against coastal flooding. Non-sustainable land-use practices, such as large-scale clear cutting of mangroves for aquaculture, ground water withdrawal and alteration of river flows, result in rapid subsidence. The collapse of aquaculture production, due to pollution and disease, is followed by coastal erosion, damage to infrastructure, intrusion of salt water and coastal flooding. Standard engineered interventions for protection often fail or are extremely expensive in these soft muddy environments. Subsidence and erosion render re-planting of mangroves in front of retreating coastlines impossible. Short-term solutions should focus on restoration of abiotic conditions, such as hydrology and sediment fluxes, to facilitate rapid establishment of protective mangrove belts. However, to ensure long-term sustainability, improved governance frameworks are required that put in place criteria for sustainable aquaculture, guide coastal infrastructure designs and limit ground water extraction

Morphological changes in the Scheldt estuary and its consequences on hydrodynamics

This paper starts with a brief physical description of the estuary and a summary of its historical developments, with emphasis on human interference, such as the loss of storage area in the basin, sediment circulation by dredging and dumping, etc. Next, the various relevant hydrodynamic processes are described, responsible for the morphodynamic development of the estuary: -tidal asymmetry, length of ebb and flood period, length of HWS and LWS-period, and -effect of the hypsometry (cross sectional shape of the estuary) on the tidal propagation. The impact of morphological changes on the overall tidal movement and on the overtides is treated in the last two sections of the paper. Where possible, the interaction between morphological changes and water movement is discussed

Regime shifts in muddy open water systems

Hydraulic EngineeringCivil Engineering and Geoscience