In this study, we investigate how changes in the vertical distribution of suspended sediment affect continuous suspended sediment flux measurements at a location in the San Francisco Estuary. Current methods for measuring continuous suspended sediment flux estimates relate continuous estimates of suspended-sediment concentration (SSC) measured at-a-point (SSCpt) to discrete cross-section measurements of depth-averaged, velocity-weighted SSC (SSCxs). Regressions that compute SSCxs from continuous estimates of SSCpt require that the slope between SSCpt and SSCxs, controlled by the vertical distribution of SSC, is fixed. However, in tidal systems with suspended cohesive sediment, factors that control the vertical SSC profile—vertical turbulent mixing and downward settling of suspended sediment mediated by flocculation of cohesive sediment—constantly vary through each tide and may exhibit systematic differences between flood and ebb tides (tidal asymmetries in water velocity or particle size). We account for changes in the vertical SSC profile on estimates of SSCxs using time series of the Rouse number of the Rouse-Vanoni-Ippen equation combined with optical turbidity measurements, a surrogate for SSCpt, to predict SSCxs from 2009 to 2011 and 2013. Time series of the Rouse number were estimated by fitting the Rouse-Vanoni-Ippen equation to SSC estimated from optical-turbidity measurements taken at two elevations in the water column. When accounting for changes in the vertical SSC profile, changes in not only the magnitude but also the direction of cumulative sediment-flux measurements were observed. For example, at a mid-depth sensor, sediment flux estimates changed from − 319 kt (± 65 kt, negative indicating net seaward transport) to 482 kt (± 140 kt, positive indicating net landward transport) for 2009–2011 and from − 388 kt (± 140 kt) to 1869 kt (± 406 kt) for 2013–2016. At the study location, estimation of SSCxs solely from SSCpt resulted in sediment flux values that were underestimates on flood tides and overestimates on ebb tides. This asymmetry is driven by covariance between water velocity and particle settling velocity (Ws) with larger Ws on flood compared to ebb tides. Results of this study indicate that suspended-sediment-flux measurements estimated from point estimates of SSC may be biased if systematic changes in the vertical distribution of SSC are unaccounted for.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
Tax calculation will be finalised during checkout.
Barnard, P.L., A.C. Foxgrover, E.P. Elias, L.H. Erikson, J.R. Hein, M. McGann, K. Mizell, R.J. Rosenbauer, P.W. Swarzenski, R.K. Takesue, and F.L. Wong. 2013. Integration of bed characteristics, geochemical tracers, current measurements, and numerical modeling for assessing the provenance of beach sand in the San Francisco Bay Coastal System. Marine Geology 345: 181–206.
Brand, A., Lacy, J.R., Hsu, K., Hoover, D., Gladding, S. and Stacey, M.T., 2010. Wind-enhanced resuspension in the shallow waters of South San Francisco Bay: Mechanisms and potential implications for cohesive sediment transport. Journal of Geophysical Research: Oceans, 115(C11).
Bricker, J.D., S. Inagaki, and S.G. Monismith. 2005. Bed drag coefficient variability under wind waves in a tidal estuary. Journal of Hydraulic Engineering 131 (6): 497–508.
Buchanan, P.A., Downing-Kunz, M.A., Schoellhamer, D.H., and Livsey, D.N., 2018. Continuous water-quality and suspended-sediment transport monitoring in the San Francisco Bay, California, water years 2014–15, U.S. Geological Survey Fact Sheet 2018-3013. Accessible online at https://doi.org/10.3133/fs20183013.
Caffrey, J.M. 1995. Spatial and seasonal patterns in sediment nitrogen remineralization and ammonium concentrations in San Francisco Bay, California. Estuaries 18 (1): 219–233.
Cheng, R.T., C.H. Ling, J.W. Gartner, and P.F. Wang. 1999. Estimates of bottom roughness length and bottom shear stress in South San Francisco Bay, California. Journal of Geophysical Research: Oceans 104 (C4): 7715–7728.
Conomos, T.J., R.E. Smith, and J.W. Gartner. 1985. Environmental setting of San Francisco Bay. In Temporal dynamics of an estuary: San Francisco Bay, 1–12. Dordrecht: Springer.
Downing, J. 2006. Twenty-five years with OBS sensors: The good, the bad, and the ugly. Continental Shelf Research 26 (17–18): 2299–2318.
Downing-Kunz, M.A., and D.H. Schoellhamer. 2013. Seasonal variations in suspended-sediment dynamics in the tidal reach of an estuarine tributary. Marine Geology 345: 314–326.
Edwards, T.K. and Glysson, G.D., 1999. Field methods for measurement of fluvial sediment: US Geological Survey Techniques of Water-Resources Investigations, book 3, chap.
Eisma, D. 1986. Flocculation and de-flocculation of suspended matter in estuaries. Netherlands Journal of Sea Research 20 (2–3): 183–199.
Elias, E., Hansen, J., and Erikson, L.H. 2013. San Francisco Bay Basic Tide Model, http://walrus.wr.usgs.gov/coastal_processes/sfbaycoastalsys/SFBay_model/, https://doi.org/10.5066/F7DN4330.
García, M.H. 2008. Sedimentation engineering: Processes, measurements, modeling, and practice (ASCE manuals and reports on engineering practice). Reston: American Society of Civil Engineers/ASCE.
Gartner, J.W., R.T. Cheng, P.F. Wang, and K. Richter. 2001. Laboratory and field evaluations of the LISST-100 instrument for suspended particle size determinations. Marine Geology 175 (1–4): 199–219.
Hager, S.W., and L.E. Schemel. 1996. Dissolved inorganic nitrogen, phosphorus, and silicon in South San Francisco Bay. I. Major factors affecting distributions. In San Francisco Bay: The ecosystem, Pacific division, ed. J.T. Hollibaugh, 189–215. San Francisco: American Association for the Advancement of Science.
Helsel, D.R. and Hirsch, R.M., 2002. Statistical methods in wter resources. Techniques of water resources investigations, Book 4, chapter A3. U.S. Geological Survey. https://doi.org/10.3133/twri04A3.
Jaffe, B., and A.C. Foxgrover. 2006. Sediment deposition and erosion in South San Francisco Bay, California from 1956 to 2005, 20. Reston: US Geological Survey.
Lee, B.J., J. Hur, and E.A. Toorman. 2017. Seasonal variation in flocculation potential of river water: Roles of the organic matter pool. Water. 9 (5): 335.
Levesque VA, Oberg KA., 2012. Computing discharge using the index velocity method: US Geological Survey Techniques and Methods 3–A23, 148 p. Also available at http://pubs.usgs.gov/tm/3a23/.2012.
Love, A.H., B.K. Esser, and J.R. Hunt. 2003. Reconstructing contaminant deposition in a San Francisco Bay marine, California. Journal of Environmental Engineering 129 (7): 659–666.
Lucas, L.V., J.R. Koseff, S.G. Monismith, and J.K. Thompson. 2009. Shallow water processes govern system-wide phytoplankton dynamics: A modeling study. Journal of Marine Systems 75: 70–86. https://doi.org/10.1016/j.marsys.2008.07.011.
Manning, A.J. 2004a. Observations of the properties of flocculated cohesive sediment in three western European estuaries. Journal of Coastal Research SI41: 70–81.
Manning, A.J. 2004b. The observed effects of turbulence on estuarine flocculation. Journal of Coastal Research SI41: 90–104.
Manning, A.J., and K.R. Dyer. 2002. The use of optics for the in-situ determination of flocculated mud characteristics. Journal of Optics A: Pure and Applied Optics 4: S71–S81.
Manning, A.J., and K.R. Dyer. 2007. Mass settling flux of fine sediments in Northern European estuaries: Measurements and predictions. Marine Geology 245: 107–122. https://doi.org/10.1016/j.margeo.2007.07.005.
Manning, A.J., and D.H. Schoellhamer. 2013. Factors controlling floc settling velocity along a longitudinal estuarine transect. Marine Geology 1 (345): 266–280.
Manning, A.J., Friend, P.L., Prowse, N. and Amos, C.L. (2007). Preliminary findings from a study of Medway Estuary (UK) natural mud floc properties using a laboratory mini-flume and the LabSFLOC system. Continental Shelf Research, doi:https://doi.org/10.1016/j.csr.2006.04.011.
Manning, A.J., Baugh, J.V., Spearman, J. and Whitehouse, R.J.S., 2010. Flocculation settling characteristics of mud: Sand mixtures. Ocean Dynamics, doi: https://doi.org/10.1007/s10236-009-0251-0.
Manning, A.J., Baugh, J.V., Soulsby, R.L., Spearman, J.R. and Whitehouse, R.J.S., 2011. Cohesive sediment flocculation and the application to settling flux modelling. In: Silvia Susana Ginsberg (Ed.), Sediment transport, Publisher: InTech (Vienna), Chapter 5, pp. 91-116, DOI: https://doi.org/10.5772/16055.
Manning, A.J., Whitehouse, R.J.S. and Uncles, R.J.. 2017. Suspended particulate matter: The measurements of flocs. In: R.J. Uncles and S. Mitchell (Eds), ECSA practical handbooks on survey and analysis methods: Estuarine and coastal hydrography and sedimentology, Chapter 8, pp. 211–260, Pub. Cambridge University Press, DOI: https://doi.org/10.1017/9781139644426, ISBN 978-1-107-04098-4.
Markussen, T.N., and T.J. Andersen. 2013. A simple method for calculating in situ floc settling velocities based on effective density functions. Marine Geology 344: 10–18.
Markussen, T.N., and T.J. Andersen. 2014. Flocculation and floc break-up related to tidally induced turbulent shear in a low-turbidity, microtidal estuary. Journal of Sea Research 89: 1–11.
McGann, M., L. Erikson, E. Wan, C. Powell, and R.F. Maddocks. 2013. Distribution of biologic, anthropogenic, and volcanic constituents as a proxy for sediment transport in the San Francisco Bay Coastal System. Marine Geology 345: 113–142.
McKee, L.J., M. Lewicki, D.H. Schoellhamer, and N.K. Ganju. 2013. Comparison of sediment supply to San Francisco Bay from watersheds draining the Bay Area and the Central Valley of California. Marine Geology 345: 47–62.
Mikeš, D., and A.J. Manning. 2010. An assessment of flocculation kinetics of cohesive sediments from the Seine and Gironde estuaries, France, through laboratory and field studies. Journal of Waterway, Port, Coastal, and Ocean Engineering (ASCE) 136 (6): 306–318. https://doi.org/10.1061/(ASCE)WW.1943-5460.0000053.
Ruhl, C.A., and M.R. Simpson. 2005. Computation of discharge using the index-velocity method in tidally affected areas, 1–41. Denver: US Department of the Interior, US Geological Survey.
Rustomji, P., and S.N. Wilkinson. 2008. Applying bootstrap resampling to quantify uncertainty in fluvial suspended sediment loads estimated using rating curves. Water Resources Research 44 (9).
Sahin, C., H.A.A. Guner, M. Ozturk, and A. Sheremet. 2017a. Floc size variability under strong turbulence: Observations and artificial neural network modeling. Applied Ocean research 68: 130–141.
Sahin, C., R. Verney, A. Sheremet, and G. Voulgaris. 2017b. Acoustic backscatter by suspended cohesive sediments: Field observations, Seine Estuary, France. Continental Shelf Research 134: 39–51.
Schraga, T.S. & Cloern, J.E., 2017, Water quality measurements in San Francisco Bay by the U.S. Geological Survey, 1969–2015. Scientific Data 4:170098 doi:https://doi.org/10.1038/sdata.2017.98.
Schraga, T.S., Nejad, E.S., Martin, C.A., and Cloern, J.E., 2018, USGS measurements of water quality in San Francisco Bay (CA), beginning in 2016 (ver. 2.0, June 2018): U.S. Geological Survey data release, https://doi.org/10.5066/F7D21WGF.
Shellenbarger, G.G., S.A. Wright, and D.H. Schoellhamer. 2013. A sediment budget for the southern reach in San Francisco Bay, CA: Implications for habitat restoration. Marine Geology 345: 281–293.
Soulsby, R.L., A.J. Manning, J. Spearman, and R.J.S. Whitehouse. 2013. Settling velocity and mass settling flux of flocculated estuarine sediments. Marine Geology. https://doi.org/10.1016/j.margeo.2013.04.006.
Webster, M.D., Pope, G.L., Friebel, M.F., Freeman, L.A., Brockner, S.J., 2005. Water resources data, California, water year 2004: Volume 2, Pacific slope basins from Arroyo Grande to Oregon state line except Central Valley. (USGS Water-Data Report CA-04-2). (445 pp.).
Winterwerp, J.C. 2002. On the flocculation and settling velocity of estuarine mud. Continental Shelf Research 22 (9): 1339–1360.
Winterwerp, J.C., A.J. Manning, C. Martens, T. de Mulder, and J. Vanlede. 2006. A heuristic formula for turbulence-induced flocculation of cohesive sediment. Estuarine, Coastal and Shelf Science 68: 195–207.
Zhang, N., C.E.L. Thompson, I.H. Townend, K.E. Rankin, D.M. Paterson, and A.J. Manning. 2018. Nondestructive 3D imaging and quantification of hydrated biofilm-sediment aggregates using X-ray microcomputed tomography. Environmental Science & Technology 52 (22): 13306–13313. https://doi.org/10.1021/acs.est.8b03997.
The Regional Monitoring Program for Water Quality in San Francisco Bay and a San Francisco Bay Water Board enforcement action provided funding for data collection.
Communicated by Neil Kamal Ganju
Electronic Supplementary Material
About this article
Cite this article
Livsey, D.N., Downing-Kunz, M.A., Schoellhamer, D.H. et al. Suspended Sediment Flux in the San Francisco Estuary: Part I—Changes in the Vertical Distribution of Suspended Sediment and Bias in Estuarine Sediment Flux Measurements. Estuaries and Coasts 43, 1956–1972 (2020). https://doi.org/10.1007/s12237-020-00734-z
- Estuarine processes
- Suspended sediment
- Sediment flux
- Sediment supply
- Cohesive sediment
- San Francisco estuary