Measurements of morphodynamic and hydrodynamic overwash processes in a large-scale wave flume

Matias, Ana; Masselink, Gerd; Castelle, Bruno; Blenkinsopp, Chris; Kroon, Aart

doi:10.1016/j.coastaleng.2015.08.005

Cited by 37 publications

(27 citation statements)

References 37 publications

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“…Analysis of z(x, t) [33] revealed that the waves in tests A1-A4 (H s = 0.8 m, T p = 8 s) reshaped the initially planar profile into a sandbar-trough system, with the sandbar crest at x ≈ 70 m. The waves in subsequent A6-A8 tests (H s = 0.6 m, T p = 12 s) transported sand onshore, causing the decay of the sandbar and the generation of a pronounced berm in the upper swash zone. During series B and C the berm and the remains of the sandbar hardly changed, while during series D and E morphological change was most pronounced at the berm and the barrier crest [34].…”

Section: Profile Datamentioning

confidence: 93%

Geometry of Wave-Formed Orbital Ripples in Coarse Sand

Ruessink

Brinkkemper

Kleinhans

2015

JMSE

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Using new large-scale wave-flume experiments we examine the cross-section and planform geometry of wave-formed ripples in coarse sand (median grain size D 50 = 430 µm) under high-energy shoaling and plunging random waves. We find that the ripples remain orbital for the full range of encountered conditions, even for wave forcing when in finer sand the ripple length λ r is known to become independent of the near-bed orbital diameter d s (anorbital ripples). The proportionality between λ r and d s is not constant, but decreases from about 0.55 for d s /D 50 ≈ 1400 to about 0.27 for d s /D 50 ≈ 11, 500. Analogously, ripple height η r increases with d s , but the constant of proportionally decreases from about 0.08 for d s /D 50 ≈ 1400 to about 0.02 for d s /D 50 > 8000. In contrast to earlier observations of coarse-grained two-dimensional wave ripples under mild wave conditions, the ripple planform changes with the wave Reynolds number from quasi two-dimensional vortex ripples, through oval mounds with ripples attached from different directions, to strongly subdued hummocky-type features. Finally, we combine our data with existing mild-wave coarse-grain ripple data to develop new equilibrium predictors for ripple length, height and steepness suitable for a wide range of wave conditions and a D 50 larger than about 300 µm.

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Section: Profile Datamentioning

confidence: 93%

Geometry of Wave-Formed Orbital Ripples in Coarse Sand

Ruessink

Brinkkemper

Kleinhans

2015

JMSE

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“…Matias et al (2008) discuss the potential influence of barrier vegetation on Ria Formosa overwash morphology but do not measure it directly. Storm deposits can drive spatial heterogeneity in vegetation growth rates; vegetation buried too deeply by a storm deposit will die, but for some dune and marsh plant species, shallow to moderate burial can stimulate growth (Maun and Perumal, 1999;Gilbert and Ripley, 2010;and Walters and Kirwan, 2016). Differential plant response to burial can thus determine spatio-temporal patterns in barrier vegetation cover, as the perimeter of a washover deposit may foster an envelope of new plant growth.…”

Section: Dynamic Allometry Of Individual Washoversmentioning

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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“…Tsunami flows commonly have Fr < 2, with values well below 1 in many cases (Matsutomi et al, 2006;Nandasena et al, 2013;Tang and Weiss, 2015;Montoya et al, 2017;Chen et al, 2018;Montoya and Lynett, 2018). Likewise, storm waves generate onshore flows that are supercritical: Fr > 1 is not uncommon (e.g., Tsai et al, 2004;Kuiry et al, 2010), and increasing numbers of studies show that wave overwash can have Fr > 2 (Holland et al, 1991;Matias et al, 2014Matias et al, , 2016.…”

Section: Significant Wave Height (H S ): Term Confusion and Its Consementioning

confidence: 99%

Systematic Review Shows That Work Done by Storm Waves Can Be Misinterpreted as Tsunami-Related Because Commonly Used Hydrodynamic Equations Are Flawed

et al. 2020

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Cox et al. Boulder Deposits and Storm Waves during storms and should therefore be re-evaluated. This is especially important for CBD that have been incorporated into long-term coastal risk assessments, which are compromised if the CBD are misinterpreted. CBD dynamics can be better determined from a combination of detailed field measurements, modeling, and experiments. A clearer understanding of emplacement mechanisms will result in more reliable hazard analysis.

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Measurements of morphodynamic and hydrodynamic overwash processes in a large-scale wave flume

Cited by 37 publications

References 37 publications

Geometry of Wave-Formed Orbital Ripples in Coarse Sand

Geometry of Wave-Formed Orbital Ripples in Coarse Sand

Dynamic allometry in coastal overwash morphology

Systematic Review Shows That Work Done by Storm Waves Can Be Misinterpreted as Tsunami-Related Because Commonly Used Hydrodynamic Equations Are Flawed

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