Sustainable development requires the quantification of human impacts, against the seafloor's ecological value. Recent impact studies have shown only localised effects, though indications of a longer-term and broader-scale degradation of the seafloor exist. This is due possibly to cumulative anthropogenically-induced effects, but the natural evolution and the response of the seafloor due to sea-level rise are poorly known. Nonetheless, it is likely that changing wave climate and an increased storminess induce different erosion/sedimentation patterns. Such evolution needs to be disentangled against the impact of dredging, aggregate extraction, fisheries and beach replenishment on the ecosystem's physical functioning. To investigate in more detail the sedimentation/erosion processes and the sediment transport system of the Belgian part of the North Sea (BPNS), site-specific measurements were performed during several RV Belgica campaigns. A multisensor benthic lander was used for longer-term measurements to determine the current structure and near-bed dynamics, as also the particle size distribution, volume concentration, the density of the suspended particulate matter and the fall velocity of mud flocs. At locations with a persistent erosion or sedimentation history, measurements on the erodibility of the sediments were performed. All of these parameters are important as input to numerical modelling. The models themselves are being upgraded with the development of integrated 2D sand/mud transport models with extension of a flocculation model. Wetting/drying schemes have been set-up to include the shallow coastal strip. Further, the spectral wave model WAM is being dynamically coupled to the COHERENS flow model and test runs are being made. Meanwhile, data is being acquired to support case studies that will be used to model the impact of the natural versus anthropogenically-induced sediment dynamics along the BPNS. In particular, the area north of the Vlakte van de Raan was targeted, as with the dumping ground Br&W S1, it is one of the main sedimentation areas. Data from very-high resolution acoustic surveys, grab sampling and vibrocoring are being analysed and their results will be integrated to quantify erosion/sedimentation trends along this area. Biological data has been gathered also; their role in local sedimentation processes will be investigated. Meanwhile, a historic reference framework is being set-up, based on the sediment and macrobenthos dataset of Gilson (~1900). In addition, long-term datasets are compiled and their analyses will be integrated, both physically and ecologically. Historical hydrographic charts are digitised to study the long-term bathymetry changes, whilst the quantification of long-term sediment volume changes is envisaged, based on repetitive surveys along fixed tracklines covering the major sandbank areas. Sediment datasets are extended to allow trend analyses of sediment changes of the past 100 years. The changes in mud content will be supported by the results of clay mineralogy analyses that are performed to study the potential mud sources. For the impact of climate change, a literature study has been performed and relevant cooperation is being sought. The impact of human activities on the seabed is mostly visible from very-high resolution acoustic data. Where relevant, the data coverages have been extended with new and external data. Together with data on the major human activities (e.g. from Electronic Monitoring Systems), this will allow evaluating the spatial extent of the impacts and to extrapolate some of the findings. Most of the seabed data is managed in GIS allowing simplified integrations of spatially diverse datasets.Year 1 has concentrated mainly on data acquisition, laboratory analyses and preparatory work for further exploration of existing datasets. Only limited conclusions and recommendations can be formulated. Still, significant results have been obtained on a better parameterisation of the sediment and sediment transport system; this was shown necessary for the improvement of model output. The importance of the temporal variability of suspended particulate matter with varying hydro-meteorological conditions and in particular storms has been highlighted. Results from the area, north of the Vlakte van de Raan, indicate varying sedimentation patterns that can be correlated to both naturally and anthropogenically-induced sediment dynamics.In the following phases of the project, the research results will be validated and further refined in the view of the sustainable management and exploitation of the EEZ. With the integration and synthesis of all results, it is aimed at distinguishing the natural from the anthropogenically-induced sediment dynamics. From this, the adaptation of the marine ecosystem on changes will be derived, including the impact of different sea-level rise scenarios.For the valorisation of the project results, a website and a leaflet have been designed. The follow-up committee has provided technical, managerial and scientific support to the partnership. |
