Marine Renewable Energy (MRE) extraction in the UK has until now focused on offshore wind turbines, with targets of 34 GW by 2020. Wave and tidal energy follow this trend, with targets of 1-2 GW1. By 2050, most accessible MRE sources will be exploited or close to being fully exploited2. However, little is known of the general effects of installation and operation. Impacts on the surrounding ecosystems have been predicted as varying from benign to adverse3,4. Experience gained over the years, and around the world, has been summarised in recent reviews, which all highlight the need for more generic modes of assessment5-7. MRE developers have also stressed the need for an improved understanding of the baseline environment8, measuring common impacts with easily adaptable technologies.
The NERC/DEFRA project FLOWBEC-4D (FLOw, Water column and Benthic ECology 4-D: http://noc.ac.uk/project/flowbec) started investigating these effects at MRE test sites in Orkney (European Marine Energy Centre: http://www.emec.org.uk) and in Cornwall (Wave Hub: http://www.wavehub.co.uk) in September 2011, with its first field deployment at EMEC in summer 20128,9. FLOWBEC-4D combines long-term measurements from a remote-sensing sonar platform 8, bird observations9, shore-based X-band radar surveys of wave and current data10 and detailed modeling of the flow and water column. It aims at quantifying the impacts of MRE devices on marine life (e.g. fish, mammals and seabirds) as well as the surrounding environments using remote sensing. This article describes the self-contained multibeam sonar platform designed and built at Bath to image the water column and seabed around MRE devices for as long as 2 weeks at a time. Section 2 explains the concept and building of the instrument. Section 3 presents the results from the 2012 survey in Orkney. Section 4 presents preliminary analyses of the wealth of measurements collected during this first deployment (> 4.5 GB/day for the multibeam instrument alone). Finally, Section 5 summarises the results so far and presents the next steps in MRE acoustic monitoring.