Thursday, September 23, 2021

Innovative Approach – Hope Valley Restoration Project Shows Early Signs Success

Multimedia: Newly-created floodplain bench, willow installation aims to improve water quality in the West Fork of the Carson River

Since construction for the Hope Valley Restoration and Aquatic Habitat Enhancement Project was completed in October of 2020, early signs of willow growth seems to bode well for the future of the West Fork Carson River. A collaborative effort led by the Alpine Watershed Group, the project’s aim is to help reduce erosion and sedimentation in the river system, ultimately improving water quality and aquatic habitat while restoring Hope Valley’s natural floodplain. 

“This project is a small piece of the bigger puzzle of reconnecting the West Fork Carson River with its floodplain,” said Mo Loden, program manager at Alpine Watershed Group. “Hope Valley was a major immigrant stop back in the 1800s and since then, it’s entered decades of grazing and these historical activities compacted the meadow, decreased water storage and caused the river to start carving out a stream channel instead of accessing the floodplain. This project will help stabilize the banks and give the river a better chance to access the floodplain.”

Funded by the National Fish and Wildlife Foundation and the California Department of Fish and Wildlife Office of Spill Prevention and Response, the restoration project took place at two primary locations. Site One is located in Hope Valley downstream from Highway 88, commonly known as “The Fourth Crossing,” an ode to its historical role on the Emigrant Trail.

Meanwhile, Site Two is about half a river mile downstream from Site One, where a log crib structure was put in place as part of a 2015 American Rivers project. Both project sites are located on California Fish and Wildlife land. 

“Site One was a really exciting project because it was an innovative, low-risk and low-impact design in that we did not work within the stream,” Loden said. “Basically we created this floodplain bench that now mimics an oxbow, a U-shape in the meadow that has been filled with all of our salvaged sod blocks, a few hundred willow stakes, live willow transplants and live willow trench packs.”


Site One and Two are marked in red. Site One is the upper area. Use this interactive map to explore the West Fork of the Carson River.



The idea behind this innovative approach is that while the stream bank at Site One continues to fail due to erosion, it will work its way back toward the newly-created floodplain bench. As this erosive process develops over time, the willow stakes and willow transplants will be able to establish strong roots in the sod and grow so they will be able to withstand high river flows in the future, thus stabilizing the currently failing and receding river bank.

“The newly-created floodplain bench has also been lowered about three feet, so by the time the failing bank recedes back to the project location, the water will have less of a hard time getting out of the river and into the floodplain,” Loden said. “In the long-term, [the established willows] will create shade in the river that lowers water temperature and protects more sediment from not running into the river, thus increasing water quality.”

An additional component to this innovative approach at Site One, according to Loden, is that the project is really a win-win scenario, even if the failing bank never recedes back to the newly-created floodplain bench. 

“We really only impacted the meadow, so we didn’t really interrupt any hydrological functions or connectivity of the river,” Loden said. “Let’s say the failing bank never recedes back to our newly-created floodplain bench, well in that case it’s really no harm, no foul because we’ve pretty much just created new bird habitat as long as our willows continue with the success that they have had. Then during the spring months, the floodplain bench fills up with water and creates nice habitat for amphibians or insects, so it’s a win-win.” 

The nature of the project at Site Two, however, varied differently in that it was largely adaptive management to the American Rivers’ 2015 project that installed a log crib structure on the riverbank of that location. The main component to Alpine Watershed’s adaptation included installing slash, a term used for conifer and willow cuttings. 

“American Rivers and California Fish and Wildlife had done a log crib structure restoration project back in 2015 and so our project was installing slash to help buy time for the willow stakes they planted on the streambank to take root, while also providing fish habitat,” Loden said. “The log crib structure itself has nice, deep pools and places for fish to hide and protect themselves or create little nests for breeding. So really, [the log crib structure] is doing a great job there.”

The adaptive management at Site Two was necessary, however, to divert high river flows from scouring, or abrasively flowing behind and damaging the installed log crib structure.

“Unfortunately in 2017, we had some pretty big river flows and the stream was actually able to gain enough energy that it was going up around the log crib structure and scouring behind it and causing more erosion than they anticipated,” Loden said. “So our project came in on the downstream end of that structure to lay the bank back slightly and at a better grade to accept new material. We then salvaged the sod of the meadow and installed a bunch of slash in between these big, heavy anchor logs and placed a bunch of willow stakes and willow transplants within the entire log crib area, so now it has better matting to help absorb stream energy as it’s coming downstream.”

From an historical perspective, Hope Valley has posed to be a challenging site for restoration projects like these. 

“Hope Valley does tend to be challenging because we do have such a short growing season and that’s what’s so hard about getting these willows to grow because Hope Valley can be covered in snow for three to six months out of the year,” Loden said. “But willows are one of those incredibly wonderful plants that can propagate easily in the right conditions and with these willows, we were able to basically harvest our willow stakes on-site from little patches nearby. Then if you keep them good and saturated from the time you harvest them until the time you install them, they can do really well.”

So as the one-year mark approaches since the Hope Valley Restoration and Aquatic Habitat Enhancement Project was completed, the early signs of willow growth, particularly at Site One, have been cause for optimism regarding the West Fork Carson River’s future. 

“One of the challenges in the past is getting willows to successfully establish and continue growing, and the willows at Site One have exceeded expectations so far,” Loden said. “A few big keys to this early success may be that the live willow transplants were larger and had a little bit of energy already stored in the plant and they were installed down to the seasonally-low groundwater level, essentially meaning these willows have access to water year-round. So we’re seeing growth on these live willow transplants that is at essentially the same [growth] that we’ve seen on projects that were done five years ago, so they’re doing really well.”

Consequently, assuming the early signs of this project’s success continue, the Alpine Watershed Group’s innovative approach could offer lessons for restoration projects like this one in the future. That being said, Loden acknowledges that nothing is guaranteed when it comes to Mother Nature.

“The science and art of meadow restoration is continuously evolving and the lessons learned each year contribute to the design of future restoration projects, so really understanding how well these live willow transplants did really is a great lesson to take away because installing them down to the seasonally-low groundwater level has been key to the success of those plants there,” Loden said. “The thing with these restoration projects is we’re working with Mother Nature and she’s not predictable, so you can make the best project ever and it might not be your year. But fortunately, we’ve had a lot of really great environments and conditions to have our project succeed so far.” 

All things considered, monitoring of the two project sites will continue through 2024 to determine if any further adaptations need to be done. But at least for now, the Hope Valley Restoration and Aquatic Habitat Enhancement Project has shown early signs of success. 

“Going back to our long term goals with this project, we are anticipating and hopeful that this project is successful in that it helps reduce erosion and sediment in the West Fork Carson, which could contribute to better water quality,” Loden said. “Then with the willows creating more fish habitat and shade within the river stream, it’s all aimed at improving water quality and helping this river connect to the natural floodplain.”


Scott King writes about science, technology, and the environment for the Ally. Support his work.


Top photo caption and credit: Meadow restoration work being done on the West Fork of the Carson River in October of 2020, Site One imagery from a drone – Photo: Carson Water Subconservancy District Watershed Specialist Shane Fryer