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Model Based Assessment of the Reflection Behavior of Tidal Waves at Bathymetric Changes in Estuaries
Open AccessArticle

Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North Sea

1
Institute of River and Coastal Engineering, Hamburg University of Technology, 21073 Hamburg, Germany
2
Hamburg Port Authority, Hydrology, 20457 Hamburg, Germany
*
Author to whom correspondence should be addressed.
Academic Editor: Yakun Guo
Water 2021, 13(6), 848; https://doi.org/10.3390/w13060848
Received: 4 March 2021 / Revised: 12 March 2021 / Accepted: 15 March 2021 / Published: 19 March 2021
(This article belongs to the Special Issue Hydrodynamics in Estuaries and Coast: Analysis and Modeling)
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. View Full-Text
Keywords: clapotis; Elbe; estuary; tidal amplification; tidal constituents; tidal reflection; tidal resonance; tidal range; tide; quarter-wavelength criterion clapotis; Elbe; estuary; tidal amplification; tidal constituents; tidal reflection; tidal resonance; tidal range; tide; quarter-wavelength criterion
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MDPI and ACS Style

Hein, S.S.V.; Sohrt, V.; Nehlsen, E.; Strotmann, T.; Fröhle, P. Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North Sea. Water 2021, 13, 848. https://doi.org/10.3390/w13060848

AMA Style

Hein SSV, Sohrt V, Nehlsen E, Strotmann T, Fröhle P. Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North Sea. Water. 2021; 13(6):848. https://doi.org/10.3390/w13060848

Chicago/Turabian Style

Hein, Sebastian S.V.; Sohrt, Vanessa; Nehlsen, Edgar; Strotmann, Thomas; Fröhle, Peter. 2021. "Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North Sea" Water 13, no. 6: 848. https://doi.org/10.3390/w13060848

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