Citation:

epic.38582.d008

Name: Spectral analysis of seabed elevation from the Danish Wadden Sea
Published: 2011-09-26
License: https://creativecommons.org/licenses/by/3.0/
Keywords: Fast Fourier Transform; Knudedyb inlet; seabed classification

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Published: 2011-09-26 • DOI registered: 2011-10-25

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Abstract:

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.

Keyword(s):

Fast Fourier Transform; Knudedyb inlet; seabed classification

Project(s):

Center for Marine Environmental Sciences (MARUM)

Coverage:

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

Event(s):

Knudedyb * Latitude: 55.315000 * Longitude: 8.497000 * Location: Vesterhavet, Denmark

Comment:

Latitude/longitude are given in WGS84.An overview map of the data is available at hdl:10013/epic.38582.d007

Parameter(s):

#	Name	Short Name	Unit	Principal Investigator	Comment
1	LATITUDE	Latitude			Geocode
2	LONGITUDE	Longitude			Geocode
3	UTM Northing, Universal Transverse Mercator	UTM north	m	Lefebvre, Alice
4	UTM Easting, Universal Transverse Mercator	UTM east	m	Lefebvre, Alice
5	UTM Zone, Universal Transverse Mercator	UTM Zone		Lefebvre, Alice
6	Wavelength	Wavelength	m	Lefebvre, Alice	of the seabed features in metres
7	Direction	Direction	deg	Lefebvre, Alice	of the seabed features
8	Height	Height	m	Lefebvre, Alice	rms of the box of seabed elevation
9	Spectral energy	Spec E	dB	Lefebvre, Alice	of the peak in the 2D spectrum
10	Spectral exponent	Spec exp		Lefebvre, Alice	slope of the power-law fit
11	Spectral strength	Spec str	m⁴	Lefebvre, Alice	y-intercept of the power-law fit

License:

Creative Commons Attribution 3.0 Unported (CC-BY-3.0)

Size:

65268 data points

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