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Strategies for and results from the investigation of migrating bedforms in the German Bight
Wever, TH.F.; Stender, I.H. (2000). Strategies for and results from the investigation of migrating bedforms in the German Bight, in: Trentesaux, A. et al. (Ed.) Marine Sandwave Dynamics, International Workshop, March 23-24 2000, University of Lille 1, France. Proceedings.
In: Trentesaux, A.; Garlan, T. (Ed.) (2000). Marine Sandwave Dynamics, International Workshop, March 23-24 2000, University of Lille 1, France. Proceedings. Université de Lille 1: Lille. ISBN 2-11-088263-8. 240 pp., more

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Keyword
    Marine

Authors  Top 
  • Wever, TH.F.
  • Stender, I.H.

Abstract
    The sandy river bed of Elbe River and sea floor of its estuary as well as the Jade estuary sea floor show pronounced migrating bedforms. Experiments to investigate the shape and behaviour of these bedforms included the deployment of sensors for the long-term monitoring of sand height variations during the passage of megaripples, a scanning sonar tower for the determination of bedform length, and a side scan sonar system. Most of the analyses reported here are based on the results of the sand height sensors. In the Elbe river sand height sensors monitored the passage of megaripples of about 50 cm height within 11 days. Assuming a minimum ripple index of 10 results in a minimum bedform length of 5 m. The resulting migration speed is 45 cm/day. This migration speed represents a minimum value. Any increase of bedform length (and ripple index) results in an increase of migration speed. Data from the Jade estuary prove a minimum migration speed of 94 cm/day. A long-term deployment of instruments in the Jade river revealed a cyclic pattern of sand height that superimposed on the general continuous increase respective decrease of burial during passage of bedforms. The cyclic pattern correlates with the tidal cycle. It is believed that this characteristic pattern reflects the re-organisation of the bedform crest in response to the tidal currents. The re-organisation of bedform crests is also detected in the variable acoustic response recorded with the scanning sonar tower.

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