Living shoreline illustration
This annotated photo shows the location of the erosion along the West Trail at Pillar Point Harbor. Illustration courtesy San Mateo County Harbor District

The San Mateo County Harbor District recently proposed construction of a living shoreline along the Pillar Point

Harbor West Trail. The West Trail, located on the western edge of the harbor, is a heavily used public space for bird-watching and walking, in addition to being a critical safety access point to Mavericks Beach.

The beaches along this trail have been disappearing, and the actual trail has experienced significant degradation due to constant coastal erosion. “If we don’t do something in the near future, the trail’s going to disappear,” said Harbor District General Manager Jim Pruett. By employing a living shoreline design, Pruett explained that they are “trying to use nature’s solution.”

The specific portion of the trail proposed to be converted into this living shoreline is 300 feet long. The project will incorporate two large rock fingers, perpendicular to each edge of the segment of trail. The rock fingers will catch sand as it moves through the system, ensuring that the sand is not recycled into a different portion of the harbor. Pruett likened these to “underground retaining walls.”

Project consultant Brad Damitz explained that smaller rocks, the size of a baseball, would be placed on top of and in between the rock fingers. Then, finally, a layer of sand would be added, sourced from nearby shoals or beaches with “a surplus rather than shortage” of sand, said Damitz.

“The term ‘living shoreline’ really refers to strategically placing habitat elements in order to achieve biological and physical goals. It's really about designing the project in a nature-based way to also help with shoreline protection,” said Marilyn Latta, project manager for the California State Coastal Conservancy. Latta was involved in the San Francisco Bay Living Shorelines Project and explained that living shorelines are a relatively new approach to restoring shorelines, dating back only to the early 2000s.

The Harbor District investigated other ideas, including some form of a seawall before eventually settling on a living shoreline design.

“These engineered solutions have been the traditional approaches to protecting shorelines,” said Katie Arkema, lead scientist at the Natural Capital Project, centered at Stanford University. She discussed mechanisms like seawalls and jetties that have traditionally been used. “Over about the last decade, scientists have observed there are these drawbacks,” she said, explaining the high cost of a sea wall or the further erosion it may cause to the beach below it.

“Whereas traditional approaches are just trying to achieve one goal, living shorelines can help us achieve multiple goals,” Arkema said. She explained how a living shoreline may help reduce erosion or flooding along a shoreline while also helping to increase the delivery of other ecosystem services, for example, providing a shoreline for people to recreate upon or nursery habitats for fish.

Pruett and Damitz said that the Pillar Point Harbor living shoreline project could re-establish a beach habitat for animals that historically existed there, but had been disrupted due to changes in the environment. For example, it could benefit birds during their feeding and nesting processes. The project would also work to re-establish native plants along the newly established shoreline, introducing a new source of seed so that native plants could then expand throughout the harbor.

“There’s this aesthetic and cultural value to living shorelines as well,” Arkema said. She referenced the opportunities for recreation that a living shoreline could provide.

“The human connection to the shoreline is pretty powerful,” Latta said. “Living shorelines can often result in open spaces that adjacent human communities can enjoy.”

“Our hope is the end of this year, the beginning of next year,” Pruett said of the completion of the project which is currently still in the permitting process. Once the project begins, it is expected to take 90 days to complete.

Since living shorelines are a relatively new idea, “there’s still a lot of work that needs to be done in terms of figuring out how well these shorelines will help us achieve these goals,” Arkema said. She stressed the importance of engaging the community and other stakeholders in the process of implementing a living shoreline. “Living shorelines can still have positive or negative impacts,” she said.

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