CGRG Bibliography of Canadian Geomorphology
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Author : Greenwood, B.
Date : 2005.
Title : The dynamics of multi-barred beaches in the Great Lakes.
Publication : Annual Meeting of the Canadian Association of Geographer. Tuesday, May 31 to Saturday, to June 4, 2005. University of Western Ontario, London, Ontario.
Issue :
Page(s) :
Abstract
Explanations for the dynamics of nearshore sand bars involve: (i) wave "break point" hypotheses; i.e. bars are produced by offshore sand transport under "roller" or "oblique helical" vortices formed under breaking waves, or by sediment convergence induced by onshore sediment transport by skewed, asymmetric waves prior to breaking and by offshore transport by undertow after breaking; (ii) infragravity wave hypotheses; i.e. drift velocities under "long" waves (surf beat) interact with short wave oscillations to cause sediment convergence to produce a variety of bar forms. (iii) self-organization hypotheses; i.e. complex, non-linear feedback between the hydrodynamics and the sand bed induce alongshore and offshore sediment transport. Cellular or meandering fluid and sediment circulations can be produced either by instabilities in the longshore current (e.g. shear waves), or by a coupling between a morphological instability and the mean flow. Such mechanisms require an initial perturbation of the profile. However, some bar characteristics are not well predicted by any of these hypotheses and a number of questions remain. Field measurements of surface gravity waves (amplitude and frequency), the near-bed oscillatory and quasi-steady current velocities, and the near-bed sediment transport across multi-barred profiles in the Great Lakes allow the primary forcing agent(s) for sediment transport and net sediment flux to be identified. The temporal and spatial variations in the frequency-dependant, near-bed sediment flux over discrete storm cycles are used to test specific hypotheses for bar formation and dynamics.
Bibliography of Canadian Geomorphology