Controls on the geomorphic response of beach-dune systems to water level rise

Davidson‐Arnott, Robin; Bauer, Bernard O.

doi:10.1016/j.jglr.2021.05.006

Cited by 31 publications

(13 citation statements)

References 148 publications

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“…This occurred because little to no sand was returned to the beach between erosion and storm periods to build a scarp fill ramp (cf. Davidson‐Arnott et al, 2018; Davidson‐Arnott & Bauer, 2021), and perhaps because the dune height was low and therefore flow acceleration and aeolian erosion of the scarp was minimal. Once a large scarp was formed in the older transgressive dunes, aeolian erosion, cannabilization and translation could occur.…”

Section: Discussionmentioning

confidence: 99%

Review and direct evidence of transgressive aeolian sand sheet and dunefield initiation

Hesp

DaSilva

Silva

et al. 2022

Earth Surf Processes Landf

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The multiple hypotheses which exist to explain the initiation of transgressive aeolian sand sheets and dunefields, are reviewed and discussed. Direct evidence supporting many of these hypotheses is largely lacking. In South Australia, the Younghusband Peninsula coastal barrier extends ~180 km and predominantly comprises transgressive and parabolic dunefields. The 42 Mile Crossing area on the barrier is undergoing significant erosion at variable rates of 0.5 to 5.0 m/yr, and a new transgressive aeolian sand sheet has rapidly developed in ~1 year and is extending landwards at an average rate of 13 m/yr. This research provides unequivocal evidence that large‐scale shoreline and dunefield erosion does lead to the development of a new transgressive aeolian sand sheet (and eventual dunefield) phase thereby demonstrating an initiation mechanism that is likely linked to future sea level rise and climate change. We also show that the initiation process, and, in particular, the subsequent rate of sand sheet transgression occurs at an incredibly rapid rate (+100 m in 8 years). Plain Language Summary Coastal sand dunes border many of the world's coastlines and are highly adapted to local climate and conditions. How coastal dunes transition from predominantly vegetated and stable systems to wind‐blown sand sheets and dunefields transgressing prior terrain is a research area of pressing relevance due to forecasts of sea level rise and climate change. The factors or triggers that are considered to initiate transgressive aeolian sand sheets and dunefields are reviewed. The formation and evolution of a new transgressive aeolian sand sheet phase triggered by large‐scale shoreline erosion in South Australia is presented. According to the results from historical and satellite images, local shoreline erosion began in the late 1970s and has continued at highly variable rates. We show that once the foredune was removed, the high scarp created by wave erosion of the relict, vegetated transgressive dunefield destabilized and was then eroded by wind processes leading to the rapid development of a transgressive aeolian sand sheet. The initiation and evolution of the sand sheet provides an excellent example of how dunefields might respond to future sea level rise and climate change.

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Section: Discussionmentioning

confidence: 99%

Review and direct evidence of transgressive aeolian sand sheet and dunefield initiation

Hesp

DaSilva

Silva

et al. 2022

Earth Surf Processes Landf

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“…This overly simplistic approach, which only considers retreat from rising water levels has been criticized by a number of researchers (e.g., Cooper and Pilkey, 2004;Ranasinghe et al, 2012). Alternative approaches to account for the cross-shore movement of the shoreline due to changes in water levels have also been discussed (e.g., Wolinsky and Murray, 2009;Gutierrez et al, 2011;Rosati et al, 2013;D'Anna et al, 2021b;Davidson-Arnott and Bauer, 2021;McCarroll et al, 2021).…”

Section: Cross-shore Modelsmentioning

confidence: 99%

Challenges and Opportunities in Coastal Shoreline Prediction

Splinter

Coco

2021

Front. Mar. Sci.

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Sandy beaches comprise approximately 31% of the world's ice-free coasts. Sandy coastlines around the world are continuously adjusting in response to changing waves and water levels at both short (storm) and long (climate-driven, from El-Nino Southern Oscillation to sea level rise) timescales. Managing this critical zone requires robust, advanced tools that represent our best understanding of how to abstract and integrate coastal processes. However, this has been hindered by (1) a lack of long-term, large-scale coastal monitoring of sandy beaches and (2) a robust understanding of the key physical processes that drive shoreline change over multiple timescales. This perspectives article aims to summarize the current state of shoreline modeling at the sub-century timescale and provides an outlook on future challenges and opportunities ahead.

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“…Although a taller foredune morphology (especially one with large volume and width) might seemingly reduce coastal vulnerability by providing improved flood protection, the long-term effectiveness of foredunes as barriers depends on their ability to maintain their form in the face of rising water level impacts and increasing severity and frequency of coastal storms(Davidson-Arnott & Bauer, 2021). As such, foredune resilienceor the ability of a foredune to rebuild and recover its morphodynamic shape and function following erosive eventsis perhaps a more important consideration than simple dune morphometric attributes controlled by vegetation canopies alone.Although our study results are short term and do not inform dune recovery, they do indicate that sand deposition occurs preferentially at the dune toe and lower stoss slope when there is vegetation cover on the stoss slope, leading to seaward progradation of the dune form during inter-storm intervals.…”

mentioning

confidence: 99%

Air flow and sediment transport dynamics on a foredune with contrasting vegetation cover

Bauer

Hesp

Smyth

et al. 2022

Earth Surf Processes Landf

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Wind flow and sediment transport across a northern California beach‐foredune system with two adjacent vegetation types are examined for the same incident wind conditions. The invasive Ammophila arenaria was taller (c. 1 m) with denser coverage than the neighbouring Elymus mollis alliance canopy (c. 0.65 m), which consisted of a variety of interspersed native plants. Wind flow was measured with rotating cup and sonic anemometry, while sediment transport was measured using laser particle counters. Wind speed profiles over the two canopies were significantly different because of differing vegetation height, coverage density, and stem stiffness. In both cases, there was a lower zone of semi‐stagnant air (below about 0.3 m) that transitioned upward to a shear zone comprising the upper part of the canopy and immediately above. The shear zone above the Elymus canopy was relatively thin (confined to 0.3–0.5 m above‐ground) whereas the shear zone in the Ammophila canopy was thicker extending from a height of about 0.5h (h is average plant height) to about 1.5h. Vertical profiles of Reynolds shear stress (RSS) and turbulence kinetic energy (TKE) are consistent with the shear layer structure over these two contrasting vegetation canopies. The degree of topographically‐forced and vegetation‐enhanced flow steering was significant, with Ammophila strongly shifting the highly oblique (55°) incident wind to essentially shore‐perpendicular trajectories. In comparison, the shore‐perpendicular steering effect was not as pronounced for the Elymus canopy. Sediment transport intensity on the beach was continuous, but decreased progressively to the dune toe, and then dropped to essentially zero once the vegetation canopy was encountered (on the stoss slope). Overall, the study illustrates the significant differences in wind flow and turbulence conditions that may occur in contrasting plant canopies on foredunes, suggesting that greater attention needs to be placed on vegetation roughness characteristics in models of foredune morphodynamics and sediment transport potential.

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Controls on the geomorphic response of beach-dune systems to water level rise

Cited by 31 publications

References 148 publications

Review and direct evidence of transgressive aeolian sand sheet and dunefield initiation

Review and direct evidence of transgressive aeolian sand sheet and dunefield initiation

Challenges and Opportunities in Coastal Shoreline Prediction

Air flow and sediment transport dynamics on a foredune with contrasting vegetation cover

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