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Article Dans Une Revue Marine Geology Année : 1994

Storm influences on a tidal sandbank's surface (Middelkerke Bank, southern North Sea)

Rik Houthuys
  • Fonction : Auteur
Alain Trentesaux

Résumé

The results are presented of two types of "pre-storm" and "post-storm" surveys, carried out on the Middelkerke Bank (southern North Sea). The first type of survey was planned to detect detailed morphological changes in two selected areas of the bank totaling 3 km2; for the survey in these shallow waters to be completed in a fast and accurate way, use was made of a special hovercraft-based hydrographie system. The other type of survey concerned grab samplings covering the sandbank in order to study spatial variations in surficial grain size. The pre-storm and post-storm morphological surveys showed that small and medium dunes disappear under stormy conditions. A 5 m westerly displacement of most of the large and very large dunes has been interpreted as the result of bedform migration under normal (fair-weather), locally dominant ebb flow. The lowering of the large dunes' crests by up to 1.2 m is considered an effect of the storms. The accretion of the lower part of the northwestern flank is attributed to the deposition of sand, derived from shallow parts of the sandbank during storms. The grain-size surveys showed that especially the central and northern parts of the sandbank were affected by grain-size changes, the northwestern flan.k showing a clear coarsening and the landward southeastern flank a fining with respect to the fair-weather situation. It is put forward that the waves approaching from the north cause an extra winnowing on the exposed flank of the bank. On the southeastern flank of the bank, which is better protected against the wave action, fine particles are then deposited.

Dates et versions

hal-04220974 , version 1 (28-09-2023)

Identifiants

Citer

Rik Houthuys, Alain Trentesaux, Peter de Wolf. Storm influences on a tidal sandbank's surface (Middelkerke Bank, southern North Sea). Marine Geology, 1994, 121 (1-2), pp.23-41. ⟨10.1016/0025-3227(94)90154-6⟩. ⟨hal-04220974⟩

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