Inundation of a barrier island (Chandeleur Islands, Louisiana, USA) during a hurricane: Observed water‐level gradients and modeled seaward sand transport

Sherwood, Christopher R.; Long, Joseph W.; Dickhudt, Patrick J.; Dalyander, P. Soupy; Thompson, David M.; Plant, Nathaniel G.

doi:10.1002/2013jf003069

Cited by 66 publications

(66 citation statements)

References 83 publications

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“…Large‐scale and local pressure gradients can oppose each other at times (Engelstad et al, ). Further, higher water levels in the back‐barrier basin than on the ocean side were observed to generate seaward flows (Engelstad et al, ; Hoekstra et al, ; Sherwood et al, ), which was also found in modeling studies (Harter & Figlus, ; Sherwood et al, ; Wesselman et al, ). In a combined observation‐modeling study of barrier island inundation in the Gulf of Mexico, Sherwood et al () found that the seaward directed water level gradient resulted in the deposition of a significant amount of sediment on the ocean side.…”

Section: Introductionmentioning

confidence: 72%

“…Further, higher water levels in the back‐barrier basin than on the ocean side were observed to generate seaward flows (Engelstad et al, ; Hoekstra et al, ; Sherwood et al, ), which was also found in modeling studies (Harter & Figlus, ; Sherwood et al, ; Wesselman et al, ). In a combined observation‐modeling study of barrier island inundation in the Gulf of Mexico, Sherwood et al () found that the seaward directed water level gradient resulted in the deposition of a significant amount of sediment on the ocean side. A modeling study by McCall et al () suggested that higher water levels in the back‐barrier relative to the surge levels in the ocean increased back‐barrier deposition and reduced deposition in the basin due to a decrease in flow velocity.…”

Section: Introductionmentioning

confidence: 72%

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Sand Suspension and Transport During Inundation of a Dutch Barrier Island

et al. 2018

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Overwash and inundation of barrier islands transport large amounts of sediment landward, which could potentially increase the aggradation of these islands in times of sea level rise. However, not much is known about the detailed processes of sediment suspension and transport during inundation. Here we analyze field data of suspended sediment, water levels, waves, and currents which were collected during five inundation events on a barrier island in the Netherlands. We found that depth‐integrated suspended sand concentrations and cross‐shore sand transport showed high variability during and between inundation events at our location, where 80% of the combined transport from all inundation events was completed before high tide. This is primarily caused by variations in cross‐shore flow velocities which were strongest (up to 1.2 m/s onshore) before high tide. However, episodically high depth‐integrated suspended sand concentrations (defined as >2kg/m2) were observed on infragravity time scales (∼20–200 s), suggesting that the contribution of infragravity waves to the combined bed shear stresses of waves and currents was important. High contributions of infragravity waves to the transport coincided with observed bore‐like wave shapes, which might partly be attributed to higher short waves riding and suspending sediment at the position of the crest. Two transport regimes were thus found to govern the transport during inundation: a flow‐driven regime when flow velocities were high (>0.5 m/s) and the ratio of infragravity wave and current related shields numbers was below 0.11 and an episodic regime when this ratio exceeded 0.11.

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Section: Introductionmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 72%

Sand Suspension and Transport During Inundation of a Dutch Barrier Island

et al. 2018

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“…Sherwood et al. () also found reversed currents as a result of higher back‐barrier water levels for the Chandeleur Islands in Louisiana, while Hoekstra et al. () concluded as well that water can reach Schiermonnikoog from both sides of the island.…”

Section: Discussionmentioning

confidence: 99%

“…, ; Sherwood et al. , ). The short waves (<20 s) move to the shore in wave groups, creating infragravity (IG) waves with a period of 20–200 s (Battjes, ; Herbers et al.…”

Section: Introductionmentioning

confidence: 99%

The effect of tides and storms on the sediment transport across a Dutch barrier island

Wesselman

Winter

Engelstad

et al. 2017

Earth Surf Processes Landf

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Under natural conditions, barrier islands might grow vertically and migrate onshore under the influence of long‐term sea level rise. Sediment is transported onshore during storm‐induced overwash and inundation. However, on many Dutch Wadden Islands, dune openings are closed off by artificial sand‐drift dikes that prevent the influx of sediment during storms. It has been argued that creating openings in the dune row to allow regular flooding on barrier islands can have a positive effect on the sediment budget, but the dominant hydrodynamic processes and their influence on sediment transport during overwash and inundation are unknown. Here, we present an XBeach model study to investigate how sediment transport during overwash and inundation across the beach of a typical mesotidal Wadden Sea barrier island is influenced by wave, tide and storm surge conditions. Firstly, we validated the model XBeach with field data on waves and currents during island inundation. In general, the XBeach model performed well. Secondly, we studied the long‐term sediment transport across the barrier island. We distinguished six representative inundation classes, ranging from frequently occurring, low‐energy events to infrequent, high‐energy events, and simulated the hydrodynamics and sediment transport during these events. An analysis of the model simulations shows that larger storm events cause larger cross‐shore sediment transport, but the net sediment exchange during a storm levels off or even becomes smaller for the largest inundation classes because it is counteracted by larger mean water levels in the Wadden Sea that oppose or even reverse sediment transport during inundation. When taking into account the frequency of occurrence of storms we conclude that the cumulative effect of relatively mild storms on long‐term cross‐shore sediment transport is much larger than that of the large storm events. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.

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“…Just as important as understanding the potential for on--or offshore sediment transport between the upper and lower shoreface (Aagaard, 2014) is an understanding of how changes in the upper shoreface are morphologically communicated offshore. The myriad processes that can change coastlines, from overwash (Donnelly et al, 2006;Sherwood et al, 2014) to alongshore sediment transport gradients (Ashton and Murray, 2006a) or even human activities such as beach nourishment (Jin et al, 2013), motivate a better understanding of how the shoreface behaves as a morphologic unit. The focus of this study is the development of a formulation for the long--term morphodynamic evolution of a sandy wave--dominated shoreface.…”

Section: Introductionmentioning

confidence: 99%

Investigating the evolution and formation of coastlines and the response to sea-level rise

Ortiz¹

2015

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To understand how waves and sea level shape sandy shoreline profiles, I use existing energetics-based equations of cross-shore sediment flux to describe shoreface evolution and equilibrium profiles, utilizing linear Airy wave theory instead of shallow-water wave assumptions. By calculating a depth-dependent characteristic diffusivity timescale, I develop a morphodynamic depth of shoreface closure for a given time envelope, with depth increasing as temporal scale increases. To assess which wave events are most important in shaping the shoreface in terms of occurrence and severity, I calculate the characteristic effective wave conditions for both cross-shore and alongshore shoreline evolution. Extreme events are formative in the cross-shore shoreface evolution, while alongshore shoreline evolution scales linearly with the mean wave climate. Bimodal distributions of weighted wave heights are indicative of a site impacted more frequently by tropical storms rather than extra-tropical storms.To understand how offshore wave climate and underlying geometry of a carbonate reef platform shapes evolution of atolls, I simulate the hydrodynamics of a simplified reef flat, using XBeach, a two-dimensional model of infragravity wave propagation. The reef flat self-organizes to a specific width and water depth depending on the offshore wave climate and characteristics of the available sediment. Formation of a sub-aerial landmass, like a motu, can be initiated by a change in offshore wave climate (like a storm), which can create a nucleation site from mobilization and deposition of coarse sediment on the reef flat. Once a motu is present, the shoreline should prograde until reaching a critical reef-flat width. Our conceptual model of reefflat evolution and motu formation is governed by understanding the hydrodynamics of the system and subsequent response of sediment transport. 4 Chapter 1 -IntroductionClimate change has many diverse and severe impacts on our planet, including accelerated rates of sea-level rise. Over the past twentieth century, eustatic sea level rose around 1.5 -2.0 mm/yr (IPCC, 2013; Cazenave et al., 2014; Hay et al., 2015), and predicted rates of eustatic sealevel could far exceed 5 mm/yr in by the end of coming century (IPCC, 2013;Horton et al., 2014;Kopp et al., 2014). Understanding the response of coastal systems to increased rates of sea-level rise is important; 10% of the world's population lives in the Low Elevation CoastalZone (IPCC, 2014; Wong et al., 2014). My research has focused on understanding the processes that shape different coastal systems and how these systems evolve. I am interested in the response of coastal sandy and carbonate sedimentary systems to changes in sea level and predicting how future climate might impact coastal evolution.Geomorphology is the study of landscape evolution through time: by understanding the processes that shape the landscape, it is possible to predict how a landscape may respond to changing forces. Changes in sediment flux can be a primary driver of coast...

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Inundation of a barrier island (Chandeleur Islands, Louisiana, USA) during a hurricane: Observed water‐level gradients and modeled seaward sand transport

Cited by 66 publications

References 83 publications

Sand Suspension and Transport During Inundation of a Dutch Barrier Island

Sand Suspension and Transport During Inundation of a Dutch Barrier Island

The effect of tides and storms on the sediment transport across a Dutch barrier island

Investigating the evolution and formation of coastlines and the response to sea-level rise

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