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Tidal oscillation and resonance in semi-closed estuaries : empirical analyses from the Elbe estuary, North Sea
Citation Link: https://doi.org/10.15480/882.3405
Publikationstyp
Journal Article
Date Issued
2021-03-19
Sprache
English
Author(s)
Institut
TORE-DOI
TORE-URI
Journal
Volume
13
Issue
6
Article Number
848
Citation
Water 13 (6): 848 (2021)
Publisher DOI
Scopus ID
Publisher
Multidisciplinary Digital Publishing Institute
Many tidal influenced estuaries and coastal basins feature tidal amplification because of, e.g., convergence and reflection. Increasing amplification rates were observed in the Elbe estuary, with consequences for construction measures, nautical manoeuvring, flood protection, riverbed morphology and ecosystems. Although many studies were conducted investigating the tidal wave transformation in estuaries, studies based on spatially well-distributed empirical data covering periods over more than a year are rare. To fill this gap, a self-developed adapted harmonic analysis method of least squares was applied to hydrographs from 25 gauges, distributed over the tidal influenced estuary from the river mouth to the tidal border which is given by the weir 160 km upstream of the river mouth. The investigation period for the harmonic analyses covers a whole nodal cycle of 18.613 a beginning in the year 2000. The tidal constituents’ oscillatory behaviour including the appearance of compound tides, generated by nonlinear shallow water processes, and the formation of reflection induced partially standing waves are determined. The tidal constituents show shared frequency-group specific partial clapotis, but also have significant differences in amplification within those groups. The latter fact contributes to the detected inverse proportionality of tidal range amplification inside the estuary to incoming tidal wave height. As reflection can cause resonance in tidal influenced rivers, tests are developed to analyse whether criteria for resonance are met. To determine the system’s specific resonance frequency, a new method was introduced with the three-parameter Lorentzian curve-fitting. As the detected resonance frequency is not close to tidal frequencies, full-established resonance of the tidal wave and of the tidal constituents is not observed in the Elbe estuary. Migrating nodes of the partially standing tidal wave hint at increasing latent resonance.
Subjects
clapotis
Elbe
estuary
tidal amplification
tidal constituents
tidal reflection
tidal resonance
tidal range
tide
quarter-wavelength criterion
DDC Class
550: Geowissenschaften
710: Landschaftsgestaltung, Raumplanung
Publication version
publishedVersion
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