Slowly varying stokes waves and submarine longshore bars

Abstract

We investigate the mass transport velocity in the Stokes boundary layer due to slowly varying Stokes waves impinging on and reflecting from a plane‐sloping beach. The resulting mass transport velocity distribution is interpreted to indicate the possible locations of submarine longshore sandbar formation. It is found that the number of bars is likely to increase when the bottom gradient is slight and that the spacing between the crests of the bars increases seaward for some distance offshore. These results are in qualitative agreement with field observations.

Systematic Variations in Inshore Bathymetry

“…This does not agree with the findings of earlier investigators, (Zenkovich 1967, Lau andTravis 1973). The size of the sample in our study, 504 profiles, and the geographic distribution, from Long Island to Texas, were sufficient to adequately establish such a relationship if it did exist.…”

“…However when there are bars under these conditions, they occur in the forward portion and at the seaward end of the profile. Lau and Travis (1973) found that "the number of bars is likely to increase when the bottom gradient is slight;" Zenkovich (1967) noted that the formation of bars was restricted to a fairly narrow range of slopes (0.02-0.005). In our eigenvector analyses of the 504 profiles of the basic data set, we found that the attribute of profile slope is independent of profile curvature elements; that is, bars.…”

“…Davis and Fox (1972) suggested a model for bar formation and migration based on wave/current interaction, and Lau and Travis (1973) found that "the number of bars is likely to increase when the bottom gradient is 'slight'". In 1973, Sonu presented an excellent review and discussion of the latest progress in this area.…”

“…Extensive wave-tank experiments and observations before, during, and just after World War II showed that the bar system was the major feature of the inshore zone. Correlations have been established between the depth of w^ler over the bar crest and the incident wave height (Evans 1940;Keulegan 1948;Shepard 1950;Shepard 1952;McKee and Sterrett 1961) and between the slope and bar occurrence (Z3nkovich 1967;Lau and Travis 1973).…”

“…For one limited coastal reach, the New Jersey coast, there was a partial positive relationship between slope and bars suggesting that the earlier work had perhaps been limited by sample size. However, the work by Lau and Travis (1973) indicated that there is theoretical support for a process-form relationship between bar occurrences and slope and thus the question merits additional study.…”