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
- Science-in-Short Podcast: Drift, Drop or Flock? An Interview with Jessie Lacy & Karen Thorne
- Are Invasive Plants Trapping the Sediment that a Healthy Estuary Needs? Sweating the Small Stuff in California’s Sacramento-San Joaquin River Delta - USGS Sound Waves, August 2018
- 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
We investigate mechanisms of sediment transport, resuspension dynamics in shoals, wave evolution in the shallows, wave attenuation in marshes, and transport of sediment between mudflats and marshes. We produce data sets for calibration of and comparison with sediment transport models, including wave parameters, suspended sediment concentration, and sediment flux. This research is part of the...
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.
Hydrodynamic and sediment transport data from San Pablo Bay and Grizzly Bay, California, 2019
USGS scientists collected hydrodynamic and sediment-transport data at shallow water sites in San Pablo Bay and Grizzly Bay, in northern San Francisco Bay between June and November 2019. The data were collected to determine hydrodynamic forcing, bed roughness, suspended-sediment concentration, and physical properties of the sediment bed. This data release includes hydrodynamic and sediment...
Near-bed velocity measurements in Monterey Bay during arrival of the 2010 Chile Tsunami
On February 27, 2010, a tsunami originating near Chile arrived in Monterey Bay, California. This data release comprises two hours of pressure and near-bed velocity data spanning the largest tsunami waves. At the time, the U.S. Geological Survey Pacific Coastal and Marine Science Center had a remotely-controlled instrumented platform deployed adjacent to the Santa Cruz Municipal Wharf (m
Aerial imagery and structure-from-motion derived data products from UAS survey of the Liberty Island Conservation Bank Wildlands restoration site, Sacramento-San Joaquin Delta, California, October 2018
Unmanned aerial systems were used to acquire high-resolution imagery of the Liberty Island Conservation Bank Wildlands restoration site in the Sacramento–San Joaquin Delta in California, with the goal of using structure-from-motion photogrammetric techniques to derive a digital surface model, orthomosaic imagery, and a topographic point cloud. The survey was conducted using two Department of...
Bed sediment properties in Little Holland Tract and Liberty Island, Sacramento-San Joaquin Delta, California, 2014 to 2019 (ver. 2.0, May 2020)
Bed sediments were collected in two submerged agricultural tracts. Samples were analyzed for grain size distribution, bulk density, or both, from multiple locations during surveys from 2014-2019. This effort was part of a large study to investigate how shallow water habitats in the Delta function and whether they provide good habitat for native fish species, including the Delta smelt.
Sediment transport and aquatic vegetation data from three locations in the Sacramento-San Joaquin Delta, California, 2017 to 2018
We measured currents, suspended-sediment concentration, bed sediment characteristics, and vegetation biomass density in the Sacramento-San Joaquin Delta in 2017-2018, as part of a project investigating the influence of invasive aquatic vegetation on flow and sediment flux. This data release includes data from three sites: Lindsey Slough, Middle River, and lower Mokelumne River.
Bathymetry, topography, and acoustic backscatter data, and a digital elevation model (DEM) of the Cache Slough Complex and Sacramento River Deep Water Ship Channel, Sacramento-San Joaquin Delta, California
This data release presents bathymetric and topographic data from surveys performed between 2017 and 2018 in the Cache Slough Complex and the Sacramento River Deep Water Ship Channel (DWSC), northern Sacramento-San Joaquin Delta, California. The shallow, highly vegetated aquatic habitats of this region necessitated a variety of survey platforms and techniques. In the deeper channels, swath...
Hydrodynamic and sediment transport data from San Pablo Bay (northern San Francisco Bay), 2011-2012
The U.S. Geological Survey Pacific Coastal and Marine Science Center collected data to investigate sediment dynamics in the shallows of San Pablo Bay in two deployments: February to March 2011 (ITX11) and May to June 2012 (ITX12). This data release includes time-series data and grain-size distributions from sediment grabs collected during the deployments. During each deployment, time
Hydrodynamic and sediment transport data from San Pablo Bay and China Camp marsh (northern San Francisco Bay), 2013-2016
The USGS Pacific Coastal and Marine Science Center collected data to investigate sediment dynamics in the shallows of San Pablo Bay (SP) and sediment exchange between bay shallows and the tidal salt marsh in China Camp State Park (CMC) in a series of deployments between December 2013 and June 2016. This data release includes two related groups of data sets, one for SP and one for CMC.
Wind-wave and suspended-sediment data from Liberty Island and Little Holland Tract, Sacramento-San Joaquin Delta, California
Investigate the influence of wind waves on sediment dynamics in two flooded agricultural tracts. Part of a large interdisciplinary study led by the USGS and funded by the U.S. Bureau of Reclamation to investigate how shallow-water habitats in the Sacramento-San Joaquin Delta function and whether they provide good habitat for native fish species, including the Delta smelt.
Digital elevation model of Little Holland Tract, Sacramento-San Joaquin Delta, California, 2015
This product is a digital elevation model (DEM) for the Little Holland Tract in the Sacramento-San Joaquin River Delta, California based on U.S. Geological Survey (USGS)-collected elevation data, merged with existing topographic and bathymetric elevation data. The USGS collected topographic and bathymetric elevation data in 2015, using a combination of methods. Topographic and shall
Cohesive sediment modeling in a shallow estuary: Model and environmental implications of sediment parameter variation
Numerical models of sediment transport in estuarine systems rely on parameter values that are often poorly constrained and can vary on timescales relevant to model processes. The selection of parameter values can affect the accuracy of model predictions, while environmental variation of these parameters can impact the temporal and spatial ranges...
Allen, Rachel; Lacy, Jessica R.; Stevens, Andrew W. Influence of invasive submerged aquatic vegetation (E. densa) on currents and sediment transport in a freshwater tidal system
We present a field study combining measurements of vegetation density, vegetative drag, and reduction of suspended-sediment concentration (SSC) within patches of the invasive submerged aquatic plant Egeria densa. Our study was motivated by concern that sediment trapping by E. densa, which has proliferated in the Sacramento–San Joaquin...
Lacy, Jessica R.; Foster-Martinez, Madeline R.; Allen, Rachel M.; Drexler, Judith Z. 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.
Are Invasive Plants Trapping the Sediment that a Healthy Estuary Needs? Sweating the Small Stuff in California’s Sacramento-San Joaquin River Delta
In recent years, invasive aquatic plants have increased exponentially in the shallow waters of California’s Sacramento-San Joaquin River Delta, clogging about 17,400 acres (nearly 30 square miles) of the waterways. Among the plants’ many effects are changes in the way mud and sand move through the region.