Navigable waterdepth in waterways with muddy water bottoms : parameters, models and measurement techniques

The navigable water depth in waterways with muddy water bottoms is a complex concept. Although it seems easy to define with e.g. a density of 1.2 kg/L, this parameter is not the only one to determine the level of navigability and manoeuvrability of ships. In this report, an overview is given of the parameters that are relevant for mud. The most important parameters related to the mud are density and viscosity. Because of the transient behavior of fluid mud, the time dependency is important. For the navigability and manoeuvrability of the ship, mud thickness and flow parameters are important.
Next, available techniques to measure in situ or in a laboratory some of the relevant parameters are described. It is clear from the overview that no perfect instrument exists for the determination of relevant parameters for fluid mud. Limitations are linked to the spatial distribution of the data, which is often point measurements, whereas surface or 3D coverage is needed.
An innovative idea is presented: to use internal waves generated by the passage of ships. The behavior of this internal wave is related to the fluid mud properties. To establish a proof of concept of tis idea, both measurements and models are required. In this report, an investigation is made of models that might be suitable for this task, notwithstanding some modifications.
The final chapter presents a list of knowledge gaps. The list is by no means complete. Also, in various institutes and market consortia, research is done to fill some of these gaps.