Stability of giant sand waves in eastern Long Island Sound, U.S.A.

Fenster, Michael S.; FitzGerald, Duncan M.; Bohlen, W. Frank; Lewis, Reed S.; Baldwin, Christopher T.

doi:10.1016/0025-3227(90)90037-k

Cited by 52 publications

(31 citation statements)

References 23 publications

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“…The values are closer to the bedform movement celerity in a similar term, water depth and same grain size measured in the field (Fenster et al, 1990) and observed in a wind tunnel (Zhu, 1962) and in desert (Zhu et al, 1981(Zhu et al, , 1988. The bedform movement celerity estimated by equilibrium-range spectra analysis provides a potential and practical application for the nearshore bedform instability evaluation.…”

Section: Precision Of Bedform Celeritysupporting

confidence: 73%

“…3). The average bedform celerities in the present study are larger than that in a term of daily dimension, with similar spatial scale, water depth and grain size measured in the fields, such as, 0.95 cm/ day in the eastern part to Long Island, America (Fenster et al, 1990), 0.25-0.75 m/day in the Adolphus Strait, Australia (Harris, 1989) and the southern Bight of the Taiwan Strait (Wang et al, 1993). But the celerity in the present study is smaller than that in a term of second dimension such as 0.01-0.09 m/s measured in the Yangtze Estuary (Cheng et al, 2001).…”

Section: Celerity and Temporal Scale Of Bedformmentioning

confidence: 84%

“…Evaluation of short-term (hourly and daily) celerity of bedform movement became practical since it can be directly measured by instruments in the field (Fenster et al, 1990;Harris, 1989;Wang et al, 1993;Cheng et al, 2001). The measured celerity is much larger than that in long term (monthly and yearly), derived from flume data using empirical and theoretical formulae (Dyer, 1986;Dalrymple et al, 1978;Feng and Li, 1994;Wang and Li, 1994;Yang et al, 1999).…”

Section: Introductionmentioning

confidence: 98%

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Nearshore bedform instability in the eastern entrance to the Qiongzhou Strait, South China Sea

Cheng

Yin

et al. 2008

Front. Earth Sci. China

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Six bathymetric transect profiles were drawn from the nautical charts of 1942, 1962 and 1992 to show that the nearshore seabed remained unstable during the recent 50 years in the middle channel of the eastern entrance to the Qiongzhou Strait, South China Sea. Our results demonstrate that the multi-year averaged seabed aggradational rate was 25 cm/a and erosion rate was 12.5 cm/a. Lateral migration rate of the sea bedform identified from the historical contours was about 100 m/a in the SE direction. Bedform measurements were made using GPY Shallow Seismic Profiler in 1994 in the study area. The records revealed four types of distinctive bedforms that were composed of fine and medium sands. The average spacing of large and small-scale sand dunes is 416 m and 144 m and the average height remains 8.8 m and 4.9 m. The spatial and temporal equilibrium-range spectra of numerical bedform records were applied to estimate short term celerity of bedform movement. Results indicate that large and small dunes migrated at an average celerity of 0.02 cm/hr eastward and 0.09 cm/hr westward in the calm sea weather, while their celerity can reach 53 cm/hr eastward during typhoon season and is only 0.008 cm/hr westward when NNE winds prevail. The results also show that the larger the temporal and spatial scale is, the smaller the bedform movement celerity appears. On the other hand, the smaller-scale bedform celerity of the present study is much greater than that of flume, empirical and theoretical data, but close to the wind tunnel and field-measured data of similar grain size.

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Section: Precision Of Bedform Celeritysupporting

confidence: 73%

Section: Celerity and Temporal Scale Of Bedformmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 98%

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Nearshore bedform instability in the eastern entrance to the Qiongzhou Strait, South China Sea

Cheng

Yin

et al. 2008

Front. Earth Sci. China

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“…One of the most striking characteristics of sand waves is that they are not static bedforms. Indeed, they migrate with their crests almost orthogonal to the direction of the velocity oscillations induced by the tide, at a rate which strongly depends on the tide characteristics and can be of up to some tens of m year À1 (Terwindt 1971;Boknniewicz et al 1977;Fenster et al 1990).…”

Section: Introductionmentioning

confidence: 99%

Migrating sand waves

et al. 2003

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A simple mathematical model is described, which reproduces the major features of sand waves' appearance and growth and in particular predicts their migration speed. The model is based on the linear stability analysis of the flat configuration of the sea bottom subject to tidal currents. Attention is focused on the prediction of the complex growth rate Gamma that bottom perturbations undergo because of both oscillatory fluid motions and residual currents. While the real part Gammar of Gamma controls the amplification or decay of the amplitude of the bedforms, the imaginary part Gammai is related to their migration speed. Previous works on the migration of the sand waves (Németh etblankal. 2002) consider a forcing tide made up by the M2 constituent (oscillatory period equal to 12 h) plus the residual current Z0 and predict always a downcurrent migration of the bedforms. However, field cases exist of upcurrent-migrating sand waves (downcurrent/upcurrent-migrating sand waves mean bedforms moving in the direction of the steady residual tidal current or in the opposite direction, respectively). The inclusion of a tide constituent characterized by a period of 6 h (M4) is the main novelty of the present work, which allows for the prediction of the migration of sand waves against the residual current Z0. Indeed, the M4 tide constituent, as does also the residual current Z0, breaks the symmetry of the problem forced only by the M2 tide constituent, and induces sand-wave migration. The model proposed by Besio etblankal. (2003a) forms the basis for the present analysis. Previous works on the subject (Gerkema 2000; Hulscher 1996a,b; Komarova and Hulscher 2000) are thus improved by using a new solution procedure (Besio etblankal. 2003a) which allows for a more accurate evaluation of the growth rate for arbitrary values of the parameter r, which is the ratio between the horizontal tidal excursion and the perturbation wavelength

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“…Symmetric bedforms are considered stationary and related to the area where net sediment transport is zero (McCave, 1971). Sandwave occurrences can be also linked to extreme marine events (Harris and Collins, 1984), and later reworking processes under returned normal marine climate setting (Fenster et al, 1990). There is a proportion between dimension of sandwaves and the acting flow currents, and therefore the larger dimension of sandwaves seems closely related to stronger marine dynamical events (Flemming, 1978).…”

Section: Discussionmentioning

confidence: 99%

Sandwaves on the Southeast Vietnam Shelf recorded by high resolution seismic profiles: formation and mechanism

Dung

Schimanski

Stattegger

et al. 2008

Front. Earth Sci. China

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The application of high resolution seismic data using boomer sound source has revealed a wide distribution of large-scale bedforms (sandwaves) on the Southeast Vietnam continental shelf. Bedforms that are a few meters high in wave height and hundreds of meters long in wavelength are primarily developed in the inner shelf (20-40 m) and considered to be formed under the presentday marine hydrodynamic conditions. Those bedforms developed in the deeper water (120 m) of the northernmost part of the continent can be interpreted as the relict morphological features formed during the latest sea-level lowstand of the late Pleistocene period. Two sediment transport paths have been identified on the basis of the bedform's leeward orientation: northeast-southwest (alongshore) and north-south (cross-shore). A quantitative bottom current map is constructed from sandwave dimensions, surface sediments and measurement data. The strongest current velocities that gradually decrease toward the southwest are indicated by large sandwaves in the north (field B). Water depth, surficial sediment composition and bottom current are three factors that control the development of bedforms.

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Stability of giant sand waves in eastern Long Island Sound, U.S.A.

Cited by 52 publications

References 23 publications

Nearshore bedform instability in the eastern entrance to the Qiongzhou Strait, South China Sea

Nearshore bedform instability in the eastern entrance to the Qiongzhou Strait, South China Sea

Migrating sand waves

Sandwaves on the Southeast Vietnam Shelf recorded by high resolution seismic profiles: formation and mechanism

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