Modes of cross-shore sediment transport on the shoreface of the Middle Atlantic Bight

Wright, L. D.; Boon, John D.; Kim, S.C.; List, Jeffrey H.

doi:10.1016/0025-3227(91)90200-n

Cited by 144 publications

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“…al., 2012;Wright, 1987;Xu and Wright, 1998). However, nearshore studies have identified inner shelf sediment transport as an essential component of coastal sediment budgets (e.g., Batton, 2003;Conley and Beach, 2003;Hinton and Nicholls, 2007;Riggs et al, 1996Riggs et al, , 1998Schwab et al, 2000;Thieler et al, 1995Thieler et al, , 2001Wehmiller et al, 1995;Wright et al, 1991). Adding to the complexity of coastal sediment budgets and coastal change is the influence of a complex geologic framework of older stratigraphic units that occur beneath and seaward of the littoral zone (Belknap and Kraft, 1985;Evans et al, 1985;Harris et al, 2005;Locker et al, 2003;Miselis and McNinch, 2006;Riggs et al, 1995;Schwab et al, 1997Schwab et al, , 2000Thieler et al, 1995Thieler et al, , 2001.…”

Section: Introductionmentioning

confidence: 99%

Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: Implications for the regional sediment budget and long-term shoreline response

Denny

Schwab

Baldwin

et al. 2013

Continental Shelf Research

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a b s t r a c tHigh-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget.The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain $ 67 M m 3 of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack of any significant modern fluvial input of sand to the region, the Holocene deposits are likely derived from reworking of relict Pleistocene and older inner-shelf deposits during the Holocene marine transgression. The Holocene sediments are concentrated in the southern part of the study area, due to a combination of ancestral drainage patterns, a regional shift in sediment supply from the northeast to the southwest in the late Pleistocene, and proximity to modern inlet systems. Where sediment is limited, only small, low relief ridges have formed and Pleistocene and older deposits are exposed on the seafloor. The low-relief ridges are likely the result of a thin, mobile veneer of sediment being transported across an irregular, erosional surface formed during the last transgression. Sediment textural trends and seafloor morphology indicate a long-term net transport of sediment to the southwest. This is supported by oceanographic studies that suggest the long-term sediment transport direction is controlled by the frequency and intensity of storms that pass through the region, where low pressure systems yield net along-shore flow to the southwest and a weak onshore component.Current sediment budget estimates for the Grand Strand yield a deficit for the region. Volume calculations of Holocene deposits on the inner shelf suggest that there is sufficient sediment to balance the sediment budget and provide a source of sediment to the shoreline. Although the processes controlling cross-shelf sediment transport are not fully understood, in sediment-limited environments such as the Grand Strand, erosion of the inner shelf likely contributes significant sediment to the beach system.Published by Elsevier Ltd.

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Section: Introductionmentioning

confidence: 99%

Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: Implications for the regional sediment budget and long-term shoreline response

Denny

Schwab

Baldwin

et al. 2013

Continental Shelf Research

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“…The wave--dominated inner shelf has long been the subject of scientific investigation (Komar, 1991;Wright et al, 1991), and it has long been understood that shoreface slopes develop as a balance between onshore and offshore sediment transport processes (Fenneman, 1902). In this paper, we use the term shoreface to describe several subdivisions of the shoreface including the surf zone, upper shoreface, lower shoreface, inner shelf, and midshelf.…”

Section: Depth Of Closure Wave Base and The Shoreface Toementioning

confidence: 99%

“…Often closure depth is also inferred as the seaward limit of measurable shoreface depth change (Hallermeier, 1978;Birkemeier, 1985;Nicholls et al, 1996). Wright et al (1991), however, argued that a measurable depth of closure should be on the order of magnitude of the rate of bed accumulation equal to local relative sea--level--rise rates-for most coasts this would require measurements with sub--cm accuracy to capture rates of mm/yr (Kemp et al, 2011).…”

Section: Depth Of Closure Wave Base and The Shoreface Toementioning

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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“…These projects include CODE (Coastal Ocean Dynamics Experiment) (Cacchione et al, 1987;Grant et al, 1984), STRESS (Sediment Transport on Shelves and Slopes) (Sherwood et al, 1994), STRATAFORM (Nittrouer, 1999), and EuroSTRATAFORM (Fain et al, 2007;Nittrouer et al, 2004). Some scholars carried out boundary layer water and sediment observations in different coastal areas and collected waves, currents, and sediment concentration data under normal or stormy weather conditions (Madsen and Wood, 1993;McClennen, 1973;Williams et al, 1999;Wright et al, 1991). Zhao and Han (2007), Yang and Hou (2004), Sun et al (2010) andWang et al (2012) collected field data in Huanghua port, Jingtang port and Jiangsu coast, and analyzed the sediment transport in silt-dominated coasts.…”

Section: Introductionmentioning

confidence: 99%

Modelling and Analysis of Fine Sediment Transport in Wave-Current Bottom Boundary Layer

Zuo¹

2018

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Although all care is taken to ensure integrity and the quality of this publication and the information herein, no responsibility is assumed by the publishers, the author nor IHE Delft for any damage to the property or persons as a result of operation or use of this publication and/or the information contained herein. A pdf version of this work will be made available as Open Access via http://repository.tudelft.nl/ihe. This version is licensed under the Creative Commons To my family AbstractThe evolution and utilization of estuarine and coastal regions are greatly restricted by sediment problems. Inspired by the Caofeidian sea area in Bohai Bay, China, this study aims to better understand silty sediment transport under combined action of waves and currents, especially in the wave-current bottom boundary layer (BBL), and to improve our modelling approaches in predicting estuarine and coastal sediment transport.Field observations were carried out in northwestern Caofeidian sea area of Bohai Bay and field data were collected on several other silt-dominated coasts. Analysis shows that silt-dominated sediments are sensitive to flow dynamics: the suspended sediment concentrations (SSCs) increase rapidly under strong flow dynamics (i.e., waves or strong tidal currents which can stir up sediments), and high concentrations cause heavy sudden back siltation in navigation channels. In the following, details of silty sediment transport are studied, focusing on the BBL and high concentration layer (HCL).From laboratory experiments and theoretical analysis, an expression for sediment incipient motion is proposed for silt-sand sediment under combined wave and current conditions. The Shields number was revised by adding the cohesive force and additional static pressure, leading to an extended Shields curve.To study the HCL, a process based 1DV model was developed for flow-sediment dynamics near the bed in combined wave-current conditions. Based on the physical processes, special approaches for sediment movement were introduced, including approaches for different bed forms (rippled bed and 'flat-bed'), hindered settling, stratification effects, mobile bed effects, reference concentration and critical shear stress. The HCL was simulated and sensitivity analysis was carried out by the 1DV model on factors that impact the sediment concentration in the HCL. The results show that the HCL is affected by both flow dynamics and bed forms; the thickness of the HCL is about twice the height of the wave boundary layer; bed forms determine the shape of the concentration profile near the bottom, and flow dynamics determine the magnitude. For finer sediment, stratification effects and mobile bed effects impact the sediment concentration greatly.Finally, based on the 1DV model, the formulations of the mean sediment concentration profile of silty sediments were studied. By solving the time-averaged diffusion equation for SSC and considering the effects of bed forms, stratification and hindered settling, expressions for time-averaged SSC profile...

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Modes of cross-shore sediment transport on the shoreface of the Middle Atlantic Bight

Cited by 144 publications

References 35 publications

Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: Implications for the regional sediment budget and long-term shoreline response

Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: Implications for the regional sediment budget and long-term shoreline response

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

Modelling and Analysis of Fine Sediment Transport in Wave-Current Bottom Boundary Layer

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