Drag and sediment transport: conditions at the bottom boundary

Science Center Objects

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.

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

USGS physical scientist Cordell Johnson, at left, and USGS research oceanographer Jessie Lacy, both from the Pacific Coastal and Marine Science Center, guide a tripod with instruments into the waters of the Mokelumne River where it meets the San Joaquin River. The Mokelumne is part of the vast Sacramento-San Joaquin River Delta in California, located east of San Francisco Bay and south of Sacramento.

(Credit: John Koster, USGS)

This research is part of the project Sediment Transport in Coastal Environments.


Investigate the influence of seafloor properties, including bed sediment grain size, bedform morphology, and vegetation characteristics, on sediment resuspension and transport.

Develop parameterizations of the influence of seafloor properties on sediment transport for inclusion in numerical models.

Investigate the temporal variability of bed sediment grain size on event and seasonal time scales, and investigate the response of bedform morphology to changes in bed sediment grain size.

Collaborate with Team members in collecting oceanographic and sediment transport data to advance understanding of coastal ecosystems and coastal hazards.


Two people install instruments atop a permanent mooring called a dolphin, large wooden pilings affixed in shallow water.

Pete Dal Ferro and Andrew Stevens, both from the USGS Pacific Coastal and Marine Science Center (PCMSC) in Santa Cruz, California, install a Vaisala WXT weather station in Grizzly Bay, east of San Pablo Bay and northeast of San Francisco. The weather station collects wind speed, temperature, air pressure, relative humidity, and rainfall, and data are transmitted to a web page in real time via a custom-built data logger and modem designed by PCMSC oceanographer Dan Nowacki. Other sensors installed in Grizzly and San Pablo Bays, collecting wave and current speed, water temperature, salinity, pressure, and more, can be used with data from this weather station to help gain a better understanding of the conditions that influence sediment movement through the Bays.

The weather station is installed on this structure which is called a "dolphin," in the middle of Grizzly Bay. Obviously, someone (not us!) long ago thought it woud be funny to install a "pedestrian crossing" sign!

(Credit: Sam McGill, USGS. Public domain.)

A nondescript white instrument box sits up high atop piers in the water with cables and a small solar panel.

The weather station gets its power from a small solar panel. Data collected from the station is transmitted via a wireless modem.

(Credit: Pete Dal Ferro, USGS. Public domain.)

A structure made of wooden pilings with a platform around the top stands in water with fog and hills in the far background.

The dolphin in Grizzly Bay with the USGS weather station installed on top. We will use the data from the weather station in conjunction with other oceanographic data, in our studies of sediment movement in the bay.

(Credit: Pete Dal Ferro, USGS. Public domain.)