An alternative explanation for the shape of 'log-spiral' bays

Journal Article

We present a simple numerical model capable of producing distinctive scalloped bays of a form found when a sandy coastline extends downdrift of a rocky headland. The shape of such bays can often be approximated by a log-spiral - a curve for which the radius of curvature increases logarithmically with distance from the headland or 'pinning point.' A considerable body of work has been published attributing this shape to the pattern of refraction and/or diffraction created as waves approaching from a dominant direction interact with the pinning point. Here, we present a fundamentally different explanation for these shapes. We use an existing one-line numerical model of wave-driven alongshore transport which includes shoaling and refraction over contours assumed to parallel local shoreline orientations. Rather than assuming a single wave angle, it generates new waves repeatedly according to an input wave climate. It does not include refraction or diffraction around the pinning point; thus, the log-spiral-like shape evolves as simply as a result of alongshore transport driven by a distribution of deep-water wave approach angles. © 2007 ASCE.

Full Text

Duke Authors

Cited Authors

  • Littlewood, R; Murray, AB; Ashton, AD

Published Date

  • September 17, 2007

Published In

  • Coastal Sediments '07 Proceedings of 6th International Symposium on Coastal Engineering and Science of Coastal Sediment Processes

Digital Object Identifier (DOI)

  • 10.1061/40926(239)26

Citation Source

  • Scopus