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THE WEISS CREEK PROJECT
Rebuilding a Salmon Stream
by Ramon Vanden Brulle
For nearly 80 years, Lower Weiss Creek ran through an 800' long ditch, cut straight across the Snoqualmie River floodplain. The ditch offered a very limited quantity and variety of rearing habitat for Weiss Creek's native coho salmon, winter steelhead, and resident rainbow and cutthroat trout. This past spring, Washington Trout completed a major restoration project at Weiss Creek, replacing the ditch with over one mile of floodplain stream, providing a full variety of functioning rearing and spawning habitats.
Washington Trout has completed all of the initial phases of a major habitat
restoration project on Weiss Creek, a tributary of the Snoqualmie River between
Carnation and Duvall.
Last summer, WT completed the excavation phases of the Weiss Creek project. Over the winter and spring crews replanted the riparian zone around the restored creek with over 12,000 native trees, shrubs, wetland plants, and grasses, installed stock fencing to protect the channel from cattle and horse grazing, and in February WT reconnected the stream to its newly restored historical channel. The completed project has re-routed the creek from an 800 foot diked ditch back into its historical channel, recovering over 5000 feet of flood plain channel and about 20 acres of wetland, rearing habitat for juvenile coho salmon, winter steelhead and cutthroat trout.
The primary phases of the project involved re-excavating the historical
channel, adding large woody debris, and connecting the restored channel to some
associated wetlands and beaver ponds. Reconnecting the stream to the restored
channel was delayed until late winter to let returning coho salmon pass through
the ditch, and to avoid harming juvenile salmon rearing in the lower creek.
During fall and early winter high flows, the stream overtopped the dike, allowing water to flow through the restored channel, but the majority of current continued to flow through the ditch. The creek was diverted into its restored channel in February to allow newly hatched down-migrating salmon to utilize the restored habitat this spring.
The Snoqualmie River Basin is one of the most productive salmonid systems in Puget Sound. Small tributaries like Weiss Creek offer spawning habitat for some species, but more importantly, rearing habitat for juvenile salmon and trout that were spawned in Weiss Creek and other parts of the system. The young salmonids, some spending up to two years in fresh water before migrating to sea, often move into smaller creeks to escape harsh conditions in the main river, including high winter flows and high summer temperatures. Small off-channel creeks like Weiss offer better and easier feeding opportunities for young salmon and trout, and refuge from predation by larger fish. The loss of off-channel rearing habitat has been identified as a critical limiting factor for salmon in the Snoqualmie Basin.
Breaching the dike to reconnect the creek to its restored channel presented some risks, including short-term sedimentation. The operation was executed during cold weather and low flow conditions to minimize any possible negative impacts. WT Science/Research Director Jamie Glasgow called the reconnection a success, and said the precautions the crew took helped to minimize impacts on the new habitat and any fish utilizing the lower creek, as well as any juvenile fish using the ditched channel.
The Weiss Creek Project was designed to restore salmon and trout rearing habitat by recreating the full range of natural stream functions in lower Weiss Creek. The stream had been straightened and diked in the 1920s to create a pasture on the floodplain. The diked channel was only about 800 feet long, providing a very limited range of stream function and available rearing habitat, significantly reducing the productive capacity of Weiss Creek. The project has restored nearly a mile of varied floodplain habitats to the system.
The goal of the project is to recreate the conditions that contributed to the original abundance of salmon in the system. So far, it appears to be a success. The new channel is functioning as expected, and juvenile fish are already utilizing the recovered habitats. The ultimate result of the project will be more wild salmon returning to the Snoqualmie system, reducing the need to rely on costly, ineffective, and damaging artificial propagation programs.
While the project design incorporated the restoration of spawning habitat on the floodplain, the most significant aspect of the project is the creation of off-channel rearing habitat within the Snoqualmie River floodplain. It will provide habitat for juvenile salmon and trout from other systems in the basin, not just fish that were spawned in Weiss Creek, and increase the productivity of the entire Snoqualmie system, including nearby Griffin Creek, the most important coho spawning stream in the Snoqualmie basin.
Cutting Edge Restoration-Ecology
An Irony of the completed project is that it looks less impressive than it actually is. The restored channel appears so natural and complete that at first glance, the project may look like the simple fencing and replanting of the riparian zone around a functioning stream. But the project represents cutting edge restoration-ecology, the full recreation of a stream, almost from scratch.
Project designers studied historical resources and carefully surveyed the immediate topography to determine the channel’s course, elevation, and gradient. Portions of the channel had to be completely re-excavated from the pasture – paying close attention to elevation and gradient controls - and the LWD elements were carefully placed using heavy equipment. Some portions of the channel were allowed to dig themselves once water began flowing through the stream. Important hydrological functions like sediment sorting, bank cutting, and pool forming were also largely left to the stream itself. The important goal of the project was not just to create artificial habitats, but to restore habitat processes to Lower Weiss Creek, to give it the opportunity to work and evolve like a natural system.
The most severly compromised process on Lower Weiss Creek in the short term will be its ability to recruit LWD. WT Field Technician Frank Staller drilling and staking LWD elements to prevent their loss from floatation during flood events.
The Weiss Creek Project incorporates a large amount of in-stream Large Woody
Debris (LWD), and extensive plantings of cedar, fir, and native hardwood trees.
Today, the Snoqualmie Valley is dominated by pasture, but historically the
entire valley floor was a complex of densely wooded wetlands, with mature
conifers, cottonwoods, alders and maple trees bordering the main river, its
back channels, and its tributaries, like Weiss Creek. These mature trees were
constantly being recruited into the river and streams, contributing to channel
complexity and creating varied in-stream habitats for the system’s resident and
anadromous fish. The project was designed to recreate these original stream
We designed and placed the LWD elements to mimic the full physical and temporal complexity of a natural stream, representing different age classes of in-stream wood. Spanner logs perched over the channel represent the "youngest" wood in the stream. Control logs imbedded in the stream bottom represent the "oldest." LWD in the stream channel would fall somewhere in between. Each type and age of LWD performs different habitat forming functions, controlling the stream gradient, armoring banks, forming pools, providing shade and cover for fish and other aquatic organisms, influencing channel migration, and contributing organic matter to the stream.
In a fully functioning system, the oldest wood eventually decomposes, and is replaced by younger wood, which is replaced by new wood recruited from the riparian corridor. Naturally functioning habitats are dynamic, which contributes to their complexity. We’ve attempted to fully recreate a temporal point in the successional history of the stream.
Other design elements of the project will help contribute to habitat complexity. Crews excavated benches in the low-gradient stretches of the channel to create micro-wetland complexes associated with the channel, and give the channel likely places to migrate. To protect the landowner’s pasture, the stream was constrained to some degree, but channels must migrate to function properly and provide dynamic complexity. The goal of the Weiss Creek Project is to restore an entire, dynamic ecosystem. Complex, dynamic habitats contribute to the genetic diversity and the long-term health of a fish population; simple, static habitats tend to put genetic diversity at risk
Historically, the Snoqualmie Valley was covered by densely wooded wetlands. To help recreate original stream conditions, and provide a future source of LWD, crews led by WT Field Biologist Mary Lou White planted nearly twelve thousand native trees, plants and grasses on the project site.
The nearly twelve thousand native trees, shrubs, and grasses planted in the
riparian zone will provide shade and cover for fish, help moderate water
temperature, filter sediments, contribute organic matter to the water, and
provide habitat for insects, birds, and other animals. Eventually, the trees
will provide a source of LWD.
Compromising With a Compromised System
Eventually, we hope that all natural processes will return to Lower Weiss Creek. But the disturbed condition of the greater Snoqualmie floodplain system required measures to protect some aspects of the restoration effort. The most severely compromised process on Lower Weiss Creek in the short term will be its ability to recruit LWD. Measures had to be taken to protect the channel from the loss of LWD during very high flows.
In an un-compromised system, the lateral migration of LWD would undoubtedly be beneficial, but since Lower Weiss Creek flows across the flood plain of the much larger Snoqualmie River, lateral migration is not a large issue. Lower Weiss Creek will very rarely reach the velocity necessary to significantly move LWD, because at water levels that high, the creek, its floodplain, and its flows will be completely submerged under the pooled floodwaters of the Snoqualmie River. The threat to Weiss Creek’s LWD is buoyancy; during major flood events, it could simply float away.
This is a natural process that Lower Weiss Creek has likely been subjected to innumerable times over the millennia. However, under historical conditions, this process would have been offset by the creek’s ability to recruit new wood, often triggered by the same event. Further, when the valley floor was covered by mature forest, the LWD would simply not have been able to float very far away. Today, with the floodplain dominated by open pasture, floating wood could migrate a mile or more from the stream. In order to preserve the LWD elements of the project, crews often drove the logs deep into the channel and banks. A log that reveals 20 feet may have another 20 feet buried into the stream bank. Spanner logs particularly were driven deep into the banks and placed on top of in-stream wood and control logs to pin them into the channel. In other cases, logs were discretely staked together with rebar or to posts driven deep into the channel or the banks. These measures will protect the project from the loss of LWD in the short term, until the plantings mature to the point that they can provide a source for LWD recruitment.
The landowner, Andy Weiss, has demonstrated an incredible commitment to the project and wild fish recovery. He originally proposed the restoration of Weiss Creek to WT. He has given up a significant amount of real estate to the project, and contributed labor, time, and equipment to the effort. He has become a tireless booster for
Landowner Andy Weiss pitches in at the controls of a small dozer during excavation of the channel.
the restoration, WT, and wild salmon and trout. For his generosity and commitment, he received Washington Trout’s 1999 Volunteer Conservationist of the Year Award. However, Weiss Creek is inescapably compromised by the reality that it flows across private property.
Weiss gave up grazing access to over 40 acres to accommodate the restoration
needs of Weiss Creek, but his property is still working acreage. He could not
afford to cede the entire floodplain back to the creek. While the project was
engineered to allow vital channel migration, subtle berms were placed some
distance back from the channel to constrain it from some areas of pasture. The
stream was fenced to keep livestock away from the stream and the banks, but two
fenced crossings were built into the channel to allow stock and light vehicle
access to pastures adjacent to the project.
These measures and compromises may affect the "purity" of the project, but they are necessary, and insure the significant, long-term benefits of the restoration. The berms and stock crossings also help create a cooperative model for stream recovery on private agricultural lands. Weiss has certainly acted out of a deep commitment to the recovery of Weiss Creek and its wild fish populations. But the project has brought other benefits to him and his property. Nearly every year, the stream was over-topping the dike and flooding the adjacent pasture, making it unusable for months at a time. While he now has fewer available grazing acres, he can more predictably manage what he has. The ability of conservation advocates and private landowners to cooperate in actually increasing the quantity and quality of habitats available to wild fish will be vital to any wider recovery effort.
A Stochastic Test
In late spring, the project was challenged by a relatively rare, significant natural event. Overnight on May 15, a beaver dam on Weiss Creek’s South Fork failed, sending a wall of sediment-laden water rushing down the canyon and onto the floodplain.
These kinds of random, stochastic events can wreak substantial changes on a system the size of Weiss Creek. This is one of the rare types of instances that would produce the combination of water volume and velocity that could have laterally moved –or even removed - the project’s LWD complexes. If the project’s designers had made any mistakes in excavating the channel’s course, the flash flood would certainly have corrected them, perhaps catastrophically. We were concerned about the amounts of fine sediments the flood might have deposited in the project reach.
Of course, beaver dam failures are natural events; Weiss Creek has likely suffered them before. From an ecological perspective, natural events can never really damage a system; they merely change it. On the other hand, WT was not exactly thrilled at the prospect of catastrophic change to the newly completed restoration of a system as disturbed as Weiss Creek.
As it turned out, the dam failure and flash flood provided a test of the project, a test it passed with flying colors. The channel demonstrated no significant change, though the flood seems to have aided in some pool-forming and bank-cutting. No wood was lost or even significantly moved, validating our pinning techniques. (As noted above, it would have been unfortunate to lose LWD at this stage in the restoration.) While the immediate floodplain around the restored channel was inundated, even the plantings nearest the channel survived for the most part, and the fine sediments and organic matter deposited by the flood will likely help the native plants and grasses. The entire event has had an interesting and by and large beneficial impact on the project.
A Model Project
Beyond the immediate benefits this project will provide for Weiss Creek and the Snoqualmie system, WT hopes it will serve as a model for similar restoration efforts. WT has already given tours of the project site to staff and officials from King
WT Science Director Jamie Glasgow gives Tolt Middle School students an in-the-field lesson in wild-fish habitat preservation and restoration.
County, the City of Redmond, the media, and to the general public. In May,
students from Tolt Middle School got hands on experience and education about
salmon habitat recovery by attending field seminars at the project site
presented by WT Science/Research Director Jamie Glasgow. A segment about the
Weiss Creek Project will appear in a video production about salmon recovery
produced by King County DNR.
Other planned public outreach initiatives include the installation of interpretive signs at the project site and on nearby public trails. WT is discussing with 911 Media Arts Center in Seattle their help in the production of a short documentary video about the project, for distribution to agencies, tribes, other conservation groups, and the general public.
public outreach and education, the approach and techniques used at Weiss Creek
will serve as a model for other restoration efforts. WT Public Outreach
Director Marilyn Tuohy answers questions from Tolt Middle School students at a
field seminar on
the project site.
The approach and techniques WT used at Weiss Creek are proving themselves.
The stream is functioning, forming habitats, responding to natural events.
Juvenile salmon and trout are utilizing the recovered habitats. The next phases
of the project will include monitoring, documenting, and communicating the
progress of the project, so that the model of restoring habitat functions and processes
can be followed on other systems.
The Weiss Creek Project was funded with grants from Jobs for the Environment, the Snohomish Work Group, and King County.