Systematic Beach Changes on the Outer Banks, North Carolina

Sonu, Choule J.; Beek, Johannes L. van

doi:10.1086/627649

Cited by 71 publications

(18 citation statements)

References 6 publications

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“…Accounting for these regional trends in grain size is difficult without sediment-transport or bed-elevation observations at different water depths, but it is postulated that wave energy was sufficient to cause offshore migration of relatively coarse beach sediment. If so, it would conform to the classical model for cyclical changes in beach volumes (Shepard 1950;Sonu and Van Beek 1971), where storm-generated waves cause beach erosion, and sediment accumulates on a winter bar or bank offshore beyond the surf zone.…”

Section: Long-term Variabilitymentioning

confidence: 79%

Autonomous bed‐sediment imaging‐systems for revealing temporal variability of grain size

Buscombe¹,

Rubin²,

Lacy³

et al. 2014

Limnology & Ocean Methods

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Variation in nearshore bed-sediment grain sizeNearshore sediment transport determines the fate of seabed nutrients, contaminants, and pathogens; asserts control on the seabed and water column as habitats; and drives changes in seafloor topography which, in turn, affect wave transformation processes, spatial gradients in energy dissipation, and nearshore hydrodynamic circulation patterns. Relatively small changes in grain size have been shown to change the sign (depositional or erosional) of nearshore net sand transport rates (Ribberink and Chen 1993); affect the vertical grain-size distribution in suspension (McFetridge and Nielsen 1985); and the shape of suspended sediment concentration profiles (Conley et al. 2008). Laboratory experiments with graded beds simulating very high energy sheet-flow conditions show preferential transport of the coarse fractions in the mixture (e.g., van der Werf et al. 2006), and that the transport of each sizefraction is strongly influenced by the presence of other fractions (e.g., Wilcock 1988).Model calculations of suspended-sediment flux have been shown to become highly inaccurate within hours if the effects of variable bed-sediment grain-size are ignored, because waves and currents can modify the spatial distribution of seabed sediments in a variety of shelf settings over this time-scale (Harris and Wiberg 2002). However, advances in modeling grainsize sorting (spatial segregation) and its underlying selective transport mechanisms are hampered by few observations at sufficient coverage/frequency with which to compare theory. The result is that most nearshore (e.g., Bailard 1981; Larson and Kraus 1995) and regional shelf (e.g., Harris and Coleman 1998;Zhang et al. 1999;Cookman and Flemings 2001) models tend to oversimplify grain-size distribution effects on sediment transport because detailed observations of the behavior of a mixture of size fractions is lacking.A more complete understanding of the role of grain size in the physics of sediment transport requires the collection of grain-size data with more temporal and spatial coverage, and AbstractWe describe a remotely operated video microscope system, designed to provide high-resolution images of seabed sediments. Two versions were developed, which differ in how they raise the camera from the seabed. The first used hydraulics and the second used the energy associated with wave orbital motion. Images were analyzed using automated frequency-domain methods, which following a rigorous partially supervised quality control procedure, yielded estimates to within 20% of the true size as determined by on-screen manual measurements of grains. Long-term grain-size variability at a sandy inner shelf site offshore of Santa Cruz, California, USA, was investigated using the hydraulic system. Eighteen months of high frequency (min to h), high-resolution (μm) images were collected, and grain size distributions compiled. The data constitutes the longest known high-frequency record of seabed-grain size at this sample frequency, at any location....

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Section: Long-term Variabilitymentioning

confidence: 79%

Autonomous bed‐sediment imaging‐systems for revealing temporal variability of grain size

Buscombe¹,

Rubin²,

Lacy³

et al. 2014

Limnology & Ocean Methods

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“…3) these steep, high-energy waves cause removal of a considerable amount of sediment from the upper foreshore with subsequent deposition in the nearshore zone. The result is a concave upward profile without berm (profile classification after Sonu and Van Beek, 1971). This type of beach development occurred during even the smallest storms when wave heights were only about one meter.…”

Section: Erosional Sequencesmentioning

confidence: 99%

Cyclic and Seasonal Beach Response: A Comparison of Oceanside and Bayside Beaches

Nordstrom

1980

Physical Geography

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This study compares the cyclic and seasonal geomorphic responses of oceanside and bayside beaches on Sandy Hook Spit, New Jersey. It was hypothesized that the different nature of onshore wind regimes at bayside and oceanside beaches would cause different types of beach change. On the east-facing ocean shoreline, rates of beach change are related to weather patterns associated with the passage of mid-latitude cyclonic storms. Bayside beach change is related to the influence of the prevailing westerlies. Storm erosion and post-storm deposition is more rapid on oceanside beaches. Swell waves occurring between storms rapidly reinstate pre-storm equilibrium conditions. Lower bayside wave energies occurring between storms have little effect on profile development, and foreshore slopes inherited from previous storms undergo little change. Bayside beaches therefore appear to be more in equilibrium with storm conditions than oceanside beaches.Changes in foreshore slope, beach volume, and beach position associated with individual storm events are compared to seasonal trends to test the applicability of the Hayes cyclic model of beach development to both oceanside and bayside beaches. There is evidence of a cyclic trend of development on the more exposed ocean sites and seasonal development on the more sheltered bayside sites, which suggests that cyclic development may be causally related to the difference among the energy levels of the storm and nonstorm wave regimes.

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“…Once this condition was approached the beach level became fairly constant for the rest of the winter only to recover again in spring and early summer. Darling associated erosion with increasing wave steepness and, while Sonu and Van Beek (1971) profile at all times to a first approximation.…”

Section: Seasonal Variabilitymentioning

confidence: 92%

Spatial and seasonal aspects of beach stability

Carr

Blackley

King

1982

Earth Surf Processes Landf

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ABSTRACT'Recent work at three contrasting sites in England and Wales has shown characteristics atypical of those frequently reported elsewhere. These differences are:(a) Taking each entire beach system there is no uniform trend of erosion or accretion, nor a progressive variation in beach elevation or volume alongshore, from one survey to the next. However, for Swansea Bay the 'long-term' (i.e. 18 months) range in profile height along that stretch of coast where the alignment of the beach is normal to the direction of wave approach, correlates well with computed wave energy derived from relevant offshore wave directions. (b) While beach variability is greatest during the 'winter' (i.e. storm) period there is no overall tendency for a drawdown of sediment from the intertidal zone at that time. Response times are relatively short. Thus high beach levels need not necessarily be associated with 'summer' conditions. (c) Although in Swansea Bay there is a tendency for the beach height to fluctuate least at mid-tide level this is not true of the other two sites. In no area does sediment eroded from the upper exposed part of the beach regularly appear to be deposited on the lowc r exposed part, or vice versa.

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Systematic Beach Changes on the Outer Banks, North Carolina

Cited by 71 publications

References 6 publications

Autonomous bed‐sediment imaging‐systems for revealing temporal variability of grain size

Autonomous bed‐sediment imaging‐systems for revealing temporal variability of grain size

Cyclic and Seasonal Beach Response: A Comparison of Oceanside and Bayside Beaches

Spatial and seasonal aspects of beach stability

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