Biodiversity Guide - The Intertwine

egional conservation strategybiodiversity guideAppendix I Watershedsconstruction of Lake Merwin in 1931, at theexpense of coniferous and mixed forest.The Lewis River is the second-largest watershedin the greater Portland-Vancouver region, makingup 12 percent of the entire region.Key facts about the Lewis River subbasin withinthe greater Portland-Vancouver region:n Has 64 percent tree cover, the highest proportionof all the region’s watersheds.n Has forest patches (i.e., patches of trees andregenerating forest that together are 30 acres orlarger) that cover 71 percent of the subbasin withinthe region. This attests to the high proportionof private and public lands managed for timber.n Is 22 percent publicly owned. This representsabout 20 percent of all privately owned lands inthe region.n Includes more than 12,000 acres that are withinFEMA 100-year floodplains and 10,700 acres ofmapped wetlands.Land use practices throughout the subbasin, inparticular dams, residential development, gravelmining, and agricultural activities, have negativelyaffected habitat conditions in the lowersubbasin. Nonetheless, the Lewis River subbasinis home to diverse fish and wildlife populations.People appreciate the kayaking, camping, wildlifewatching, hiking, and fishing opportunitiesoffered by the subbasin’s riparian and uplandhabitat.North Fork Characteristics. The North Fork subbasin’swatersheds include Fly Creek, Lower CanyonCreek, Marble Creek, Cedar Creek, and the LewisRiver. Stream conditions in the lower North Forksubbasin are generally better than in the EastFork subbasin because the human population isless and more of the subbasin is forested. Watertemperatures at Amboy and at the mouth ofCedar Creek are elevated and potential affectingsteelhead juveniles. High temperatures have beenattributed to agriculture, grazing, water withdrawals,surface water runoff, residential development,forestry operations, and the constructionof illegal dams and diversions. Water qualityinformation is lacking for other lower Lewistributaries.The upper and middle portions are generallyforested. Stand-replacement fires burned largeportions in the subbasin during the first threedecades of the 1900s, including the large YacoltBurn. The resulting impacts to vegetation andsoil stability likely exacerbated major floods in1931 and 1934. The lower subbasin lies in a broadalluvial valley characterized by agriculture andresidential uses, which are largely protected fromflooding by dikes. This section is extensivelychannelized and tidally influenced in some areas.The valley begins to narrow for the next 8 miles,eventually forming a canyon from the confluenceof Cedar Creek to Merwin Dam, which blockspassage to 80 percent of the historical anadromoussalmon habitat.Historically, the upstream area was a majorproduction area coho salmon, spring andfall Chinook salmon, and winter and summersteelhead. These species have declined drasticallyin number, and they are listed under the federalEndangered Species Act; mitigation programshave attempted to reestablish historical salmonruns, with limited success. However, the NorthFork mainstem from RM 15 to Merwin Damprovides a highly productive spawning area forfall Chinook salmon. All three reservoirs (Merwin,Yale, and Swift) support populations of bulltrout and Dolly Varden. In the upper river, threestreams provide rearing and spawning habitat forbull trout: Pine and Rush creeks, which flow intoSwift Reservoir, and Cougar Creek, which flowsinto Yale Reservoir. The North Fork subbasinalso supports cutthroat trout and Pacific lamprey.Cedar Creek and its tributaries, including Pup,Bitter, Beaver, and Chelatchie creeks, currentlyprovide most of the productive tributary habitatfor anadromous salmon.East Fork Characteristics. The East Fork Lewis Riverhas its source near Green Lookout Mountainin the Gifford Pinchot National Forest, elevation4,442 feet. The subbasin’s watersheds withinthe greater Portland-Vancouver region includethe Coyote, Basket, Rock and Lockwood Creekwatersheds. The East Fork’s headwaters are characterizedby steep slopes and narrow valleys thatare dominated by bedrock and boulder substrates.Copper Creek and upper Rock Creek are the twolargest tributaries in the upper subbasin.Stream conditions are generally fair to goodin the upper watershed and poor to fair in themiddle and lower watershed. The mid-lowerwatershed is affected by low summer flows, highstream temperatures, and coliform bacteria, andthe mainstem and tributaries are listed on the303(d) list of impaired water bodies. Water bodiesplaced on the 303(d) list require the preparationof a total maximum daily load (TMDL) toidentify and quantify sources of the impairmentsand to recommend implementation strategies forreducing point and nonpoint source pollutantloads. The Washington Department of Ecologyis analyzing temperature and bacteria data andis expected to begin holding Advisory Committeemeetings to determine the control measuresthat will be incorporated into the TMDL watercleanup plan.The East Fork subbasin still retains significantpopulations of salmonids, including chum,fall Chinook, and coho salmon and winter andsummer steelhead, all of which are listed asthreatened under the federal Endangered SpeciesAct. The East Fork mainstem is completely freeflowing, with no manmade obstructions or dams.Lucia Falls is a natural barrier, above which onlysteelhead routinely pass. Some tributary streamshave fish-blocking road culverts. Upstreammigration for steelhead was essentially blockedat Sunset Falls (RM 33) until 1982, when the fallswere notched. Below Lucia Falls the river flowsthrough a narrow valley that forms a canyon inplaces, until it opens up around RM 14 into abroad alluvial valley.Wildlife, Habitat, and Connectivity. The subbasin’swildlife habitat varies and includes extensivenear-stream wetlands, bottomland forest andfloodplains, scattered intact headwater wetlands,and some interesting linear wetland sequencesformed by the Missoula floods at the end of thelast ice age. Native prairie and oak remnants arescattered through the western lowlands. Substantialintact forested areas support diverse wildlifecommunities. Agricultural lands, though disturbed,provide important habitat to grasslandbirds, small mammals, and other wildlife, as wellas providing some connectivity between naturalhabitat areas. Invasive species such as knotweedare a problem in some riparian areas, and Scot’sbroom and other invasive species have invadedsome upland areas. Efforts to control invasivespecies are ongoing.The Washington Department of Fish andWildlife’s Comprehensive Wildlife ConservationStrategy identifies specific areas and actions tohelp sensitive habitats and wildlife species. TheWDFW’s Priority Habitats and Species programidentifies the mainstem, associated floodplains,and major low-lying tributaries as important habitatareas for breeding and over-wintering baldeagles and waterfowl, including concentrations ofgeese, ducks, and wintering populations of tundraswans. The Woodland bottomlands support largeconcentrations of wintering waterfowl, includingdusky and cackling Canada geese, resident geese,tundra swans, and migrating sandhill cranes. Bea-242 243