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Tidal sand waves are large-scale bed forms found in shallow sandy seas, which show a migration of several meters per year. Field data from the Dutch part of the North Sea revealed a migration pattern causing bidirectional migration of sand waves over a sand bank, resulting in sand wave migration uphill from both sides of the sand bank. In order to understand the physical mechanisms behind this migration behaviour, we study the inclusion of a sand bank under a sand wave field using the numerical model Delft3D. First, the schematized model set-up (i.e. schematized bathymetry and simple tidal forcing) showed that the alteration of the tidal flow by a sand bank resulted in tide-averaged horizontal flow towards the top of the sand bank, causing the bidirectional migration of sand waves over the sand bank. Second, a case study was performed in which a more complex model set-up was used (bathymetry and tidal forcing identical to a study site in the North Sea where an offshore wind farm is developed). Here, the model results revealed migration directions comparable to field observations. The results open opportunities to explore modelling migration patterns of sand wave fields for offshore wind farm development in areas with complex bathymetric environments.

When building offshore wind turbines with monopile foundations, scour protection typically is placed to avoid scouring of the soil close to the monopile. An important aspect is that the scour protection itself causes erosion, inflicted by the local increase in current and/or wave velocities and in turn increased bed shear stresses. Scour of the edge material alongside the scour protection may cause deformations and failure of the scour protection of offshore wind turbine foundations. This can reduce the stability of the stone layer and cause exposure of cables running between the monopiles where they go from buried to the transition piece on the foundation. Although much information is available on the design of scour protection systems around monopiles, little is known on the mechanisms causing edge scour and the equilibrium stages of the edge scour process in steady current, waves and combined waves and current. This paper presents an extensive experimental campaign to explain the edge scour process in current and combined irregular waves and current, as well as tidal current. The three-dimensional flow field around the pile and scour protection is resolved by particle image velocimetry and bed shear stress measurements, showing a local increase in the flow velocities and bed shear stresses leading to increased sediment transport and scour. The governing process in steady current is a pair of symmetrical counter-rotating vortices emerging in the near bed region in the wake of the pile and scour protection, causing a significant downstream scour hole. It is found that the equilibrium scour hole depth and length scales with the pile diameter and the ratio between the thickness- and the width of the scour protection. In the second part of the present paper, the results from the experimental campaign are compared with the edge scour experienced in practice, outlined by a survey program of the offshore wind park Egmond Aan Zee and a published field investigation of Scroby Sands OWF by Whitehouse et al. (2011).

Installation and maintenance strategies regarding offshore wind farm operations involve extensive logistics. The main focus is the right temporal and spatial placement of personnel and equipment, while taking into account forecasted meteorological and ocean conditions. For these operations to be successful, weather windows characterized by certain permissive wave conditions are of enormous importance, whereas unforeseen events result in high cost and risk of safety. Numerical modelling of waves, water levels and current related variables has been used extensively to forecast ocean conditions. To account for the inherited model uncertainty, several error modelling techniques can be implemented for the numerical model forecasts to be corrected. In this study, various Bayesian Network (BN) models are incorporated, in order to enhance the accuracy of the significant wave height predictions and to be compared with other techniques, in conditions resembling the real-time nature of the application. The implemented BN models differ in terms of training and structure and provide overall the most satisfying performance. Supplementary, it is shown that the BN models illustrate significant advantages as both quantitative and conceptual tools, since they produce estimates for the underlying uncertainty of the phenomena, while providing information about the incorporated variables’ dependence relationships through their structure.

A 600 MW offshore wind farm is under construction in the Netherlands Exclusive Economic Zone at a site called Gemini situated 55 km north of the Wadden Sea island of Schiermonnikoog and 85 km from the nearest Dutch port of Eemshaven. This chapter investigates the option of introducing a multi-use design for the Gemini site by adding mussel cultivation (48 kt wet weight per year) and seaweed cultivation (480 kt wet weight per year) to the wind farm. An institutional analysis indicates a political will in the Netherlands to support the development of adding uses to offshore wind farms, but a number of implementation obstacles are also identified. Those obstacles include an absence of licences for multi-use production and legal restrictions against third-party access to wind farms. There is therefore a need for a regulatory framework for multi-use and trust-building among actors involved in multi-use installations. A financial and economic assessment, and a cost-benefit analysis also taking into account monetized changes in CO2 emissions, indicate that adding mussel cultivation to the wind farm is likely to be both financially and socio-economically viable. Including a seaweed cultivation function is probably not financially and socio-economically viable under current technical and economic conditions. Knowledge gaps and uncertainties in these assessments with respect to, for example, missing site-specific data and non-monetized externalities suggest further research, also including pilot cultivations of mussels and seaweed in planned single-use or multi-use installations.

European seas are encountering an upsurge in competing marine activities and infrastructures. Traditional exploitation such as fisheries, tourism, transportation, and oil production are accompanied by new sustainable economic activities such as offshore windfarms, aquaculture, and tidal and wave energy. One proposed solution to overcome possible competing claims at sea lies in combining these economic activities as part of Multi-Use Platforms at Sea (MUPS). MUPS can be understood as areas at sea, designated for a combination of activities, either completely integrated in a platform or in shared marine space. MUPS can potentially benefit from each other in terms of infrastructure, maintenance, etc. Developing MUPS in the marine environment demands adequate governance. In this article, we investigate four European sites to find out how governance arrangements may facilitate or complicate MUPs. In particular, we apply a framework specifying policy, economic, social, technical, environmental, and legal (PESTEL) factors to explore governance arrangements in four case study sites in different sea basins around Europe ( the Mediterranean Sea, the Atlantic Ocean, the North Sea, and the Baltic Sea). The article concludes with policy recommendations on a governance regime for facilitating the development of MUPS in the future.

European oceans are subject to rapid development. New activities such as aquaculture and ocean energy have gained importance. This triggers interest in ?multi-use platforms at sea? (MUPS), i.e., areas at sea in which different activities are combined. MUPS are complex features with regards to technology, governance, and financial, socioeconomic, and environmental aspects. To identify realistic and sustainable solutions and designs for MUPS, the MERMAID project applied a participatory design process (PDP) involving a range of stakeholders representing companies, authorities, researchers, and NGOs. This paper evaluates if and how the participatory design process contributed to the design of multi-use platforms. It is based on interviews with the managers of the case study sites and a questionnaire administered to all stakeholders participating in the PDP workshops. Analyzing the four case studies, we conclude that the participatory design process has had a valuable contribution to the development of the four different designs of MUPS, even though the preconditions for carrying out a participatory design process differed between sites. In all four cases, the process has been beneficial in generating new and shared knowledge. It brought new design issues to the table and increased knowledge and understanding among the different stakeholders. This research was funded under the Seventh Framework Program, Theme [OCEAN.2011-1]. “Innovative Multi-purpose off-shore platforms: planning, design and operation” Grant Agreement no.: 288710.

In this chapter, authors put forward a port layout design approach for an exposed container terminal. This is an unusual approach for this type of terminal because of the associated strict vessel motion criteria. Nevertheless, in view of increasingly bigger container ships that will respond less to environmental conditions, the proposed approach departs from traditional ideas on wave sheltering in ports. The chapter discusses associated advantages and disadvantages. Aside from potential economic benefits, advantages of such an approach could be smaller coastal impacts and larger sustainability . For the disadvantages we present possible directions in which we foresee that solutions could be found to overcome those (technical) limitations. After the remaining technical issues have been solved, and when the business plans of ports can facilitate this new approach, the concept of an open water port is expected to form a more sustainable alternative to traditional port layout design approaches.