Beach Study Hopes to Unlock Mystery
By Ryder W. Miller
An erosion study at Ocean Beach is currently underway
to better understand sediment transport processes
Dr. Patrick Barnard, a research geologist for the
United States Geological Survey (USGS), is the principal
investigator for the study. The study began in October
2003 and Barnard has been collecting data since April
2004. Supporting agencies include The National Park
Service and SF Department of Public Works.
"I chose Ocean Beach based on my knowledge of
what was going on there," said Barnard, who lived
in San Francisco for a number of years.
Because of his knowledge about the erosion problems
at Ocean Beach, Barnard found funding through the
USGS to explore the local sediment transport processes.
Erosion problems continue to damage the parking lot
south of Sloat Boulevard since the El Nino/La Nina
weather phenomenon of 1997 and 1998.
"I thought it would be an excellent project
to provide some independent research," Barnard
He pointed out that it was highly unlikely that concerned
parties, like the local Surfrider Foundation, US Army
Corp of Engineers and National Park Service, would
call for the building of a seawall south of Sloat
Boulevard, preferring a soft solution (rebuilding
with rocks and sand) instead. The erosion threatens
to undermine the Great Highway at the location.
"We can give them an indication of which way
is the best to go," he said.
Tamara Williams, National Park Service liaison for
the Golden Gate National Recreation Area (GGNRA),
said, "Anything that helps us better understand
the coastal processes and the dynamics that are going
on at Ocean Beach really does help us in our management
Williams added, "Certainly one of our goals
there is to allow the natural processes to operate.
The better we understand those, the better we can
work with the challenges associated with them."
Sand elevation patterns at Ocean Beach are seasonal.
During the tranquil months (April to December) sand
accumulates at Ocean Beach and during the winter sand
elevation levels shrink due to ocean waves removing
the sediment. Barnard has observed sand elevation
changes as large as 5 to 6 feet south of Sloat Boulevard.
Recent innovations in field equipment and techniques,
remote sensing and computer modeling make it possible
to perform detailed analyses of the changing physical
processes at Ocean Beach and at other high-energy
Barnard said small academic institutions cannot afford
to use the techniques the USGS is using in the study,
such as a Kinematic GPS (global positioning system),
bathymetric surveys, 3D Beach Mapping, Grain Size
Analysis, Real-Time Monitoring and Nearshore Mapping
(for roughly 1.2 miles out to sea). Most of
the techniques Barnard is using were developed during
the last 10 years.
"Our elevation control is very accurate with
GPS," said Barnard, who will evaluate the behavior
of sediment on the beach on a monthly basis.
Equipment being used for the study includes a camera
atop the Cliff House, a GPS system connected to more
than half a dozen space satellites, digital cameras
to determine sand grain size, personal water craft
and all-terrain vehicles.
Some results thus far include an accurate bathymetric
modeling of the nearby ocean bottom. Barnard has been
able to clearly delineate sand waves moving up and
down Ocean Beach due to the power of the tides.
Barnard hopes to be able to determine the net direction
of tidal currents. Some of the unanswered questions
involve quantifying the interaction of tidal currents
and wave-driven currents, the development of a sophisticated
model for sediment transport and the prediction of
beach evolution over time.
"There have been prior limitations," said
Barnard, who will need more funding for the study
to continue. "It will provide data for our coastal
Meanwhile, collaborative efforts led by the California
Resources Agency and the U.S. Army Corp of Engineers
are underway to develop a California Coastal Sediment
Management Master Plan.
These efforts can also help the City resolve the
erosion problems at Ocean Beach.
Concerned parties met at the California State Hiram
Johnson Building last May.
"There are lots of questions we don't have answers
to," said Lesly Ewing, a California Coastal Commission
senior coastal engineer. Ewing said 86 percent of
the California coast is presently facing erosion problems.
"Sometimes you need to know why the problem
is happening," Ewing said.
Clifton Davenport, the Coastal Sediment Management
Workgroup project manager at the California Geological
Survey, said the California Coastal Sediment Management
Master Plan should be completed by July 2005. Barnard
hopes to publish some of the results of his Ocean
Beach sediment transport research study by the end
of the summer.