EGU2020-1609, updated on 12 Jun 2020
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Controls on coastal overwash morphology in natural and built environments

Hannah Williams1, Luke Taylor1, Evan Goldstein2, and Eli Lazarus1
Hannah Williams et al.
  • 1Environmental Dynamics Lab, School of Geography and Environmental Science, University of Southampton, Southampton, SO17 1BJ, UK
  • 2Department of Geography, Environment and Sustainability, University of North Carolina at Greensboro, Greensboro, NC, USA

Overwash is a key mechanism controlling the flux of sediment from the front of a barrier island to the top and back of an island during a storm event. The process is essential for barrier environments to maintain their height and width relative to sea level. Barrier topography and vegetation – and also road networks and buildings – can direct overwash flow, and thus the shape and size of sedimentary deposits that overwash leaves behind. Controls on overwash deposition have been examined more closely in natural settings than in developed zones. But overwash poses a major hazard to coastal infrastructure, and accurate prediction of storm impacts requires quantitative insight into the dynamics of overwash morphology in built settings. Here, we compare barrier floodplain controls across a range of spatial "fabrics", both natural and built (e.g., sparse to dense vegetation coverage; sparse to dense configurations of roads and buildings), to explore how these fabrics affect scaling relationships for overwash morphology. Integrating empirical measurements from post-storm imagery, trials of an analogue model in a small experimental basin, and results from a numerical toy model, we identify thresholds at which floodplain fabrics cause scaling relationships to change, or "break". Our findings illustrate a continuum in overwash pattern formation between endogenous self-organisation and exogenous forcing templates, and set up further inquiry into the dynamics of flood deposition in built environments.

How to cite: Williams, H., Taylor, L., Goldstein, E., and Lazarus, E.: Controls on coastal overwash morphology in natural and built environments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1609,, 2019


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