Preprints
https://doi.org/10.5194/esurf-2021-29
https://doi.org/10.5194/esurf-2021-29

  14 Apr 2021

14 Apr 2021

Review status: this preprint is currently under review for the journal ESurf.

The effects of storms and a transient sandy veneer on the interannual planform evolution a low-relief coastal cliff and wave-cut platform at Sargent Beach, Texas, USA

Rose V. Palermo1,2, Anastasia Piliouras1,3, Travis E. Swanson1,4, Andrew D. Ashton5, and David Mohrig1 Rose V. Palermo et al.
  • 1Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, 78712, USA
  • 2Joint Program in Oceanography/Applied Ocean Science and Engineering, Massachusetts Institute of Technology/Woods Hole Oceanographic Institution, Woods Hole, 02543, USA
  • 3Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, 87545, USA
  • 4Department of Geology and Geography, Georgia Southern University, P.O. Box 8149, Statesboro, 30460, USA
  • 5Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, 02543, USA

Abstract. Coastal cliff erosion is alongshore-variable and episodic, with retreat rates that depend upon sediment as either tools of abrasion or protective cover. However, the feedbacks between coastal cliff planform morphology, retreat rate, and sediment cover are poorly quantified. This study investigates Sargent Beach, Texas, USA at the annual to interannual scale to explore (1) the relationship between temporal and spatial variability in both cliff retreat rate and roughness and (2) the response of retreat rate and roughness to changes in sediment cover of the underlying mud substrate and the impact of major storms, using the low-lying mudstone cliff as a rapidly evolving model of a larger cliff system. A storm event in 2009 increased the planform roughness and sinuosity of the coastal cliff at Sargent Beach, TX. Following the storm, satellite image-derived shorelines with annual resolution show a decrease in average alongshore erosion rates from 4 to 12 m yr−1, coincident with a decrease in shoreline roughness and sinuosity (smoothing). A storm event in 2017 again increased the planform roughness and sinuosity of the cliff. The occurrence of storms and the presence of sediment to laterally erode the cliff influence the planform morphology and subsequent retreat. Over shorter timescales, monthly retreat of the sea cliff occurred only when the platform was sparsely covered with sediment cover on the wave cut platform, indicating that the tools and cover effects can significantly affect short-term erosion rates. The timescale to return to a smooth shoreline with a long-term steady-state erosion rate following a storm or roughening event is approximately five years, with the long-term rate suggesting a minimum of ~38 years until Sargent Beach breaches, compromising the Gulf Intracoastal Waterway (GIWW) under current conditions and assuming no future storms or intervention. The observed retreat rate varies, both spatially and temporally, with cliff face morphology, demonstrating the importance of multi-scale measurements and analysis for interpretation of coastal processes and patterns of cliff retreat.

Rose V. Palermo et al.

Status: open (until 30 May 2021)

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Rose V. Palermo et al.

Rose V. Palermo et al.

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Short summary
At Sargent Beach, Texas, USA, a rapidly eroding soft-sediment cliff system, we study the planform evolution of the cliff face in response to storms and sediment cover. Through this analysis, we characterize the feedbacks between morphology and retreat rate of a cliff face. We find that after a storm event, the roughness and sinuosity of the cliff face increase, which sustains higher retreat rates for years following.