Morphological analysis and decadal trends at Groenendijk, Mariakerke and De Haan until Summer 2019. Deliverable D3.3.1 (1) CREST (Climate Resilient Coast) VLAIO/IWT project 150028
Houthuys, R. (2019). Morphological analysis and decadal trends at Groenendijk, Mariakerke and De Haan until Summer 2019. Deliverable D3.3.1 (1) CREST (Climate Resilient Coast) VLAIO/IWT project 150028. [S.n.]: [s.l.]. 35 pp.
Long-term (since 1983/1992) morphological trends and processes are described for the CREST project areas and, for comparison, also of the coast at De Haan (since 1981/1987). The coast at Mariakerke and at De Haan suffers long-term structural erosion. In both cases, the tidal flow channel found just off the beach tends to deepen and to shift landward. This makes the shoreface steeper and narrower, and is followed by more intense storm erosion of the beach. In De Haan, the 1992-1997 large-scale beach and nearshore nourishments effectively repaired the coast. The erosion rates of the upper shoreface and beach have significantly declined since then and no significant storm erosion occurred. However, an increased frequency of maintenance nourishments is now observed and it is remarked that this may reflect the end of the protective action of the shoreface nourishment and the renewed encroachment of the tidal channel on the coastal barrier. At and near Mariakerke, the successive nourishments reached the same protective effect. The longer-term evolution will also there be renewed encroachment of the tidal channel Kleine Rede. The shore at Groenendijk shows pluri-decadal growth. This is possible because the shoreface is wide and shallow. The seaward side of the shoreface is affected by mild, long-term erosion. This might eventually affect the beach at Groenendijk. However, nourishments are taking place at De Panne and Koksijde. A part of the supplied sand disappears offshore and may well contribute to temporary accretion of the shoreface at Groenendijk. Also, the shoreface-attached sandbank Broers Bank, situated 4 km westward, shows a long-term, slow migration eastward by 15 m/yr. The study location at Groenendijk probably benefits indirectly from the nourishments more to the west and natural supply from the offshore by way of the Broers Bank.
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