Leave it to beavers: Mimicking nature’s dam-makers is one way San Luis Obispo is reinvigorating its natural spaces

On a warm May day at the Johnson Ranch trailhead, Cooper Lienhart extends a hug and looks at the infographics displayed on a large sign describing the area.

Shielding his eyes from the sun, Lienhart gestures northwest and says that the creek bed ahead lives up to its name upon first glance: Dry Creek.

“It runs dry every year. It’s spring fed and it’s kind of a small system,” he says. “We’ll be walking first through the dry and then up. And then we should hopefully get to some water.”

The president of local nonprofit Nature’s Engineers—an organization that restores creeks and rivers by mimicking beaver dam activity—and his team built beaver dam analogs (BDAs) in Dry Creek last October. The team built 30 of the man-made structures that mimic the architecture and function of beaver-made dams.

He compared the process of building these dams to making lasagna.

“We took branches, sycamore branches, whatever was around—it’s all natural on-site materials—laid them across the channel, and put the leaves facing upstream, so it can kind of catch the flow,” he says. “So you layer them all across and make kind of a dense layer, stomp on it, then you take some soil from the banks that we dug with shovels and layer it on top. … It eventually creates this triangular pyramid shape across the channel, and you keep on doing that.”

As he hikes, he points out the first installment of a beaver dam analog, consisting of exactly what he’d described. Unless you’re looking for them, they aren’t that noticeable—just rows of rocks, branches, and dirt about a foot tall.

But Lienhart is pleased as he picks up some of the sediment that the dams collected from recent rains.

“You can see all this fresh sediment and gravel it was able to catch behind the structure,” he says. “Now we’re starting to build up the creek channel. This is like several inches deep of sediments and lots of fresh mud on the sides here.”

His beaver mimicry is working, and that’s just what the city of San Luis Obispo is hoping for as it aims to reintroduce water to the dried-out landscape—a natural method that also absorbs carbon and can prevent further fires.

It takes a village

Nature’s Engineers installed the BDAs thanks to SLO’s aim to create a more resilient city under its Local Climate Change Adaptation plan, said SLO Sustainability and Natural Resources Analyst Lucia Pohlman.

“Climate action has been a major city goal. We have a lot of urgency locally to think about how we can address climate change and help our beloved open space ecosystems adapt,” Pohlman said. “One of the things that we hear every community forum, which is a big event where tons of community members come out to help prioritize city resources through the budget process, and we always hear how much people love open space. It’s a clear community priority here.”

SLO owns about 4,000 acres of open space, Pohlman said. Johnson Ranch holds about 242 of those. The city has an additional 4,000 acres in conservation easements on private properties as well.

“We have this huge undeveloped green belt surrounding the city, and those landscapes can draw down carbon, and they can also be managed to help grow resilience,” she said. “That resilience can benefit the critters that depend on that ecosystem today but also help folks who perhaps live downtown or live in the city be more safe from climate impacts like floods and wildfires.”

One way to develop this land is through process-based restoration, a technique that uses materials already on-site to slow, spread, and sink water from a riparian corridor, hence the work on Dry Creek.

Pohlman said the beaver dam analogs installed at Johnson Ranch started after she applied for a grant from the Wildlife Conservation Board that offers funding for projects designed to create climate-smart and resilient restoration projects for working landscapes.

“They really loved the thought of bringing process-based restoration to the Central Coast,” Pohlman said. “[BDAs] have been taking off in other parts of the state, particularly a little bit more in the northern part of California, before the project at Johnson Ranch had been installed. So there begins a big chapter of learning, but thankfully, we got this grant from the [Wildlife Conservation Board] to advance this work.”

Under the grant, the city is responsible for making two things happen in three years: to install the 30 BDAs and also to anchor the new sediment that accumulates with vegetation.

While Nature’s Engineers was contracted to handle the BDAs, Pohlman said nonprofit ECOSLO took on the task of planting more vegetation in recent months.

“We’re planting a total of 360 trees and riparian plants throughout the Dry Creek project site, and that’s all happening with volunteers. We had four volunteers last winter who successfully had an incredible time out there, planting a whole suite of native plants,” she said. “We really want to have this project have a community-supported feel … because I believe that getting your hands dirty is the best way to learn about what climate solutions exist in your community that you can help out with.” 

Clarification: Pohlman reached out to New Times after this story was published to clarify the number of ECOSLO volunteers who helped plant vegetation in Dry Creek last winter. It was more than 100. 

Beaver believers

Nature’s Engineers’ Lienhart studied environmental engineering at Cal Poly after being “blown away” by the issue of climate change in high school.

“As a kid in suburbia in Chicago, I was like, there’s got to be a way we can just use technology to suck CO2 back out of the atmosphere,” he said. “I thought we were going to build synthetic trees to suck CO2 out and so I was really juiced on that.”

But after a study abroad program through Cal Poly, his chain of thinking changed, he said.

“I got a chance to study abroad in Iceland and Greenland—a program all about climate change—and that’s where I learned that our natural ecosystems, especially wetlands, can be our greatest carbon sinks. Wetlands are the most efficient land ecosystem at absorbing and storing carbon from the atmosphere because they have so much plant growth and so much water to encourage that plant growth,” he said, “Then the plants and animals can decay and get locked underground to restore that carbon. And so I was like, OK, I just want to restore wetlands as my career.”

In 2020, Lienhart met the SLO Beaver Brigade, a local organization dedicated to educating the community about the benefits of the large rodents, and that’s where the idea struck: Beavers were the solution.

“When I went out to the beaver ponds in Atascadero on the Salinas [River], then it all clicked for me. I was like, ‘Oh my gosh, it’s this amazing carbon sink,'” he said. “We walk through a half mile of dry flood plain, and then you see it. It’s this lush, life-filled wetland. This is a carbon sink and so much else at the same time—life, fire protection, water recharge—the beavers got it figured out. And so anything I can do to support the beavers, that’s what I want to do.”

Nature’s Engineers is under contract with SLO until the end of 2026. Last October, Lienhart said he and a group of five built the 30 analogs in six days. Now during the next two Octobers, they are tasked with maintaining the dams and making sure they remain intact and serve their intended purpose.

At the end of the contract, ideally the analogs won’t require any more maintenance and will help keep the creek bed and nearby plains wet.

Being self-sustaining means the creek bed will have the ability to hold water both above and below ground. And with more water comes more life, Lienhart said, adding that he’s already seen endangered species like red-legged frogs and steelhead trout inhabiting the water upstream in Dry Creek.

“All of the species that need water to survive, like 80 percent of native wildlife in North America, rely on riparian areas at some point in their life cycle. So if you want to restore wildlife, you start where the water is,” he said. “It also addresses erosion concerns and reverses the process and improves water quality because it allows pollutants to settle and get cycled underground. Anything that you can think of.

“Putting [in] these beaver dam-like structures really has a positive impact.”

Dammed if you do, damned if you don’t

SLO isn’t the first city in the county to mimic the ancient methods of beavers.

Last August, the city of Atascadero wanted to revive dry portions of the Salinas Riverbed by harvesting willow stakes, a process involving the trimming of live willows and replanting those pieces along unstable riverbeds. The willow stakes eventually form new root structures and provide soil stability, similar to beaver dams, and prevent further erosion along the bed.

Morro Bay also has upcoming plans for Walter’s Creek later this summer.

Actual beaver dams have proven their effectiveness in the Salinas Riverbed in Atascadero. The SLO Beaver Brigade observes this portion of the river that’s maintained fully by families of local beavers.

Beaver Brigade Founder Audrey Taub is a big advocate when it comes to learning from the hardworking critters.

“We are thrilled and so excited about Nature’s Engineers,” she said. “The work that they are bringing to this county is really going to contribute to a more resilient Central Coast. We couldn’t be more excited.”

The stretch of the Salinas Riverbed maintained by the beavers holds about 4 feet of water, making the surrounding space lush and cool in temperature—an ideal riparian corridor as opposed to the dry portions of the riverbed just miles up and down stream.

“We’re at this place now where the beavers have been removed from the landscape for a very long time, hundreds of years. So now we’re dealing, in some places, with habitat that’s just not suitable anymore at this point for beavers. So it makes restoration tricky,” Taub said.

Right now, Johnson Ranch is no place for a beaver to thrive. But by installing BDAs, maybe it could be.

“[BDAs] start to create the ability for water to be stored so that the riparian can come back, and at some point, if a beaver finds it, it may become a beaver habitat,” she said. “But even without beavers, you can start to get some of the benefits that beavers provide.”

During the recent Gifford Fire, which burned 131,000 acres of land across SLO and Santa Barbara counties, Taub said she thought of beavers and how they could have potentially reduced the blaze.

“That fire really made me think, ‘Wow. If the Salinas River was lush and full of beavers the entire length, it wouldn’t be such a worry.’ You know, if all of our creeks and rivers were full of beavers, we would have a lot of water in our creeks and rivers. We would have very wet vegetation. We would have very wet soil,” she said. “All of that is really, really hard, if not impossible, to burn, and that would be just such a big help for these conditions we’re in right now.”

Branch by branch

Another element of SLO’s Local Climate Change Adaptation plan, in addition to installing BDAs and planting vegetation, is cultural burns in partnership with the YTT Northern Chumash Tribe of SLO, said Sustainability and Natural Resources Analyst Pohlman. Such burns are part of an effort to revive the native grasses that historically dominated the flood banks and the floodplains of Dry Creek.

“Today, we have a lot of invasive species that are just outside of the creek corridor, and so we’re partnering with them to explore a myriad of ways to help transition invasive grasslands into perennial bunch grasses,” Pohlman said.

The first successful cultural burn performed by the tribe was completed last November, just across the trail from the beaver dam analogs on Johnson Ranch.

“It’s really reviving an ancestral land stewardship practice that, due to the level of displacement and colonization and genocide that occurred here on the Central Coast, there wasn’t the ongoing land tenure for tribal members to maintain their ancestral practices,” Pohlman said. “So it was a really monumental day last year, seeing tribal members bring fire back to their ancestral landscapes for the first time in living memory.”

Pohlman said the relationship between cultural burns and BDAs is symbiotic—the burns remove flammable vegetation in a controlled way and return the soil back to a healthy state. The BDAs capture that sediment from the fire, and then the vegetation planting anchors the nutrients back into the land.

While the Wildlife Conservation Board grant funds the BDA installations, it doesn’t cover cultural burns. But Pohlman said the city intends to continue them annually at Johnson Ranch and hopes to find another grant to cover those burns.

Between all efforts in that area though, Pohlman said the best-case scenario is that in three years, Dry Creek will accumulate so much sediment that the water will spill into the plains. The city should have a better idea of how the BDAs are working this spring after the rainy season, but monitoring will continue year-round.

“We anticipate that for this stretch of Dry Creek that the structures will function into the future without maintenance,” she said. “That doesn’t mean we’re done installing beaver dam analogs on the city on riparian corridors. We’re currently partnering on a grant application that could expand BDAs beyond Johnson Ranch to three additional city open space properties, and we’ll definitely be sharing with the public when we hear back about that grant application.”

Dam good results

On the journey upstream at Dry Creek that day in May, Lienhart, of Nature’s Engineers, takes notice of some BDAs that were washed out after a storm sent water rushing down the corridor and knocked some of the analogs free.

He says they’ll repair them this October.

“This was all blown out just on the left side,” he says, pointing to the creek bed full of debris. “Because it’s a multi-year project, what we’re going to do is come back in and rebuild the left side, but in a slightly different way. … We’re going to curve it further this time. I think [that] will help it hold a pond and hopefully not get blown out.”

Lienhart doesn’t mind repairing the structures. Just because they didn’t last doesn’t mean they were a failure—it’s now an opportunity to learn and rebuild, just like the beavers do every day.

The most rewarding day of the project was in March, Lienhart recalls, when the rainwater rushed down the creek bed and he saw a steelhead trout in the waters for the first time—a species not present, obviously, when the bed is dry.

“That was a magical day,” he says.

Near the highest installed BDA up Dry Creek, the landscape is nearly unrecognizable from how it first appeared downstream. The creek bed is easily holding 3 feet of water, and it’s 10 degrees cooler. Willow trees canopy the water, and Lienhart hops from rock to rock in an effort to not get wet. Vibrant moss sways in the water current, and small minnows bolt away as he points to them.

It’s an oasis, thanks to a little inspiration from beavers.

Lienhart has a pretty cool job.

“I really do,” he says, laughing. “It’s the best when you’re in the creek being a beaver.” Δ

Reach Staff Writer Libbey Hanson at newtimesslo.com.

This article appears in Aug 28 – Sep 7, 2025.