Skip to main content
U.S. flag

An official website of the United States government

Jessie Lacy

Research Oceanographer with the USGS Pacific Coastal and Marine Science Center

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

Science and Products

link
View from the sky looking at mouth of river with lots of sediment deposited at a beach.

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 natural...
By
Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Sediment Lab Suite and Carbon Analysis Laboratory
link

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 natural...
Learn More
link
View from the air across a tidal march, mudflat, and channels with bay water to the right and a city in the background.

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.
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center
link

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.
Learn More
link
Two people hold onto a large metal tripod with instruments suspended from a cable as they guide it into the water.

Drag and sediment transport: conditions at the bottom boundary

Research on bed sediment grain size, bedform morphology, vegetation characteristics, and sediment resuspension and transport.
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Sediment Lab Suite and Carbon Analysis Laboratory
link

Drag and sediment transport: conditions at the bottom boundary

Research on bed sediment grain size, bedform morphology, vegetation characteristics, and sediment resuspension and transport.
Learn More
link
Invasive Aquatic Vegetation

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.
By
California Water Science Center, Pacific Coastal and Marine Science Center
link

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.
Learn More

Hydrodynamic, sediment transport, and sediment flocculation data from south San Francisco Bay, California, summer 2020

The U.S. Geological Survey (USGS) Pacific Coastal and Marine Science Center collected hydrodynamic and suspended sediment flocculation data at channel and shallow water sites in south San Francisco Bay in July 2020. The data were used to determine water column stratification, turbulence profiles, and floc size evolution. The goal of this project was to bound the controls on floc size and floc sett
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Hydrodynamic and sediment transport data from San Pablo Bay and Grizzly Bay, California, 2020

The U.S. Geological Survey Pacific Coastal and Marine Science Center collected hydrodynamic and sediment-transport data at shallow water sites in San Pablo Bay and Grizzly Bay, in northern San Francisco Bay between January and September 2020. The data were collected to determine hydrodynamic forcing, bed roughness, suspended-sediment concentration, and physical properties of the sediment bed. This
By
Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Hydrodynamic and sediment transport data from San Pablo Bay and Grizzly Bay, California, 2019

The U.S. Geological Survey Pacific Coastal and Marine Science Center 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 dat
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

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 (mean depth 9
By
Pacific Coastal and Marine Science Center

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 (UAS) 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 (SfM) photogrammetric techniques to derive a digital surface model, orthomosaic imagery, and a topographic point cloud. The survey was conducted using two Depart
By
Pacific Coastal and Marine Science Center

Bed sediment properties in Little Holland Tract and Liberty Island, Sacramento-San Joaquin Delta, California, 2014 to 2017

Bed sediments were collected by the USGS Pacific Coastal and Marine Science Center (PCMSC) in two submerged agricultural tracts, Liberty Island and Little Holland Tract, in the northern Sacramento-San Joaquin Delta, California. Samples were analyzed for grain size distribution, bulk density, or both. Analyses were conducted using PCMSC sediment lab standard techniques (see Process Step in metadata
By
Pacific Coastal and Marine Science Center

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 (SSC), 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 (IAV) on flow and sediment flux. This data release includes data from three sites: Lindsey Slough (April 2017), Middle River (March 2018) and the l
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

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 bathymet
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

Wind-wave and suspended-sediment data from Liberty Island and Little Holland Tract, Sacramento-San Joaquin Delta, California (ver. 2.0, September 2019)

Data were collected by the U.S. Geological Survey (USGS) Pacific Coastal and Marine Science Center to investigate the influence of wind waves on sediment dynamics in two flooded agricultural tracts in the northern Sacramento-San Joaquin Delta: Little Holland Tract and Liberty Island. This effort is part of a large interdisciplinary study led by the USGS California Water Science Center and funded b
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

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 series of cur
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center, Sediment Lab Suite and Carbon Analysis Laboratory

Hydrodynamic and sediment transport data from San Pablo Bay and China Camp marsh (northern San Francisco Bay), 2013-2016

The U.S. Geological Survey Pacific Coastal and Marine Science Center collected data to investigate sediment dynamics in the shallows of San Pablo Bay and sediment exchange between bay shallows and the tidal salt marsh in China Camp State Park in a series of deployments between December 2013 and June 2016. This data release includes two related groups of data sets. The first group, denoted by names
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center
Filter Total Items: 30

Numerical simulation of the boundary layer flow generated in Monterey Bay, California by the 2010 Chilean tsunami: Case study

This work presents a case study involving the numerical simulation of the unsteady boundary layer generated by the 2010 Chilean tsunami, as measured by field equipment in Monterey Bay, California, USA. A one-dimensional vertical (1DV) boundary layer model is utilized, solving Reynolds-averaged Navier–Stokes equations, coupled with two-equation k–ω turbulence closure. Local effects of convective ac
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

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 of sediment fluxes, erosion, and deposition in the r

By
Natural Hazards, Coastal and Marine Hazards and Resources Program, Mendenhall Research Fellowship Program, Pacific Coastal and Marine Science Center

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 Delta, is impacting marsh accretion and reducing turbidity. In

By
Natural Hazards, Water Resources, Coastal and Marine Hazards and Resources Program, California Water Science Center, Mendenhall Research Fellowship Program, Pacific Coastal and Marine Science Center

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 sediment transport and local bed changes during perio
By
Natural Hazards, Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

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 measured carbon accumulation (CARs) and inorganic sedimentation rates in su
By
Water Resources, Coastal and Marine Hazards and Resources Program, California Water Science Center, Pacific Coastal and Marine Science Center

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 pacifica (pickleweed) predominates on the marsh plain
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

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, and suspended sediment data were measured at sites

By
Coastal and Marine Hazards and Resources Program, Mendenhall Research Fellowship Program, Pacific Coastal and Marine Science Center

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 estimates of settling velocity. We deployed both instru

By
Natural Hazards, Coastal and Marine Hazards and Resources Program, Mendenhall Research Fellowship Program, Pacific Coastal and Marine Science Center

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 rate of 25 Hz. On the lower and middle tidal flats,
By
Pacific Coastal and Marine Science Center

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 measured near the mouths of two tidal creeks during three
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

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 employing two‐size classes which are representative of m
By
Coastal and Marine Hazards and Resources Program, Pacific Coastal and Marine Science Center

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, we examine the evolution of wave height across a tid
By
Pacific Coastal and Marine Science Center
link

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...

Read Article
link

Making Waves and Ripples in a Giant Flume in Japan

Sand on the seafloor is rarely flat, particularly close to the shore. Currents and waves interact with bed sediment to produce bedforms: ripples...

Read Article
link

Eelgrass in Puget Sound—A New Study of Flow, Sediment Transport, and Zostera marina

Meadows of eelgrass (Zostera marina) provide essential habitat to a wide range of fish and wildlife in the nearshore parts of Puget Sound, Washington...

Read Article
Two men in a small boat, one is at the wheel, the boat is in a calm waterway with trees in the background.
link
A small boat sits on calm waters with trees in the distance, and a cloudy sky.
link
Photos show people preparing data and sample collection devices to go into the water.
link
Two photos show a metal frame that holds instruments to collect data in murky water.
link
video thumbnail: Turbid Bay: Sediment in Motion link

Science and Products