SF-ROCKS Research Projects
The Different Faces of San Francisco's Ocean Beach: Analyzing
Sand Size and Beach Shape
Faculty Advisor: Karen Grove
Ocean Beach is located along the western edge of San Francisco adjacent
to the Pacific Ocean. Erosion along the southern part of the beach
is threatening a nearby highway and water treatment plant. To better
understand this beach and the processes that form it, our SF-ROCKS
research group collected data from seven locations along its length.
We used an auto-level surveying instrument to measure beach profiles
and we collected sand samples that were measured using sieves and
a sieve shaker. We plotted profiles and grain-size data using Excel and Surfer software.
The sediment is mostly fine sand, and the means of all samples range
between 0.19-0.26 mm. There may be little variation along the beach
because only small sand grains have survived the long journey from
their Sierra Nevada source. Profile shape does vary along the beach.
The profile at the northern end is about three times wider than the
profile at the southern end. The northern profile is flatter overall,
but all profiles had a steep beach face in August, when the data
were collected. The differences in beach profiles may be related
to position relative to the offshore bar, which appears to provide
sand to the northern part of the beach. Our group will collect more
data in November to see what changes have occurred after the large-wave
season has begun. We will use Surfer software to compare
summer and fall profiles, to see where sediment has been added and
where sediment has been removed. We will also compare our results
to the data collected by Dr. Patrick Barnard and his research group
at the U.S. Geological Survey, who are using an All-Terrain Vehicle
to measure beach profiles and a camera to measure sediment size.
We will use our analysis of beach variations to make recommendations
for reducing beach erosion.
Beach analysis group with their poster at the 2004 AGU meeting.
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