Jessie Lacy
My research interests include: Hydrodynamics of the coastal ocean, estuaries, and lakes; Lateral dynamics in estuaries with complex topography, and their influence on mixing; The dynamics of stratification and baroclinic transport; Estimation of bottom roughness, bottom shear stress, and sediment resuspension in wave-dominated environments; Interaction between aquatic vegetation and hydrodynamics
Biography
Links
- Turbid Bay: Sediment in Motion - Video of sediment transport research in the shallows of San Francisco Bay
- Making Waves and Ripples in a Giant Flume in Japan - USGS Sound Waves, April 2005
- Eelgrass in Puget Sound: A New Study of Flow, Sediment Transport, and Zostera marina - USGS Sound Waves, September 2004
- USGS Pacific Coastal and Marine Science Center
- South Bay Salt Pond Restoration Project
- Elkhorn Slough Tidal Wetland Program
- Environmental Fluid Mechanics Laboratory, Stanford University
Science and Products
Sediment transport between estuarine habitats in San Francisco Bay
This research is part of the project “Sediment Transport in Coastal Environments”
Sediment Transport in Coastal Environments
Our research goals are to provide the scientific information, knowledge, and tools required to ensure that decisions about land and resource use, management practices, and future development in the coastal zone and adjacent watersheds can be evaluated with a complete understanding of the probable effects on coastal ecosystems and communities, and a full assessment of their vulnerability to...
Drag and sediment transport: conditions at the bottom boundary
Research on bed sediment grain size, bedform morphology, vegetation characteristics, and sediment resuspension and transport is part of the Sediment Transport in Coastal Environments project.
Ecosystem Engineers: Impacts of Invasive Aquatic Vegetation on the Delta’s Critical Ecosystems
The Sacramento-San Joaquin Delta (Delta) is home to a diverse community of plants and animals and is the hub of California’s freshwater delivery system. The Delta supplies water for over 25 million Californians and supports millions of acres of farming, commercial and sport fishing, shipping and ports, and recreational boating.
The role of surges during periods of very shallow water on sediment transport over tidal flats
Periods of very shallow water (water depth in the order of 10 cm) occur daily on tidal flats because of the propagation of tides over very gently sloping beds, leading to distinct morphodynamical phenomena. To improve the understanding of the characteristics of velocity and suspended sediment concentration (SSC) surges and their contribution to...
Zhang, Qian; Gong, Zheng; Zhang, Changkuan; Lacy, Jessica R.; Jaffe, Bruce E.; Xu, Beibei; Chen, Xindi Carbon storage and sediment trapping by Egeria densa Planch., a globally invasive, freshwater macrophyte
Invasive plants have long been recognized for altering ecosystem properties, but their long-term impacts on ecosystem processes remain largely unknown. In this study, we determined the impact of Egeria densa Planch, a globally invasive freshwater macrophyte, on sedimentation processes in a large tidal freshwater region. We...
Drexler, Judith Z.; Khanna, Shruti; Lacy, Jessica R. Seasonal variation in sediment delivery across the bay-marsh interface of an estuarine salt marsh
Sediment transport across bay–marsh interfaces depends on wave energy, vegetation, and marsh-edge morphology, and varies over a range of timescales. We investigated these dynamics in a tidal salt marsh with a gently-sloped, vegetated edge adjacent to northern San Francisco Bay. Spartina foliosa (cordgrass) inhabits the lower marsh and Salicornia...
Lacy, Jessica R.; Foster-Martinez, Madeline R.; Allen, Rachel (Contractor); Ferner, Matthew C.; Callaway, John C. Seasonal, spring-neap, and tidal variation in cohesive sediment transport parameters in estuarine shallows
Numerical models for predicting sediment concentrations and transport rely on parameters such as settling velocity and bed erodibility that describe sediment characteristics, yet these parameters are rarely probed directly. We investigated temporal and spatial variation in sediment parameters in the shallows of San Pablo Bay, CA. Flow, turbulence...
Allen, Rachel; Lacy, Jessica R.; Mark T. Stacey; Variano, Evan A Measuring settling velocity in a strongly tidal estuary
Predicting sediment transport in estuarine systems requires understanding sediment settling velocity, its range of fluctuations, and the shortcomings of the tools to measure it. Previous studies have used Laser In-Situ Scattering and Transmissometry (LISST) instruments to measure particle size and Acoustic Doppler Velocimeters (ADV) to return...
Allen, Rachel; Lacy, Jessica R.; Variano, Evan A Bed shear stress estimation under wave conditions using near-bottom measurements: Comparison of methods
Understanding the influence of waves on bed shear stress is critical for predicting morphodynamical behaviours in coastal areas. Near-bed flow was measured on the middle and lower intertidal mudflats along the Jiangsu coast, China, using a three-dimensional acoustic velocimeter that collected a 3.5-cm vertical profile at 1mm resolution and sample...
Zhang, Qian; Gong, Zheng; Zhang, Changkuan; Lacy, Jessica R.; Jaffe, Bruce E.; Xu, Beibei The influence of neap-spring tidal variation and wave energy on sediment flux in salt marsh tidal creeks
Sediment flux in marsh tidal creeks is commonly used to gage sediment supply to marshes. We conducted a field investigation of temporal variability in sediment flux in tidal creeks in the accreting tidal marsh at China Camp State Park adjacent to northern San Francisco Bay. Suspended-sediment concentration (SSC), velocity, and depth were...
Lacy, Jessica R.; Ferner, Matthew C.; Callaway, John C. Three-dimensional modeling of fine sediment transport by waves and currents in a shallow estuary
A suspended sediment transport model is implemented in the unstructured‐grid SUNTANS model and applied to study fine‐grained sediment transport in South San Francisco Bay. The model enables calculation of suspension of bottom sediment based on combined forcing of tidal currents and wind waves. We show that accurate results can be obtained by...
Chou, Yi-Ju; Nelson, Kurt S.; Holleman, Rusty C.; Fringer, Oliver B.; Stacey, Mark T.; Lacy, Jessica R.; Monismith, Stephen G.; Koseff, Jeffrey R. Wave attenuation across a tidal marsh in San Francisco Bay
Wave attenuation is a central process in the mechanics of a healthy salt marsh. Understanding how wave attenuation varies with vegetation and hydrodynamic conditions informs models of other marsh processes that are a function of wave energy (e.g. sediment transport) and allows for the incorporation of marshes into coastal protection plans. Here,...
Foster-Martinez, Madeline R.; Lacy, Jessica R.; Ferner, Matthew C.; Variano, Evan A. Wave attenuation in the shallows of San Francisco Bay
Waves propagating over broad, gently-sloped shallows decrease in height due to frictional dissipation at the bed. We quantified wave-height evolution across 7 km of mudflat in San Pablo Bay (northern San Francisco Bay), an environment where tidal mixing prevents the formation of fluid mud. Wave height was measured along a cross shore transect (...
Lacy, Jessica R.; MacVean, Lissa J. Model-based interpretation of sediment concentration and vertical flux measurements in a shallow estuarine environment
A one-dimensional numerical model describing tidally varying vertical mixing and settling was used to interpret sediment concentrations and vertical fluxes observed in the shoals of South San Francisco Bay by two acoustic Doppler velocimeters (ADVs) at elevations of 0.36 m and 0.72 m above bed. Measured sediment concentrations changed by up to 100...
Brand, Andreas; Lacy, Jessica R.; Gladding, Steve; Holleman, Rusty; Stacey, Mark T. Lateral baroclinic forcing enhances sediment transport from shallows to channel in an estuary
We investigate the dynamics governing exchange of sediment between estuarine shallows and the channel based on field measurements at eight stations spanning the interface between the channel and the extensive eastern shoals of South San Francisco Bay. The study site is characterized by longitudinally homogeneous bathymetry and a straight channel,...
Lacy, Jessica R.; Gladding, Steve; Brand, Andreas; Collignon, Audric; Stacey, Mark T.