University of Twente Student Theses


The stochastic characteristics of geometric properties of sand waves in the North Sea

Koning, M.F. de (2007) The stochastic characteristics of geometric properties of sand waves in the North Sea.

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Abstract:In shallow shelf seas such as the North Sea several rhythmic patterns occur, among which sand waves are found. Sand waves occur as a result of the interaction between water and sediment. Sand waves can have lengths up to 500 metres and amplitudes up to 5 metres. In literature sand waves are sometimes schematised as regular idealised sinusoidal waves with a mean sand wave length and mean sand wave height. Existing models predict mean values for sand wave height and sand wave length. However, in reality sand waves are irregular in size and shape and three-dimensional in plan view. For several economic activities, information on mean geometric properties of sand waves is not sufficient. Often additional knowledge is needed on the more extreme values of, for example, the sand wave height or the crest and trough elevations. For navigation for instance, information is needed on the highest sand waves. Knowledge on the variability in sand wave height contributes to a more efficient dredging program. Pipelines and cables, which are buried in the North Sea for transport of fossil fuels and electricity, should not get exposed to the flow and the occurrence of free spans, as a result of migrating sand wave troughs, should be avoided (Németh and Hulscher, 2003). Knowledge on the deepest troughs is therefore important. In the present research the irregularity in geometric properties of sand waves is investigated by analysing field data from the North Sea. By looking at plan views of different areas, a difference between short crested sand wave fields and long crested sand wave fields is seen. In this study long crested sand waves from the Ecomorf 3 are analysed and also short crested sand wave fields from two areas (Noordhinder and TWIN) are analysed. In the TWIN area dredging takes place, which may affect the stochastics of the sand waves in that area. All the bathymetry data used was obtained in 2003 and the grid size is 5m×5m.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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