Improved Lower South Bay suspended-sediment flux measurements Active
Tidal marshes provide animal habitats and prevent erosion. Expanding towns and cities have claimed major parts of San Francisco Bay’s marshland. Sediment deposits are essential to rebuilding tidal marshes and keeping existing marshes intact. In the southern part of the Bay, the largest tidal wetland restoration project on the west coast is underway. Sediment flux measurements are key in deciding how to manage water resources and in ensuring water quality for human, aquatic, and environmental health.
Problem
Current USGS methods for measuring suspended-sediment flux do not accurately account for the effect of flocculation (sediment clumping together). A proper knowledge of flocculation is important in determining sediment levels. Recently, a new method for understanding flocculation in estuarine sediment flux measurements has impacted sediment flux calculation for the lower South Bay. Using this new method, changes in flocculation size and density are estimated from a settling-velocity parameter derived from turbidity (cloudiness) measurements taken at different depths. Preliminary results indicates that flocculation coincides with the tidal cycle and is more significant on flood tides. However, this has not been completely validated.
Objectives
- Improve estimates of lower South Bay sediment flux by accounting for the effect of flocculation.
- Compare sediment flux estimates from optical and acoustic surrogate measures of suspended-sediment concentration.
Science Plan
Scientists will validate the newly proposed method with in-situ flocculation size, particle size distribution, suspended-sediment concentrations, and optical turbidity measurements through entire flood-ebb cycles during spring and neap tides. Initial analyses of previous settling velocity data (measured by flocculation camera) suggests that the settling-velocity parameter is reasonable. However, such data has not been collected through entire flood-ebb cycles, nor for all seasons. Seasonal and spring-neap sampling is still needed to determine settling velocities and confirm settling-velocity parameters for all time periods. Sediment flux monitoring will follow previously established USGS methods, as well as grain-size analyzation using an LISST-100x laser. To measure suspended-sediment throughout tidal cycles, scientists will collect water samples at 30-minute intervals using an automatic water sampler.
Below are publications associated with this project.
Wetland Accretion Rate Model of Ecosystem Resilience (WARMER) and its application to habitat sustainability for endangered species in the San Francisco Estuary
Factors controlling floc settling velocity along a longitudinal estuarine transect
A sediment budget for the southern reach in San Francisco Bay, CA: Implications for habitat restoration
Guidelines and standard procedures for continuous water-quality monitors: Station operation, record computation, and data reporting
Computation of discharge using the index-velocity method in tidally affected areas
Below are partners associated with this project.
- Overview
Tidal marshes provide animal habitats and prevent erosion. Expanding towns and cities have claimed major parts of San Francisco Bay’s marshland. Sediment deposits are essential to rebuilding tidal marshes and keeping existing marshes intact. In the southern part of the Bay, the largest tidal wetland restoration project on the west coast is underway. Sediment flux measurements are key in deciding how to manage water resources and in ensuring water quality for human, aquatic, and environmental health.
Problem
Current USGS methods for measuring suspended-sediment flux do not accurately account for the effect of flocculation (sediment clumping together). A proper knowledge of flocculation is important in determining sediment levels. Recently, a new method for understanding flocculation in estuarine sediment flux measurements has impacted sediment flux calculation for the lower South Bay. Using this new method, changes in flocculation size and density are estimated from a settling-velocity parameter derived from turbidity (cloudiness) measurements taken at different depths. Preliminary results indicates that flocculation coincides with the tidal cycle and is more significant on flood tides. However, this has not been completely validated.
Objectives
- Improve estimates of lower South Bay sediment flux by accounting for the effect of flocculation.
- Compare sediment flux estimates from optical and acoustic surrogate measures of suspended-sediment concentration.
Science Plan
Scientists will validate the newly proposed method with in-situ flocculation size, particle size distribution, suspended-sediment concentrations, and optical turbidity measurements through entire flood-ebb cycles during spring and neap tides. Initial analyses of previous settling velocity data (measured by flocculation camera) suggests that the settling-velocity parameter is reasonable. However, such data has not been collected through entire flood-ebb cycles, nor for all seasons. Seasonal and spring-neap sampling is still needed to determine settling velocities and confirm settling-velocity parameters for all time periods. Sediment flux monitoring will follow previously established USGS methods, as well as grain-size analyzation using an LISST-100x laser. To measure suspended-sediment throughout tidal cycles, scientists will collect water samples at 30-minute intervals using an automatic water sampler.
- Publications
Below are publications associated with this project.
Wetland Accretion Rate Model of Ecosystem Resilience (WARMER) and its application to habitat sustainability for endangered species in the San Francisco Estuary
Salt marsh faunas are constrained by specific habitat requirements for marsh elevation relative to sea level and tidal range. As sea level rises, changes in relative elevation of the marsh plain will have differing impacts on the availability of habitat for marsh obligate species. The Wetland Accretion Rate Model for Ecosystem Resilience (WARMER) is a 1-D model of elevation that incorporates bothAuthorsKathleen M. Swanson, Judith Z. Drexler, David H. Schoellhamer, Karen M. Thorne, Michael L. Casazza, Cory T. Overton, John C. Callaway, John Y. TakekawaFactors controlling floc settling velocity along a longitudinal estuarine transect
A 147 km longitudinal transect of flocculated cohesive sediment properties in San Francisco Bay (SFB) was conducted on June 17th, 2008. Our aim was to determine the factors that control floc settling velocity along the longitudinal axis of the estuary. The INSSEV-LF video system was used to measure floc diameters and settling velocities at 30 stations at a distance of 0.7 m above the estuary bed.AuthorsA.J. Manning, David H. SchoellhamerA sediment budget for the southern reach in San Francisco Bay, CA: Implications for habitat restoration
The South Bay Salt Pond Restoration Project is overseeing the restoration of about 6000 ha of former commercial salt-evaporation ponds to tidal marsh and managed wetlands in the southern reach of San Francisco Bay (SFB). As a result of regional groundwater overdrafts prior to the 1970s, parts of the project area have subsided below sea-level and will require between 29 and 45 million m3 of sedimenAuthorsGregory Shellenbarger, Scott A. Wright, David H. SchoellhamerGuidelines and standard procedures for continuous water-quality monitors: Station operation, record computation, and data reporting
The U.S. Geological Survey uses continuous water-quality monitors to assess the quality of the Nation's surface water. A common monitoring-system configuration for water-quality data collection is the four-parameter monitoring system, which collects temperature, specific conductance, dissolved oxygen, and pH data. Such systems also can be configured to measure other properties, such as turbidity oAuthorsRichard J. Wagner, Robert W. Boulger, Carolyn J. Oblinger, Brett A. SmithComputation of discharge using the index-velocity method in tidally affected areas
Computation of a discharge time-series in a tidally affected area is a two-step process. First, the cross-sectional area is computed on the basis of measured water levels and the mean cross-sectional velocity is computed on the basis of the measured index velocity. Then discharge is calculated as the product of the area and mean velocity. Daily mean discharge is computed as the daily average of thAuthorsCatherine A. Ruhl, Michael R. Simpson - Partners
Below are partners associated with this project.