Preprints
https://doi.org/10.5194/esurf-2020-79
https://doi.org/10.5194/esurf-2020-79

  10 Nov 2020

10 Nov 2020

Review status: a revised version of this preprint is currently under review for the journal ESurf.

The Influence of Dune Aspect Ratio, Beach Width and Storm Characteristics on Dune Erosion for Managed and Unmanaged Beaches

Michael Itzkin1, Laura J. Moore1, Peter Ruggiero2, Sally D. Hacker3, and Reuben G. Biel1 Michael Itzkin et al.
  • 1Department of Geological Sciences, University of North Carolina, 104 South Road, Mitchell Hall, Campus Box 3315, Chapel Hill, North Carolina 27515, USA
  • 2College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, 104 CEOAS Administration Building, Corvallis, OR 97331, USA
  • 3Department of Integrative Biology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA

Abstract. Dune height is an important predictor of dune impact during a storm event given that taller dunes have a lower likelihood of being overtopped. However, the temporal dominance of the wave collision regime, wherein significant volume loss (erosion) from the dune will occur through dune retreat without the dune being overtopped, suggests that dune width must also be considered when evaluating the vulnerability of dunes to erosion. We use XBeach, a numerical model that simulates hydrodynamic processes, sediment transport, and morphologic change during a storm, to analyze dune erosion as a function of dune aspect ratio (i.e., dune height versus dune width) for storms of varying intensity and duration. We find that low aspect ratio (low and wide) dunes lose less volume than high aspect ratio (tall and narrow) dunes during longer storms, especially if they are fronted by a narrow beach. During more intense storms, low aspect ratio dunes experience greater erosion as they are more easily overtopped than high aspect ratio dunes. In managed scenarios where sand fences are used to construct a fenced dune seaward of the existing natural dune, we find that the fenced dune effectively prevents the natural dune behind it from experiencing any volume loss until the fenced dune is sufficiently eroded, reducing the magnitude of erosion of the natural dune by up to 50 %. We also find that beach width exerts a significant influence on dune erosion; a wide beach offers the greatest protection from erosion in all circumstances regardless of dune morphology or storm characteristics. These findings suggest that efforts to maintain a wide beach may be effective at protecting coastal communities from dune loss. However, in maintaining wide beaches and dunes, the protection offered in the short-term must be considered against long-term detrimental effects of potentially limiting overwash fluxes, which are critical to maintaining island elevation as sea level rises.

Michael Itzkin et al.

 
Status: final response (author comments only)
Status: final response (author comments only)
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Michael Itzkin et al.

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The Influence of Dune Aspect Ratio, Beach Width and Storm Characteristics on Dune Erosion for Managed and Unmanaged Beaches Data Itzkin, Michael, Moore, Laura J., Ruggiero, Peter, Hacker, Sally D., and Biel, Reuben G. https://doi.org/10.5281/zenodo.4059885

Michael Itzkin et al.

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Short summary
Studies of the impact of storms on dunes typically focus on the importance of dune elevation, here we analyze the protective services offered by the dune height and width, the morphology of the beach fronting the dune, and artificial dune construction via the use of sand fences. We find that dune volume loss most strongly correlates to beach width rather than dune shape, although when beach width is controlled for low/wide dunes offer greater protection than tall/narrow dunes.