The role of beach state and the timing of pre-storm surveys in determining the accuracy of storm impact assessments

Straub, Jessamin A.; Rodriguez, Antonio B.; Luettich, Richard A.; Moore, Laura J.; Itzkin, Michael; Ridge, Justin T.; Seymour, Alexander C.; Johnston, David W.; Theuerkauf, Ethan J.

doi:10.1016/j.margeo.2020.106201

Cited by 8 publications

(3 citation statements)

References 41 publications

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“…That assumption has received some criticism 53 . Accurate storm-impact assessments require beach slope and dune height to be constrained immediately preceding or during a storm, even when water level and wave characteristics are well constrained [54][55][56] . The difficulty in accurately predicting the modern occurrence of overwash without updated information on beach morphology suggests interpreting hurricane magnitude from a paleo-washover deposit using a modern washover as an analog could be misleading and increasingly so the further back in time a storm record extends.…”

Section: Discussionmentioning

confidence: 99%

Long-term washover fan accretion on a transgressive barrier island challenges the assumption that paleotempestites represent individual tropical cyclones

Rodriguez

Theuerkauf

Ridge

et al. 2020

Sci Rep

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Barrier island overwash occurs when the elevation of wave runup exceeds the dune crest and induces landward transport of sediment across a barrier island and deposition of a washover deposit. Washover deposition is generally attributed to major storms, is important for the maintenance of barrier island resilience to sea-level rise and is used to extend hurricane records beyond historical accounts by reconstructing the frequency and extent of washover deposits preserved in the sedimentary record. Here, we present a high-fidelity 3-year record of washover evolution and overwash at a transgressive barrier island site. During the first year after establishment, washover volume and area increased 1595% and 197%, respectively, from at least monthly overwash. Most of the washover accretion resulted from the site morphology having a low resistance to overwash, as opposed to being directly impacted by major storms. Washover deposits can accrete landward over multi-year time scales in the absence of large storms; therefore, paleotempestites can be more complex than single event beds.

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Section: Discussionmentioning

confidence: 99%

Long-term washover fan accretion on a transgressive barrier island challenges the assumption that paleotempestites represent individual tropical cyclones

Rodriguez

Theuerkauf

Ridge

et al. 2020

Sci Rep

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“…Given that wave runup and erosion during a storm is lower for wider, more gently sloping beaches (i.e., 230 Ruggiero, Holman, & Beach, 2004;Stockdon et al, 2006;Straub et al, 2020), we were interested in analyzing the separate effects of beach width on dune erosion (Figure 9). In particular, for dunes in which dune toes are aligned, beach width would be held constant for all aspect ratios and thus would not affect the outcome for erosion.…”

Section: Beach Width Effects On Dune Erosionmentioning

confidence: 99%

The Influence of Dune Aspect Ratio, Beach Width and Storm Characteristics on Dune Erosion for Managed and Unmanaged Beaches

Itzkin

Moore

Ruggiero

et al. 2020

Preprint

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Abstract. Dune height is an important predictor of dune impact during a storm event given that taller dunes have a lower likelihood of being overtopped. However, the temporal dominance of the wave collision regime, wherein significant volume loss (erosion) from the dune will occur through dune retreat without the dune being overtopped, suggests that dune width must also be considered when evaluating the vulnerability of dunes to erosion. We use XBeach, a numerical model that simulates hydrodynamic processes, sediment transport, and morphologic change during a storm, to analyze dune erosion as a function of dune aspect ratio (i.e., dune height versus dune width) for storms of varying intensity and duration. We find that low aspect ratio (low and wide) dunes lose less volume than high aspect ratio (tall and narrow) dunes during longer storms, especially if they are fronted by a narrow beach. During more intense storms, low aspect ratio dunes experience greater erosion as they are more easily overtopped than high aspect ratio dunes. In managed scenarios where sand fences are used to construct a fenced dune seaward of the existing natural dune, we find that the fenced dune effectively prevents the natural dune behind it from experiencing any volume loss until the fenced dune is sufficiently eroded, reducing the magnitude of erosion of the natural dune by up to 50 %. We also find that beach width exerts a significant influence on dune erosion; a wide beach offers the greatest protection from erosion in all circumstances regardless of dune morphology or storm characteristics. These findings suggest that efforts to maintain a wide beach may be effective at protecting coastal communities from dune loss. However, in maintaining wide beaches and dunes, the protection offered in the short-term must be considered against long-term detrimental effects of potentially limiting overwash fluxes, which are critical to maintaining island elevation as sea level rises.

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“…In a study on the effects of dune grass removal to restore Western snowy plover habitats in the PNW, Biel et al (2017) used XBeach (Roelvink et al, 2009) to explore dune erosion and found that where beachgrasses were removed, dunes maintained a lower elevation and were predicted to be more vulnerable to erosion compared to foredunes where beachgrasses were not removed and grew to a stable elevation. Beach nourishment may also be used to widen the beach (and decrease its slope), limiting wave impacts to the dune and stimulating dune growth (e.g., Van Puijenbroek et al, 2017;Ruggiero et al, 2001Ruggiero et al, , 2004.…”

Section: Introductionmentioning

confidence: 99%

The relative influence of dune aspect ratio and beach width on dune erosion as a function of storm duration and surge level

et al. 2021

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Abstract. Dune height is an important predictor of impact during a storm event given that taller dunes have a lower likelihood of being overtopped than shorter dunes. However, the temporal dominance of the wave collision regime, wherein volume loss (erosion) from the dune occurs through dune retreat without overtopping, suggests that dune width must also be considered when evaluating the vulnerability of dunes to erosion. We use XBeach, a numerical model that simulates hydrodynamic processes, sediment transport, and morphologic change, to analyze storm-induced dune erosion as a function of dune aspect ratio (i.e., dune height versus dune width) for storms of varying intensity and duration. We find that low aspect ratio (low and wide) dunes lose less volume than high aspect ratio (tall and narrow) dunes during longer and more intense storms when the beach width is controlled for. In managed dune scenarios, where sand fences are used to construct a “fenced” dune seaward of the existing “natural” dune, we find that fenced dunes effectively prevent the natural dune behind them from experiencing any volume loss until the fenced dune is sufficiently eroded, reducing the magnitude of erosion of the natural dune by up to 50 %. We then control for dune morphology to assess volume loss as a function of beach width and confirm that beach width exerts a significant influence on dune erosion; a wide beach offers the greatest protection from erosion in all circumstances while the width of the dune determines how long the dune will last under persistent scarping. These findings suggest that efforts to maintain a wide beach may be effective at protecting coastal communities from dune loss. However, a trade-off may exist in maintaining wide beaches and dunes in that the protection offered in the short-term must be considered in concert with potentially long-term detrimental effects of limiting overwash, a process which is critical to maintaining island elevation as sea level rises.

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The role of beach state and the timing of pre-storm surveys in determining the accuracy of storm impact assessments

Cited by 8 publications

References 41 publications

Long-term washover fan accretion on a transgressive barrier island challenges the assumption that paleotempestites represent individual tropical cyclones

Long-term washover fan accretion on a transgressive barrier island challenges the assumption that paleotempestites represent individual tropical cyclones

The Influence of Dune Aspect Ratio, Beach Width and Storm Characteristics on Dune Erosion for Managed and Unmanaged Beaches

The relative influence of dune aspect ratio and beach width on dune erosion as a function of storm duration and surge level

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