For the Instructor

These student materials complement the Coastal Processes, Hazards and Society Instructor Materials. If you would like your students to have access to the student materials, we suggest you either point them at the Student Version which omits the framing pages with information designed for faculty (and this box). Or you can download these pages in several formats that you can include in your course website or local Learning Managment System. Learn more about using, modifying, and sharing InTeGrate teaching materials.

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Protection of Ocean Beach, San Francisco, CA

Assignment:

The objective of this activity is to help you develop an appreciation for coastal erosion and associated risks when placing major infrastructure proximal to coastal hazards.

Ocean Beach is a sandy beach backed by erodible bluffs that forms the boundary between the western edge of the city of San Francisco, CA and the Pacific Ocean. Like many sandy coasts around the world, portions of Ocean Beach have experienced significant erosion in the past decades. The long-term erosional trend along the southern reach of the beach has been punctuated by periods of intense erosion during particularly severe winter El Niño storm seasons, when the beach and backing bluffs can be exposed to very high waves.

The situation is complicated by the presence of critical infrastructure within the coastal zone. The Great Highway, an important transportation link, is located on top of the bluffs backing Ocean Beach, and recent erosional events damaged parking areas and forced the closure of one direction of traffic for much of the storm season. More importantly, a large sewage tunnel runs under the Great Highway, transporting the city's wastewater south to a treatment plant. Continued erosion threatens this piece of expensive, critical wastewater infrastructure, and it must be protected in the near term to prevent both the environmental consequences of a tunnel failure and the huge cost of relocation. During the most intense erosion episode during the 2009-2010 El Niño winter, the city constructed an emergency revetment of armored stone along the eroding bluff to protect the wastewater infrastructure; however, the use of "hard" coastal protection structures met stiff opposition from environmentalists and local regulatory agencies due to the inevitable loss of beach in front of the structure.

Reading

Read the following article, detailing the coastal erosion and management issues at Ocean Beach:

SPUR: The Future of Ocean Beach

Figure 7.16: A parking lot and bench between the Great Highway and the bluff edge at Ocean Beach before (2009) and after (2011) severe erosion.

Image Credit: SPUR @ http://www.spur.org/publications/urbanist-article/2012-04-17/vision-ocea...

Google Earth

Navigate to Ocean Beach, San Francisco by searching for the coordinates 37 °44'51"N; 122 °30'32"W. Turn on "borders and places", and "roads" by checking the appropriate boxes in the lower left menu in Google Earth. Start at an eye altitude of ~9 km. Ocean Beach stretches from the rocky headland at Sutro Heights to the north (near Seal Rocks) to the Fort Funston, Lake Merced area (near the San Francisco Zoo) to the south. Zoom in and explore the full length of the beach, noting how the width varies and any structures on the beach.

Now navigate to the Fort Funston area at 37 °43'44"N; 122 °30'25"W and zoom in to an eye altitude of ~500 m. Note the position of the shoreline, bluff toe, roadway, and armor stone revetment. Turn on "Historical Imagery" using the "View" menu or by clicking the icon on the menu bar at the top of the screen that looks like a clock winding backward. To see how much the shoreline position has changed through time, adjust the slider to the following dates: