Equilibrium Profile of a Beach with Varying Grain Size

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by Magnus Larson, Univ of Lund, Lund, Sweden,

Document Type: Proceeding Paper

Part of: Coastal Sediments:

Abstract: The classical concave equilibrium profile shape proposed by Bruun (1954) and Dean (1977) is modified to incorporate a varying grain size across-shore. On most beaches the median grain size decreases with distance offshore, producing a profile that is steeper inshore and more gently sloping offshore than predicted by the standard 2/3-power curve. The present derivation of the profile shape, still assuming constant wave energy dissipation per unit water volume at equilibrium in accordance with Dean (1977), more accurately describes beaches with a grain size varying across-shore. The modified equilibrium profile equation was applied to three different field sites, namely Point Pleasant, New Jersey; Duck, North Carolina; and Baie Rouge, St. Martin in the Caribbean, and improved agreement was achieved in comparison to using a 2/3-power curve. The parameter values obtained from the least-square fit to the measured profile data indicated median grain sizes that are in agreement with information derived from sand sampling.

Subject Headings: Equilibrium | Beach profiles | Grain (material) | Curvature | Flow measurement | Agreements and treaties | Energy dissipation | Hydro power | New Jersey | North America | United States | North Carolina

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