INTERACTIONS OF TIDAL INLET MIGRATION AND A LARGE-SCALE GROYNE

摘要

The longshore sediment transport along the southern North Sea coast effects resultingly a drift from west to east. Therefore most of the East Frisian tidal inlets tend to migrate into the same direction. The eastward migration of the Harle inlet was accelerated by the adaption of tidal basin and inlet to the resedimentation of a medieval storm surge bay. Since 1940 a large-scale groyne at the western shore of the island of Wangerooge in the Harle inlet prevents further migration, keeps the main channel in position and restricts the extent of a secondary channel. But with the redistribution of tidal gullies in the catchment area since the middle of the 1980s the tidal prism of the secondary channel has significantly increased and accordingly its cross-section started to expand. Investigations by phenomenological analysis and empirical equilibrium relations indicate that the partial cross-sections in the Harle inlet experience a retarded adjustment to the modified morpho-dynamical conditions. Further convergence towards morphodynamical equilibrium is expected leading to further erosion in the secondary channel in future.