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Title: Acoustic investigation of the hydrodynamics and ecology of a tidal channel and the impacts of a marine renewable energy installation
Author: Fraser, Shaun
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2017
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Dynamic tidal channel environments are currently being targeted by the marine renewable energy industry, with the first arrays of marine current turbines now being constructed in Scotland. Tidal channels are characterised by high flow velocities and extreme turbulence, and are important habitats for a range of marine animals. The hydrodynamics and ecology of such sites are poorly understood and so detailed measurements of the natural conditions and the impacts of marine renewable energy installations (MREIs) are required. This project is based on the analysis of acoustic data collected at the Fall of Warness tidal channel at the European Marine Energy Centre, UK. Velocity and backscatter measurements were taken during deployments of a multi-instrument mooring, with data collected in the natural flow and in the wake of a full-scale MREI. Using an interdisciplinary approach, a range of new methods were developed to obtain detailed information on the distribution of biological targets and the physical dynamics of the study site. In the near-bed environment, velocity data were used to study the structure of turbulence which was linked by the analysis of physical backscatter to processes in the water column. Bed-generated coherent motions and wave-wind-current interactions dominated the hydrodynamics of the study site. Results showed that the MREI wake was characterised by the breakdown of the natural flow structure, with a reduced mean flow velocity and increased levels of turbulence intensity recorded. The analysis of backscatter also revealed the behaviour of observed biota, in particular aggregating fish species, and was used to interpret the composition of biological targets. The vertical distribution and schooling characteristics of fish were found to be environmentally driven by daylight and tidal phase. Results showed that natural behavioural patterns were disturbed in the vicinity of the MREI, with evidence of significant fish attraction and avoidance effects. The interdisciplinary outputs of this project are a timely contribution to emerging areas of research with applications to the development of a sustainable marine renewable energy industry.
Supervisor: Not available Sponsor: Natural Environment Research Council ; Marine Collaboration Research Forum ; University of Aberdeen ; Department for Environment and Rural Affairs
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Tidal currents ; Turbulence ; Offshore structures ; Renewable energy sources