LONG-TERM MORPHOLOGICAL DEVELOPMENT OF THE ACCUMER EE TIDAL INLET AND ITS IMPACT ON ISLAND BEACHES AND ENGINEERING REPSONSES

U. Abels, H. Kunz, G. Ragutzki, H.-J. Stephan

Abstract


At the East-Frisian coast (Germany) morphological changes of tidal inlets - anthropogenically or naturally caused - can have substantial effects on the sediment supply of adjacent beaches. Erosion periods of beach and dune areas occur, which necessitate engineering countermeasures to preserve the present shoreline. The East- Frisian barrier islands are integrated into the coastal protection strategy for the mainland as they reduce the impact of sea-forces on the flood defences. On the other hand, shoreline and foredunes have to be maintained to protect the urban and tourism infrastructures on the island itself. The maintenance by solid engineering works, like seawalls and groynes, is not favourable because it has drawbacks on the natural morphodynamic processes. Therefore, the technique of beach- and foreshore nourishment is implemented as an instrument of 'active coastal protection' whenever possible. The paper deals with an actual erosion problem on the island of Langeoog caused by morphological changes of its tidal inlet Accumer Ee. It discusses the longterm morphological development of the tidal inlet with its ebb delta shoals and of the adjacent shoreline. A coastal engineering solution for the coastal defence problem has been achieved by means of an integrative approach regarding the natural morphological processes, the ecological objectives, and the safety of the island population.

Keywords


island beach; engineering response; Accumer Ee Inlet; tidal inlet

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