Operations report : BGS project 03/03 marine geophysics survey 2003 RV Prince Madog : Outer Bristol Channel marine habitat study

This report describes the operation for BGS Project 03/03, managed and run by BGS Marine Operations and Engineering. The report covers the mobilisation on the 30th October, the geophysical survey and the demobilisation on the 14th November 2004. The main objective of the survey was to provide baseline physical and geological data for the sustainable development of sea-bed resources. This survey is part of a larger BGS project ‘The Outer Bristol Channel Marine Habitat Study’ The operational aims of the survey project were: • To carry out a planned programme of 100% data coverage for 11 corridors, 1km wide of multibeam and sidescan sonar • Additional run the centre line for each corridor with surface tow boomer • Map any interesting features found during the survey The geophysical techniques employed were high-resolution multibeam bathymetry, highresolution sidescan sonar and single channel seismic reflection, (surface tow boomer). All systems were digitally recorded. This is the first time BGS has mobilised a high-resolution multibeam bathymetry system for one project and the first time BGS has used a high speed, high-resolution SSS system. The vessel used was the RV Prince Madog. This platform proved reliable and fuel-efficient. Laboratory space was adapted to provide adequate area. An over the side pole mounted multibeam transducer produced good data collected in marginal weather conditions, the data suffering slightly from pole vibrations. Poor line steerage proved to be a concern and reduced the efficiency of the survey. The poor weather played a large part in the survey, which both confirmed the concerns of the Party Chief at the planning stage of carrying out an operation in the Outer Bristol Channel at this time of year and put added pressure on all aspects of the survey. Despite weather and technical problems encountered over 1500 km of multibeam, over 500 km of SSS and 38 km of surface tow boomer data were collected. It must be noted that without the multibeam being able to collect data in very marginal weather conditions this survey would not have been successful as even with this capability the survey suffered from 16% weather down time. Thanks must be given to the officers, crew and survey personnel who kept going despite being thrown around for days on end.