Reef Design Innovations for Living Shorelines
What are those angular objects along the shore?
On a low tide at three locations in San Francisco Bay, you can see a pilot experiment to test a new oyster reef design for Living Shorelines in San Francisco Bay.
The reef system seen along shores at low tide.
OLYMPIA OYSTER (Ostrea lurida)
These reefs are home to native Olympia oysters and seaweeds, which provide food for crabs, fish, and birds. Native oysters are a key foundation species in the Bay; given a hard surface to attach to, oysters help to build a habitat that other species can then use.
What are the scientists monitoring?
Partners at San Francisco State University’s Estuary & Ocean Science Center and the Smithsonian Environmental Research Center are studying how the design you see works as habitat and how it holds up under high wave conditions during storms. If the reefs perform well, the same design will be built into larger reef arrays to protect shorelines from storm surge and erosion that is increasing with sea level rise.
The scientists are interested in knowing if the degree of openness of the elements affects how they perform. If there is a large hole in the otherwise solid side of a reef element, that means it requires less concrete. Less concrete means it is lighter to handle and also costs less to make. But will it hold up as well in big storms? Will it be as useful for habitat? There are three levels of openness repeated three times, for a total of nine units, or clusters, of reef elements.
The reef system was designed to sit off-shore in the intertidal zone where bay waters fluctuate between low and high tides.
A living shoreline is a restored habitat for native species that also helps to protect the land at the water’s edge.
Living shorelines are a type of nature-based adaptation being piloted in the San Francisco Bay to buffer wave action and storm surge as sea levels rise.
Shown here: Oyster shell bags, a reef ball, and eelgrass.
GREAT EGRET (Ardea alba)
This land could include a tidal marsh or even a low-lying neighborhood. A living shoreline can include oyster reefs, eelgrass (an aquatic plant), marsh plants, and even small rocks, shell, or sand made into mounds or berms to reduce the energy of the waves.
Living shorelines can be less costly and more adaptable than traditional engineering solutions to protect shores, while also providing wild life habitat.
This reef design is being tested at three locations in Marin County.
Why this particular reef design for a living shoreline?
The project’s scientists convened a technical advisory committee from around the US to help develop a new design for oyster reefs in San Francisco Bay. Other types of oyster reefs used in living shorelines include reef balls, concrete blocks that stack, or mounded bags of oyster shell that come from oysters that are farmed for food.
In this project, the group sought to create reefs that have an internal space, permitting animals to hide inside, and that are lightweight enough that community members can help fabricate and install them. The aim was to create individual “elements” that gain strength through placing them together in “units”, groups of elements that rest against each other. In this pilot project, a unit consists of four elements.
Volunteers helped to cast more than 150 oyster reef elements used in three pilot locations.
The oyster reef elements are fabricated to interlock. Although they are currently being prototyped as units made from four elements, they can be expanded horizontally and vertically in the future to create larger reef systems.
The Studio for Urban Projects in Sausalito designed a reef fabrication system that could be easily reproduced, and assembled; they started with the geometry of a tetrahedron – a shape that, in combination, naturally interlocks.
They designed a mold from plywood that can be re-used and flat-packed for ease of transportation to new fabrication locations. They added a texture to the cast concrete that resembles corrugated cardboard, which the scientists expect will encourage animal use (like native oyster attachment and crab climbing). Volunteers from around the region helped with fabrication at the Estuary & Ocean Science Center.
Reef Architecture
Watch this short film by Packard Jennings examining the development and testing of the new reef design for living shorelines in three locations in San Francisco Bay. Hear from the team that worked on the reef design including Marilyn Latta of the California Coastal Conservancy, Katharyn Boyer of San Francisco State’s Estuary & Ocean Science Center, and Designer Richard Johnson of the Studio for Urban Projects.
Contact us
Dr. Kathy Boyer
Estuary & Ocean Science Center, San Francisco State University
Dr. Chela Zabin
Smithsonian Environmental Research Center
Marilyn Latta
State Coastal Conservancy
Rick Johnson
Studio for Urban Projects