PLAN GEOMETRY OF HEADLAND-BAY BEACHES.
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 engineer's 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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1964
- Accession Number
- AD0608875
Entities
People
- Warren E. Yasso
Organizations
- Columbia University