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  • 1
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    Tidal variation in cohesive sediment distribution and sensitivity to flocculation and bed consolidation in an idealized, partially mixed estuary (2020)
    MDPI
    Details
    Publication Date: 2022-10-27
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tarpley, D. R. N., Harris, C. K., Friedrichs, C. T., & Sherwood, C. R. Tidal variation in cohesive sediment distribution and sensitivity to flocculation and bed consolidation in an idealized, partially mixed estuary. Journal of Marine Science and Engineering, 7(10), (2019): 334, doi: 10.3390/jmse7100334.
    Description: Particle settling velocity and erodibility are key factors that govern the transport of sediment through coastal environments including estuaries. These are difficult to parameterize in models that represent mud, whose properties can change in response to many factors, including tidally varying suspended sediment concentration (SSC) and shear stress. Using the COAWST (Coupled Ocean-Atmosphere-Wave-Sediment Transport) model framework, we implemented bed consolidation, sediment-induced stratification, and flocculation formulations within an idealized two-dimensional domain that represented the longitudinal dimension of a micro-tidal, muddy, partially mixed estuary. Within the Estuarine Turbidity Maximum (ETM), SSC and median floc diameter varied by a factor of four over the tidal cycle. Downstream of the ETM, the median floc size and SSC were several times smaller and showed less tidal variation (~20% or less). The suspended floc distributions only reached an equilibrium size as a function of SSC and shear in the ETM at peak tidal flow. In general, flocculation increased particle size, which reduced SSC by half in the ETM through increased settling velocity. Consolidation also limited SSC by reduced resuspension, which then limited floc growth through reduced SSC by half outside of the ETM. Sediment-induced stratification had negligible effects in the parameter space examined. Efforts to lessen the computation cost of the flocculation routine by reducing the number of size classes proved difficult; floc size distribution and SSC were sensitive to specification of size classes by factors of 60% and 300%, respectively.
    Description: This research was funded by NSF, grant number OCE-1459708.
    Keywords: COAWST ; Numerical model ; Flocculation dynamics ; Cohesive sediment
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Shoaling wave shape estimates from field observations and derived bedload sediment rates (2022)
    MDPI
    Details
    Publication Date: 2022-10-27
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kalra, T. S., Suttles, S. E., Sherwood, C. R., Warner, J. C., Aretxabaleta, A. L., & Leavitt, G. R. Shoaling wave shape estimates from field observations and derived bedload sediment rates. Journal of Marine Science and Engineering, 10(2), (2022): 223, https://doi.org/10.3390/jmse10020223.
    Description: he shoaling transformation from generally linear deep-water waves to asymmetric shallow-water waves modifies wave shapes and causes near-bed orbital velocities to become asymmetrical, contributing to net sediment transport. In this work, we used two methods to estimate the asymmetric wave shape from data at three sites. The first method converted wave measurements made at the surface to idealized near-bottom wave-orbital velocities using a set of empirical equations: the “parameterized” waveforms. The second method involved direct measurements of velocities and pressure made near the seabed: the “direct” waveforms. Estimates from the two methods were well correlated at all three sites (Pearson’s correlation coefficient greater than 0.85). Both methods were used to drive bedload-transport calculations that accounted for asymmetric waves, and the results were compared with a traditional excess-stress formulation and field estimates of bedload transport derived from ripple migration rates based on sonar imagery. The cumulative bedload transport from the parameterized waveform was 25% greater than the direct waveform, mainly because the parameterized waveform did not account for negative skewness. Calculated transport rates were comparable to rates estimated from ripple migration except during the largest event, when calculated rates were as much as 100 times greater, which occurred during high period waves.
    Description: USGS Coastal and Marine Hazards and Resources Program.
    Keywords: Asymmetric waveform ; Wave shape parameterization ; Sediment transport
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
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    Advantages and limitations to the use of optical measurements to study sediment properties (2019)
    MDPI
    Details
    Publication Date: 2022-10-27
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Boss, E., Sherwood, C. R., Hill, P., & Milligan, T. Advantages and limitations to the use of optical measurements to study sediment properties. Applied Sciences-Basel, 8(12), (2018):2692, doi:10.3390/app8122692.
    Description: Measurements of optical properties have been used for decades to study particle distributions in the ocean. They are useful for estimating suspended mass concentration as well as particle-related properties such as size, composition, packing (particle porosity or density), and settling velocity. Measurements of optical properties are, however, biased, as certain particles, because of their size, composition, shape, or packing, contribute to a specific property more than others. Here, we study this issue both theoretically and practically, and we examine different optical properties collected simultaneously in a bottom boundary layer to highlight the utility of such measurements. We show that the biases we are likely to encounter using different optical properties can aid our studies of suspended sediment. In particular, we investigate inferences of settling velocity from vertical profiles of optical measurements, finding that the effects of aggregation dynamics can seldom be ignored.
    Description: This work was supported by the Office of Naval Research and the United States Geological Survey Coastal and Marine Geology Program. The unique instrument platform and data acquisition system was designed and built by technical staff lead by Marinna Martini at the United States Geological Survey Woods Hole Coastal and Marine Science Center. This team was also responsible for deployment and recovery of the instrumentation. We thank the Woods Hole Oceanographic Institution (WHOI) MVCO staff for support during this experiment, and we thank the captains and crews of the R/V Connecticut and the R/V Tioga. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the United States Government. This paper has benefited significantly from insightful comments from D. Stramski, A. Aretxabaleta and two anonymous reviewers.
    Keywords: Particle dynamics ; Optical properties ; Suspended sediment
    Repository Name: Woods Hole Open Access Server
    Type: Article
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