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

Publication ,  Journal Article
Littlewood, R; Murray, AB; Ashton, AD
Published in: Coastal Sediments '07 - Proceedings of 6th International Symposium on Coastal Engineering and Science of Coastal Sediment Processes
September 17, 2007

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.

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Published In

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

DOI

Publication Date

September 17, 2007
 

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Littlewood, R., Murray, A. B., & Ashton, A. D. (2007). An alternative explanation for the shape of 'log-spiral' bays. Coastal Sediments ’07 - Proceedings of 6th International Symposium on Coastal Engineering and Science of Coastal Sediment Processes. https://doi.org/10.1061/40926(239)26
Littlewood, R., A. B. Murray, and A. D. Ashton. “An alternative explanation for the shape of 'log-spiral' bays.” Coastal Sediments ’07 - Proceedings of 6th International Symposium on Coastal Engineering and Science of Coastal Sediment Processes, September 17, 2007. https://doi.org/10.1061/40926(239)26.
Littlewood R, Murray AB, Ashton AD. An alternative explanation for the shape of 'log-spiral' bays. Coastal Sediments ’07 - Proceedings of 6th International Symposium on Coastal Engineering and Science of Coastal Sediment Processes. 2007 Sep 17;
Littlewood, R., et al. “An alternative explanation for the shape of 'log-spiral' bays.” Coastal Sediments ’07 - Proceedings of 6th International Symposium on Coastal Engineering and Science of Coastal Sediment Processes, Sept. 2007. Scopus, doi:10.1061/40926(239)26.
Littlewood R, Murray AB, Ashton AD. An alternative explanation for the shape of 'log-spiral' bays. Coastal Sediments ’07 - Proceedings of 6th International Symposium on Coastal Engineering and Science of Coastal Sediment Processes. 2007 Sep 17;

Published In

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

DOI

Publication Date

September 17, 2007