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

Cox, Rónadh; Ardhuin, Fabrice; Dias, Frédéric; Autret, Ronan; Beisiegel, Nicole; Earlie, Claire; Herterich, James G.; Kennedy, Andrew; Paris, Raphaël; Raby, Alison; Schmitt, Pál; Weiss, Robert

doi:10.3389/fmars.2020.00004

Cited by 47 publications

(72 citation statements)

References 133 publications

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“…the average of the largest third of waves over a one hour period) reached as much as 17.6m (on 1 February 2014). These deep‐water values translate to 9–13m SWH at the coast (Janjić, ; Cox et al ., ). Maximum wave heights (for rare individual waves) may have been as much as twice the SWH; and nonlinear interactions with uneven topography near the steep coasts may have generated additional amplifications (Brennan et al ., ; Herterich and Dias, ).…”

Section: Winter 2013–2014: the North Atlantic ‘Storm Factory’ And Itsmentioning

confidence: 97%

Megagravel deposits on the west coast of Ireland show the impacts of severe storms

Cox

2020

Weather

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Graphical abstractCoastal boulder deposits on Inishmore, one of the Aran Islands off Ireland's west coast, showcase many of the classic features. Note the adult human for scale (in the yellow circle). The cliff‐collapse block in the foreground is the largest ever documented to be moved by storm waves. Weighing 620t, it was shifted several metres during the storms of 2013–2014. The platform on which it sits is 5m above high water, and the block is 30m inland. The cliff at this site is 9m high. The boulder ridges behind the figure on the cliff top are 11–15m above high water, and the front of the pile ranges from 45–64m inland. A number of the biggest blocks on the upper platform, which weigh several tens of tonnes, were also moved sideways during the 2013–2014 storms; and within the ridge, the pale grey colours show smaller (1–15t) boulders that were overturned. Drone photograph taken by Dr Eugene Farrell (NUI Galway). Used with permission.

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Section: Winter 2013–2014: the North Atlantic ‘Storm Factory’ And Itsmentioning

confidence: 97%

Megagravel deposits on the west coast of Ireland show the impacts of severe storms

Cox

2020

Weather

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“…By using Equations (3)-(6), H m values even close to 6 m are obtained, while, by using Equations (7) and (8), H m does not exceed 4 m, except for Boulders e, h, and k. However, we remark that these hydrodynamic equations have limitations. Reference [50] pointed out that, apart from flaws in the formulas, the estimation of both C L and C D is critical; therefore, instead of applying values excerpted from the literature, the estimation should be accomplished with strict reference to the local physical conditions. As an example, higher values than the one (0.178) usually used for C L were obtained by both field and modeling investigations [51,52].…”

Section: Boulder Displacements and Wave Energymentioning

confidence: 99%

Storm-Induced Boulder Displacements: Inferences from Field Surveys and Hydrodynamic Equations

et al. 2020

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The storm of 12–13 November 2019 provoked the displacements of boulders on a central Mediterranean rocky coast; with reference to a selected area, prone to boulder production and geomorphologically monitored for years, a field-oriented study approach was applied for the phenomenon, by collating data concerning the pre-storm locations and kinematics of these boulders. The number of displaced boulders is 11, that is in terms of the morphological imprint of a specific storm, one of the major study cases for the Mediterranean. In addition, based on widely used hydrodynamic equations, the minimum wave height required to displace the boulders is assessed. The values conform with the expected values for the wave climate dominating during the causative meteorological event and give a measure of the energy of the storm slamming the coast. Boulder dislodgement usually plays a key role in determining the rate of the coastal recession, likely also in the investigated area. In view of an adverse climate evolution with a possible increase of the energy and frequency of severe storms, the results deriving from the study of this morphodynamics should be considered for hazard assessment and coastal management.

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“…The test site exhibits well-developed boulder ridges that sit 8-15 m above high water,~30-70 m inland ( Figure 1), and contain boulders with characteristic masses of tonnes to several tonnes, with intermediate axes of order 1 m [99] (sites S31-S33 in Table A2 of Ronadh . Individual blocks in the ridges (often concentrated at the seaward edge: Figure 3) tend to be larger, and commonly weigh tens of tonnes, up to ≈100 t in some cases (intermediate axes of order 2-5 m, density 2.66 t m −3 [65,76].…”

Section: Study Areamentioning

confidence: 99%

Measuring Change Using Quantitative Differencing of Repeat Structure-From-Motion Photogrammetry: The Effect of Storms on Coastal Boulder Deposits

Nagle-McNaughton

Cox

2019

Remote Sensing

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Repeat photogrammetry is increasingly the go-too tool for long-term geomorphic monitoring, but quantifying the differences between structure-from-motion (SfM) models is a developing field. Volumetric differencing software (such as the open-source package CloudCompare) provides an efficient mechanism for quantifying change in landscapes. In this case study, we apply this methodology to coastal boulder deposits on Inishmore, Ireland. Storm waves are known to move these rocks, but boulder transportation and evolution of the deposits are not well documented. We used two disparate SfM data sets for this analysis. The first model was built from imagery captured in 2015 using a GoPro Hero 3+ camera (fisheye lens) and the second used 2017 imagery from a DJI FC300X camera (standard digital single-lens reflex (DSLR) camera); and we used CloudCompare to measure the differences between them. This study produced two noteworthy findings: First, volumetric differencing reveals that short-term changes in boulder deposits can be larger than expected, and that frequent monitoring can reveal not only the scale but the complexities of boulder transport in this setting. This is a valuable addition to our growing understanding of coastal boulder deposits. Second, SfM models generated by different imaging hardware can be successfully compared at sub-decimeter resolution, even when one of the camera systems has substantial lens distortion. This means that older image sets, which might not otherwise be considered of appropriate quality for co-analysis with more recent data, should not be ignored as data sources in long-term monitoring studies.Despite these improvements in protocols for data collection and analysis, quantifying change via repeat photogrammetry remains a challenge, generally requiring manipulation of digital terrain models (DTMs) using Geographic Information Systems (GIS) [45,46]. But recent innovations in 3D differencing software, as implemented in the open-source package CloudCompare (www.danielgm.net/cc/) enable rapid, objective, and replicable quantitative differencing [47]. CloudCompare is a cross-platform 3D point cloud and mesh processing package, which provides a suite of features for direct comparison of dense point clouds (>10 million points) and meshes on standard consumer computer hardware [48,49]. Accessibility and ease of use make CloudCompare an attractive tool, and it is applied increasingly in a variety of fields, including mapping [50,51], archaeology [52,53], and geomorphology [54][55][56][57].Another issue relevant to long term monitoring studies is how to deal with repeat imagery captured using different kinds of hardware, with different resolutions and/or distortion levels. The ultra-wide-angle (fisheye) lenses mounted on the popular consumer camera brand GoPro capture a~120 • field of view, but have barrel distortion due to their short focal length. Despite their limitations, GoPro cameras are popular tools for acquiring UAV imagery [24,31,[58][59][60], they are relatively inexpensive, are light enou...

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

Cited by 47 publications

References 133 publications

Megagravel deposits on the west coast of Ireland show the impacts of severe storms

Megagravel deposits on the west coast of Ireland show the impacts of severe storms

Storm-Induced Boulder Displacements: Inferences from Field Surveys and Hydrodynamic Equations

Measuring Change Using Quantitative Differencing of Repeat Structure-From-Motion Photogrammetry: The Effect of Storms on Coastal Boulder Deposits

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