Accession Number:

AD0608875

Title:

PLAN GEOMETRY OF HEADLAND-BAY BEACHES.

Descriptive Note:

Technical rept. no. 7,

Corporate Author:

COLUMBIA UNIV NEW YORK

Personal Author(s):

Report Date:

1964-01-01

Pagination or Media Count:

35.0

Abstract:

A headland-bay beach is defined as a beach lying in the lee of a headland subjected to a predominant direction of wave attack. Such beaches characteristically have a seaward-concave plan shape resulting from erosion caused by refraction, diffraction, and reflection of waves into the shadow zone behind the headland. Tide-induced currents have no direct effect on the plan shape of headland-bay beaches. Increasing radius of plan curvature with distance from the headland suggested testing the logarithmic spiral, r e theta cot alpha, as an approximation to the shape of headland-bay beaches. Four natural beaches were selected for testing goodness of fit to the logspiral approximation Spiral Beach, Sandy Hook, New Jersey Halfmoon Bay Beach, California Drakes Beach and Limantour Spit Beach lying along the Drakes Bay shoreline to the north of San Franscisco, California. Published maps were used as a source of data on shoreline shape except for Spiral Beach which was mapped by the writer using engineers transit in a longitudinal survey technique. IBM 7090 computer was programmed to generate a best fitting log-spiral to each shoreline curve. Results range from excellent to good with the best fit being to Spiral Beach curvature. Author

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Distribution Statement:

APPROVED FOR PUBLIC RELEASE