Scaling laws for coastal overwash morphology

Lazarus, Eli D.

doi:10.1002/2016gl071213

Cited by 36 publications

(134 citation statements)

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“…) or on morphological change after a storm (e.g. Nielsen and Nielsen, ), but the underlying processes have not been studied in detail yet (Lazarus, ). One of the reasons for this is that it is difficult to measure the hydrodynamics and sediment transport during storm conditions (Donnelly et al.…”

Section: Introductionmentioning

confidence: 99%

“…The scarce studies on overwash and inundation processes at barriers in mesotidal, extra-tropical conditions focused on the influence of island geometries on the occurrence of overwash and inundation (Matias et al, 2009) or on morphological change after a storm (e.g. Nielsen and Nielsen, 2006), but the underlying processes have not been studied in detail yet (Lazarus, 2016). One of the reasons for this is that it is difficult to measure the hydrodynamics and sediment transport during storm conditions (Donnelly et al, 2006;Van Dusen et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 99%

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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“…Dune height is an important morphometric to examine the influence of framework geology on barrier island morphology, since initial patterns in dune height and dune crest elevation can persist through time (Houser, 2012;Weymer et al, 2015b;Lazarus, 2016) and determine the response of a barrier island to storms (Sallenger, 2000). Areas of tall dunes are more likely to limit washover and inundation during a storm, and instead be partially eroded from the dune and deposited on the beach and 15 nearshore (Sallenger, 2000;Houser, 2012).…”

Section: Discussionmentioning

confidence: 99%

“…Based on the combination of a variable framework geology and a dominant alongshore current it is feasible that the framework geology may influence barrier island geomorphology at discrete spatial scales and that this influence may be asymmetric. Central to this hypothesis is the idea that the modern island morphology itself is scale-dependent, which has been 15 proposed and supported by previous studies (Lazarus et al, 2011;Lazarus and Armstrong, 2015;Lazarus, 2016;Houser, 2012;Houser et al, 2015). Padre Island National Seashore (PAIS) on North Padre Island, Texas, represents an ideal location to test this hypothesis because previous studies have documented significant variability in the subsurface framework geology (Fig 1;Wernette et al, 2018;Fisk, 1959;Anderson et al, 2016;Weymer, 2016Weymer, , 2012Weymer et al, 2018) and there is substantial alongshore variation in beach and dune morphology.…”

mentioning

confidence: 85%

“…This implies that variations in the framework geology, such as paleo-channels, do not influence long-term shoreline change, but as noted, shoreline change is influenced by the alongshore variation in beach and dune morphology and the dissipative behavior of shoreline change does not negate the importance of framework geology . 5 In addition to framework geology, the alongshore variation in dune morphology is influenced by the distribution of vegetation in both space and time (Lazarus et al, 2011;Lazarus, 2016;Goldstein et al, 2017), creating a self-organized behavior that is ultimately set up by the variation in beach and dune morphology forced by the framework geology (see Houser, 2012;Weymer et al, 2015b;Stallins and Parker, 2003).…”

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confidence: 99%

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Long-range dependence in coastal framework geology: Asymmetries and implications for barrier island resiliency

Wernette

Houser

Weymer

et al. 2018

Preprint

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Barrier island transgression is influenced by the alongshore variation in beach and dune morphology, which 10 determines the amount of sediment moved landward through washover. While several studies have demonstrated how variations in dune morphology affect island response to storms, the reasons for that variation and the implications for island management remain unclear. This paper builds on previous research by demonstrating that the framework geology can influence beach and dune morphology asymmetrically alongshore. The influence of relict paleo-channels on beach and dune morphology on Padre Island National Seashore, Texas was quantified by isolating the long-range dependence (LRD) parameter 15 in autoregressive fractionally-integrated moving average (ARFIMA) models. ARFIMA models were fit across all scales and a moving window approach was used to examine how LRD varied with computational scale and location along the island. The resulting LRD matrices were plotted by latitude to place the results in context of previously identified variations in the framework geology. Results indicate that the LRD is not constant alongshore for all surface morphometrics. Many flares in the LRD plots correlate to relict infilled paleo-channels in the framework geology, indicating that the framework geology has 20 a significant influence on the morphology of PAIS. Barrier island surface morphology LRD is strongest at large paleo-channels and decreases to the north. The spatial patterns in LRD surface morphometrics and framework geology variations demonstrate that the influence of paleo-channels in the framework geology can be asymmetric where the alongshore sediment transport gradient was unidirectional during island development. The asymmetric influence of framework geology on coastal morphology has long-term implications for coastal management activities because it dictates the long-term behavior of a barrier 25island. Coastal management projects should first seek to understand how the framework geology influences coastal processes in order to more effectively balance long-term natural variability with short-term societal pressure.

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Barrier breaching versus overwash deposition: parameterizing the morphologic impact of storms on coastal barriers

Nienhuis

Heijkers

Ruessink

2021

Preprint

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Waves and water level setup during storms can create overwashing flows across barrier islands. Overwashing flows can cause erosion, barrier breaching, and inlet formation, but their sediments can also be deposited and form washover fans. These widely different outcomes remain difficult to predict. Here we suggest that a breach develops when the sediment volume transported by overwashing flows exceeds the barrier subaerial volume. We form a simple analytical theory that estimates overwashing flows from storm characteristics, barrier morphology, and dune vegetation, and which can be used to assess washover deposition and breaching likelihood. Our theory suggests that barrier width and storm surge height are two important controls on barrier breaching. We test our theory with the hydrodynamic and morphodynamic model Delft3D as well as with field observations of 21 washover fans and 6 breaches that formed during hurricane Sandy. There is reasonable correspondence for natural but not for developed barrier coasts, where traditional sediment transport equations do not readily apply. Our analytical formulations for breach formation and overwash deposition can be used to improve long-term barrier island models.

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Scaling laws for coastal overwash morphology

Cited by 36 publications

References 56 publications

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

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

Long-range dependence in coastal framework geology: Asymmetries and implications for barrier island resiliency

Barrier breaching versus overwash deposition: parameterizing the morphologic impact of storms on coastal barriers

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