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  • Estuary  (11)
  • Estuarine circulation  (4)
  • Circulation/ Dynamics  (3)
  • Fluid mud
  • 11
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    Bigger tides, less flooding: Effects of dredging on barotropic dynamics in a highly modified estuary. (2019)
    American Geophysical Union
    Details
    Publication Date: 2022-10-20
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124 (2019): 196-211, doi:10.1029/2018JC014313.
    Description: Since the late nineteenth century, channel depths have more than doubled in parts of New York Harbor and the tidal Hudson River, wetlands have been reclaimed and navigational channels widened, and river flow has been regulated. To quantify the effects of these modifications, observations and numerical simulations using historical and modern bathymetry are used to analyze changes in the barotropic dynamics. Model results and water level records for Albany (1868 to present) and New York Harbor (1844 to present) recovered from archives show that the tidal amplitude has more than doubled near the head of tides, whereas increases in the lower estuary have been slight (〈10%). Channel deepening has reduced the effective drag in the upper tidal river, shifting the system from hyposynchronous (tide decaying landward) to hypersynchronous (tide amplifying). Similarly, modeling shows that coastal storm effects propagate farther landward, with a 20% increase in amplitude for a major event. In contrast, the decrease in friction with channel deepening has lowered the tidally averaged water level during discharge events, more than compensating for increased surge amplitude. Combined with river regulation that reduced peak discharges, the overall risk of extreme water levels in the upper tidal river decreased after channel construction, reducing the water level for the 10‐year recurrence interval event by almost 3 m. Mean water level decreased sharply with channel modifications around 1930, and subsequent decadal variability has depended both on river discharge and sea level rise. Channel construction has only slightly altered tidal and storm surge amplitudes in the lower estuary.
    Description: Funding for D. K. R., W. R. G., and C. K. S. was provided by NSF Coastal SEES awards OCE-1325136 and OCE-1325102. Funding for S.T. and H. Z. was provided by the U.S. Army Corps of Engineers (award W1927 N-14-2-0015), and NSF (Career Award 1455350). Data supporting this study are posted to Zenodo (https://doi.org/10.5281/zenodo.1298636).
    Description: 2019-06-11
    Keywords: Barotropic tides ; Flood frequency ; Storm surge ; Dredging ; Estuary ; Tidal river
    Repository Name: Woods Hole Open Access Server
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  • 12
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    Response to channel deepening of the salinity intrusion, estuarine circulation, and stratification in an urbanized estuary (2019)
    American Geophysical Union
    Details
    Publication Date: 2022-10-20
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124(7), (2019): 4784-4802, doi: 10.1029/2019JC015006.
    Description: Modifications for navigation since the late 1800s have increased channel depth (H) in the lower Hudson River estuary by 10–30%, and at the mouth the depth has more than doubled. Observations along the lower estuary show that both salinity and stratification have increased over the past century. Model results comparing predredging bathymetry from the 1860s with modern conditions indicate an increase in the salinity intrusion of about 30%, which is roughly consistent with the H5/3 scaling expected from theory for salt flux dominated by steady exchange. While modifications including a recent deepening project have been concentrated near the mouth, the changes increase salinity and threaten drinking water supplies more than 100 km landward. The deepening has not changed the responses to river discharge (Qr) of the salinity intrusion (~Qr−1/3) or mean stratification (Qr2/3). Surprisingly, the increase in salinity intrusion with channel deepening results in almost no change in the estuarine circulation. This contrasts sharply with local scaling based on local dynamics of an H2 dependence, but it is consistent with a steady state salt balance that allows scaling of the estuarine circulation based on external forcing factors and is independent of depth. In contrast, the observed and modeled increases in stratification are opposite of expectations from the steady state balance, which could be due to reduction in mixing with loss of shallow subtidal regions. Overall, the mean shift in estuarine parameter space due to channel deepening has been modest compared with the monthly‐to‐seasonal variability due to tides and river discharge.
    Description: Funding was provided by NSF Coastal SEES (OCE 1325136). Data supporting this study are posted to Zenodo (https://doi.org/10.5281/zenodo.2551285) or are available by contacting the author.
    Description: 2019-12-07
    Keywords: Estuarine circulation ; Salinity intrusion ; Stratification ; Dredging ; Hudson River
    Repository Name: Woods Hole Open Access Server
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  • 13
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    Mechanisms of exchange flow in an estuary with a narrow, deep channel and wide, shallow shoals (2021)
    American Geophysical Union
    Details
    Publication Date: 2022-10-20
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geyer, W. R., Ralston, D. K., & Chen, J. Mechanisms of exchange flow in an estuary with a narrow, deep channel and wide, shallow shoals. Journal of Geophysical Research: Oceans, 125(12), (2020): e2020JC016092, https://doi.org/10.1029/2020JC016092.
    Description: Delaware Bay is a large estuary with a deep, relatively narrow channel and wide, shallow banks, providing a clear example of a “channel‐shoal” estuary. This numerical modeling study addresses the exchange flow in this channel‐shoal estuary, specifically to examine how the lateral geometry affects the strength and mechanisms of exchange flow. We find that the exchange flow is exclusively confined to the channel region during spring tides, when stratification is weak, and it broadens laterally over the shoals during the more stratified neap tides but still occupies a small fraction of the total width of the estuary. Exchange flow is relatively weak during spring tides, resulting from oscillatory shear dispersion in the channel augmented by weak Eulerian exchange flow. During neap tides, stratification and shear increase markedly, resulting in a strong Eulerian residual shear flow driven mainly by the along‐estuary density gradient, with a net exchange flow roughly 5 times that of the spring tide. During both spring and neap tides, lateral salinity gradients generated by differential advection at the edge of the channel drive a tidally oscillating cross‐channel flow, which strongly influences the stratification, along‐estuary salt balance, and momentum balance. The lateral flow also causes the phase variation in salinity that results in oscillatory shear dispersion and is an advective momentum source contributing to the residual circulation. Whereas the shoals make a negligible direct contribution to the exchange flow, they have an indirect influence due to the salinity gradients between the channel and the shoal.
    Description: The ideas in this paper were influenced by discussions with Robert Chant. Funding was provided by National Science Foundation grants OCE‐1325136, OCE‐1634490, and OCE‐1736539.
    Description: 2021-04-29
    Keywords: Estuarine circulation ; Tidal dispersion ; Lateral circulation
    Repository Name: Woods Hole Open Access Server
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  • 14
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    Sources, mechanisms, and timescales of sediment delivery to a New England salt marsh (2022)
    American Geophysical Union
    Details
    Publication Date: 2022-10-20
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Baranes, H., Woodruff, J., Geyer, W., Yellen, B., Richardson, J. & Griswold, F. Sources, mechanisms, and timescales of sediment delivery to a New England salt marsh. Journal of Geophysical Research: Earth Surface, 127, (2022): e2021JF006478, https://doi.org/10.1029/2021jf006478.
    Description: he availability and delivery of an external clastic sediment source is a key factor in determining salt marsh resilience to future sea level rise. However, information on sources, mechanisms, and timescales of sediment delivery are lacking, particularly for wave-protected mesotidal estuaries. Here we show that marine sediment mobilized and delivered during coastal storms is a primary source to the North and South Rivers, a mesotidal bar-built estuary in a small river system impacted by frequent, moderate-intensity storms that is typical to New England (United States). On the marsh platform, deposition rates, clastic content, and dilution of fluvially-sourced contaminated sediment by marine material all increase down-estuary toward the inlet, consistent with a predominantly marine-derived sediment source. Marsh clastic deposition rates are also highest in the storm season. We observe that periods of elevated turbidity in channels and over the marsh are concurrent with storm surge and high wave activity offshore, rather than with high river discharge. Flood tide turbidity also exceeds ebb tide turbidity during storm events. Timescales of storm-driven marine sediment delivery range from 2.5 days to 2 weeks, depending on location within the estuary; therefore the phasing of storm surge and waves with the spring-neap cycle determines how effectively post-event suspended sediment is delivered to the marsh platform. This study reveals that sediment supply and the associated resilience of New England mesotidal salt marshes involves the interplay of coastal and estuarine processes, underscoring the importance of looking both up- and downstream to identify key drivers of environmental change.
    Description: The project described in this publication was in part supported by Grant or Cooperative Agreement No. G20AC00071 from the U.S. Geological Survey and a Department of Interior Northeast Climate Adaptation Science Center graduate fellowship awarded to H.E.B (G12AC00001).
    Keywords: Salt marsh ; Sediment ; Estuary ; Tides ; Massachusetts
    Repository Name: Woods Hole Open Access Server
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  • 15
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    Observations and modeling of wave-supported sediment gravity flows on the Po prodelta and comparison to prior observations from the Eel shelf (2007)
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © The Authors, 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Continental Shelf Research 27 (2007): 375-399, doi:10.1016/j.csr.2005.07.008.
    Description: A mooring and tripod array was deployed from the fall of 2002 through the spring of 2003 on the Po prodelta to measure sediment transport processes associated with sediment delivered from the Po River. Observations on the prodelta revealed wave-supported gravity flows of high concentration mud suspensions that are dynamically and kinematically similar to those observed on the Eel shelf (Traykovski et al., 2000). Due to the dynamic similarity between the two sites, a simple one-dimensional across-shelf model with the appropriate bottom boundary condition was used to examine fluxes associated with this transport mechanism at both locations. To calculate the sediment concentrations associated with the wave-dominated and wave-current resuspension, a bottom boundary condition using a reference concentration was combined with an “active layer” formulation to limit the amount of sediment in suspension. Whereas the wave-supported gravity flow mechanism dominates the transport on the Eel shelf, on the Po prodelta flux due to this mechanism is equal in magnitude to transport due to wave resuspension and wind-forced mean currents in cross-shore direction. Southward transport due to wave resuspension and wind forced mean currents move an order of magnitude more sediment along-shore than the downslope flux associated wave-supported gravity flows.
    Description: This work funded by the U.S. Office of Naval Research under grant number #N00014-02-10378, under the direction of program manager, Tom Drake.
    Keywords: Po River ; Adriatic Sea ; Sediment transport ; Turbidity currents ; Fluid mud
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 16
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    Sediment transport due to extreme events : the Hudson River estuary after tropical storms Irene and Lee (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 40 (2013): 5451–5455, doi:10.1002/2013GL057906.
    Description: Tropical Storms Irene and Lee in 2011 produced intense precipitation and flooding in the U.S. Northeast, including the Hudson River watershed. Sediment input to the Hudson River was approximately 2.7 megaton, about 5 times the long-term annual average. Rather than the common assumption that sediment is predominantly trapped in the estuary, observations and model results indicate that approximately two thirds of the new sediment remained trapped in the tidal freshwater river more than 1 month after the storms and only about one fifth of the new sediment reached the saline estuary. High sediment concentrations were observed in the estuary, but the model results suggest that this was predominantly due to remobilization of bed sediment. Spatially localized deposits of new and remobilized sediment were consistent with longer term depositional records. The results indicate that tidal rivers can intercept (at least temporarily) delivery of terrigenous sediment to the marine environment during major flow events.
    Description: This research was supported by grants from the Hudson Research Foundation (002/07A) and the National Science Foundation (1232928).
    Description: 2014-04-18
    Keywords: Sediment transport ; Tidal river ; Estuary ; Sediment trapping
    Repository Name: Woods Hole Open Access Server
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  • 17
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    Sediment transport time scales and trapping efficiency in a tidal river (2018)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Earth Surface 122 (2017): 2042–2063, doi:10.1002/2017JF004337.
    Description: Observations and a numerical model are used to characterize sediment transport in the tidal Hudson River. A sediment budget over 11 years including major discharge events indicates the tidal fresh region traps about 40% of the sediment input from the watershed. Sediment input scales with the river discharge cubed, while seaward transport in the tidal river scales linearly, so the tidal river accumulates sediment during the highest discharge events. Sediment pulses associated with discharge events dissipate moving seaward and lag the advection speed of the river by a factor of 1.5 to 3. Idealized model simulations with a range of discharge and settling velocity were used to evaluate the trapping efficiency, transport rate, and mean age of sediment input from the watershed. The seaward transport of suspended sediment scales linearly with discharge but lags the river velocity by a factor that is linear with settling velocity. The lag factor is 30–40 times the settling velocity (mm s−1), so transport speeds vary by orders of magnitude from clay (0.01 mm s−1) to coarse silt (1 mm s−1). Deposition along the tidal river depends strongly on settling velocity, and a simple advection-reaction equation represents the loss due to settling on depositional shoals. The long-term discharge record is used to represent statistically the distribution of transport times, and time scales for settling velocities of 0.1 mm s−1 and 1 mm s−1 range from several months to several years for transport through the tidal river and several years to several decades through the estuary.
    Description: Hudson River Foundation Grant Number: 004/13A; National Science Foundation Grant Number: 1325136
    Description: 2018-05-02
    Keywords: Tidal river ; Sediment age ; Trapping efficiency ; Estuary ; Sediment transport
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  • 18
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    Tidal dispersion in short estuaries (2022)
    Woods Hole Oceanographic Institution
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    Publication Date: 2022-10-21
    Description: The salinity distribution of an estuary depends on the balance between the river outflow, which is seaward, and a dispersive salt flux, which is landward. The dispersive salt flux at a fixed cross-section can be divided into shear dispersion, which is caused by spatial correlations of the cross-sectionally varying velocity and salinity, and the tidal oscillatory salt flux, which results from the tidal correlation between the cross-section averaged, tidally varying components of velocity and salinity. The theoretical moving plane analysis of Dronkers and van de Kreeke (1986) indicates that the oscillatory salt flux is exactly equal to the difference between the “local” shear dispersion at a fixed location and the shear dispersion which occurred elsewhere within a tidal excursion – therefore, they refer to the oscillatory salt flux as “nonlocal” dispersion. We apply their moving plane analysis to a numerical model of a short, tidally dominated estuary and provide the first quantitative confirmation of the theoretical result that the spatiotemporal variability of shear dispersion accounts for the oscillatory salt flux. Shear dispersion is localized in space and time and is most pronounced near regions of flow separation. Notably, we find that dispersive processes near the mouth contribute significantly to the overall salt balance, especially under strong river and tidal forcing. Furthermore, while mechanisms of vertical shear dispersion produce the majority of the dispersive salt flux during neap tide and high river flow, lateral mechanisms associated with flow separation provide the dominant mode of dispersion during spring tide and low flow. Dataset used in support of manuscript "Tidal dispersion in short estuaries". The dataset includes the model output from the idealized estuary for 16 different forcing conditions, corresponding to 4 tidal conditions (weak〈neap〈intm〈spring) and 4 river flow conditions (q01〈q03〈q10〈q30), as well as along-channel salinity measurements in the North River (Marshfield, MA, USA) during a 2017 field campaign.
    Description: This work was funded under NSF Grant OCE-1634490 and NSF Graduate Research Fellowship, Grant No. #1122374
    Keywords: Shear dispersion ; Estuary
    Repository Name: Woods Hole Open Access Server
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  • 19
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    Mechanisms of exchange flow in an estuary with a narrow, deep channel and wide, shallow shoals (2020)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-10-21
    Description: Delaware Bay is a large estuary with a deep, relatively narrow channel and wide, shallow banks, providing a clear example of a “channel-shoal” estuary. This numerical modeling study addresses the exchange flow in this channel-shoal estuary, specifically to examine how the lateral geometry affects the strength and mechanisms of exchange flow. We find that the exchange flow is exclusively confined to the channel region during spring tides, when stratification is weak, and it broadens laterally over the shoals during the more stratified neap tides, but still occupies a small fraction of the total width of the estuary. Exchange flow is relatively weak during spring tides, resulting from oscillatory shear dispersion in the channel augmented by weak Eulerian exchange flow. During neap tides, stratification and shear increase markedly, resulting in a strong Eulerian residual shear flow, with a net exchange flow roughly 5 times that of the spring tide. During both spring and neap tides, lateral salinity gradients generated by differential advection at the edge of the channel drive a tidally oscillating cross-channel flow, which strongly influences the stratification, along-estuary salt balance and momentum balance. The lateral flow also causes the phase variation in salinity that results in oscillatory shear dispersion during both spring and neap tides and is a significant advective momentum source driving the residual circulation. Thus, although the shoals make a negligible direct contribution to the exchange flow, the salinity gradients between the channel and the shoal are critical to the stratification and exchange flow within the estuarine channel.
    Description: National Science Foundation (NSF): OCE-1325136; National Science Foundation (NSF): OCE-1634490; National Science Foundation (NSF): Jia-Lin Chen OCE-1736539
    Keywords: Estuarine circulation ; Tidal dispersion ; Lateral circulation
    Repository Name: Woods Hole Open Access Server
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  • 20
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    Data and numerical methods for determining the dynamics and kinematics of Newark Bay, NJ (2019)
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    Publication Date: 2022-10-21
    Description: These observational data and numerical methods were used to investigate the subtidal salt balance of Newark Bay, a sub-estuarine network connected to the Hudson River estuary through New York Harbor. The moored data were collected in 2008 by Chant and Sommerfield, and in 2016 by Corlett, Geyer, and Ralston. Corlett devised the included numerical methods. Shipboard measurements of the vertical salinity profile near each mooring were used to reconstruct the tidally-varying vertical salinity profile from near-bed and near-surface salinity measurements at each mooring. The effects of tidal processes, such as frontal advection, on the exchange flow were investigated by applying the isohaline total exchange flow (TEF) framework to the mooring-based observations in multiple reaches of the estuarine network. In addition, a TEF-based salt balance was derived for the purpose of directly comparing the TEF framework with the standard Eulerian framework.
    Description: NSF Coastal SEES Grant #OCE-1325136 and Hudson River Foundation Grants #008/07A and #GF/01/17
    Keywords: Newark Bay ; Estuary ; Salt balance ; Exchange flow ; TEF
    Repository Name: Woods Hole Open Access Server
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