Does vegetation accelerate coastal dune erosion during extreme events?

Feagin, Rusty A.; Innocenti, Rachel A.; Bond, Hailey; Wengrove, Meagan; Huff, Thomas P.; Lomónaco, Pedro; Tsai, Benjamin; Puleo, Jack A.; Pontiki, Maria; Figlus, Jens; Chávez, Valeria; Silva, Rodolfo

doi:10.1126/sciadv.adg7135

Cited by 20 publications

(9 citation statements)

References 33 publications

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“…Hinsdale Wave Research Laboratory, Oregon State University, Corvallis, OR, USA, to obtain simultaneous measurements of wave forcing, currents, sediment transport, and morphodynamics. A pre‐storm beach profile from Mantoloking, New Jersey, USA, typical of many sandy beaches (Luijendijk et al., 2018) was simulated (Feagin et al., 2023). The beach profile was constructed after applying scaling laws (Equations 1 and 2, Van Rijn et al., 2011) using natural sand sourced from South Beach in Newport, Oregon.…”

Section: Methodsmentioning

confidence: 99%

Geomorphic Response of a Coastal Berm to Storm Surge and the Importance of Sheet Flow Dynamics

Pontiki,

Puleo,

Bond

et al. 2023

JGR Earth Surface

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During a storm, as the beach profile is impacted by increased wave forcing and rapidly changing water levels, sand berms may help mitigate erosion of the backshore. Yet, the mechanics of berm morphodynamics have not been fully described. In this study, twenty‐six trials were conducted in a large wave flume to explore the response of a near‐prototype berm to scaled storm conditions. Sensors were used to quantify hydrodynamics, sheet flow dynamics, and berm evolution. Results indicate that berm overtopping, and offshore sediment transport were key processes causing berm erosion. During the morphological evolution of the beach profile, two sand bars were formed offshore that attenuated subsequent wave energy. The landward extent of that energy was confined to the seaward foreshore inhibiting inundation of the backshore. Net offshore‐directed transport was dominant when infragravity motions increased in the swash zone. Conversely, the influence of incident‐band motions on sediment transport was relatively greater in the inner‐surf zone. Near‐bed flow velocities and sheet flow layer thicknesses were larger in the swash zone than in the inner‐surf zone. This paper also provides a valuable analysis between morphology‐estimated total sediment transport rates and rates derived from in situ measurements. Sheet flow dynamics dominated foreshore cross‐shore sediment processes constituting the largest portion of the total sediment transport load throughout the berm erosion.

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Section: Methodsmentioning

confidence: 99%

Geomorphic Response of a Coastal Berm to Storm Surge and the Importance of Sheet Flow Dynamics

Pontiki,

Puleo,

Bond

et al. 2023

JGR Earth Surface

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“…Examples of process controls include an increase in wave energy, a change in the angle of wave approach (van Bemmelen et al., 2020), or elevated water levels (Sherman & Nordstrom, 1985). Examples of structural controls include beach nourishments (van Bemmelen et al., 2020), frozen beaches, vehicle tracks (Sherman & Nordstrom, 1985), or vegetation (Feagin et al., 2023). Structural controls like the transition from beach to foredune in the beach profile may also cause scarp formation when exposed to energetic wave conditions.…”

Section: Introductionmentioning

confidence: 99%

Beach and Dune Subsurface Hydrodynamics and Their Influence on the Formation of Dune Scarps

Bond,

Wengrove,

Puleo

et al. 2023

JGR Earth Surface

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Erosive beach scarps influence beach vulnerability, yet their formation remains challenging to predict. In this study, a 1:2.5 scale laboratory experiment was used to study the subsurface hydrodynamics of a beach dune during an erosive event. Pressure and moisture sensors buried within the dune were used both to monitor the water table and to examine vertical pressure gradients in the upper 0.3 m of sand as the slope of the upper beach developed into a scarp. Concurrently, a line‐scan lidar tracked swash bores and monitored erosion and accretion patterns along a single cross‐shore transect throughout the experiment. As wave conditions intensified, a discontinuity in the slope of the dune formed; the discontinuity grew steeper and progressed landward at the same rate as the R2% runup extent until it was a fully formed scarp with a vertical face. Within the upper 0.15 m of the partially saturated sand, upward pore pressure gradients were detected during backwash, influencing the effective weight of sand and potentially contributing to beachface erosion. The magnitude and frequency of the upward pressure gradients increased with deeper swash depths and with frequency of wave interaction, and decreased with depth into the sand. A simple conceptual model for scarp formation is proposed that incorporates observations of upward‐directed pressure gradients from this study while providing a reference for future studies seeking to integrate additional swash zone sediment transport processes that may impact scarp development.

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“…That is, depending on dune morphology and winter conditions, large dunes can erode more substantially than smaller dunes (van Puijenbroek, Nolet, et al, 2017), which we found in our experiment. While vegetation is generally found to reduce erosion in winter, the extent to which this happens depends on the morphological characteristics of the species and environmental conditions (e.g., wind and wave conditions) (Feagin et al, 2023;Innocenti et al, 2021;Maximiliano-Cordova et al, 2019). Since sand couch has a relatively dispersed shoot organization and short shoots, it is less effective at reducing erosion than, for example, marram grass (van Puijenbroek, Nolet, et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

“…While in general vegetation is expected to reduce erosion, it has recently been found that in extreme storm conditions vegetation can increase erosion (Feagin et al, 2023). Moreover, I found that larger dunes formed by sand couch eroded more than smaller dunes in winter (Chapter 4).…”

Section: Effects Of Global Change On Early Dune Developmentmentioning

confidence: 96%

“…Therefore, the clonal expansion strategy not only determines their sediment capturing ability but also partly determines their resistance to erosion. Sand couch, with its dispersed growth, likely leaves the dune body more susceptible to erosion than marram grass that grows more dense (Chapter 2, Feagin et al, 2023;Innocenti et al, 2021;Maximiliano-Cordova et al, 2019).…”

Section: Effects Of Global Change On Early Dune Developmentmentioning

confidence: 99%

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A sandy symphony

Lammers

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The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license. More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverneamendment.made (infra)structure (Feagin et al., 2005;. Furthermore, extreme climatic events, such as drought, storms or heat waves, could affect species interactions and subsequently ecosystem structure.To halt or reverse losses of ecosystems, and their vital functions, there is increasing interest in restoration of these ecosystems (Silliman et al., 2015;Temmink et al., 2020;van der Heide et al., 2021). There are some common restoration practices that happen in many vegetated coastal ecosystems, for example, increasing soil stability and sediment capture by creating structures such as brushwood check dams, and/or planting of ecosystem engineering vegetation (Bakker et al., 2002;Bridges et al., 2018;Ministerie V&W, 2000). While other practices are system specific, such as sand suppletion on sandy shores that are in an erosive state (Ministerie V&W, 2000). Classically, planting of vegetation is done in competition limiting arrays. However, in physically stressful environments neighbors can ameliorate physical stress, increasing survival success (Bertness & Hacker, 1994;Bruno et al., 2003). Over the last decades, inclusion of facilitation in restoration by clumped planting or mimicking larger plant patches gained interest Temmink et al., 2020). However, the success of these novel facilitationpromoting designs is context dependent (Fischman et al., 2019;Woods et al., 2023). The study system -Coastal dunesCoastal dunes occur along sandy shores, which make up about one-third of the world's coastline . They provide many services such as flood protection, drinking water and recreation (Martínez et al., 2007;. At locations with a positive sand budget and a dominant onshore wind direction, dune areas can expand and develop . This thesis focusses on the emergence and early development of the dunes, from beach to embryonic dunes, which depends on establishment and growth of dune grasses. Early dune development -Beach to foredunesGenerally, different developmental stages of dunes can be found on a cross-shore gradient from beach to dunes, corresponding to the biogeomorphic succession and primary succession gradient (Figure 1.1 & 1.3). Closest to the shore are bare beach areas that are frequently overwashed (i.e., the physical phase in biogeomorphic succession, Figure 1.1). From the sea, sediment ends up on the beach through currents and waves (Fredsoe & Deigaard, 1992;Swift, 1976). If the sediment dries

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Does vegetation accelerate coastal dune erosion during extreme events?

Cited by 20 publications

References 33 publications

Geomorphic Response of a Coastal Berm to Storm Surge and the Importance of Sheet Flow Dynamics

Geomorphic Response of a Coastal Berm to Storm Surge and the Importance of Sheet Flow Dynamics

Beach and Dune Subsurface Hydrodynamics and Their Influence on the Formation of Dune Scarps

A sandy symphony

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