Shellfish as a protection of revetments: A case study in the Port of Rotterdam

• Main Author: Dommisse, Wilmine (author)
• Other Authors: van Koningsveld, M. (mentor), Hofland, B. (graduation committee), Herman, P.M.J. (graduation committee), Wilms, T. (graduation committee), Wolf, R. (graduation committee), Delft University of Technology (degree granting institution)
• Format: Master Thesis
• Language: English
• Published: 2020
• Subjects: Port of Rotterdam; Shellfish; Pacific oyster; Stability; Revetment; Pacific; Crassostrea gigas
• Online Access: http://resolver.tudelft.nl/uuid:9311cad1-465f-4c93-b316-3bab6b353b50

The main objective of this thesis is to increase the understanding of the effect of shellfish presence on the stability of loose rock revetments and to investigate the possibilities in the design. Pacific oyster (Crassostrea gigas) and blue mussel (Mytilus edulis) presence on loose rock revetments was quantified. C. gigas and M. edulis are common shellfish species in the port area and act as ecosystem engineers. They require a certain salinity level, water temperature, phytoplankton ratio, and sufficient submersion time for daily feeding and respiration. The current presence of shellfish in the port area was predicted based on salinity levels generated by an OSR model. Outcomes were compared to qualitative measurements of C. gigas and M. edulis presence performed in the port area. C. gigas is present on revetments where salinity levels exceed 16‰, which is the case at Maasvlakte 2, Beerkanaal, and Calandkanaal. M. edulis were hardly observed in the port area on revetments. M. edulis can move relatively easily and detach from the surface after mortality occurs in contrast to C. gigas. They are, therefore, not considered a reliable structural addition, so only the effect from C. gigas was studied. C. gigas presence leads to binding of stones in revetments. This binding of stones will increase the stability of stones in the revetment. The relationship between the presence of oysters and stability upgrading is described using a connectivity model. The relationship between the presence of oysters and binding of stones is measured in the port area, these measurements are used to validate the model. Measurements showed that the cumulative coverage ratio of dead and living C. gigas decreases as one moves up to the intertidal zone from the mean low water level (MLW). The binding of stones increases when the coverage ratio of C. gigas is larger. This shows that there is a relationship between the coverage ratio of oysters and the binding of stones, and this assumes that there is a relationship between the coverage ratio ...