scholarly journals Emergence and Migration of a Nearshore Bar: Sediment Flux and Morphological Change on a Multi-Barred Beach in the Great Lakes

2007 ◽  
Vol 60 (1) ◽  
pp. 31-47 ◽  
Author(s):  
Brian Greenwood ◽  
Allana Permanand-Schwartz ◽  
Christopher A. Houser
Keyword(s):  
Great Lakes ◽  
Suspended Sediment ◽  
Surf Zone ◽  
Sandy Beaches ◽  
Sediment Flux ◽  
Accommodation Space ◽  
Longshore Transport ◽  
Sediment Balance ◽  
And Migration ◽  
Equilibrium Morphology

Abstract Burley Beach (southeastern Lake Huron) exhibits a multi-barred shoreface, the long-term equilibrium morphology characteristic of many low angle, sandy beaches in the Canadian Great Lakes. During a single major storm, a new bar emerged 50-60 m offshore as an irregular trough-crest form, through differential erosion of an existing shore terrace. Emergence, bar growth and offshore migration were associated with: (a) an overall negative sediment balance in the inner surf zone initially (‑2.30 m3>/m beach width), but with a large positive sediment balance (+5.10 m3/m) subsequent to the storm peak and during the storm decay; (b) progradation of the beach step to produce a new shore terrace; and (c) offshore migration of the two outer bars to provide the accommodation space necessary for the new bar. The primary transport mechanisms accounting for emergence of the new bar, its growth and migration were: (a) the mean cross-shore currents (undertow), which always transported suspended sediment offshore; and (b) the onshore transport of suspended sediment by incident gravity wave frequencies early in the storm and subsequently by infragravity waves (at the storm peak and the decay period). The longshore transport of sediment was significant in terms of the gross transport, although the net result was only a small transport to the south-west (historic littoral transport direction). It did not cause bar initiation, but it may have supplied some of the sediment for bar growth. The primary mechanism for bar initiation and growth was the cross-shore displacement of sediment by wave-driven (oscillatory) transport and cross-shore mean currents (undertow).

scholarly journals Surf Zone Turbulence and Suspended Sediment Dynamics—A Review

2021 ◽  
Vol 9 (11) ◽  
pp. 1300
Author(s):  
Troels Aagaard ◽  
Joost Brinkkemper ◽  
Drude F. Christensen ◽  
Michael G. Hughes ◽  
Gerben Ruessink
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Surf Zone ◽  
Sediment Concentration ◽  
Sandy Beaches ◽  
Suspended Sediment Transport ◽  
Velocity Signal ◽  
Wave Phase ◽  
Turbulence Production

The existence of sandy beaches relies on the onshore transport of sand by waves during post-storm conditions. Most operational sediment transport models employ wave-averaged terms, and/or the instantaneous cross-shore velocity signal, but the models often fail in predictions of the onshore-directed transport rates. An important reason is that they rarely consider the phase relationships between wave orbital velocity and the suspended sediment concentration. This relationship depends on the intra-wave structure of the bed shear stress and hence on the timing and magnitude of turbulence production in the water column. This paper provides an up-to-date review of recent experimental advances on intra-wave turbulence characteristics, sediment mobilization, and suspended sediment transport in laboratory and natural surf zones. Experimental results generally show that peaks in the suspended sediment concentration are shifted forward on the wave phase with increasing turbulence levels and instantaneous near-bed sediment concentration scales with instantaneous turbulent kinetic energy. The magnitude and intra-wave phase of turbulence production and sediment concentration are shown to depend on wave (breaker) type, seabed configuration, and relative wave height, which opens up the possibility of more robust predictions of transport rates for different wave and beach conditions.

scholarly journals LONGSHORE TRANSPORT OF SUSPENDED SEDIMENT

1972 ◽  
Vol 1 (13) ◽  
pp. 53 ◽  
Author(s):  
John C. Fairchild
Keyword(s):  
Suspended Sediment ◽  
Surf Zone ◽  
Laboratory Data ◽  
Sediment Concentration ◽  
Nozzle Height ◽  
Unidirectional Flow ◽  
Longshore Transport ◽  
Average Sampling ◽  
Scatter Plots ◽  
The City

In excess of 800 suspended sediment samples were collected from stations along the City Pier, Ventnor, New Jersey and Jennettes Pier, Nags Head, North Carolina using a tractor-mounted pump sampler. Most samples were collected within the surf zone at the Ventnor site. At the Nags Head site, sample collections included the surf zone, but generally extended over a wider range of the nearshore zone. Average sampling time was 3 minutes. Nozzle elevation varied from 3 inches above the bottom up to a maximum about mid-depth, generally not greater than 2.5 feet above bottom. Maximum concentrations at Ventnor ranged up to 2.6 ppt by weight and at Nags Head were about 4.0 ppt. Median size at Ventnor ranged from 0.12 to 0.15 mm and averaged about 0.20 mm in depths of 4 feet and less at Nags Head. Results are summarized in a series of scatter plots which relate suspended sediment concentration to nozzle height, wave height, water depth and sampling distance from an observed wave-breaker-line. Results are compared to CERC laboratory data, to two excerpted concentrations from unidirectional flow tests and to the CERC TR-4 design curve of longshore wave energy versus longshore transport.

scholarly journals NEARSHORE SUSPENDED SEDIMENT LOAD DURING STORM AND POSXTSTORM CONDITIONS

1980 ◽  
Vol 1 (17) ◽  
pp. 70
Author(s):  
Timothy W. Kana ◽  
Larry G. Ward
Keyword(s):  
Suspended Sediment ◽  
Energy Flux ◽  
Wave Energy ◽  
Surf Zone ◽  
Field Research ◽  
Bulk Water ◽  
Total Load ◽  
Zone Width ◽  
Longshore Transport ◽  
Wave Energy Flux

As part of the DUCK-X experiment at the CERC field research facility at Duck, North Carolina in September, 1978, suspended sediment measurements were made along the CERC pier. In situ bulk water samples were collected during a moderate northeast storm and two days later during post-storm wave conditions. Concentrations varied from approximately 0.01 g/1 to over 10.0 g/1. Vertical arrays of suspended sediment samples indicated that concentration decreases rapidly up to two meters above the bed, then remains relatively constant, reflecting the nature of the suspension; intermittent suspension of sand near the bed, and continuous washload higher in the water column. Concentrations were at a maximum during storm conditions when measured values were 3 to 5 times higher than during non-storm conditions. The total load of sediment in a pier cross section during sampling periods in storm and post^storm conditions was calculated from arrays of 49 samples each. With H1/3 exceeding 2.3 HI and the surf zone width over 300 m during the storm, the total load of sediment in suspension was approximately 10 times higher than during poststorm conditions (Hi 73 - 1.2 m and surf zone width approximately 100 m) . Estimates of the longshore flux of suspended sediment indicate that as much as 60 times more sediment was transported during storm than during post-storm conditions. Longshore transport of sediment measured from 5 cm above the bed to the surface reached the equivalent of 22,330 m^/day. This value corresponds very closely to longshore transport predicted from wave energy flux. During post-storm conditions, on the other hand, transport of suspended sediment accounts for less than one-third of the transport predicted from wave energy flux.

scholarly journals O Controle da Deriva Litorânea no Desenvolvimento do Campo de Dunas e da Antepraia no Litoral Médio do Rio Grande do Sul

2006 ◽  
Vol 33 (2) ◽  
pp. 35 ◽  
Author(s):  
ELÍRIO TOLDO JR ◽  
LUIZ ALMEIDA ◽  
LUCIANO ABSALONSEN ◽  
NELSON GRUBER
Keyword(s):  
Sediment Transport ◽  
Surf Zone ◽  
Rio Grande ◽  
Fine Sand ◽  
Sediment Flux ◽  
Sand Transport ◽  
Rio Grande Do Sul ◽  
Coastal Jet ◽  
Longshore Transport ◽  
Alongshore Sediment Transport

Zones of erosion and accretion were delimited by comparing a DGPS shoreline mapping in 1997 and the beach line reproduced from the army chart collection of 1975. The results show extensive shore retreat along of Rio Grande do Sul central coast, while accretion was observed in Mostardas and Dunas Altas beach. Mathematical estimative of the regional longshore transport potential along the Rio Grande do Sul coast, a 630-km long holocenic fine sand barrier, resulted in a large net northward annual sand volume. Additionally, the estimated potential of sediment transport based on the CERC formula predicts a substantial variation of the energy flux into the surf zone, due to little changes in shoreline alignments and in the potential alongshore sediment transport. The reduction in the sediment flux due to changes in the shoreline alignment produce a jam in the longshore transport, meaning that part of the sediment arriving from the upstream stretch may be deposited or diverted offshore by coastal jet. Based on that, it is possible that changes in the net longshore sand transport are responsible for the increase in the shoreface width from less than 1 km to more than 3 km in Mostardas beach and Dunas Altas beach. Interesting to note that wider dune fields are associated to those beaches where shoreface is also wider. In this way, the volume of longshore sand transport and the sediment jam provide by changes on shoreline alignment in Mostardas and Dunas Altas beaches are important for both coastal dune fields and shoreface width.

scholarly journals FIELD INVESTIGATIONS OF SUSPENDED SEDIMENT TRANSPORT IN THE NEARSHORE ZONE

1984 ◽  
Vol 1 (19) ◽  
pp. 120 ◽  
Author(s):  
R.W. Sternberg ◽  
N.C. Shi ◽  
John P. Downing
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Surf Zone ◽  
Pressure Sensors ◽  
Sediment Concentration ◽  
Daily Basis ◽  
Transport Rate ◽  
Suspended Sediment Transport ◽  
Sediment Distribution ◽  
Longshore Transport

The suspended sediment distribution and longshore sediment transport characteristics at Leadbetter Beach, Santa Barbara, California were investigated using a series of miniature optical backseatter sensors which can measure particle concentrations as high as 180 gm/£ and have 10 Hz frequency response. Vertical arrays of sensors were maintained at up to four positions across the surf zone during 7-25 February 1980 and were operated concurrently with pressure sensors and current meters. Data were collected on a daily basis over 2-4 hour periods. The data were analyzed to reveal concentration profiles of suspended sediment, the average suspended sediment loads, and the longshore particle flux in relation to varying wave conditions. Results show that sediment transport occurs as individual suspension events related to incident wave motions and infragravity motion oscillations within the surf zone; suspended sediment concentration decreases approximately logarithimically away from the seabed; the maximum values of longshore transport rates occur in the mid-surf zone; and the measured suspended sediment longshore transport rate is equal to the total longshore transport rate as predicted by existing transport equations.

scholarly journals Insights on the Impacts of Hydroclimatic Extremes and Anthropogenic Activities on Sediment Yield of a River Basin

Earth ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 32-50
Author(s):  
Rocky Talchabhadel ◽  
Jeeban Panthi ◽  
Sanjib Sharma ◽  
Ganesh R. Ghimire ◽  
Rupesh Baniya ◽  
...  
Keyword(s):  
Suspended Sediment ◽  
River Basin ◽  
Extreme Precipitation ◽  
Suspended Sediment Concentration ◽  
Anthropogenic Activities ◽  
Sediment Concentration ◽  
Sediment Flux ◽  
Mountain River ◽  
Ecological Processes ◽  
Precipitation Indices

Streamflow and sediment flux variations in a mountain river basin directly affect the downstream biodiversity and ecological processes. Precipitation is expected to be one of the main drivers of these variations in the Himalayas. However, such relations have not been explored for the mountain river basin, Nepal. This paper explores the variation in streamflow and sediment flux from 2006 to 2019 in central Nepal’s Kali Gandaki River basin and correlates them to precipitation indices computed from 77 stations across the basin. Nine precipitation indices and four other ratio-based indices are used for comparison. Percentage contributions of maximum 1-day, consecutive 3-day, 5-day and 7-day precipitation to the annual precipitation provide information on the severity of precipitation extremeness. We found that maximum suspended sediment concentration had a significant positive correlation with the maximum consecutive 3-day precipitation. In contrast, average suspended sediment concentration had significant positive correlations with all ratio-based precipitation indices. The existing sediment erosion trend, driven by the amount, intensity, and frequency of extreme precipitation, demands urgency in sediment source management on the Nepal Himalaya’s mountain slopes. The increment in extreme sediment transports partially resulted from anthropogenic interventions, especially landslides triggered by poorly-constructed roads, and the changing nature of extreme precipitation driven by climate variability.

scholarly journals Tidal Asymmetry in Ocean-Boundary Flux and In-Estuary Trapping of Suspended Sediment Following Watershed Storms: San Francisco Estuary, California, USA

2021 ◽  
Author(s):  
Maureen A. Downing-Kunz ◽  
Paul A. Work ◽  
David H. Schoellhamer
Keyword(s):  
Suspended Sediment ◽  
San Francisco ◽  
Sediment Resuspension ◽  
San Francisco Estuary ◽  
Sediment Flux ◽  
Golden Gate ◽  
Storm Events ◽  
Suspended Sediment Flux ◽  
Field Campaigns ◽  
Ocean Boundary

AbstractSuspended-sediment flux at the ocean boundary of the San Francisco Estuary—the Golden Gate—was measured over a tidal cycle following peak watershed runoff from storms to the estuary in two successive years to investigate sediment transport through the estuary. Observations were repeated during low-runoff conditions, for a total of three field campaigns. Boat-based measurements of velocity and acoustic backscatter were used to calculate water and suspended-sediment flux at a location 1 km landward of the Golden Gate. Suspended-sediment concentration (SSC) and salinity data from up-estuary sensors were used to track watershed-sourced sediment plumes through the estuary. Estimates of suspended-sediment load from the watershed and net suspended-sediment flux for one up-estuary subembayment were used to infer in-estuary trapping of sediment. For both post-storm field campaigns, observations at the ocean boundary were conducted on the receding limb of the watershed hydrograph. At the ocean boundary, peak instantaneous suspended-sediment flux was tidally asymmetric and was greater on flood tides than on ebb tides for all three field campaigns, due to higher average SSC in the cross-section on flood tides. Shear-induced sediment resuspension was greater on flood tides and suggests the presence of an erodible pool outside the estuary. The storms in 2016 led to less export of discharge and sediment from the watershed and greater sediment trapping within one up-estuary subembayment compared to that observed in 2017. Results suggest that substantial trapping of watershed sediments occurred during both storm events, likely due to the formation of estuarine turbidity maxima (ETM) at different locations in the estuary. ETM locations were forced nearer the ocean boundary in 2017. Additional measurements and modeling are required to quantify the long-term sediment flux at the Golden Gate.

Muted responses of streamflow and suspended sediment flux in a wildfire-affected watershed

Geomorphology ◽  
2013 ◽  
Vol 202 ◽  
pp. 128-139 ◽  
Author(s):  
P.N. Owens ◽  
T.R. Giles ◽  
E.L. Petticrew ◽  
M.S. Leggat ◽  
R.D. Moore ◽  
...  
Keyword(s):  
Suspended Sediment ◽  
Sediment Flux ◽  
Suspended Sediment Flux

scholarly journals Energy Dissipation During Subglacial Abrasion at Nisqually Glacier, Washington, U.S.A.

1979 ◽  
Vol 23 (89) ◽  
pp. 233-246 ◽  
Author(s):  
Richard C. Metcalf
Keyword(s):  
Energy Balance ◽  
Suspended Sediment ◽  
Water Flux ◽  
Gravitational Energy ◽  
Sediment Flux ◽  
Normal Stresses ◽  
Mount Rainier ◽  
Suspended Sediment Flux ◽  
Basal Sliding ◽  
Order Of Magnitude

AbstractThis study examines the effect of subglacial abrasion on the basal sliding term of the gravitational energy balance of the dynamic, temperate Nisqually Glacier on Mount Rainier, Washington, U.S.A. Subglacial water flux is estimated as 3 × 107 m3 a–1 and suspended sediment flux as 3 × 107 kg a–1. Suspended-sediment flux is assumed to represent, within an order of magnitude, the annual mass eroded by subglacial abrasion.Subglacial abrasion involves both brittle fracture and plastic deformation. Field observations of bas-relief and grooved depression striations appear to have exact counterparts in rock mechanics experiments approximating subglacial velocities and normal stresses. Boulton's ([Cl974]) abrasion model and a new attritivity model proposed herein are shown to predict subglacial abrasion-rates within the limits of natural variability and the error range of measurements. The first crude gravitational energy balance for lower Nisqually Glacier (1.96 km2) is attempted and probably has only order-of-magnitude accuracy. The importance of subglacial abrasion in dissipating basal sliding energy at Nisqually Glacier is confirmed.

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