For future strategies in water depth maintenance in the Port of Hamburg, determining the navigability limit (i.e., the safe nautical depth) is of major importance. For this purpose, the project Nautical Depth was set up at the Hamburg Port Authority. The aim of the project is to measure a safe nautical depth under various boundary conditions and to identify limits for a safe passage in port areas with fluid mud. Among other things, the project is conducted in close collaboration with the Port of Antwerp Bruges, the Port of Rotterdam, and TU Delft within the research platform MUDNET (www.tudelft.nl/mudnet).

To gain the necessary acceptance for a reassessment of the nautical depth, it is important to determine the rheological properties of the sediment in-situ. Several existing survey devices for monitoring nautical relevant rheological sediment properties have been tested. However, these devices cannot be used for spatial determination of rheological properties as they only provide cross-sectional measurements and depth profiles. Therefore, new evaluation algorithms were developed to correlate echo sounding data with in-situ rheological properties to ensure spatial coverage of a safe nautical depth.

As a first step, hydrographic surveys and sampling campaigns were carried out to provide system knowledge of the water column and the riverbed. Basic scientific research on the rheological behaviour of the fluid mud was also carried out. In a second step, the safe conditions for adapting the fluid mud layers at the berths for the nautical bottom concept were investigated and new nautical depth approaches were introduced at different locations in the Port of Hamburg. The next step was to analyse the effect of the fluid mud on the manoeuvrability of the ships. To this end, existing Computational Fluid Dynamics (CFD) models were extended to determine the non-linear effects and forces of non-Newton fluids on ship hull, rudder, and propeller efficiency. The results of the CFD model have been and are being validated with hydraulic model tests (scale 1:60) and in-situ measurements in the Port of Hamburg. In a final step, the results of the CFD model will be used to adapt the software of existing ship handling simulators. These simulations will be used to define the safe boundary conditions and limits for a new nautical depth for vessels to navigate through the fluid mud.@en