Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North Sea
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...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-03-01
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| Series: | Water |
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| Online Access: | https://www.mdpi.com/2073-4441/13/6/848 |
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| author | Sebastian S. V. Hein Vanessa Sohrt Edgar Nehlsen Thomas Strotmann Peter Fröhle |
| author_facet | Sebastian S. V. Hein Vanessa Sohrt Edgar Nehlsen Thomas Strotmann Peter Fröhle |
| author_sort | Sebastian S. V. Hein |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-03-10T13:03:53Z |
| format | Article |
| id | doaj.art-6fc093e55f1d47d099a0ac972e35f939 |
| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-10T13:03:53Z |
| publishDate | 2021-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Water |
| spelling | doaj.art-6fc093e55f1d47d099a0ac972e35f9392023-11-21T11:15:04ZengMDPI AGWater2073-44412021-03-0113684810.3390/w13060848Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North SeaSebastian S. V. Hein0Vanessa Sohrt1Edgar Nehlsen2Thomas Strotmann3Peter Fröhle4Institute of River and Coastal Engineering, Hamburg University of Technology, 21073 Hamburg, GermanyInstitute of River and Coastal Engineering, Hamburg University of Technology, 21073 Hamburg, GermanyInstitute of River and Coastal Engineering, Hamburg University of Technology, 21073 Hamburg, GermanyHamburg Port Authority, Hydrology, 20457 Hamburg, GermanyInstitute of River and Coastal Engineering, Hamburg University of Technology, 21073 Hamburg, GermanyMany 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.https://www.mdpi.com/2073-4441/13/6/848clapotisElbeestuarytidal amplificationtidal constituentstidal reflection |
| spellingShingle | Sebastian S. V. Hein Vanessa Sohrt Edgar Nehlsen Thomas Strotmann Peter Fröhle Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North Sea Water clapotis Elbe estuary tidal amplification tidal constituents tidal reflection |
| title | Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North Sea |
| title_full | Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North Sea |
| title_fullStr | Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North Sea |
| title_full_unstemmed | Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North Sea |
| title_short | Tidal Oscillation and Resonance in Semi-Closed Estuaries—Empirical Analyses from the Elbe Estuary, North Sea |
| title_sort | tidal oscillation and resonance in semi closed estuaries empirical analyses from the elbe estuary north sea |
| topic | clapotis Elbe estuary tidal amplification tidal constituents tidal reflection |
| url | https://www.mdpi.com/2073-4441/13/6/848 |
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