Complex drivers of reef-fronted beach change

Mikkelsen, Anna B.; Anderson, Tiffany R.; Coats, Sloan; Fletcher, Charles H.

doi:10.1016/j.margeo.2022.106770

Cited by 4 publications

(5 citation statements)

References 75 publications

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“…Volume gains were especially notable during periods in which south swell energy flux above the identified threshold coincided with periods of trade-wind energy flux of less than 0.25 × 10 5 W/m 2 ; however, when wave energy flux exceeding the given threshold coincided with trade-wind energy flux exceeding 1 × 10 5 W/m 2 , losses in surface area and volume occurred as observed during early July. These findings are consistent with those of Mikkelsen et al (2022) [27] that identified correlations between erosional events and peaks in trade-wind swell and correlations between accretional events and increases in south swell energy flux.…”

Section: Changes In Surface Area and Volumesupporting

confidence: 91%

“…In late May, 964.2 ± 97.5 m 3 of sediment were eroded, and in September, 1233.0 ± 103.7 m 3 were lost. These findings reinforce and explain the Mikkelsen et al (2022) [27] finding that high windspeed trade winds drive accelerated erosion on the eastern beach extent and reduced accretion on the western beach end, as well as the finding that strong wind speeds alter predominant longshore and cross-shore currents.…”

Section: Trade-wind-driven Transition From Dual Cell To Single Cell B...supporting

confidence: 85%

“…Additionally, they observed a long-term east-to-west transport accompanied by cross-shore transport, with nearshore sand fields acting as both a sand source (during storm-related swell events) and sink (during non-storm periods) depending on seasonal conditions. A study of Royal Hawaiian Beach used aerial surveying and image classification methods to track changes in beach morphology [27] and found that water level variability and wave energy flux were the primary drivers of beach change through a combination of longshore and cross-shore sediment exchange.…”

Section: Surveyingmentioning

confidence: 99%

“…The data were obtained for the grid cell most proximate to the study area (21.27 • N, 157.827 • W). A proxy for wave energy flux generated by southern hemisphere swell (wave periods: 14-30 s; wave direction: 147-220 • N) and locally generated trade-wind waves (wave periods: 3-10 s; wave direction: 45-160 • N) were calculated following Mikkelsen et al (2022) [27] in which spectral measurements were obtained from offshore buoys [71,72], and energy density of the relevant frequencies and directional bins of the wave spectrum was multiplied with peak wave period [27] (Figure 5b,c).…”

Section: Shoreline Response To Wave Forcingmentioning

confidence: 99%

“…However, despite the capacity to collect data at higher (e.g., weekly, daily, etc.) temporal resolutions, there are few published studies of beach dynamics using sUASs at these frequencies [27].…”

Section: Introductionmentioning

confidence: 99%

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Weekly Small Uncrewed Aerial System Surveys, Structure from Motion, and Empirical Orthogonal Function Analyses Reveal Unique Modes of Sediment Exchange Generated by Seasonal and Episodic Phenomena: Waikīkī, Hawaiʻi

et al. 2022

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Small uncrewed aerial systems (sUASs) provide an efficient way to reveal processes controlling the morphology of sandy shorelines so that they can be more effectively managed. One of Hawaiʻi’s most popular tourist destinations, Waikīkī’s Royal Hawaiian Beach, features patterns of sediment transport driven by trade-wind activity, seasonal wave conditions, tropical storm activity, and other phenomena that make it an effective laboratory for the study of beach morphology. To evaluate the efficacy of using consumer-grade sUASs to monitor subaerial sand volume and processes that drive beach morphodynamics, we conducted weekly aerial and ground surveys from which high-resolution point clouds, digital elevation models, and orthomosaics were generated through structure from motion (SfM) photogrammetry. Our period of observation (April to November 2018) bracketed the Central Pacific hurricane season and the season of elevated southerly swell. Both phenomena are known to significantly influence sediment transport in the study area. Using empirical orthogonal function (EOF) analysis, we described combinations of single and dual littoral cell behavior generated by both longshore sediment transport and abrupt episodic fluctuations in cross-shore transport. While past studies have investigated morphological change at this location, this unique single and dual cell behavior within the greater littoral system had not been previously revealed. This study demonstrates that sUASs are capable of capturing high-resolution spatial and temporal topographic data that allow for detailed evaluation of both seasonal processes and abrupt perturbations of beach systems. These processes drive significant changes in beach area, volume, and overall beach morphology and their understanding critical to effective management in an era of sea level rise-driven change. The employed methodology was designed to be highly efficient and universally applicable to sandy shorelines whilst also being relatively inexpensive and instrumentation readily available, allowing for a more comprehensive understanding of these unique coastal environments.

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Section: Changes In Surface Area and Volumesupporting

confidence: 91%

Section: Trade-wind-driven Transition From Dual Cell To Single Cell B...supporting

confidence: 85%

Section: Surveyingmentioning

confidence: 99%

Section: Shoreline Response To Wave Forcingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations