geosciences Article Insights into the Short-Term Tidal Variability of Multibeam Backscatter from Field Experiments on Different Seafloor Types Giacomo Montereale-Gavazzi 1,2,*, Marc Roche 3, Koen Degrendele 3, Xavier Lurton 4, Nathan Terseleer 1, Matthias Baeye 1, Frederic Francken 1 and Vera Van Lancker 1,2 1 Royal Belgian Institute of Natural Sciences, Operational Directorate of Nature, Gulledelle 100, B, 1200 Brussels, Belgium;
[email protected] (N.T.);
[email protected] (M.B.);
[email protected] (F.F.);
[email protected] (V.V.L.) 2 Department of Geology, Renard Centre of Marine Geology, Ghent University, Krijgslaan 281 s.8, B-9000 Gent, Belgium 3 Federal Public Service Economies, Continental Shelf Service, Boulevard du Roi Albert II, 16, 1000 Brussels, Belgium;
[email protected] (M.R.);
[email protected] (K.D.) 4 Ifremer, Underwater Acoustics Laboratory, IMN/NSE/AS, CS 10070, 29280 Plouzané, France;
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[email protected] Received: 4 December 2018; Accepted: 2 January 2019; Published: 10 January 2019 Abstract: Three experiments were conducted in the Belgian part of the North Sea to investigate short-term variation in seafloor backscatter strength (BS) obtained with multibeam echosounders (MBES). Measurements were acquired on predominantly gravelly (offshore) and sandy and muddy (nearshore) areas. Kongsberg EM3002 and EM2040 dual MBES were used to carry out repeated 300-kHz backscatter measurements over tidal cycles (~13 h). Measurements were analysed in complement to an array of ground-truth variables on sediment and current nature and dynamics. Seafloor and water-column sampling was used, as well as benthic landers equipped with different oceanographic sensors.