High-resolution monitoring of wave transformation in the surf zone using a LiDAR scanner array

Martins, Kévin; Blenkinsopp, Chris; Power, Hannah E.; Bruder, Brittany; Puleo, Jack A.; Bergsma, Erwin W. J.

doi:10.1016/j.coastaleng.2017.07.007

Cited by 52 publications

(44 citation statements)

References 17 publications

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“…The present study uses LiDAR data collected during the field experiments performed at Saltburn‐by‐the‐Sea, UK (see Figure a for location) during April 2016 (Martins et al, ). The field experiments and the raw data processing are described in these two references, but some basic information is repeated here.…”

Section: Methodsmentioning

confidence: 99%

“…The surface roller properties presented in this paper are extracted from individual broken waves that are tracked in the inner surf zone using the algorithms developed in Martins et al (2016Martins et al ( , 2017aMartins et al ( , 2017bMartins et al ( , 2017c. The tracking works by detecting the wave crests as maxima in the surface elevation time series.…”

Section: Wave-by-wave Analysis: Extraction Of Roller Propertiesmentioning

confidence: 99%

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Energy Dissipation in the Inner Surf Zone: New Insights From LiDAR‐Based Roller Geometry Measurements

et al. 2018

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The spatial and temporal variation of energy dissipation rates in breaking waves controls the mean circulation of the surf zone. As this circulation plays an important role in the morphodynamics of beaches, it is vital to develop better understanding of the energy dissipation processes in breaking and broken waves. In this paper, we present the first direct field measurements of roller geometry extracted from a LiDAR data set of broken waves to obtain new insights into wave energy dissipation in the inner surf zone. We use a roller model to show that most existing roller area formulations in the literature lead to considerable overestimation of the wave energy dissipation, which is found to be close to, but smaller than, the energy dissipation in a hydraulic jump of the same height. The role of the roller density is also investigated, and we propose that it should be incorporated into modified roller area formulations until better knowledge of the roller area and its link with the mean roller density is acquired. Finally, using previously published results from deepwater wave breaking studies, we propose a scaling law for energy dissipation in the inner surf zone, which achieves satisfactory results at both the time‐averaged and wave‐by‐wave scales.

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Section: Methodsmentioning

confidence: 99%

Section: Wave-by-wave Analysis: Extraction Of Roller Propertiesmentioning

confidence: 99%

Energy Dissipation in the Inner Surf Zone: New Insights From LiDAR‐Based Roller Geometry Measurements

et al. 2018

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“…The use of the fraction of wave breaking pattern L Hs /24 assessed overall good results at all five sites, although it is worth noting that at the case study beach slope ranged between 0.005 and 0.035, and topography measurements were not available at the additional four sites. In this perspective, progresses about the hydrodynamic properties and dependences of L Hs may be investigated, for instance, by LiDAR technique, which can provide high resolution data of wave transformation [50,51] and easily coupled to video [47].…”

Section: Methods 2: Hs Bv24mentioning

confidence: 99%

Breaking Wave Height Estimation from Timex Images: Two Methods for Coastal Video Monitoring Systems

2020

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The breaking wave height is a crucial parameter for coastal studies but direct measurements constitute a difficult task due to logistical and technical constraints. This paper presents two new practical methods for estimating the breaking wave height from digital images collected by shore-based video monitoring systems. Both methods use time-exposure (Timex) images and exploit the cross-shore length ( L H s ) of the typical time-averaged signature of breaking wave foam. The first method ( H s b , v ) combines L H s and a series of video-derived parameters with the beach profile elevation to obtain the breaking wave height through an empirical formulation. The second method ( H s b , v 24 ) is based on the empirical finding that L H s can be associated with the local water depth at breaking, thus it can be used to estimate the breaking wave height without the requirement of local bathymetry. Both methods were applied and verified against field data collected at the Portuguese Atlantic coast over two days using video acquired by an online-streaming surfcam. Furthermore, H s b , v 24 was applied on coastal images acquired at four additional field sites during distinct hydrodynamic conditions, and the results were compared to a series of different wave sources. Achievements suggest that H s b , v method represents a good alternative to numerical hydrodynamic modeling when local bathymetry is available. In fact, the differences against modeled breaking wave height, ranging from 1 to 3 m at the case study, returned a root-mean-square-error of 0.2 m. The H s b , v 24 method, when applied on video data collected at five sites, assessed a normalized root-mean-square-error of 18% on average, for dataset of about 900 records and breaking wave height ranging between 0.1 and 3.8 m. These differences demonstrate the potential of H s b , v 24 in estimating breaking wave height merely using Timex images, with the main advantage of not requiring the beach profile. Both methods can be easily implemented as cost-effective tools for hydrodynamic applications in the operational coastal video systems worldwide. In addition, the methods have the potential to be coupled to the numerous other Timex applications for morphodynamic studies.

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“…Using this method of high frequency laser pulses, very high frequency and high spatial resolution data of various morphological and hydrodynamic features at beaches can be obtained. To date, data provided by the deployment of fixed lidar systems at the coast include a cross-shore 2D scan of the dune and dry beach profile, swash, and nearshore breaking waves [81][82][83][84][85][86][87][88]. The timescales of hydrodynamic and morphological processes that can be quantified and analyzed by these data extend from the shoreward propagation and runup at the beachface of an individual wave, through to the tide-by-tide and multi-year evolution of the subaerial beach and dunes.…”

Section: Fixed Scanning Lidarmentioning

confidence: 99%

Remote Sensing Is Changing Our View of the Coast: Insights from 40 Years of Monitoring at Narrabeen-Collaroy, Australia

2018

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Narrabeen-Collaroy Beach, located on the Northern Beaches of Sydney along the Pacific coast of southeast Australia, is one of the longest continuously monitored beaches in the world. This paper provides an overview of the evolution and international scientific impact of this long-term beach monitoring program, from its humble beginnings over 40 years ago using the rod and tape measure Emery field survey method; to today, where the application of remote sensing data collection including drones, satellites and crowd-sourced smartphone images, are now core aspects of this continuing and much expanded monitoring effort. Commenced in 1976, surveying at this beach for the first 30 years focused on in-situ methods, whereby the growing database of monthly beach profile surveys informed the coastal science community about fundamental processes such as beach state evolution and the role of cross-shore and alongshore sediment transport in embayment morphodynamics. In the mid-2000s, continuous (hourly) video-based monitoring was the first application of routine remote sensing at the site, providing much greater spatial and temporal resolution over the traditional monthly surveys. This implementation of video as the first of a now rapidly expanding range of remote sensing tools and techniques also facilitated much wider access by the international research community to the continuing data collection program at Narrabeen-Collaroy. In the past decade the video-based data streams have formed the basis of deeper understanding into storm to multi-year response of the shoreline to changing wave conditions and also contributed to progress in the understanding of estuary entrance dynamics. More recently, 'opportunistic' remote sensing platforms such as surf cameras and smartphones have also been used for image-based shoreline data collection. Commencing in 2011, a significant new focus for the Narrabeen-Collaroy monitoring program shifted to include airborne lidar (and later Unmanned Aerial Vehicles (UAVs)), in an enhanced effort to quantify the morphological impacts of individual storm events, understand key drivers of erosion, and the placing of these observations within their broader regional context. A fixed continuous scanning lidar installed in 2014 again improved the spatial and temporal resolution of the remote-sensed data collection, providing new insight into swash dynamics and the often-overlooked processes of post-storm beach recovery. The use of satellite data that is now readily available to all coastal researchers via Google Earth Engine continues to expand the routine data collection program and provide key insight into multi-decadal shoreline variability. As new and expanding remote sensing technologies continue to emerge, a key lesson from the long-term monitoring at Narrabeen-Collaroy is the importance of a regular re-evaluation of what data is most needed to progress the science.

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High-resolution monitoring of wave transformation in the surf zone using a LiDAR scanner array

Cited by 52 publications

References 17 publications

Energy Dissipation in the Inner Surf Zone: New Insights From LiDAR‐Based Roller Geometry Measurements

Energy Dissipation in the Inner Surf Zone: New Insights From LiDAR‐Based Roller Geometry Measurements

Breaking Wave Height Estimation from Timex Images: Two Methods for Coastal Video Monitoring Systems

Remote Sensing Is Changing Our View of the Coast: Insights from 40 Years of Monitoring at Narrabeen-Collaroy, Australia

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