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Lefebvre, Alice; Ernstsen, Verner Brandbyge; Winter, Christian (2011): Spectral analysis of seabed elevation from the Danish Wadden Sea [dataset]. PANGAEA,, Supplement to: Lefebvre, A et al. (2011): Bedform characterization throuth 2D spectral analysis. (Proceedings of the 11th International Coastal Symposium), Szczecin, Poland, ISSN 0749-0208, Journal of Coastal Research, Sl 64, 781-785, hdl:10013/epic.38582.d008

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Bedforms both reflect and influence shallow water hydrodynamics and sediment dynamics. A correct characterization of their spatial distribution and dimensions is required for the understanding, assessment and prediction of numerous coastal processes. A method to parameterize geometrical characteristics using two-dimensional (2D) spectral analysis is presented and tested on seabed elevation data from the Knudedyb tidal inlet in the Danish Wadden Sea, where large compound bedforms are found. The bathymetric data were divided into 20x20 m areas on which a 2D spectral analysis was applied. The most energetic peak of the 2D spectrum was found and its energy, frequency and direction were calculated. A power-law was fitted to the average of slices taken through the 2D spectrum; its slope and y-intercept were calculated. Using these results the test area was morphologically classified into 4 distinct morphological regions. The most energetic peak and the slope and intercept of the power-law showed high values above the crest of the primary bedforms and scour holes, low values in areas without bedforms, and intermediate values in areas with secondary bedforms. The secondary bedform dimensions and orientations were calculated. An area of 700x700 m was used to determine the characteristics of the primary bedforms. However, they were less distinctively characterized compared to the secondary bedforms due to relatively large variations in their orientations and wavelengths. The method is thus appropriate for morphological classification of the seabed and for bedform characterization, being most efficient in areas characterized by bedforms with regular dimensions and directions.
Fast Fourier Transform; Knudedyb inlet; seabed classification
Median Latitude: 55.314657 * Median Longitude: 8.506722 * South-bound Latitude: 55.310274 * West-bound Longitude: 8.497136 * North-bound Latitude: 55.318952 * East-bound Longitude: 8.516705
Knudedyb * Latitude: 55.315000 * Longitude: 8.497000 * Location: Vesterhavet, Denmark
Latitude/longitude are given in WGS84.An overview map of the data is available at hdl:10013/epic.38582.d007
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
3UTM Northing, Universal Transverse MercatorUTM northmLefebvre, Alice
4UTM Easting, Universal Transverse MercatorUTM eastmLefebvre, Alice
5UTM Zone, Universal Transverse MercatorUTM ZoneLefebvre, Alice
6WavelengthWavelengthmLefebvre, Aliceof the seabed features in metres
7DirectionDirectiondegLefebvre, Aliceof the seabed features
8HeightHeightmLefebvre, Alicerms of the box of seabed elevation
9Spectral energySpec EdBLefebvre, Aliceof the peak in the 2D spectrum
10Spectral exponentSpec expLefebvre, Aliceslope of the power-law fit
11Spectral strengthSpec strm4Lefebvre, Alicey-intercept of the power-law fit
65268 data points

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