Mapping gradients in seafloor characteristics in the Belgian part of the North Sea: MBES based classification of the diverse sediment types.
This research (COPCO project RP 2021-05) is part of the study of the impact of human activities on the seabed and water column in collaboration with ILVO and RBINS/OD Nature, and supports and frames within the continuous monitoring and mapping of the impact of sand and gravel extraction on the Belgian Continental Shelf and in the Belgian territorial sea.
Over the last 20 years, multibeam echosounder (MBES) bathymetry and backscatter data and sediment samples have been acquired at regular intervals to monitor the impact of marine aggregate extraction in the Belgian part of the North Sea (BPNS). Although very valuable to monitor changes in seabed characteristics, no systematic and repetitive classifications of the seafloor were produced with these data until now.
Anticipating on the next era in multibeam monitoring with the new RV Belgica and RV Simon Stevin, a specific approach will be developed to (1) classify gradients in seafloor characteristics based on MBES data acquired at different frequencies and (2) identify gradual changes in seafloor characteristics over time. To achieve this, a detailed characterization of the acoustic, sedimentological, geotechnical and macrobenthic properties of archetypal morpho-sedimentological environments of the BPNS is required on reference areas.
During the cruises predefined reference area’s will be studied in detail: multi- frequency acoustic mapping with EM2040D multibeam echosounder and sedimentological definition of the elementary sediment types through multiple sampling and imaging/video recording with accurate positioning on the seafloor. The location of the ground truthing positions will be defined on the basis of the backscatter and acoustic classification maps, constructed onboard after the initial multibeam survey.
The quantitative acoustic approach requires a prior quality evaluation and calibration of the acoustic measurements with the EM2040D with surveys on the Kwinte reference zone.
The research is part of the tasks of the Continental Shelf Service: to carry out continuous research into the influence of the exploitation of non-living resources of the territorial sea and the continental shelf on the sediment deposits and the marine environment (Law of 13 June 1969 on the exploration and exploitation of non-living resources of the territorial sea and the continental shelf), and aims to enhance the scientific knowledge and expertise on this subject.
The regular (and legally required) monitoring of the impact of sand extraction is done with RV Belgica.
This specific project, in collaboration with the scientific institutions ILVO and RBINS/OD Nature, will be carried out with both RV Simon Stevin and RV Belgica. Both vessels have the same MBES (EM2040D) and can apply the same sampling techniques in the context of this project. The measurements and results of the research with both research vessels are therefore highly combinable, and will contribute to an extensive joint quality evaluation and optimally promote the future interchangeability of the acoustic measurements.