Estuaries and tidal basins form the transition zones between land and sea. They contain important habitats for flora and fauna and are extensively used by people, like for navigation. For ecological and navigational purposes, it is important to understand and predict the evolution of channels and shoals, including sedimentation rates and the composition of the bed sediments. The bed material of large estuaries and tidal basins largely consists of mixtures of mud and sand, with predominantly sandy channels and mainly muddy intertidal areas. The interaction between sand and mud, in combination with currents and waves, leads to complex dynamics in these areas, with migrating channels and shoals
Much is known about the behaviour of the individual sediment fractions, but the knowledge and understanding of sand-mud interaction remains limited, as do the available tools and models to accurately predict the bed evolution and sediment transport rates in sand-mud areas. Existing models, like the ones by Van Ledden (2003), Soulsby & Clarke (2005) or Van Rijn (2007) have only limitedly been verified with observations due to a lack of good quality observational data. Also, none of the available approaches cover the complete spectrum of sand-mud interaction, which includes settling, erosion processes, waves and currents, and the bed shear stress. Therefore, in practice, sand- and mud fractions are often treated separately. This decoupled approach limits the predictive capacity of numerical models, and therefore the impact of human intervention such as deepening of channels and port construction on maintenance dredging volumes and other morphological changes.
In the MUSA-research project, a consortium of contractors, consultants and research organizations joins forces to increase the understanding of the dynamics of sand-mud mixtures through flume tests and field measurements. The developed knowledge, insights and data will be incorporated in engineering tools and in numerical modelling software. The three-year project consists of the following activities:
▪ Literature analysis
▪ Laboratory experiments
▪ Field measurements
▪ Development and improvement of formulations on sand-mud dynamics
▪ Development of engineering tools
▪ Implementation of formulations in numerical software
The project started in May 2020 and will end in january 2023.
At the moment we are finalizing the literature analysis and started with the first phase of laboratory experiments.