Wind tunnel tests inform Ammophila planting spacing for dune management

Charbonneau, Bianca R.; Casper, Brenda B.

doi:10.31223/osf.io/aeuhb

Cited by 5 publications

(8 citation statements)

References 36 publications

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“…In a less extreme example, seasonal periods of high winds can lead to high amounts of dune grass burial, which also have the effect of decreasing the canopy cover during the times of year when the most aeolian‐driven morphological development occurs. Our model for

L_{D}

and the observations of Hesp et al (2019) and Charbonneau and Casper (2018) suggest that these temporary reductions in vegetation cover lead to time periods where the importance of

L_{D}

increases. Longer term modeling studies and field observations are needed to evaluate seasonal variations in

L_{D}

and resulting impacts on morphological development.…”

Section: Discussionsupporting

confidence: 69%

Observations and modeling of shear stress reduction and sediment flux within sparse dune grass canopies on managed coastal dunes

DICKEY

Wengrove

Cohn³

et al. 2023

Earth Surf Processes Landf

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Wind flow over coastal foredunes adapts to vegetation, resulting in spatial gradients in bed shear stresses that contribute to the formation of localized bedforms. Understanding, and having the capability to numerically predict, the distribution of sediment deposited within sparsely vegetated dune complexes is critical for quantifying the ecological, protective, and economic benefits of dune management activities. Data from wind tunnel experiments have indicated that there is a spatial lag from the canopy leading edge to a downwind location where sediment deposition first occurs. The length scale of this deposition lag is further quantified here using new field measurements of aeolian sediment transport across sparsely vegetated managed dune systems in Oregon, USA. We develop a deposition lag length scale parameter using both lab and this new field data and then incorporate this parameter into the process‐based aeolian sediment transport model, Aeolis, which also includes a new far‐field shear stress coupler. Results from numerical simulations suggest that the spatial deposition lag effect is significant for model skill in sparsely vegetated dunes. We observe with field and laboratory observations that, as canopy density increases, the length of the deposition lag decreases. As such, within the model framework the implementation of the deposition lag length does not affect the results of models of coastal dune geomorphological evolution within higher density canopies. Dune canopy density can vary due to natural (e.g., storm overwash, burial, die‐off) or anthropogenic (e.g., managed plantings, dune grading) processes.

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L_{D}

and the observations of Hesp et al (2019) and Charbonneau and Casper (2018) suggest that these temporary reductions in vegetation cover lead to time periods where the importance of

L_{D}

increases. Longer term modeling studies and field observations are needed to evaluate seasonal variations in

L_{D}

and resulting impacts on morphological development.…”

Section: Discussionsupporting

confidence: 69%

Observations and modeling of shear stress reduction and sediment flux within sparse dune grass canopies on managed coastal dunes

DICKEY

Wengrove

Cohn³

et al. 2023

Earth Surf Processes Landf

View full text Add to dashboard Cite

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“…In addition, dune grass species differ in the average number of shoots produced per rhizome, a factor that varies from a single shoot to multiple shoots. These two features, when combined, produce species-specific differences in aboveground shoot density and spacing (i.e., from evenly spaced to clumped) and differences in the relative amount of lateral versus vertical spread across the foredune, all of which directly affect sand capture and dune shape [4,5,[10][11][12]18,19,24]. Overall, these studies show that sparse, evenly spaced, and/or laterally spreading growth forms produce shorter and wider dunes compared to dense, clumped, and/or vertical growing forms, which create taller, steeper, and narrower foredunes.…”

Section: Introductionmentioning

confidence: 99%

Species-Specific Functional Morphology of Four US Atlantic Coast Dune Grasses: Biogeographic Implications for Dune Shape and Coastal Protection

et al. 2019

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Coastal dunes arise from feedbacks between vegetation and sediment supply. Species-specific differences in plant functional morphology affect sand capture and dune shape. In this study, we build on research showing a relationship between dune grass species and dune geomorphology on the US central Atlantic Coast. This study seeks to determine the ways in which four co-occurring dune grass species (Ammophila breviligulata, Panicum amarum, Spartina patens, Uniola paniculata) differ in their functional morphology and sand accretion. We surveyed the biogeography, functional morphology, and associated change in sand elevation of the four dune grass species along a 320-kilometer distance across the Outer Banks. We found that A. breviligulata had dense and clumped shoots, which correlated with the greatest sand accretion. Coupled with fast lateral spread, it tends to build tall and wide foredunes. Uniola paniculata had fewer but taller shoots and was associated with ~42% lower sand accretion. Coupled with slow lateral spread, it tends to build steeper and narrower dunes. Panicum amarum had similar shoot densities and associated sand accretion to U. paniculata despite its shorter shoots, suggesting that shoot density is more important than morphology. Finally, we hypothesize, given the distributions of the grass species, that foredunes may be taller and wider and have better coastal protection properties in the north where A. breviligulata is dominant. If under a warming climate A. breviligulata experiences a range shift to the north, as appears to be occurring with U. paniculata, changes in grass dominance and foredune morphology could make for more vulnerable coastlines.

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“…Since these experiments use marram-grass surrogates like artificial cylinders, stem bundles or even dead plant material, they do not represent the realized morphology of dune vegetation, which precludes further progress in understanding the feedbacks between sediment capture and plant growth. Clusters of tillers enhance sand deposition by lowering wind speed and associated shear stress within the vegetation canopy (Charbonneau and Casper, 2018). Larger tussocks are able to capture more sand, thereby imposing a positive feedback on their own development and vigor.…”

Section: Dynamic Feedbacks Between Aeolian Fluxes and Vegetation Developmentmentioning

confidence: 99%

Biomorphogenic Feedbacks and the Spatial Organization of a Dominant Grass Steer Dune Development

et al. 2021

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Nature-based solutions to mitigate the impact of future climate change depend on restoring biological diversity and natural processes. Coastal foredunes represent the most important natural flood barriers along coastlines worldwide, but their area has been squeezed dramatically because of a continuing urbanization of coastlines, especially in Europe. Dune development is steered by the development of vegetation in interaction with sand fluxes from the beach. Marram grass (Calamagrostis arenaria, formerly Ammophila arenaria) is the main dune building species along most European coasts, but also in other continents where the species was introduced. Engineering of coastal dunes, for instance by building dunes in front of dikes, needs to be based on a solid understanding of the species’ interactions with the environment. Only quantitative approaches enable the further development of mechanistic models and coastal management strategies that encapsulate these biomorphogenic interactions. We here provide a quantitative review of the main biotic and physical interactions that affect marram grass performance, their interactions with sand fluxes and how they eventually shape dune development. Our review highlights that the species’ spatial organization is central to dune development. We further demonstrate this importance by means of remote sensing and a mechanistic model and provide an outlook for further research on the use of coastal dunes as a nature-based solution for coastal protection.

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Wind tunnel tests inform Ammophila planting spacing for dune management

Cited by 5 publications

References 36 publications

Observations and modeling of shear stress reduction and sediment flux within sparse dune grass canopies on managed coastal dunes

Observations and modeling of shear stress reduction and sediment flux within sparse dune grass canopies on managed coastal dunes

Species-Specific Functional Morphology of Four US Atlantic Coast Dune Grasses: Biogeographic Implications for Dune Shape and Coastal Protection

Biomorphogenic Feedbacks and the Spatial Organization of a Dominant Grass Steer Dune Development

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