Sediment Dispersal in Norderneyer Seegat, West Germany
- S.-D. Nio,
- R. T. E. Shüttenhelm and
- Tj. C. E. Van Weering
Published Online: 29 JUN 2009
Copyright © 1981 The International Association of Sedimentologists
Holocene Marine Sedimentation in the North Sea Basin
How to Cite
Nummedal, D. and Penland, S. (1981) Sediment Dispersal in Norderneyer Seegat, West Germany, in Holocene Marine Sedimentation in the North Sea Basin (eds S.-D. Nio, R. T. E. Shüttenhelm and Tj. C. E. Van Weering), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303759.ch14
- Published Online: 29 JUN 2009
- Published Print: 23 DEC 1981
Print ISBN: 9780632008582
Online ISBN: 9781444303759
- sediment dispersal model for high wave-energy;
- wave versus tidal energy;
- changes in morphology;
- The Nordergriinde Bars;
- be ‘offset’ - shoreline on downdrift barrier
The paper presents a sediment dispersal model for a high wave-energy, mesotidal inlet on the southern coast of the North Sea. The model has been derived through the integrated analysis of historical–morphological data, sub- and intertidal bedform distributions, aerial photography, intertidal fluorescent tracer dispersal studies and long-term current velocity time series.
Long-term historical–morphological data permit the reconstruction of Norderney and environs since the year 1350. Over the last 300 years the island has been subject to sustained growth. Annual inlet maps over about three decades demonstrate that this growth is related to the steady migration of bars around the arcuate margin of the ebb-tidal delta from the island of Juist eastward to Norderney.
The pattern of sediment bypassing is not simple. Sand is delivered to the inlet by wave induced longshore transport from the shoreface at Juist and sources further west. As it enters the inlet system, sediment is moved offshore and eastward through a complex set of alternating ebb- and flood-dominated channels. It is delivered to the strongly ebb-dominated main channel through a major marginal flood channel and across large bars (ebb-shields) which form the landward termini of many of the smaller flood ramps. The expanding ebb jet delivers this sediment to two major terminal lobe bar complexes. Once deposited at the terminal lobe the sediment is subject to further eastward movement in the form of large bars. The morphology of the bars demonstrates that they are subject to significant tidal current influence near the updrift (western) margin of the terminal lobe. Tidal influence decreases eastward and the bars become shore-parallel ‘swash -bars’ before they weld to the island shore about 5 km east of the west end of Norderney.
The overall asymmetry of the Norderneyer Seegat ebb tidal delta, and its pronounced degree of downdrift offset, are deduced to be functions of the strongly eastward-directed momentum of the waves and the residual tidal current. The mechanism of ‘wave pumping’ is proposed to account for the maintenance of a stable updrift marginal flood channel as contrasted with the highly transient and migratory channels on the downdrift side.