Suspended-sediment dynamics in the tidal reach of a San Francisco Bay tributary

Ocean Dynamics
California State Coastal Conservancy; US Army Corps of Engineers; the Regional Monitoring Program for Water Quality in San Francisco Bay; USGS Priority Ecosystems Science Program; Santa Clara Valley Water District
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To better understand suspended-sediment transport in a tidal slough adjacent to a large wetland restoration project, we deployed continuously measuring temperature, salinity, depth, turbidity, and velocity sensors in 2010 at a near-bottom location in Alviso Slough (Alviso, California, USA). Alviso Slough is the downstream reach of the Guadalupe River and flows into the far southern end of San Francisco Bay. River flow is influenced by the Mediterranean climate, with high flows (∼90 m3 s−1) correlated to episodic winter storms and low base flow (∼0.85 m3 s−1) during the summer. Storms and associated runoff have a large influence on sediment flux for brief periods, but the annual peak sediment concentrations in the slough, which occur in April and May, are similar to the rest of this part of the bay and are not directly related to peak discharge events. Strong spring tides promote a large upstream sediment flux as a front associated with the passage of a salt wedge during flood tide. Neap tides do not have flood-directed fronts, but a front seen sometimes during ebb tide appears to be associated with the breakdown of stratification in the slough. During neap tides, stratification likely suppresses sediment transport during weaker flood and ebb tides. The slough is flood dominant during spring tides, and ebb dominant during neap tides. Extreme events in landward (salt wedge) and bayward (rainfall events) suspended-sediment flux account for 5.0 % of the total sediment flux in the slough and only 0.55 % of the samples. The remaining 95 % of the total sediment flux is due to tidal transport, with an imbalance in the daily tidal transport producing net landward flux. Overall, net sediment transport during this study was landward indicating that sediment in the sloughs may not be flushed to the bay and are available for sedimentation in the adjacent marshes and ponds.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Suspended-sediment dynamics in the tidal reach of a San Francisco Bay tributary
Series title Ocean Dynamics
DOI 10.1007/s10236-015-0876-0
Volume 65
Issue 11
Year Published 2015
Language English
Publisher Springer
Publisher location Berlin
Contributing office(s) California Water Science Center
First page 1477
Last page 1488
Country United States
State California
City Alviso
Other Geospatial Alviso Slough
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