Modes of Berm and Beachface Recovery Following Storm Reset: Observations Using a Continuously Scanning Lidar

Phillips, Matthew S.; Blenkinsopp, Christopher; Splinter, Kristen D.; Harley, Mitchell D.; Turner, Ian L.

doi:10.1029/2018jf004895

Cited by 54 publications

(39 citation statements)

References 43 publications

(70 reference statements)

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“…provide field scientists with a set of reference values for key local variables that serve as a starting template for observation" (NRC, 2010). Morphometric scaling relationships can be used to test numerical morphodynamic models (Lesser et al, 2004;Roelvink et al, 2009) to either confirm modelled outputs or identify areas for improvement. Our work thus reiterates the utility of morphometric allometry as a window into dynamical behaviour, especially for geomorphic phenomena -such as those formed during extreme forcing events -that still confound direct observation.…”

Section: Resultsmentioning

confidence: 99%

Dynamic allometry in coastal overwash morphology

2020

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Abstract. Allometry refers to a physical principle in which geometric (and/or metabolic) characteristics of an object or organism are correlated to its size. Allometric scaling relationships typically manifest as power laws. In geomorphic contexts, scaling relationships are a quantitative signature of organization, structure, or regularity in a landscape, even if the mechanistic processes responsible for creating such a pattern are unclear. Despite the ubiquity and variety of scaling relationships in physical landscapes, the emergence and development of these relationships tend to be difficult to observe – either because the spatial and/or temporal scales over which they evolve are so great or because the conditions that drive them are so dangerous (e.g. an extreme hazard event). Here, we use a physical experiment to examine dynamic allometry in overwash morphology along a model coastal barrier. We document the emergence of a canonical scaling law for length versus area in overwash deposits (washover). Comparing the experimental features, formed during a single forcing event, to 5 decades of change in real washover morphology from the Ria Formosa barrier system, in southern Portugal, we find differences between patterns of morphometric change at the event scale versus longer timescales. Our results may help inform and test process-based coastal morphodynamic models, which typically use statistical distributions and scaling laws to underpin empirical or semi-empirical parameters at fundamental levels of model architecture. More broadly, this work dovetails with theory for landscape evolution more commonly associated with fluvial and alluvial terrain, offering new evidence from a coastal setting that a landscape may reflect characteristics associated with an equilibrium or steady-state condition even when features within that landscape do not.

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Section: Resultsmentioning

confidence: 99%

Dynamic allometry in coastal overwash morphology

2020

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“…Data frequency and sparseness both pose issues for bridging scales. Recently, high-resolution terrestrial lidar scanners have been utilized to explore beach and dune dynamics at high spatial resolution (centimeters) and, in some cases, with high frequency (e.g., [52][53][54][55][56]). These high-density data provide an opportunity to expand the scientific understanding of complex dune eco-morphodynamics that was not previously attainable.…”

Section: Introductionmentioning

confidence: 99%

Spatial Variability of Coastal Foredune Evolution, Part A: Timescales of Months to Years

Brodie

Conery

Cohn

et al. 2019

JMSE

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Coastal foredunes are topographically high features that can reduce vulnerability to storm-related flooding hazards. While the dominant aeolian, hydrodynamic, and ecological processes leading to dune growth and erosion are fairly well-understood, predictive capabilities of spatial variations in dune evolution on management and engineering timescales (days to years) remain relatively poor. In this work, monthly high-resolution terrestrial lidar scans were used to quantify topographic and vegetation changes over a 2.5 year period along a micro-tidal intermediate beach and dune. Three-dimensional topographic changes to the coastal landscape were used to investigate the relative importance of environmental, ecological, and morphological factors in controlling spatial and temporal variability in foredune growth patterns at two 50 m alongshore stretches of coast. Despite being separated by only 700 m in the alongshore, the two sites evolved differently over the study period. The northern dune retreated landward and lost volume, whereas the southern dune prograded and vertically accreted. At the start of and throughout the study, the erosive site had steeper foredune faces with less overall vegetation coverage, and dune growth varied spatially and temporally within the site. Deposition occurred mainly at or behind the vegetated dune crest and primarily during periods with strong, oblique winds (>∼45 ∘ from shore normal). Minimal deposition was observed on the mostly bare-sand dune face, except where patchy vegetation was present. In contrast, the response of the accretive site was more spatially uniform, with growth focused on the heavily vegetated foredune face. The largest differences in dune response between the two sections of dunes occurred during the fall storm season, when each of the systems’ geomorphic and ecological properties modulated dune growth patterns. These findings highlight the complex eco-morphodynamic feedback controlling dune dynamics across a range of spatial scales.

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“…In coastal settings, especially, novel methods by which to directly measure hydrodynamics and sediment transport, particularly under storm conditions, are bringing field, experimental, and numerical studies into ever better alignment (Leatherman, 1976;Leatherman and Zaremba, 1987;Matias et al, 2010;Sherwood et al, 2014;Englestad et al, 2018;Splinter et al, 2018;Phillips et al, 2019;Simmons et al, 2019;Vos et al, 2019;Wiggins et al, 2019;Dodet et al, 2019;Wesselman et al, 2019). Within the frame of geomorphology's grand challenges, such advances make dynamic coastlines 285 "process 'hot spots' -areas where a high level of activity concentrated in a small location can be identified from relatively simple morphologic measures", especially when "topographically based estimates…provide field scientists with a set of reference values for key local variables that serve as a starting template for observation" (NRC, 2010).…”

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confidence: 99%

Dynamic allometry in coastal overwash morphology

Lazarus¹,

Davenport²,

Matias³

2019

Preprint

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Abstract. Allometry refers to a physical principle in which geometric (and/or metabolic) characteristics of an object or organism are correlated to its size. Allometric scaling relationships typically manifest as power laws. In geomorphic contexts, scaling relationships are a quantitative signature of organisation, structure, or regularity in a landscape, even if the mechanistic processes responsible for creating such a pattern are unclear. Despite the ubiquity and variety of scaling relationships in physical landscapes, the emergence and development of these relationships tend to be difficult to observe – either because the spatial and/or temporal scales over which they evolve are so great, or because the conditions that drive them are so dangerous (e.g., an extreme hazard event). Here, we use a physical experiment to examine dynamic allometry in overwash morphology along a model coastal barrier. We document the emergence of a canonical scaling law for deposit (washover) length versus area. Comparing the experimental features, formed during a single forcing event, to four decades of change in real washover morphology from the Ria Formosa barrier system, in southern Portugal, we show that features forming at the event scale might exhibit a different pattern of change over longer time scales. This work reinforces the potential importance of initial conditions in landscape evolution, such that a landscape may reflect characteristics associated with an equilibrium or steady-state condition even when features within that landscape do not.

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Modes of Berm and Beachface Recovery Following Storm Reset: Observations Using a Continuously Scanning Lidar

Cited by 54 publications

References 43 publications

Dynamic allometry in coastal overwash morphology

Dynamic allometry in coastal overwash morphology

Spatial Variability of Coastal Foredune Evolution, Part A: Timescales of Months to Years

Dynamic allometry in coastal overwash morphology

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