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San Francisco Bay Delta

SF Bay Projects

San Francisco Delta Projects

Delta Sediment Transport

Contact: Tara Morgan-King, Hydrologist, tamorgan@usgs.gov

Declines in the populations of several species of pelagic fishes in the San Francisco Estuary delta smelt, longfin smelt, striped bass, and threadfin shad have led to new studies and research on the biology and ecology of all four species (Sommer et al. 2007, Baxter et al. 2008). However, while these studies are being conducted, it is desirable to develop predictive tools for suspended sediment (and turbidity) so that management actions that attempt to improve smelt habitat through manipulation of the turbidity field can be evaluated.

While some data on sediment transport and geomorphology exist for the Delta, there are major data gaps that preclude accurate specification of model boundary and initial conditions. Further research and studies are needed to more precisely define the relationships between turbidity, habitat, and smelt movement, along with, measurements that constrain model parameters related to various physical processes, such as erosion rates and settling velocities.

The purpose of the proposed work is to collect data that will support the development, calibration, and validation of numerical models of sediment transport and turbidity in the Sacramento-San Joaquin Delta.

Relevant Work:

Oltmann, R.N., Schoellhamer, D.H., and Dinehart, R.L., 1999, Sediment inflow to the Sacramento-San Joaquin Delta and the San Francisco Bay: Interagency Ecological Program newsletter, v. 12, no. 1, pp. 30-33.

Schoellhamer, D.H., Wright, S.A., and Drexler, J.Z.,in press, Conceptual Model of Sedimentation in the Sacramento - San Joaquin River Delta: San Francisco Estuary and Watershed Science. (IP-021663)

Wright, S.A., and Schoellhamer, D.H., 2004, Suspended sediment transport where rivers become estuaries: Sacramento - San Joaquin River Delta, water years 1999-2002: Eos Transactions AGU, v. 85, no. 47, Fall Meeting Supplement, Abstract H53C-1262.

Wright, S.A., and Schoellhamer, D.H., 2005, Estimating sediment budgets at the interface between rivers and estuaries with application to the Sacramento-San Joaquin River Delta. Water Resources Research, 41, W09428, doi:10.1029/2004WR003753.


Cache Slough Sediment Transport Processes

Contact: Tara Morgan-King, Hydrologist, tamorgan@usgs.gov

Declining turbidity is one of several factors that may explain a severe decline in the abundance of delta smelt and other fish species in the 2000s, known as the Pelagic Organism Decline (POD). Past research has shown declines in sediment budgets in the San Francisco Delta, while recently the Cache Slough complex has had higher suspended solid concentrations. This anomaly has led to the examination of the mechanisms that account for the high turbidity in this area.

This project focuses on sediment sources and sinks of the complex and addresses two research questions: 1) Does Liberty Island play a dominant role on the hydrodynamics and sediment concentrations of the Cache Slough complex and 2) Is the turbidity within the Cache Slough complex dependent on localized production from wind-wave and tidal resuspension? Continuous measurements consist of conductivity, temperature, depth, optical turbidity, velocity and stage. Cross sectional flow and suspended sediment discharge are calculated from which we analyze sediment transport into and out of the region.

Relevant work:

Hestir, E.L., Schoellhamer, D.H., Morgan-King, T., and Ustin, S., 2010, An Observed Step Change in River Delta Turbidity Following 1982-1983 El Nino Floods: Proceedings of the American Geophysical Union Meeting, San Francisco, Calif., December 13-17, 2010.

Morgan-King, T.L., and Schoellhamer, D.H., 2010, Sedimentation processes and turbidities favoring endangered fish, Northern Sacramento-San Joaquin River Delta: Proceedings of the 2010 Bay-Delta Science Conference, Sacramento, California, September 27-29, 2010.


Delta sediment measurements to support numerical modeling of turbidity

Contact: Scott Wright, Research Hydrologist, sawright@usgs.gov

Project page

The purpose of the proposed work is to collect data that will support the development, calibration, and validation of numerical models of sediment transport and turbidity in the Sacramento-SanJoaquin Delta. While some data on sediment transport and geomorphology exist for the Delta, there are major data gaps that preclude accurate specification of model boundary and initial conditions. Also, measurements are needed to constrain model parameters related to various physical processes, such as erosion rates and settling velocities. These measurements could begin almost immediately and data would be provided, provisionally, on an ongoing basis to facilitate model development in the near-term.

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