Investigating terrain changes around artificial reefs by using a multi-beam echosounder

Abstract

Although sidescan may be used for approximate delimitation of the boundaries of artificial reefs, multi-beam echosounding technology provides a superior alternative for obtaining quantitative information on sea-bottom morphology and terrain changes around individual reef units. The accuracy of depth measurements of the system used during our trials was around 0.20 m. This allows a grey-scale or colour-code bathymetric map to be drawn from surveying results to demonstrate scouring and sand ripples around reef units. Horizontal movements and subsidence of individual units may be identified from appropriate cross-sections. We found that terrain changes were highly correlated with the direction of local waves and currents. Average width and depth of scouring around concrete reef units and wrecks were approximately equal to the height and to half the height of each unit, respectively. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.