During berthing operations vessels use their bow thruster(s) to improve their manoeuvrability, making them less dependent on the assistance of tugboats. The jet from a bow thruster reflects on the quay wall. It is directed towards the bottom where it reflects, causing high flow velocities over the bed. This may scour the nearby bed when it is left unprotected, leading to instability of the quay wall. Over the years, the shipping industry has been developing continuously, characterized primarily by the upscaling in size of inland- and sea-going vessels. As a result, vessels have more power and larger thruster diameters leading to higher hydraulic loads on quay walls and bed protections of berthing facilities. The most common type of bed protection is rip-rap (partially) penetrated with concrete. However, due to the complex flow field of the reflected jet, the decay profile of the near-bed flow velocities is unknown. This results in uncertainties in the design of bed protections and the required width of these protections that must be penetrated with concrete. In this research, the decay of the near-bed flow velocity in perpendicular direction to the quay wall induced by a 4-channel bow thruster is researched. The eventual goal is to provide a better indication to what extent the bed protection must be penetrated with concrete. Field measurements have been conducted in the North Sea Port of Gent with the Somtrans XXV, one of the largest inland vessels in the Netherlands. The flow velocities near the bed, induced by the bow thruster, have been measured with Acoustic Doppler Velocimeters (ADV), Acoustic Doppler Current Profilers (ADCP) and Ott meters (Ott). The results from the flow velocity measurements have been analysed on three main parameters: influence of the applied bow thruster power, the distance between the measurement instrument frame and the bow thruster and quay wall clearance. The highest flow velocities are measured near the quay wall in the order of 1 m/s reaching up to a maximum of 1.8 m/s. Further away from the quay, the flow rapidly declines towards a more constant level of approximately 0.3-0.4 m/s. To define the maximum load on the bed, the mean flow velocity plus three times the standard deviation is used resulting in a maximum load ranging between 1.6-2.8 times the mean horizontal flow velocity. The Dutch and German guidelines for determining the near-bed flow velocities generally overestimate the measurement results. In addition, the dependency of the Dutch method on the total travelled distance by the jet, based on the sum of the quay wall clearance, the height of the bow thruster above the bed and the distance x from the quay wall, are not reflected in the measurement results. It is recommended that this extensive and unique data set acquired through the field measurements in Gent is further used to analyse the flow field of a reflected jet on a vertical quay wall by validating numerical and scale models. Combining these three different methodologies will contribute to a better understanding of this phenomenon with the eventual goal of optimizing the design of bed protections. ... Read more

The Tsleil-Wautuh Nation (TWN) reserve, Sleil-Waututh, located at the north shore of the Burrard Inlet in Vancouver (British Columbia, Canada) is strongly influenced by climate change. Sea level rise, coastal flooding and shoreline erosion are contributing to loss of land, damages to infrastructure, ecosystem changes and exposure of historic sites with cultural value. The TWN are a First Nation, a recognized group of aboriginal people in Canada, and have lived in harmony on the lands and waters of the Burrard Inlet since time out of mind. As TWN has a sacred obligation to be caretakers of the land, they retained Kerr Wood Leidal (KWL) to conduct a climate change hazard and vulnerability assessment and to design a ten year climate change adaptation action plan. The existing conditions in the area are investigated from a technical, environmental and sociological point of view, including a study of the community context of the TWN. Climate change exposes the project area to hazards such as sea level rise, acidification and water temperature changes among others. After conducting a hazard assessment, the following climate change induced hazards are evaluated: Coastal flooding, coastal erosion, intertidal area change, ocean acidification, harmful algae blooms and other ocean conditions (water temperature, e.g.). The impact of waves and rising sea levels are assessed through an Xbeach model. The impact of harmful algae blooms and other ocean conditions are evaluated though literature research. The potential of four different approaches, varying from traditional to building with nature-based solutions, to mitigate the identified hazards are discussed: a rip rap, a nourishment, a salt marsh and a clam garden. They are evaluated based on technical, environmental, economic and social feasibility. For each alternative a trade-off exists between protection against the identified hazards – mainly between the ability of each of the solutions to prevent or mitigate coastal flooding and erosion while preserving the local ecosystem and intertidal area. All alternatives help the TWN in their own way and although further research has to be done, this report provides an insight in four possible alternatives that could support the process of developing a satisfactory solution for the coastal hazards that cause problems for the TWN people and their reserve. ... Read more