Cherry Valley Floodplain Restoration and Protection Project

by Jamie Glasgow

The Snoqualmie River in King County Washington is listed on the 303(d)-water quality impaired list for exceeding temperature, total suspended sediments, and fecal coliform standards. The majority of these impacts associated with Cherry Creek, a tributary to the main stem Snoqualmie located just north of Duvall, derive from agricultural land use practices. The lower reaches of the Creek, including a ditched tributary network, are located within the Washington Department of Fish and Wildlife Cherry Valley Wildlife Unit (the Unit). Within the Unit, grazing by cattle is the method of choice to control reed canary grass, an invasive noxious weed. However, uncontrolled animal access to flood plain tributaries and mainstem Cherry Creek would have adverse impacts on fish, fish habitat and water quality through bank erosion, sediment input, fecal coliform input and degeneration of riparian shade producing vegetation.

Ditched tributaries within the Unit are known to provide low gradient rearing habitat for coho salmon, cutthroat trout, and other native fishes, but few data are available to document summer low flow water quality parameters that may preclude fish use or in fact contribute to fish mortality. The off-channel habitat types protected and enhanced by this project have been identified as limited in quantity and quality within the Snohomish basin by the WRIA 07 ESA Technical Committee.

In 1999, Washington Trout received funding from the King County Department of Natural Resources Water Works grant program to implement the Cherry Valley Monitoring and Fencing Project. The project has complemented previously completed Washington Trout riparian restoration work in the Cherry Creek drainage to protect water quality and fish habitat in the Unit. The project will improve water quality and fish habitat, benefit other wildlife species, and enhance human recreational and agricultural use on the Unit. It will also provide data of relevance to recent King County Best Management Practices for ditch maintenance and will allow evaluation of the effects of current King County Livestock Ordinances, which permit cattle to graze as close as 25 feet to a stream.

Volunteers Jeff Martin and Bosco assist with the revegatation of Cherry Creek.

The project was comprised of three components. First, baseline biological and water quality data were collected in the Cherry Creek tributaries within the Unit. In cooperation with the Tulalip Tribes, water temperature, dissolved oxygen, and fecal coliform counts were collected from twelve points in the lower Cherry valley. Several biological samples were also taken to determine fish and amphibian species presence and relative abundance. The results of the fish species composition and relative abundance work further underscore the necessity to remove or repair the pumphouse/floodgate located at the confluence of Lateral A and Cherry Creek.

Aquatic species relative abundance in the Cherry Valley Wildlife Unit, samples summed.

Second, two cattle pastures, each approximately 300 acres, were created with 12,000 feet of fence line. The two fenced pastures, occupied by 90 head of cattle, will reduce unit maintenance costs by minimizing the need to mow the fields. Because the fence lines for the pastures are at the required distance of 25 feet from the tributaries, the two pastures also give Washington Trout the opportunity to evaluate King County Best Management Practices for agricultural production districts.

Third, 2745 trees were planted in 15 experimental plots within the riparian areas of the Cherry Creek tributaries within the Unit. Fifteen identical 28-foot by 75-foot experimental plots, each abutting a tributary, were each planted with a total of 2745 trees. One of five different treatments was randomly assigned to each of the fifteen plots, providing three replicates of each treatment. Treatments included different site preparations, the use of different sizes of trees, the use of different rodent guards, and the use of plastic sheeting or cardboard sheet mulching to control the growth of reed canary grass around the newly planted trees

In addition to providing shade and allochthonous inputs to the tributaries, the plantings will help shade out the invasive noxious weed reed canary grass that has infested the floodplain. Also, the experimental nature of the planting has allowed and will continue to allow Washington Trout to evaluate five different treatments for planting in reed canary grass.

Preliminary results from the vegetation monitoring show minor losses, mostly due to natural causes, likely transplant trauma. As of August 2000, only 3% of the planted trees and whips had died. This number is surprisingly low, considering the presence of a well-established beaver population in the Cherry Valley floodplain. The sites will be revisited in 2001 to evaluate the success of the five different rodent guard and plot preparation treatments.

Fish, vegetation, and water quality data collected at Cherry Valley in the coming years will allow us to assess the success of the fencing and revegetation project, as well as assess the effectiveness of the King County Best Management Practices for Agricultural Production Districts.

TOP