A streambank rehabilitation project done on Copsey Creek in Lake County in August of 1997 benefited not only this particular creek, but the individuals who did the work, the property owner, the local economy, and the aesthetic appeal of Clear Lake.
In 1996, the Lake County Career Center obtained disaster relief funding, and by l997 had put 93 displaced and long term unemployed people to work doing cleanup, repair and preventative measures on streams which had been damaged by winter flooding. This program (still active) teaches participants how to do stream management work and gives them valuable employment experience. Environmentally, the program has helped many creeks return to healthier functioning, and is aiding in a solution to an algae imbalance problem in Clear Lake.
The Copsey Creek project was the largest of many taken on by 15 crews in the summer of 1997, and set an example of how to work with nature to restore natural functioning.
I don't use the term "restoration" here because we are not working on a '56 Chevy. We can't literally restore what nature has created, and the topsoil lost at Copsey Creek could not have been economically replaced by the truck load. The most we can do is to help restore natural functioning and rehabilitate damage to a level where natural process can again proceed.
Clear Lake is notorious for its prolific summer algae blooms. The lake is shallow and warm, capable of producing and sustaining a wide diversity of life, including huge masses of algae. The problem with the algae (besides navigational hazards and boat stains) is that it dies, decays and floats, and then its stench is blown by the winds, creating a stink bomb from hell.
The cause of this phenomenon is primarily the sediment that is transported into Clear Lake by winter storm runoff. Lake County soils are high in iron and phosphorus, which play a major role in fertilizing the algae. The chronic algae is a natural occurrence, exaggerated by human impacts.
The most positive thing the people of Lake County can do about this problem is to limit the amount of soil that ends up in stream channels. It should be noted that erosion is a natural process. It moves nutrients, spawning gravel, organic matter and other essential components throughout water channels. The challange is not to eliminate erosion, but to bring it back to a natural level.
Defining "natural" is often problematic, as each situation is unique. The Copsey Creek project demonstrates how rehabilitation work helped restore natural functioning at one specific site.
Trouble began at Copsey Creek when several small oak trees dislodged from somewhere upstream and jammed into a narrow, sharp bend in the channel (See Fig. 1, "A"). The trees caught more debris coming downstream and diverted the flood water into the streambank; then the bank was eroded into the flood terrace to get around the blockage. As it eroded, the landowner's well casing ("B") was exposed, and a large valley oak fell directly into the stream ("C"), completely blocking the old channel. All of the flood water was forced into the newly created channel for the rest of the winter, gouging into the fifteen-foot high flood terrace.
Stream rehabilitation work began with removal of the trees and other debris. This was done with hand tools, chains and a back hoe (Fig. 2and3). At its deepest point the gravel deposit was over six feet thick. It was stored nearby and used later to help reconstruct the old streambank. The material was a mixture of sand, gravel and soil, which provides a good medium for the reintroduction of vegetation.
A willow mattress was used to stabilize the newly constructed streambank. A trench was dug along the base of the new bank and lined with a thick layer of living willow branches, cut nearby. After the willow was placed, the trench was filled half-full with the gravel and soil mixture (Fig. 4). Large rocks were then placed to finish filling the trench, extending up the willow cuttings to a height of three feet. The rock and willow mattress was then covered with the remaining gravel to protect the cuttings from drying out.
Behind this, the newly-reconstructed bank had to be protected from eroding out again. The backside of the new bank had to be lined with rock as well. The downstream end of the eroded area was blocked with a barrier of rock three feet high and another willow mattress with rock was built along the new outside wall of the channel to protect the landowner's exposed well-casing.
The object was to allow high water flows to pass over the rock barriers during storm events, but not with enough force to cause additional erosion. The rock barriers (Fig 5 and 6 ) trap the winter flows and create a ponding action, allowing more time for the sediment carried within the water column to settle out.
This new floodplain will allow for relief from high winter flows and continue to trap sediment as more vegetation grows in it. Techniques such as this work with the stream system and encourage the rebuilding of the natural processes that have been lost.
In the spring and early summer the water held in the side channel ponds provided off-stream pool habitat for wildlife such as deer, frogs, snakes and turtles. The ponds at this site trapped an estimated 400 cubic feet of top soil in just one winter.
As the willows and other vegetation grow, their bodies will slow the water flow, collecting more sediment. Their roots will hold the rock and streambank in place (Fig.7). The vegetation will increase the wildlife values in the stream channel.
This is how Nature originally designed these systems. This solution allows the stream to function naturally, protects the land, enhances the wildlife, and helps protect the property owner's interests.
This project took a month to complete with a five person crew. Along with stabilizing this critical area, they learned life and interpersonal skills needed to hold a job and work in a group situation.
Although the work done in Copsey Creek is itself very important, it demonstrates that while working to enhance natural systems we can also address local economic needs and long-term solutions for land and water quality issues.
Copyright Mendocino Environmental Center 1999
Permission granted to excerpt or use this article if source is cited