September 20, 2022 — Erosion is a form of pollution, especially alongside waterways, as pieces of the terrestrial landscape make their way into rivers and streams, damaging fishbearing habitat.
Now, several private landowners in Laytonville are working with the Eel River Recovery Project, using EPA money distributed by the State Water Resources Control Board, to remediate over 600 feet of erosion on four creeks that feed into the South Fork of the Eel River. Patrick Higgins, the director of the Eel River Recovery Project, gave an overview on Saturday morning as he led a tour along Cahto Creek. The four projects are “relatively substantial,” he said. “Two on Cahto Creek here, along the Cahto Trail. And one at Mill Creek, above Little Case Creek. And one at Black Oak Ranch along Streeter Creek. And these are all salmonid-bearing streams.” Each site ranges from a hundred feet to about 180 feet long, so Higgins notes that “they’re pretty big open sores, where dirt’s pouring into the creek. And that’s not good for the private land interests, but it’s also a form of pollution,” which fills in downstream pools and salmon nests. It can also cause rivers to get shallower, widening and heating up as the cold water comes to the surface. The Eel River Recovery Project sent surveys to all the landowners in the basin, asking them if they had problems with riparian erosion, then chose to work on the four sites that had the highest potential for sediment pollution and the most significance for fish habitat.
The work is scheduled to take place between July and October of next year. Mostly, it consists of engineering features that will affect the velocity of the river where its flows have been altered by human activity — or the lack of it, like building bridges and roads, and allowing conifers to overtop oak forests and absorb groundwater that some scientists believe would otherwise join the river.
Dennis Hogan owns property near what he calls the Mulligan Bridge. He’s working on improving forest health and remediating a section of riverbank that he says has receded steadily since he moved onto the place in 1989. He’s also raising willow and other riparian saplings to plant on the newly engineered riverbank, once the heavy machinery gets out of the way. “The streambed is lower than it used to be, by quite a bit,” he told visitors on Saturday. The nearby bridge has concrete abutments, which could account for narrowing the river channel, causing the water to rush through with great velocity. And Hogan said the rate of erosion seems to have increased since a large oak on the riverbank came down about five years ago.
Philip Buehler is the foreman of BioEngineering Associates in Laytonville, which designs riverbank stabilization projects. On Saturday afternoon, he told a small group of landowners and nature lovers about the forces at work in the creek under Mulligan Bridge. He’s taken a lead role in designing the structures that will be installed next year, and will be in charge of the crew that puts them in
“What’s happening here is really common on creeks,” he said. “You can see we’re on a slight outside bend of the creek here on this side. With any outside bend, the water is moving faster over here than it is on the inside…we have all this blackberry and other vegetation that is strengthening that side of the creek. You can see where Dennis has cleared, just behind the blackberry, it’s really sandy, fine sediment. During high flows, when that part of the bank is inundated over there, you’re getting slower water velocity in all of that vegetation. The vegetation is absorbing the energy of the flowing creek, and slowing the water down. When it’s slowed down, sediment drops out and gets deposited over there. That’s what’s moving this creek eighty feet this way, is sediment being deposited over there, vegetation growing up over time. Over here (on the eroded side), we have no erosion-resistant vegetation, so it’s stronger over there than it is over here.”
Buehler took a few moments to talk more about bioengineering at the end of the tour on Streeter Creek at the Hog Farm. That’s another erosion site where a section of fencing dangles in midair about ten feet from the edge of the riverbank. “Bioengineering is a type of technology where we build living structures, generally out of locally harvested willow plants,” he said. “So we build our structures out of rock, live willow, and erosion control fabrics…the gist of it is, the projects are living things. They grow over time, they stabilize the river bank, and they have a lot of benefits for the creek in general.”
At Hogan’s property, Buehler plans to put in five structures made out of boulders, live willow branches, and root wads to coax the river into creating more deep water pools for young salmonids. “What we want to do here is move the channel, so it’s flowing in the middle here, more to that side, rather than against this bank,” he explained. He expects the root wads to create turbulence in the channel as the water flows over them, scouring out a pool downstream, giving the fish a place to spend the summer, “until it rains, and we get a creek here again.”
The next day, Laytonville got well over an inch and a half of rain.
