Tidal distortion in shallow estuaries
Citable URI
https://hdl.handle.net/1912/8830DOI
10.1575/1912/8830Keyword
Tidal currents; Inlets; Estuarine oceanographyAbstract
The offshore tide becomes distorted as it propagates into shallow inlet/estuarine systems. Time asymmetries develop in the rise and fall of sea
surface with consequent time and magnitude asymmetries in tidal currents.
Flood-dominant estuaries are characterized by longer falling tides and
stronger flood currents while ebb-dominant estuaries have longer rising
tides and stronger ebb currents. The asymmetries are reflected in the non-linear
growth of harmonics and compound tides of the principal equilibrium
tidal constituents. This dissertation consists of three papers which
examine the development of tidal asymmetries in shallow estuarine systems:
a study of the recent migration history of Nauset Inlet (MA), a shallow
estuarine system located on Cape Cod; an analysis of the results of a series
of field experiments conducted at Nauset; a numerical model study of the
types of estuarine characteristics controlling tidal asymmetry. The analysis
of field results focuses on sea surface measurements. Non-linear
distortion of the tide at Nauset is characterized by the strong growth of
harmonics and compound constituents particularly in the quarter-diurnal
band. Phase relationships between the forced constituents and their parent
produce a flood-dominant estuary. Numerical modeling of M2 tidal propagation
in shallow estuarine channels utilizes the one-dimensional equations
of motion. Shallow, frictionally dominated channels with moderate tidal
flat area develop a flood-dominant asymmetry while deeper channels with
extensive tidal flats develop an ebb-dominant asymmetry. Model results
are supported by observations of tidal asymmetry in natural estuaries.
Implications of non-linear tidal distortion on bedload and suspended
material transport are profound. Flood-dominant estuaries tend to import
sediment if the supply is adequate whereas ebb-dominant estuaries can flush
entering sediment effectively. Over long time periods, flood-dominant
estuaries may eventually fill. Ebb-dominant estuaries may represent more
stable long-term configurations.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution March 1984
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Suggested Citation
Thesis: Speer, Paul E., "Tidal distortion in shallow estuaries", 1984-03, DOI:10.1575/1912/8830, https://hdl.handle.net/1912/8830Related items
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