Restoration Project Introduction
The South Bay Salt Pond Restoration Project helped fund a three-year study by the Bay Regional Monitoring Program's Sediment Working Group of Lower South Bay continuous suspended sediment monitoring. This report presents results of the three years of monitoring. The third year of modeling used an improved calibration to relate turbidity with suspended sediment concentrations.
Key results include:
- Turbidity and suspended sediment concentration showed patterns of higher values in slough sites than shoal or deep channel sites.
- Shoals showed mostly low turbidity and suspended sediment concentration with periods of elevated levels from wave-driven resuspension of benthic sediments.
- A wave gauge at Hayward showed increased wave height with windspeed, and increased turbidity with wave height.
- Storms are a major driver of increased turbidity and suspended sediment concentration in the region.
Future work by the Sediment Working Group will use this dataset for detailed studies of Bay sediment dynamics.
Executive Summary
This report presents results from a three-year effort (2022-2024) to estimate continuous suspended sediment concentration (SSC) in the South Bay (SB) and Lower South Bay (LSB) subembayments of San Francisco Bay (SFB). We used discrete SSC samples to calibrate high-frequency (15-min) turbidity measurements from the Nutrient Management Strategy’s (NMS) moored sensor array, resulting in high-frequency SSC estimates at eight study sites. This effort represents a collaboration between the NMS, San Francisco Bay Regional Monitoring Program, and South Bay Salt Pond Restoration Project.
The moored sensor array used for turbidity data collection consisted of 7 YSI EXO2 multiparameter sondes and 1 PME C7 turbidity-only sensor. We evaluated several turbidity-SSC models for the 7 EXO2 sites, ultimately selecting a series of three slope-only (y-intercept = 0) least squares linear regressions (LSLRs) from log10-log10 transformed data grouped together based on the three habitat types in SB and LSB (channel, slough, and shoal). This calibration model represents a change from Year 1 and Year 2 reports, which utilized a linear mixed effect model (LMM). Turbidity from the C7 site was also calibrated using a slope-only LSLR from log10-log10 data. Calibrations at all sites showed reasonable agreement between log10(turb) and log10(SSC), with R2 = 0.89, 0.87, and 0.85 for regressions at the channel, slough, and shoal sites, respectively, and R2 = 0.93 for the C7 site. From these calibrations we created continuous 15-min SSC datasets at 8 locations, representing 1 channel, 4 shoal, and 3 slough sites. These high-frequency SSC data are designed for use in more targeted studies of SFB SSC dynamics, and will be made available for download from the San Francisco Estuary Institute (SFEI) website.
Suggested citation:
Volaric, M; Mourier, L.; Montgomery, L.; Noland, K.; Senn, D.; Chelsky, A. 2025. Continuous Suspended Sediment Monitoring in South and Lower South San Francisco Bay: Final Report. SFEI Contribution No. 1229. San Francisco Estuary Institute: Richmond, CA.