Posted on October 9, 2023
Additional sand nourishment and the utilization of artificial retention devices highlighted some of the solutions suggested to rescue critically vulnerable San Clemente beaches at a community meeting on Sept. 27.
Residents and other stakeholders gathered in the Council Chambers at City Hall to learn about and provide feedback regarding early concepts for coastal resiliency, in relation to the city’s ongoing Nature Based Coastal Resiliency Project Feasibility Study.
New Coastal Administrator Leslea Meyerhoff and Chris Webb, principal coastal scientist with the city’s contracted consultant, Moffatt & Nichol, spoke about the study’s objectives and progress. Community Development Director Cecilia Gallardo-Daly was also present to facilitate and answer other questions.
Webb noted the proven effectiveness of beach nourishment when enough sand is placed, saying that placing more sand north and south of the upcoming San Clemente Shoreline Protection Project would be ideal in order to keep sand within the city limits.
He also mentioned the expenses associated with bringing in sand and the possibility of sand damaging local ecosystems if it buries rocky outcrops and other features that create surf breaks.
“Let’s have nourishment in the mix, but let’s try to hold it in place with whatever kind of concepts (that) make sense,” he said. “Since there are these wave-dissipation natural structures down at Trestles that work great, those became an obvious model to us. …If we did exactly what’s there, I’ve got to believe it’s going to work.”
During the meeting, Webb also noted that the city would likely focus on implementing one project at a time and analyzing its success.
The plan marked another step toward achieving the feasibility study’s objective of devising sand retention solutions to halt the trend of coastal erosion at city beaches.
Meyerhoff spoke about the study’s background, and Webb gave an in-depth presentation detailing the draft concepts for aiding eight sections of the San Clemente coastline that have been categorized as in stable, threatened or critical condition.
In June, Moffatt & Nichol sent a memo to city officials that marked four of the sections as critical “hotspots” for erosion—those being Shorecliffs, Capistrano Shores, Mariposa Beach and Cyprus Shores. Webb, his partner, coastal scientist Justin Peglow, and his team of scientists came to that conclusion after using five measurements to estimate the health of varying sections, or transects, in the city.
“We call things ‘critical’ if they have three critical components of the five, or if they have two of the critical components and two threatened,” said Webb. “If there’s two of those five components in the threatened category, they get a threatened (rating). And if none of that stuff’s happening, it gets a stable rating.”
After the analysis to complete the first identifying report was completed, the project team developed criteria by which to develop preliminary sand retention concepts, according to Meyerhoff.
They focused on the critical and threatened transects first, and considered the level of access to the public through public transportation or access to city Marine Safety Division personnel, the number of amenities and surf resources, the amount of existing native vegetation, and whether public safety was adversely affected by erosion at each location. Then, the team devised small, medium, and large concepts.
Starting from the northern end of San Clemente, Webb presented both a small and medium concept for Shorecliffs, which mostly consists of private property. The small project would install sand dunes with vegetation to create a “living shoreline,” further helped by sand nourishment high on the beach berm; the medium project included placing a groin at the south end of the section to catch pre-filled sand nourishment along the shoreline.
“A living shoreline is essentially a sand dune,” Webb said. “It’s a sand dune with growth on it that’s an actual habitat, (and) the growth acts to trap sand and can continue to grow. If you can get enough sand trapped, it’s a positive feedback thing where the vegetation growth attracts more sand, which generates more vegetation growth.”
He referenced an existing living shoreline at Cardiff State Beach in Encinitas as a successful example.
The groin, which is a structure that extends perpendicular to the shoreline, interrupts the flow of sand and would be intended to keep sand in the area.
Webb also presented two project options at Capistrano Shores, this time both large projects. One would install five, equally spaced groins along the section to assist pre-filled nourishment, and the other included constructing three living breakwaters in addition to nourishment.
The use of multiple groins has previously worked in Newport Beach, Webb said. Regarding the breakwater, sand would be carried by the water until it reaches a “shadow zone” where some of the sand drops deeper into the ocean, and the rest would continue moving, forming a bulge behind the breakwater known as a salient.
“What might be possible at a place like Capistrano Shores is to put some sort of linear breakwater feature out there, nourish behind it, build the salient proactively, and then let Mother Nature allow sand that would be moving along the shoreline to continue moving across the salient and move downcoast,” said Webb.
Segmenting one large breakwater into three would allow water through the segments and allow waves to pass through, providing surf breaks toward the beach. The “living” part would mean having kelp and algae grow on the structures to essentially create a rock reef.
At the Mariposa Beaches transect, Webb proposed a large concept of creating a triangular, artificial headland of cobble, boulders or large river rock, in addition to nourishment. The goal there, as well as at North Beach, would be to mimic the natural environment at Upper and Lower Trestles that does well to dissipate high-wave energy.
“This has never been done, that I’m aware of, in the United States of America successfully,” Webb said. “I think there’s been attempts outside of the USA with different substances that have worked. But, when we say nature-based (concepts), we want to have—yeah, it can be rock, but it should be natural rock, if possible.”
In addition to the “boulder delta,” as Webb referred to it, a project at the “threatened” North Beach could also include creating a living shoreline. Since the delta concept is unproven, Webb said the project team would likely need to replicate it on a smaller scale in a laboratory setting before moving forward.
Down at the Linda Line & Pier Bowl subsection that was identified as threatened, which will be the main benefactor of the 250,000 cubic yards from the U.S. Army Corps of Engineers, the proposed project would only add a passive living shoreline and additional piles under the pier to slow sand movement.
Webb said the Huntington Beach pier was a good model in how it interrupts high energy currents.
“If you can interrupt that and confuse it, knock it down, cause it to swirl, get rid of the straight flow direction and have it start to become something other than that, what you’ll get is riptides, and you’ll get sand dropping out of the transport path,” he said.
He next talked about T-Street, another subsection that is “stable,” calling the area an “A-plus.” He advised people to watch and document it, as he still was searching for ways to duplicate the transect’s geology that features a natural bedrock reef connected to the shore.
No concept was proposed at T-Street, and the stable transects of Boca Del Canon and State Beaches would only receive a living shoreline if a project were to go through.
All living shorelines throughout San Clemente would feature educational signage.
Lastly, Webb displayed a large project at Cyprus Shores that would include nourishment and a boulder delta.
Next, Webb, Meyerhoff, and Gallardo-Daly listened to feedback from the audience and answered questions.
Suzie Whitelaw, San Clemente resident and technical advisor for the nonprofit Save Our Beaches San Clemente, emphasized the importance of speaking with local surfers to map out surf resources and incorporating those lesser-known surf spots in the project’s geographic information system. She also mentioned needing a feasible plan for the coastline as a whole, in addition to the individual transects, called the boulder delta concept problematic, and said T-Street would be a better model to follow than Trestles.
“Let’s look at the T-Street reef, figure out how that’s shaped, how that affects the wave action and try to recreate that both at North Beach and at the south end beaches,” Whitelaw told San Clemente Times on Sept. 28. “That’s what’s proving effective on our coastline already.”
She also spoke to the concept of living breakwaters, which she felt should be placed away from existing surf breaks and not designed in a straight line.
The Surfrider Foundation was also present at the meeting, with three officials to share their opinions on subjects such as emphasizing more natural structures over groins. Angela Howe, Surfrider legal director, spoke with SC Times.
“Living shorelines and healthy dunes, native plants, those are all things that help existing dune habitats, water quality, (and) sand stabilization,” Howe said. “There’s a lot of coastal benefits associated with those projects. On the other hand, hardened coastal armoring and extreme shoreline manipulation structures like groins and breakwaters should really be excluded from the list of nature-based solutions.”
She applauded the study’s focus on sustaining recreational resources and simultaneously urged the city to protect existing coastal resources.
The next phase of the Nature Based Coastal Resiliency Project Feasibility Study should arrive in early 2024 with the Draft Resiliency Design Concept Report, according to Meyerhoff. That document will be followed by the Draft Nature Based Feasibility Study near the end of 2024 and the release of the Final Nature Based Feasibility Study by Dec. 31, 2025.