City of Bothell Streams and Riparian Areas: Best Available Science

DRAFT

Submitted to City of Bothell October 7, 2004

Steward and Associates 120 Avenue A, Suite D Snohomish, Washington 98290 Tel (360) 862-1255 Fax (360) 563-0393 www.stewardandassociates.com Citation: Steward and Associates. 2004. DRAFT - City of Bothell Streams and Riparian Areas: Best Available Science. Prepared for City of Bothell. October, 2004. City of Bothell Streams and Riparian Areas: Best Available Science

TABLE OF CONTENTS

Table of Contents ...... i List of tables...... iii Executive summary...... 1 1 Purpose and organization...... 3 2 Anadromous Salmon in the Planning Area ...... 4 2.1 Chinook salmon ...... 4 2.1.1 Status...... 4 2.1.2 Life History...... 5 2.1.3 Habitat Use...... 7 2.2 Coho Salmon...... 8 2.2.1 Status...... 8 2.2.2 Life History...... 9 2.2.3 Habitat Use...... 9 2.3 Steelhead...... 10 2.3.1 Status...... 10 2.3.2 Life history...... 10 2.3.3 Habitat use ...... 11 2.4 Sockeye salmon ...... 11 2.4.1 Status...... 11 2.4.2 Life history...... 12 2.4.3 Habitat use ...... 12 2.5 Kokanee salmon...... 12 2.5.1 Status...... 12 2.5.2 Life history...... 13 2.5.3 Habitat use ...... 13 3 Salmon Habitat Stressors ...... 13 4 Riparian area Structure, Functions and Values ...... 17 4.1 Riparian structure and ecosystem processes...... 17 4.2 Riparian area functions and values ...... 20 4.3 Riparian buffer function and effectiveness...... 21 4.3.1 Wildlife habitat ...... 22

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4.3.2 Temperature and microclimate control...... 23 4.3.3 Sediment removal ...... 24 4.3.4 LWD recruitment...... 25 4.3.5 Nutrient and pollutant removal ...... 26 4.3.6 Streambank stabilization...... 27 5 City of Bothell Sub-basin Summaries ...... 27 5.1 Sammamish River Mainstem...... 27 5.1.1 Land Use ...... 27 5.1.2 Fish Utilization...... 27 5.1.3 Habitat Conditions ...... 28 5.2 North Creek...... 29 5.2.1 Land Use ...... 29 5.2.2 Fish Utilization...... 30 5.2.3 Habitat Conditions ...... 30 5.3 North Creek Tributaries ...... 31 5.3.1 Coal Creek ...... 31 5.3.2 Palm Creek...... 32 5.3.3 Perry Creek ...... 32 5.3.4 Queensborough Creek...... 33 5.3.5 Joco Creek...... 33 5.3.6 Royal Anne Tributaries...... 33 5.3.7 Filbert Creek ...... 34 5.4 Horse Creek ...... 34 5.4.1 Land Use ...... 34 5.4.2 Fish Utilization...... 34 5.4.3 Habitat Conditions ...... 34 5.5 Swamp Creek...... 35 5.5.1 Land Use ...... 35 5.5.2 Fish Utilization...... 35 5.5.3 Habitat Conditions ...... 35 5.6 Sammamish Independent Tributaries ...... 36 5.6.1 Land Use ...... 36 5.6.2 Fish Utilization...... 36

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5.6.3 Habitat Conditions ...... 36 5.7 Unique watershed characteristics...... 37 6 Synthesis of Best Available Science and Local Conditions ...... 38 6.1 Sammamish river mainstem...... 38 6.2 North Creek...... 39 6.3 North Creek tributaries ...... 39 6.4 Horse Creek ...... 40 6.5 Swamp Creek...... 40 6.6 Sammamish independent tributaries...... 40 7 References...... 43

LIST OF TABLES

Table 1. General life histories of salmonids known to occur in the project vicinity (Source: Spence et al. 1996; Cederholm et al. 2000, Busby et al., 1996; Gustafson et al., 1997, WDF et al., 1993)...... 7

Table 2. Habitat stressors that impact salmon survival, behavior and distribution. Listed by species and life-stage...... 14

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City of Bothell Streams and Riparian Areas: Best Available Science

EXECUTIVE SUMMARY

The Growth Management Act (GMA) requires that cities and counties “include the best available science” in the process they use to designate critical areas and protect their “functions and values”, giving “special consideration to conservation or protection measures necessary to preserve or enhance anadromous fisheries.” (RCW 36.70A.172) “Critical areas” include wetlands, frequently flooded areas, geologically hazardous areas, critical aquifer recharge areas and fish and wildlife habitat conservation areas. This paper focuses on the last category, primarily streams and adjacent riparian areas. It also reviews aspects of wetlands and floodplains related to fish and wildlife habitat, giving special consideration to their importance to salmonids.

The two most important stream systems within the City of Bothell are North Creek, whose drainage basin includes most of the City but extends further north into Everett and unincorporated Snohomish County, and the Sammamish River, which passes through the City of Bothell in its course from Lake Sammamish to Lake Washington. North Creek ultimately flows into the Sammamish River, as do other smaller independent streams within the City, both north and south of the river. The Sammamish River is an important migratory corridor for salmon from Bear Creek, Issaquah Creek and other streams upstream and downstream of Bothell. It is one of the highest priority areas for salmon recovery in the Greater Lake Washington Watershed (Water Resource Inventory Area, or WRIA, 8). (WRIA 8 2004) North Creek is also important for salmon recovery in the watershed, both for its existing salmon runs (which include Chinook, coho, sockeye, kokanee, and steelhead) and for its potential through restoration to broaden the geographic distribution of these species in sustainable numbers across the North Lake Washington area.

Though almost all (98%) of the North Creek basin is within the Urban Growth Area, it currently has a higher level of biological integrity (as measured through an index based on the number, kind and diversity of aquatic insects found there) than most urban streams, in part because it has such extensive wetlands, which buffer some of the typical impacts of urbanization on water quality and flows. It also has reaches (particularly between 240th St. SE and 228th St. SE) and tributaries (particularly Palm and Coal Creeks) with remarkably good stream and riparian habitat for an urban area. Protecting these reaches and tributaries should be a high priority for Bothell’s critical area regulations.

Salmon require suitable substrate, water quality, water quantity, water temperature, water velocity, cover/shelter, food, riparian vegetation, space and safe passage conditions to survive and thrive. This paper describes these needs in greater detail (by species, life history stage and time of year), summarizes scientific findings regarding their relationship to riparian and upland conditions, and discusses potential implications of these findings for critical area regulations within the City of Bothell. Since the findings note that urban development and the land clearing that typically comes with it have cumulative impacts on waterbodies downstream that cannot be addressed strictly within the typical scope of critical area regulations, this paper also briefly discusses other issues that must be addressed to meet the GMA’s ultimate test of protecting the “functions and values” of critical areas. These include low-impact approaches to stormwater management; protection of seeps and shallow aquifers that are important perennial sources of cool, clean water to both North Creek and the

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Sammamish River; clustering of development to preserve forest cover; and habitat restoration projects.

A second paper will apply results from this review of the “best available science” for stream and riparian areas in an evaluation of the State of Washington’s example code provisions for fish and wildlife habitat conservation areas and the City of Bothell’s existing critical area codes. Combined, these two papers should provide the City of Bothell with the relevant scientific information it needs to meet the GMA’s requirements for fish and wildlife habitat conservation areas.

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1 PURPOSE AND ORGANIZATION

The purpose of this report is to provide the scientific foundation for updating the Critical Areas Ordinance (CAO) and related environmental policies and programs within the City of Bothell (City) and surrounding, designated urban growth area (UGA). This report specifically focuses on the protection of streams, rivers and their associated wetlands and riparian areas. Special emphasis is placed on the habitat functions and values critical to the protection and recovery of anadromous salmon in the planning area. The focal species considered in this report include chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), steelhead (O. mykiss, the anadromous form of rainbow trout), sockeye salmon (O. nerka) and kokanee (also O. nerka), the non-anadromous form of sockeye. The habitat requirements and life-history diversity of this suite of species provide a useful lens for assessing environmental conditions within the planning area and for identifying priority functions and values to be addressed by the CAO.

The report is organized as follows:

Section 2 provides a summary of species status, life history and habitat requirements for each of the four focal salmonid species, providing a foundation for understanding the impacts of land use, habitat alteration and other human activities on various life stages of interest.

Section 3 provides a summary list and discussion of “stressors” that can adversely affect the survival, behavior and distribution of each species at various lifestages. This discussion is limited to those lifestages that are likely to occur in the planning area. By identifying specific stressors related to conditions in the watershed, this section facilitates the coupling of the basic habitat requirements of each species to the functions and values that may be addressed through the protection of critical areas.

Section 4 describes the best available science related to the structure, functions and values of riparian areas and stream-associated wetlands. The discussion also includes a summary of research related to the effectiveness of “buffers” in protecting desired functions and values in critical areas.

Section 5 describes the primary sub-basins in the planning area, including a summary of land use, known or presumed fish utilization, and habitat quality. The sub-basins include the mainstem Sammamish, North Creek and its tributaries, Horse Creek, a portion of the Swamp Creek basin and a set of independent, unnamed tributaries to the Sammamish River originating along the south side of the river. This section also describes certain unique aspects of the sub-basin in the area in terms of topography, groundwater influence and other factors.

Finally, Section 6 couples the best available science pertaining to the protection of critical area functions and values with the specific conditions and challenges encountered within the planning area. This section will form the basis for making recommendations for the protection and restoration of functions and values through amendment to the CAO and associates policies and programs.

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2 ANADROMOUS SALMON IN THE PLANNING AREA

The Sammamish River and its tributaries within the planning area are utilized by several species of salmonids, including resident and anadromous life-history types. This section provides a summary of species status, life history and habitat use for the four focal species of anadromous salmonids found in the planning area: chinook salmon, coho salmon, steelhead and sockeye salmon.

2.1 Chinook salmon

2.1.1 Status

In 1998, NOAA Fisheries determined that indigenous chinook populations within the Puget Sound drainage constitute an “evolutionarily significant unit” (ESU); that is, a genetically distinct subset of the biological species (Myers et al., 1998). Following a formal status review, NOAA Fisheries listed Puget Sound ESU chinook on 24 March 1999 (64 FR 14308) as threatened. Chinook are widely distributed in Puget Sound streams and rivers. Although the total abundance of Puget Sound ESU chinook is relatively high, much of this production is hatchery-derived. Population levels are trending downward, with several local populations exhibiting severe short-term declines (Myers et al., 1998). Due to the Federal listing, the State of Washington considers Puget Sound Chinook to be a Species of Concern. Moreover, the State also considers the species to be a Candidate for listing under State law. State Candidate species include:

“…fish and wildlife species that the Department will review for possible listing as State Endangered, Threatened, or Sensitive. A species will be considered for designation as a State Candidate if sufficient evidence suggests that its status may meet the listing criteria defined for State Endangered, Threatened, or Sensitive.” (WDFW Policy M-6001)

Puget Sound chinook populations have declined as a result of loss, damage or change to their natural environment. Several factors have been implicated:

• fishing pressure • high temperatures and low dissolved oxygen concentrations • low flows • physical barriers that limit or add stress to migrations • lack of deep holding pools • sedimentation • high turbidity • lack of structure or cover providing habitat • lack of large woody debris • competition • predation, and • pollution.

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The 1992 Washington State Salmon and Steelhead Inventory (WDFW, 1994) described three summer/fall chinook (Oncorhynchus tshawytscha), two coho (O. kisutch), three sockeye (O. nerka) salmon stocks, and one winter steelhead (O. mykiss) stock in the Greater Lake Washington Watershed (WRIA 8).

The SASSI divided the Lake Washington Basin summer/fall chinook into Issaquah Creek, North Lake Washington tributaries and Cedar River (and associated tributaries) stocks. Issaquah Creek chinook, a non-native hatchery origin stock, were classified as “Healthy” while the native, naturally produced North Lake Washington tributary and Cedar River stocks had “Unknown” stock status. Chinook in the Bothell vicinity are part of the North Lake Washington stock, which are distributed in North, Swamp, Bear, Little Bear and Cottage Lake creeks (WDF et al., 1993).

The June 2004 Draft of the WRIA 8 Chinook Salmon Conservation Plan (WRIA 8 2004) also divides Lake Washington summer/fall chinook into three populations in these areas, though revisions for the public review draft will note that there is uncertainty whether the North Lake Washington and Issaquah populations may effectively be one, heavily hatchery- influenced population. Studies are underway to help clarify how genetically distinct these fish are from each other and from Cedar River chinook. Results should be available in early 2005, though they may not resolve these issues conclusively. The Draft WRIA 8 Plan currently identifies “the severe contraction of [geographic] distribution” as an important limiting factor for North Lake Washington chinook, which would raise the importance of habitat restoration in North Creek.

2.1.2 Life History

A generalized chinook life history summary is presented in Table 1. Adult chinook return to freshwater to spawn in the late summer and fall, destined for upstream mainstem and tributary spawning areas. “Summer” chinook arrive first, ascending the river in September and early October to spawn. “Fall” chinook return to spawn between September and the end of October, sometimes continuing into December.

Lake Washington Basin adult chinook first arrive at the Ballard Locks in mid-June. The peak time of entry through the locks and into the Lake Washington Basin occurs in mid to late August and is generally complete by early November. Lake Washington Basin summer/fall chinook stocks spawn from mid-September through November, peaking around the second week of October. Emergence from spawning nests (redds) is dependent on water temperatures but begins in January and ends in March.

The summer/fall chinook in the Lake Washington area are known as “ocean-type”1. Ocean- type chinook typically rear in their natal freshwater environment for one to four months prior to their seaward migration. Lake Washington Basin chinook are unlike other Puget Sound stocks of chinook is that as juveniles they must enter, rear for some period of time, and

1 Chinook stocks are often characterized as either “ocean-type” or “stream-type” depending on their juvenile life history. “Stream-type” stocks typically spend a full year rearing in streams prior to their seaward migration.

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Juvenile chinook are believed to incubate in the gravel until emergence in late January through early March. Outmigration of North Lake Washington chinook generally appears to be delayed, with the large majority rearing in the creeks where they spawned until mid- to late spring before migrating to the Sammamish River and quickly to Lake Washington and Puget Sound. (Mobrand Biometrics 2003) However, this pattern has been studied only in Bear Creek, where the Washington Department of Fish and Wildlife has operated a smolt trap since the late 1990s. It is not certain that this same pattern would hold for North Creek and other spawning tributaries, though that is believed likely. (Mobrand Biometrics 2003)

During their freshwater residency, juvenile chinook feed primarily on zooplankton and aquatic insects. Upon reaching saltwater, juvenile chinook spend several months in estuaries and nearshore areas before beginning a more protracted, coastally-oriented ocean migration (Shepard, 1981). Chinook return to spawn after 2 to 4 years at sea (i.e., at 3 to 5 years of age) and die after spawning.

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Table 1. General life histories of salmonids known to occur in the project vicinity (Source: Spence et al. 1996; Cederholm et al. 2000, Busby et al., 1996; Gustafson et al., 1997, WDF et al., 1993; Berge and Higgins 2003).

Species Spawning Spawning Spawning Life History Most Migration Period Area Common Age at Maturity

Chinook Summer to Late Rivers and 2-4 months fresh- 4 Salmon fall summer to large water, 1-4 years (ocean) early tributaries. ocean. winter

Coho Fall to early Fall to Small 1-2 years fresh- 3 Salmon winter early lowland water, 18 months winter and adult ocean. headwater streams

Steelhead Winter to March to Medium to Variable. 4 (winter) spring June large Typically 2 years rivers and freshwater, 2 years streams. adult ocean. Some repeat spawning.

Sockeye Summer to Late Lake inlet Variable. 1-2 years 4-5 fall summer to and outlet in lakes, 1-3 years fall tribs, in ocean. beaches

Kokanee Summer to Late Lake inlet Variable. 3-4 years 4 fall summer to and outlet in lakes. fall tribs, beaches

Most chinook spend two to four years feeding in the North Pacific before returning to spawn as 3, 4 or 5 year olds. Others spend their entire marine residency in Puget Sound and in the Strait of Georgia. Like other semelparous species of salmon, chinook die after reproduction.

2.1.3 Habitat Use

Salmonids require adequate substrate, water quality, water quantity, water temperature, water velocity, cover/shelter, food, riparian vegetation, space, and safe passage conditions to persist and thrive. Chinook have proven to be particularly sensitive to loss of spawning and rearing habitat and poor water quality in freshwater. Juvenile chinook are adversely affected by low flows and poor water quality during the summer months. They are also vulnerable to the

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effects of winter flooding. Eggs may be lost by scouring or suffocated by silt deposition (Spence et al. 1996; Myers et al. 1998).

Because they are anadromous, chinook salmon occupy a wide variety of habitats during different phases of their life. Chinook favor mainstem rivers and large streams for spawning, but are also found in smaller tributaries. Chinook spawning habitat typically consists of riffles and the tail-outs of pools with clean substrates dominated by cobbles. Recently emerged chinook fry seek out low-velocity environments along the channel margin, often moving into backwater habitats and in close proximity to physical structure that provide refuge from predation to complete the early rearing phase. As they grow larger, chinook juveniles redistribute into pools and other slow water habitats to rear and stage prior to beginning their seaward migration.

2.2 Coho Salmon

2.2.1 Status

Coho populations in Puget Sound, Hood Canal, and the Strait of Georgia form a distinct genetic/ecological cluster relative to populations found elsewhere, and are therefore considered a single ESU by the NOAA Fisheries (Weitkamp et al., 1995). Coho populations in the northern portion of the Puget Sound/Strait of Georgia ESU have declined significantly from historical levels. However, the abundance of the ESU as a whole is not depressed and recent trends have not been downward. From a consideration of available evidence, NOAA Fisheries decided to not list the Puget Sound/Strait of Georgia Coho ESU (Weitkamp et al., 1995).

There is, nonetheless, substantial risk of future declines due to several natural and anthropogenic factors. Coho survival is largely dependent on discharge rates and water temperatures; both factors are sensitive to human activities. Other risk factors include widespread and intensive artificial propagation, overfishing, extensive habitat degradation, a recent dramatic decline in adult size, and persistent periods of poor ocean conditions. On the basis of these risk factors, NOAA Fisheries designated coho salmon a Candidate species in 1995 (60 FR 38011). Recently, despite the absence of an updated Status Review, NOAA Fisheries removed the Puget Sound/Strait of Georgia Coho ESU from the list of Candidate species and designated it a Species of Concern (69 FR 19975). Importantly, this change in status does not reflect any reduction in the level of concern for the status of coho salmon, but rather it is the result of a change in the interpretation of Candidate designation.

The 1992 SASSI (WDFW, 1994) separates Lake Washington coho stocks into the Cedar River stock and Lake Washington/Sammamish Tributaries stock. The Cedar River stock is naturally reproducing, although it is thought to be a mixed genetic stock of native and non- native origin due to hatchery supplementation. The stock is considered “Healthy”. Coho occupying Bothell streams are part of the broader Lake Washington/Sammamish Tributaries stock, which is also a stock of mixed origin and has been affected by extensive hatchery supplementation in the area. The stock is considered “Depressed” by WDFW due to severe short-term declines in abundance.

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2.2.2 Life History

Table 1 provides a general summary of coho salmon life history. Lake Washington Basin coho adults typically enter fresh water from August to early December. Coho favor smaller tributaries for spawning and rearing. They often mill near the river and creek mouths or in lower river pools until the fall freshets occur. The onset of coho salmon spawning is often triggered by the first significant fall freshet. Spawning usually occurs in tributary streams between November and early December, but is sometimes as early as mid-October. High stormwater flows in the tributaries can destroy redds while high levels of sediment can suffocate eggs.

Fry emerge in spring and rear in freshwater for 12-18 months. The seaward migration of coho smolts begins in early April, peaks in May, and continues through June. Coho typically spend 16-20 months rearing in the ocean before returning to freshwater to spawn as three- year-old adults (Cederholm et al. 2000). The Lake Washington Basin coho juveniles remain in freshwater for a full year after emergence. As smolts, they travel in surface-oriented schools numbering up to several hundred fish. Like chinook, sub-adult coho salmon reside in estuaries and nearshore for significant periods of time, foraging and growing before venturing into open water.

The ocean migratory route followed by Puget Sound coho salmon appears to be related to the geographic area of their natal streams. Significant numbers of coho remain in Puget Sound throughout their marine residency. However, as a general rule, coho from streams and hatcheries in Puget Sound are likely to be caught off the coast of Washington and British Columbia (as opposed to Oregon and Alaska), presumably because they spend most of their time in these waters.

2.2.3 Habitat Use

Coho favor smaller tributaries for spawning and rearing. They typically spawn in low gradient riffles with clean substrates ranging from gravel to cobble size substrate. Juveniles prefer low gradient habitats, including pools, off-channel ponds, and tree-lined stream margins and side channels containing significant quantities of large woody debris (Henry 1995). Coho juveniles often redistribute from their summer rearing habitats to overwinter in beaver ponds and other off-channel habitats. Coho production in freshwater is particularly sensitive to summer base flows and the availability of suitable overwintering habitat.

Juvenile coho establish and defend territories, and feed on aquatic macroinvertebrates and terrestrial insects. Coho production in freshwater is particularly sensitive to summer base flows and the availability of suitable overwintering habitat. Summer low flows can lead to problems such as a physical reduction in available habitat, increased stranding, decreased dissolved oxygen, increased temperature, and increased predation.

Juvenile coho are highly territorial and can occupy the same area for long periods of time (Hoar, 1958). Streams with healthy riparian systems contribute large woody debris (LWD), which improves stream structure, and leaf litter, which stimulates food production. Such

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streams support more coho, not only because they provide more territories (useable habitat), but they also provide more food and cover (Scrivener and Andersen, 1982).

2.3 Steelhead

2.3.1 Status

The Puget Sound Steelhead ESU occupies river basins in Hood Canal, portions of the Strait of Juan de Fuca as well as Puget Sound. While there are some indications of genetic differences between stocks in northern and southern Puget Sound, NOAA Fisheries did not consider the ecological or life history differences to be of sufficient magnitude to warrant division into separate ESUs (Busby et al., 1996). NOAA Fisheries does not consider the current status of the ESU to warrant protection under the ESA. Similarly, WDFW does not list this ESU as a Candidate for State listing or as a State Species of Concern.

Like most of the stocks in this ESU, Lake Washington steelhead are primarily winter-run fish (Busby et al., 1996), also commonly referred to as “winter steelhead”. WDFW considers the stock to be native to the basin and of wild origin. The status of the stock in the latest WDFW review is listed as Depressed, i.e., “… one whose production is below expected levels, based on available habitat and natural variation in survival rates, but above where permanent damage is likely”. The Depressed listing for this stock is based primarily on chronically low escapement (WDF et al., 1993). Geographical isolation exists between spawning steelhead in numerous tributaries, but the degree of straying and mixing is unknown (WDF et al., 1993). Nehlsen et al. (1991) considered the Lake Washington stock to be at “Moderate Risk of Extinction”.

2.3.2 Life history

Table 1 provides a general description of steelhead life history in the Puget Sound region. Steelhead feature an extraordinarily complex suite of life-history characteristics compared to other salmonids in the region. Importantly, unlike other pacific salmon, steelhead are iteroparous, i.e., an individual may spawn more than once during its lifetime. Freshwater residence time, ocean residence time and the prevalence of repeat spawning can be highly variable both within and between populations. Moreover, the distribution of the freshwater resident form of the species, known as rainbow trout, may occupy the same streams as the anadromous form. In some circumstances, one form (anadromous or resident) may yield offspring of the opposite form (Busby et al., 1996).

Winter steelhead adults enter freshwater in a sexually mature state in the winter and early spring, and spawn soon thereafter. In contrast, summer steelhead enter streams in a sexually immature state and spend several months in freshwater prior to spawning in the spring. The Lake Washington steelhead stock enters freshwater between December and May (Busby et al., 1996) and features an early March to mid-June spawning period (WDF et al., 1993).

Like coho salmon, steelhead spend an extended period rearing in freshwater prior to entering the ocean. While specific data on the Lake Washington stock is sparse, the vast majority of Puget Sound steelhead spend two years rearing in freshwater (Busby et al., 1996).

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Most west coast steelhead spend two years rearing in the ocean prior to their first spawning migration. This pattern is prevalent for most Puget Sound stocks, though a substantial percentage also returns after three years in the ocean. Repeat spawning is relatively rare for Puget Sound steelhead; in most stocks, repeat spawners represent less than 10% of the spawning population (Busby et al., 1996). However, due to their larger size, repeat spawners may produce a somewhat disproportionate share of subsequent offspring.

2.3.3 Habitat use

Steelhead utilize a wide variety of freshwater habitat types. For spawning, steelhead generally prefer fast water in small-to-large mainstem rivers, and medium-to-large tributaries. Due to their superior leaping ability, steelhead may access stream reaches that are inaccessible to most other salmonids. Steelhead may spawn in streams with steep gradients and large substrate, utilizing low-gradient stream segments between steeper portions where the water is flatter and the substrate is small enough to dig into.

Unlike coho salmon that prefer to rear in slower-moving pools, steelhead fry will seek out areas of fast water and large substrate for rearing. They utilize eddies behind large rocks, allowing the river to transport food in the form of insects, salmon eggs, and smaller fish.

Due to their extended freshwater rearing period, older juvenile steelhead can be piscivorous, and may utilize other juvenile salmonids as prey.

2.4 Sockeye salmon

2.4.1 Status

A substantial amount of uncertainty remains regarding the historical presence of sockeye in Lake Washington prior to extensive planting of sockeye in the 1930s-1950s (Gustafson et al., 1997). Sockeye salmon in the Lake Washington watershed are not part of an ESU identified by NOAA Fisheries. Moreover, within the Lake Washington watershed, distinctions are evident between different spawning populations. The population occupying Big Bear Creek and its tributaries is thought to be distinct from those spawning in the Cedar River, Issaquah Creek and other tributaries in the Lake Washington/Lake Sammamish drainage (Gustafson et al., 1997). In its 1997 Status Review, NOAA Fisheries identified the Big Bear Creek stock as a provisional ESU. Lacking ESU designation, Lake Washington sockeye are not formally designated pursuant to the ESA.

The State has not designated Lake Washington sockeye as a Species of Concern or as a Candidate for listing. The State recognizes three stocks of sockeye in the Lake Washington basin: Cedar River, Lake Washington/Sammamish Tributaries and Lake Washington Beach Spawners. The North Creek population is subsumed under the Lake Washington/Sammamish Tributaries stock, which also includes Bear Creek (WDF et al., 1993). The stock is considered Depressed due to a long-term negative trend in escapement.

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2.4.2 Life history

Table 1 provides a summary of sockeye life history characteristics for stocks in the Puget Sound region. Lake Washington sockeye adults enter freshwater as early as May and continue into the fall. Spawning typically takes place between September and December. Fry emerge in the Spring, although different populations in the same area can have substantial variation in emergence timing (Gustafson, 1997).

Sockeye are unique among pacific salmon in that they express a very strong preference for spawning in close proximity to large lakes. Following emergence from the gravel, sockeye fry exhibit a variety of behaviors, including immediate migration to lake rearing areas and protracted stream rearing. The lakes are subsequently used for rearing for a period of 1-3 years, with most stocks in the Lake Washington basin rearing for one year (Gustafson et al., 1997). Smolt migration typically occurs between April and early July. Ocean rearing may last from one to three years, with certain stocks exhibiting a diverse mix of age classes in the spawning population. For example, in 1992-1993, Big Bear Creek spawners were well distributed between one, two, and three-year ocean rearing fish, although two-year ocean fish represented a slight majority (Gustafson et al., 1997).

2.4.3 Habitat use

Though most spawning takes place in the inlet and outlet streams of rearing lakes, spawning also occurs along beaches in the lakes themselves (Gustafson et al., 1997; Burgner, 1991), especially in areas of upwelling groundwater (Burgner, 1991). Generally, for stream- spawning sockeye, spawning occurs in the mainstems of tributaries, presumably to provide direct access to lake rearing areas. Preferred substrate size can vary substantially, particularly for lake spawners, which are known to utilize relatively fine substrates in areas of strong upwelling as well as large cobble that is too large to move through digging action (Burgner, 1991). In streams, substrate sizes are typically modest and readily cleaned of fine sediment by digging (Burgner, 1991).

Sockeye fry in Lake Washington are typically found in the offshore limnetic zone, rather than in the nearshore littoral zone (WDFW, 1996, cited in Gustafson, 1997). Sockeye juveniles are known to undergo diel migrations throughout the year, spending daytime hours in deeper waters and nighttime hours nearer to the surface.

2.5 Kokanee salmon

2.5.1 Status

There appear to be three different populations of kokanee in the greater Lake Washington watershed: an early run in Issaquah Creek (now believed to be extinct); a middle run in larger tributaries of the Sammamish River, including North Creek; and a late run that spawns in tributaries to Lake Sammamish. (Berge and Higgins 2003)

The least is known about the middle run, which is found in largest numbers in Bear Creek and to a lesser extent in Little Bear, but also North and Swamp creeks. It appears closely

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related to Bear Creek sockeye, and may in fact be residualized sockeye. The two life forms are very closely related. Bear Creek sockeye may in turn be the descendants of native kokanee, which took on an anadromous life history pattern after the outlet of Lake Washington was re-routed through the Lake Washington Ship Canal in the early 20th Century. North Creek was said to have a “very excellent” native run of kokanee in 1946 (Garlick, as cited in Berge and Higgins 2003), which may now be extinct.

2.5.2 Life history

Table 1 provides a summary of kokanee life history characteristics, for the middle run that spawns in Sammamish River tributaries. Kokanee (or residualized sockeye) in North Creek now spawn from September through November, with an apparent peak in late September, though survey numbers have been so small this is uncertain. (Berge and Higgins 2003) It is not known whether they rear in Lake Washington or Lake Sammamish, though it is suspected that they follow sockeye to Lake Washington. Middle run kokanee are smaller than either the early run or late run kokanee in the Lake Washington system. This may be due to competition with sockeye for many of the same food sources.

2.5.3 Habitat use

Kokanee spawn in small gravels in the lower reaches of streams, which makes them vulnerable to high storm flows as well as sedimentation from upstream. Since their run time overlaps with sockeye and chinook, their redds are also at risk of superimposition from these other species. The middle run race of kokanee does not appear to be limited by the amount of available spawning habitat, but the quality of that habitat may not be adequate. (Berge and Higgins 2003).

3 SALMON HABITAT STRESSORS

One of the greatest long-term threats to the viability of salmon and other aquatic organisms is the continuing loss and degradation of freshwater, estuarine, and marine habitat. Broadly speaking, fish habitat is the geographic area where the species occurs at any time during its life cycle. Habitats can be characterized by various attributes including biological, physical, and chemical parameters, location, and time. Ecologically, salmon distributions and behaviors are controlled or modified by characteristics of habitats that include structural components (e.g., pools, large woody debris, spawning gravels, and migration barriers) and other factors that may be less obvious to the human eye but are critical nonetheless in determining when and how salmon make use of a particular area. Examples include several water quality parameters such as dissolved oxygen, temperature, and turbidity. Because these factors vary both spatially and temporally, habitat use may shift over time and space (NOAA Fisheries, 1998).

The distribution and quality of habitats used by salmon for spawning, rearing, migration, feeding, growth, and shelter are vulnerable to disturbances caused by human activities and by natural processes. Changes in habitat and the effects they have on salmon depend on the nature of the disturbance and prevailing conditions. The effects are not always predictable or even quantifiable due to the complex processes involved. For example, the biological

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response depends on the species and life stages present at the time of the disturbance, their relative abundance and distribution, and a host of other ecological factors. With the exception of extreme stressors, such as fish passage obstructions and catastrophic contaminant spills, a strict cause-and-effect relationship between an environmental disturbance and salmon viability cannot always be discerned.

Salmon are vulnerable to a variety of habitat stressors (e.g., high temperature, passage barriers) during different stages of their life cycle. Species that feature a protracted freshwater rearing period are vulnerable to many different types of stressors in the stream/river environment, whereas those species that migrate quickly into the ocean may experience a more limited (though not necessarily less significant) set of challenges related particularly to spawning and incubation. Table 2 summarizes the types of stressors that affect specific life-stages of each species of interest while in the freshwater environment. Stressors prevalent in specific portions of the planning area are described elsewhere. The purpose of this section is to couple species-specific life history information with the types of habitat stressors that may be addressed by the updated CAO.

Some of the factors identified below as stressors may be present to a certain degree in pristine, natural environments as well, depending on environmental conditions during a particular year. However, discussed further in Section 5, the frequency and magnitude of many watershed processes is dramatically altered by urbanization and other land-use changes, such as sediment input, high-flow magnitude, low flow magnitude, temperature, etc.

Table 2. Habitat stressors that impact salmon survival, behavior and distribution. Listed by species and life-stage.

Chinook Salmon(ocean type) Period Activity Stressors Summer to Adult migration High temperature. Low flow migration barriers. Lack of early fall deep holding pools due to lack of LWD. Early fall Spawning High temperature. Poor gravel conditions due to fine sediment. Limited spawning area due to low flow and migration barriers. Incubation Low intra-gravel dissolved oxygen. High temperature. Late fall and Spawning Poor gravel conditions due to fine sediment. Limited early winter spawning area due to low flow and migration barriers. Incubation Scour of redds due to high flow. Egg suffocation due to burial by sediment. Late winter Pre-emergent alevin in Scour due to high flows. Burial by sediment. gravel Early spring Fry emergence Lack of low-velocity, backwater habitat. Lack of instream cover (LWD) for concealment. High flows may cause premature migration. Macroinvertebrate food supply may be limited in poor riparian areas.

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Late spring, Smolt migration Lack of instream cover. Macroinvertebrate food supply. early summer Coho salmon Summer to Juvenile rearing High temperature. Lack of pools and instream cover. Water early fall quality (many parameters). Low flow reduces habitat quantity and water quality. Early fall Spawning High temperature. Poor gravel conditions due to fine sediment. Limited spawning area due to low flow and migration barriers. Juvenile rearing Lack of pools and instream cover. Macroinvertebrate food supply. Water quality. Incubation Low intra-gravel dissolved oxygen. High temperature. Late fall and Spawning Passage barriers, some exacerbated by high flows. Lack of early winter suitable spawning gravels. Juvenile rearing Lack of pools and instream cover. Beaver ponds and off- channel habitat critical. Water quality. Incubation Scour of redds due to high flow. Egg suffocation due to burial by sediment. Late winter Pre-emergent alevin in Scour due to high flows. Burial by sediment. gravel Juvenile rearing Lack of pools and instream cover, beaver ponds and off- channel habitat. Early spring Fry emergence Lack of low-velocity, backwater habitat. Lack of instream cover (LWD) for concealment. High flows may cause premature migration. Macroinvertebrate food supply dependent in part on riparian condition. Juvenile rearing Lack of pools and instream cover, beaver ponds and off- channel habitat. Late spring, Juvenile rearing (fry, Lack of pools and instream cover, beaver ponds and off- early summer parr) channel habitat. Macroinvertebrate food supply. Water quality. Smolt migration Lack of instream cover for concealment. Macroinvertebrate (yearling) food supply. Steelhead Summer to Incubation and pre- Low intra-gravel dissolved oxygen. High temperature. Water early fall emergent alevin quality. Dewatering by low flows. Juvenile rearing High temperature. Lack of pools and instream cover. Water quality (many parameters). Low flow reduces habitat quantity and water quality. Early fall Juvenile rearing Lack of pools and instream cover. Macroinvertebrate food supply. Water quality. Low flow stranding.

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Late fall and Juvenile rearing Lack of pools, instream cover, off-channel habitat. early winter Late winter Adult migration Passage barriers Juvenile rearing Lack of pools and instream cover, beaver ponds and off- channel habitat. Early spring Spawning Lack of suitable spawning habitat. Passage barriers. Incubation Scour by high flows. Burial be sediment. Juvenile rearing Lack of pools and instream cover, beaver ponds and off- channel habitat. Late spring, Juvenile rearing (fry, Lack of pools and instream cover, beaver ponds and off- early summer parr) channel habitat. Water quality. Spawning Lack of suitable spawning habitat. Passage barriers. Incubation Scour by high flows. Burial be sediment. Dewatering by low flows. Water quality. Smolt migration Lack of instream cover for concealment. (yearling) Sockeye and kokanee (lake rearing stressors not discussed) Summer and Adult migration High temperature. Low flow migration barriers. Lack of early fall deep holding pools due to lack of LWD. Early fall Spawning High temperature. Poor gravel conditions due to fine sediment. Limited spawning area due to low flow and migration barriers. Incubation High temperature. Low intra-gravel DO due to low flow and water quality. Late fall and Spawning Passage barriers, some exacerbated by high flows. Lack of early winter suitable spawning gravels due to excess sediment. Incubation Scour of redds by flood flows. Burial by excess sediment input. Early spring Incubation Scour of redds by flood flows. Burial by excess sediment input. Emergence Lack of instream cover to avoid predation. Late spring and Fry migration to lakes Lack of instream cover to avoid predation. early summer

While each species is vulnerable to a different suite of stressors at different times, certain general patterns apply.

• For all species, spawning opportunities are limited by passage barriers (such as poorly designed culverts) and by a shortage of clean gravels of an appropriate size. While digging behavior can remove a substantial amount of fines, excess fine sediment has a significant impact on spawning habitat.

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• For fall spawners (all but steelhead), high stream temperature can delay spawning migration and reduce water quality. Low fall flows reduce available spawning habitat and concentrate spawning in the middle of the channel where redds are most vulnerable to scour furing high flows.

• For fall spawning species and early spawning steelhead, high flows pose a substantial risk of scour during incubation. When high flows are coupled with excessive sediment input, eggs may suffocate due to burial by excess fines.

• While the specific habitat preferences of juveniles vary by species and age-class, a lack of instream structure and complexity (e.g., LWD, boulders, pools, side channels) severely limits the availability of rearing habitat. Moreover, poor riparian cover may substantially reduce the availability of macroinvertebrates, which are a critical food source for juvenile life-stages.

• Species with an extended stream rearing phase (coho, steelhead), the lack of low-energy backwater areas, riparian wetlands and pools is a major stressor during winter and summer rearing. Beaver ponds in particular are a preferred over-winter habitat for coho salmon. For these same species, low flow coupled with high temperature in the late summer leads to thermal stress, particularly when coupled with the absence of pools.

• Poor water quality is a stressor for all life stages, but incubation and pre-emergent alevin life-stages are especially vulnerable to low DO and high turbidity.

4 RIPARIAN AREA STRUCTURE, FUNCTIONS AND VALUES

The importance of protecting riparian areas and their functions has been recognized as a priority on a national scale. The National Research Council (NRC) considers the conservation of riparian functions to be a national goal (NRC, 2002). As a transition zone between aquatic and terrestrial environments, riparian areas perform critical functions for both aquatic and upland species. In proportion to their area within a broader watershed, riparian areas perform more biologically productive and critical functions than do upland areas (NRC, 2002).

4.1 Riparian structure and ecosystem processes

Riparian areas generally refer to areas of land and vegetation around streams, rivers, lakes and wetlands that are influenced by intermittent or perennial water (Naiman and Bilby, 1998). The NRC (2002) defines riparian areas as follows:

“Riparian areas are transitional zones between terrestrial and aquatic ecosystems and are distinguished by gradients in biophysical conditions, ecological processes, and biota. They are areas through which surface and subsurface hydrology connect waterbodies with their adjacent uplands. They include those portions of terrestrial ecosystems that significantly influence

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exchanges of energy and matter with aquatic ecosystems. Riparian areas are found adjacent to perennial, intermittent and ephemeral streams, lakes, estuaries, and marine shorelines.”

Naiman et al. (1993) describe the lateral dimension of the riparian area as extending to where vegetation is influenced by an elevated water table, flooding, or soils capable of holding water and also encompasses portions of the streambank between the low and high-water marks. For WDFW (Knutson and Naef, 1997), the riparian area begins at the ordinary high water mark and includes that portion of the terrestrial landscape that directly influences the aquatic ecosystem, including the entire floodplain. Riparian areas also have a vertical dimension, including the canopy of surrounding vegetation (Gregory et al., 1992).

Riparian areas associated with streams and rivers are often referred to as riparian corridors. In natural ecosystems of the Pacific Northwest (PNW), riparian corridors are typically well vegetated and continuous throughout a broader channel network (Naiman and Bilby, 1998). The corridor concept is an important one in that it relates directly to key functions of riparian areas, such as connectivity of habitat for avian, amphibian and terrestrial species. Moreover, as discussed below, discontinuity in a riparian corridor due to road crossings and other intrusions can severely compromise certain riparian functions.

Riparian areas often include riparian wetlands, as is the case for many streams in the planning area. Riparian wetlands represent a diverse assemblage that includes forested wetlands, marshes, bogs, fens, wet meadows, shrub swamps, wooded swamps and beaver ponds (May, 2003). Isolated wetlands, which are not directly connected to streams or Puget Sound even during high flows or high tides, still play important roles in protecting salmon habitat. They protect stream flows by detaining and infiltrating stormwater into the ground, which increases baseflows fed by groundwater and reduces floods that scour spawning gravels and streambanks. Isolated wetlands also filter pollutants and provide important habitat for amphibians and birds, which often depend on them for breeding and foraging.

The terms “buffer” or “riparian buffer” are often loosely used as synonyms for riparian areas. However, the term buffer is typically applied in a specific management context to denote an area set aside and managed to protect a natural area from the effects of surrounding land-use or human activities (May, 2003; Knutson and Naef, 1997). Depending on the specific context, buffers may be designed to perform a specific function or set of functions, such as filtering pollutants or providing shade (May, 2003). A discussion of research related to buffer width and buffer quality is provided in Section 4.3, below.

The floodplains of rivers and streams alike are an integral part of the riparian ecosystem. Typically, a floodplain is a relatively flat, low lying area outside of and adjacent to the main channel. The temporary inundation of floodplains is an integral and natural part of the hydrologic regime. Flood-induced erosion and channel migration are also natural phenomena (May, 2003), but can be substantially exacerbated by human activities. Complex, dynamic, well defined floodplains are typically associated with the lower reaches of large rivers. In smaller streams, especially low-gradient tributaries along valley floors (e.g., North Creek), floodplains nevertheless perform critical functions for both natural resources and human interests, such as providing refuge for fish from high flows, supplying

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nourishment to riparian vegetation in the form of sediment, and dissipation of flood energy and associated adverse impacts.

Due to the dynamic nature of river and stream ecosystems, many streams also have a characteristic channel migration zone (CMZ), which refers to the process of the channel moving laterally within the floodplain (May, 2003). Typically, channel migration is a gradual process, but it may also occur abruptly through a process called avulsion (Dunne and Leopold, 1977). In smaller streams flowing through ravines or narrow valleys, the CMZ may be non-existent. This is the case with most of the tributaries in the planning area, but low- gradient, unconfined portions of North Creek may have a defined CMZ.

The dynamic and diverse characteristics of streams and their associated riparian areas are shaped by a combination of ecosystem processes, including the hydrologic regime, geomorphic processes, and inputs of organic and inorganic materials from upland areas (Gregory et al., 1991; Naiman et al., 2000). The hydrologic regime of a particular river or stream system refers to the spatial and temporal patterns and dynamics that describe the movement of water through the ecosystem. The hydrologic regime includes climatic patterns of precipitation, rainfall-runoff relationships, interaction between surface and groundwater flow, water storage capacity, and other factors.

Streamflow quantity and timing are critical factors in shaping a stream/riparian ecosystem and in defining its ability to provide specific functions and values. The strong correlation of streamflow with many physiochemical characteristics of rivers (such as water temperature, channel geomorphology and habitat diversity) can be considered critical to the structure and function of the stream/riparian ecosystem (Naiman et al., 2000; May, 2003). Depending on the balance of flow during storms as well as baseflow, three categories of streams are typically recognized: perennial, intermittent and ephemeral streams (Dunne and Leopold, 1977). Perennial streams flow year-round even in the absence of rainfall. Intermittent streams flow during certain times, generally during the rainy season. Ephemeral streams flow for short periods only during or immediately after periods of rainfall.

The size and shape of a stream channel are generally determined by a combination of discharge, gradient and sediment load (Dunne and Leopold, 1977). Changes in any one factor can dramatically change the channel form. For example, a change in the quantity and timing of streamflow (i.e., discharge) or sediment load (e.g., via accelerated rates of erosion) can have profound impacts on the stream or river channel and surrounding riparian areas. The hydrologic pattern of a watershed also drives several key geomorphic processes, including upland erosion, sediment transport and sediment deposition (Naiman et al., 1992; Poff et al., 1997; Naiman et al., 2000). Erosion and sedimentation are natural processes critical to the formation and proper functioning of the stream/riparian ecosystem. However, human activities can dramatically alter the magnitude, frequency and location of both erosion and sediment deposition, profoundly altering the stream/riparian ecosystem.

The transport and deposition of sediment, large woody debris (LWD) and other organic and inorganic materials are key to the formation of channel characteristics and aquatic features (May, 2003). LWD influences the routing of water and sediment, as well as the bottom topography of a stream, including the formation and distribution of pools (Booth et al., 1996;

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May et al., 1997; Naiman et al., 2000). LWD also dissipates energy during flood flows by increasing the coarseness of the stream channel, slowing erosion and sediment transport, while retaining smaller-sized organic debris (Naiman et al., 1992).

4.2 Riparian area functions and values

Riparian corridors, including wetlands, perform a broad suite of functions at the interface of terrestrial and aquatic ecosystems. The most commonly cited functions include:

• Providing habitat for terrestrial, avian, amphibian and aquatic animals.

• Providing thermal regulation.

• Reducing sediment input from upland areas via filtering and retention.

• Providing coarse particulate organic matter (CPOM) and LWD to the stream channel.

• Filtering and uptake of nutrients and pollutants.

• Streambank stabilization.

Many animals (amphibians in particular) reside almost exclusively within the riparian corridor, while for others it provides seasonal or occasional habitat for foraging, reproduction or other life stages. According to Knutson and Naef (1997), fully 85% of Washington’s terrestrial vertebrates utilize the stream-riparian ecosystem during some or all of their life histories. Continuous riparian corridors provide migratory pathways for many avian and terrestrial species, including some large mammals (e.g., elk and deer). For fish, riparian areas provide a refuge from high flows and low-energy backwaters, oxbows and side- channels for juvenile rearing.

Riparian corridors composed of trees and tall shrubs provide shade for streams and wetlands, reducing thermal stress for a variety of aquatic animals including incubating, rearing and spawning salmonids. Moreover, lower water temperatures correlate with higher water quality by increasing dissolved oxygen levels and slowing the rate of organic decomposition. Cooler temperatures within the corridor itself also maintain soil moisture which can be important for the establishment of riparian vegetation.

In natural and anthropogenically altered landscapes alike, riparian areas serve an important function by trapping sediment from upland sources, thereby protecting instream habitat conditions. This is particularly important for salmonids that need clean gravels for spawning and are at risk from egg burial by fine sediment during the incubation phase.

The provision of CPOM (e.g., leaf litter) and LWD to the stream channel by adjacent riparian vegetation serves several key roles. In smaller headwater streams where the forest canopy substantially blocks sunlight from aquatic plants, leaf litter and other CPOM form an essential base of nutrients for aquatic organisms (May, 2003). Aquatic insects and other microorganisms break down organic matter into forms usable by other organisms (May, 2003). In turn, these aquatic invertebrates or larger, predatory invertebrates are an important

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component of the diet for juvenile salmonids in particular. LWD performs a number of critical functions in PNW streams and rivers, including the creation and modification of instream complexity and bottom topography. Formation of pools often occurs in conjunction with individual, large pieces LWD as well as larger LWD jams. LWD also captures sediments and creates complex instream hydraulic conditions that in turn facilitate the formation of diverse substrate and channel margin conditions. During high flows, LWD retards the movement of water and sediment, reducing the transport of sediment and protecting downstream habitat as well as human life and property interests alike.

The importance of LWD also varies by location on the watershed (May, 2003). In small, headwater streams, LWD may have a substantial effect on instream hydraulics (Naiman et al., 1992) where it reduces erosion and delays the transport of sediment and organic materials. In mid-sized tributaries, the importance of LWD to creating and maintaining fish habitat increases dramatically (May, 2003) through the creation of pools and other elements of instream complexity.

Riparian areas also perform the function of filtering and uptake of nutrients and anthropogenic pollutants. While these functions occur to a lesser degree in natural systems, this issue is more specifically related to the discussion of buffers and related protective measures in the following section.

The importance of mature, well-vegetated riparian areas in stabilizing streambanks cannot be overstated. Erosion of the streambank is of course a natural process that occurs as a result of channel migration, hydraulic changes due to LWD input and other factors. Immature or poorly vegetated riparian areas lack the root strength to withstand high flows of a natural magnitude, not to mention high flows exacerbated by human activities. Frequent episodes of bank erosion threaten numerous instream values as well as surrounding properties and municipal infrastructure (e.g., bridges, utility lines, etc.).

4.3 Riparian buffer function and effectiveness

This section summarizes research related to the functions and effectiveness of buffers, including buffers composed of natural, mature vegetation, as well as engineered solutions, such as vegetated swales and filter strips.

Different buffers are appropriate for different waterbodies, depending on the type and size of the waterbody. In many cases, buffer widths of a given size may be satisfactory for most functions important to salmon, yet may still be too small for functions important to birds and wildlife. The “special consideration” clause of the GMA, however, places extra weight on functions necessary to recover salmon.

The larger a stream channel is, the less impact a riparian zone of a given width will have on conditions within it. A 100-foot buffer with mature vegetation provides near-total shade for small streams, for example, but may shade only a small part of a big river. More generally, the proportion of water, sediment, wood and nutrients from upstream rather than adjacent areas is much greater in big rivers than in small streams. This does not mean a 100-foot buffer is of little value on a large river, or that an even wider buffer would not provide

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greater value. But the ecological functions of most concern for riparian areas adjacent to large rivers differ from those for small streams.

As the term implies, buffers are generally intended to reduce or eliminate the impacts of surrounding land uses on resources of interest, such as wetlands, streams, wildlife habitat, aquifer recharge areas, etc. The ability of a buffer to perform protective functions depends on several factors, including size (usually as width), intensity of adjacent land use, buffer quality (e.g., type, density and maturity of vegetation) and slope. Depending on the type and intensity of land use, as well as the nature of the resource that is being protected, buffers may be composed of more than one ‘layer’ or ‘band’ of protection. For example, a salmon- bearing stream buffer ideally features a wide, mature, forested riparian corridor that provides many or all of the functions described in Section 4.2, above. In addition, if residential or industrial development is planned for the surrounding area, an engineered buffer area, such as a vegetated filter strip (VFS), may be used to treat stormwater before it enters the “natural” riparian corridor to reduce the influx of pollutants and sediment.

4.3.1 Wildlife habitat

As discussed above, riparian areas provide critical, unique habitat for a wide variety of wildlife, including year-round occupants like amphibians, seasonal foragers, nesting and migratory birds, countless invertebrates, beavers and larger mammals. The diversity of wildlife species is best served by an abundance and diversity of riparian habitat. Riparian vegetation is often quite unique in terms of structural complexity and species composition (Kauffman et al., 2001), with structural complexity represented by features such as multiple layers of canopy (e.g., deciduous and coniferous; shrubs and trees) as well as snags and downed trees (Knutson and Naef, 1997; Kauffman et al., 2001).

The results of research on effective buffer widths for providing wildlife habitat functions is as varied as the wildlife species that have been studied. A minimum buffer measuring 30 m on each side of a stream serves the functions of macroinvertebrate production, according to several studies (Roby et al., 1977; Newbold et al., 1980; Erman et al., 1983). Generally speaking, all larger animals require larger buffers. Amphibians, for example, may require buffers measuring 100 m (Gomez and Anthony, 1996; Burbrink et al., 1998). Birds, on the other hand, require buffers measuring 70 m to more than 100 m (Kinley and Newhouse, 1997; Keller et al., 1993; Darveau et al., 1995). Certain species, such as Great Blue Heron and Bald Eagle, may require much wider buffer areas, ranging from 100-250 m (Grubb, 1980; Stalmaster, 1980; Short and Cooper, 1985).

One species of particular importance to salmonid habitat is beaver. Beaver ponds are critical to stream-rearing salmonids as lower energy, off-channel habitats, particularly during winter rearing. For example, in the Stillaguamish basin, winter rearing of coho salmon was historically dominated by beaver ponds, accounting for roughly 65% of total rearing capacity (Pess et al., 1999). Beavers require a substantial amount of habitat for effective foraging and are vulnerable to disturbance by human activities. Buffer width required for beaver habitat protection has been estimates as 100 m by NRCS (1995) and 30-100 m for foraging needs by Allen (1983).

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Larger mammals, such as deer and elk, require riparian areas up to 200 m in width to provide a full suite of habitat and migration corridor functions (FEMAT, 1993).

4.3.2 Temperature and microclimate control

One of the most important functions of riparian buffers is the maintenance of cool water temperatures in the stream itself and the regulation of the microclimate in the surrounding riparian corridor.

Low water temperature is essential for a large variety of species and lifestages of salmonids and other organisms, as well as for the maintenance of water quality. Daily and seasonal temperature variability is attributable to a number of factors, including elevation, shade, type and quality of water sources, discharge rate, stream velocity, surface area, depth, undercut embankments and the type and amount of organic debris (Allen, 1992). The effectiveness of riparian vegetation in providing shade is dependent on species composition, density, height and aspect relative to solar radiation. In small headwater streams and moderately sized tributaries, shading by riparian vegetation is critical to the maintenance of cool temperatures in both surface water and shallow groundwater (May, 2003).

As streams increase in size, riparian vegetation is less effective in moderating stream temperature (May, 2003). Clearly, the ability of a riparian area to effectively shade a stream decreases as the stream gets wider. Moreover, the higher volume of water in a larger stream is less responsive to changes in the amount of shade; temperature in larger streams is more reflective of the temperature of incoming tributaries and other factors. This does not mean that mature riparian vegetation is not important around large rivers, only that its significance in directly regulating stream temperature is reduced.

Current research suggest that at a minimum, a continuous forested corridor of 30 m (approx. 100 ft) on each side of a stream will provide adequate shade to maintain natural stream temperature regulation (May, 2003; CH2M Hill, 2000; Spence et al., 1996; Beschta et al., 1987). It is extremely important to consider the quality as well as the width of the buffer in terms of temperature regulation. Mature (tall) forested buffers are fundamentally more effective that ones that primarily feature smaller, deciduous species, such as willow and alder (May, 2003). This issue presents two important points: 1) buffer width may need to be greater if mature forest is not present, although this may depend in part on the aspect/configuration of the valley (May, 2003); and 2) active management of impacted riparian areas is required to foster the development of mature, forested vegetation over time.

In the broader riparian corridor, vegetation plays a strong role in regulating the microclimate by protecting the riparian area against climatic forces. Whereas shading serves to block solar radiation, the riparian area also functions as a layer of insulation that tempers the effects of abrupt environmental changes, such as periods of extreme heat, extreme cold, and wind. The uniqueness of the microclimate in riparian corridors compared to upland areas is attributable to the proximity to water, which influences soil moisture, temperature and relative humidity (Thomas et al., 1979; Swanson et al., 1982; Naiman et al., 1992; Pollock and Kennard, 1998; Kauffman et al., 2001). Riparian areas tend to be more moist and mild than surrounding areas, which creates unique, diverse habitat characteristics that are essential for a broad range

-23- City of Bothell Streams and Riparian Areas: Best Available Science of species, particularly year-round residents, such as amphibians, as well as ungulates and other large mammals during spells of extreme heat or cold (Knutson and Naef, 1997). Soil moisture and soil temperature are maintained to a significant degree by a buffer measuring roughly 1 Site Potential Tree Height (SPTH), while the full suite of natural microclimate conditions is maintained by a forested buffer measuring roughly 3 SPTH (FEMAT, 1993). As the name suggests, SPTH varies by location and is dependent on soil types and other factors. The Washington State Department of Natural Resources (DNR) uses a range of SPTH values from 90-200 ft. for Western Washington, depending on the particular Site Class. Not surprisingly, the range of estimated buffer widths required to protect the riparian microclimate is rather broad, ranging from a low of 20-30 m (65-100 ft) to reduce windthrow effects, to roughly 150 m (490 ft) to maintain the natural microclimate (FEMAT, 1993).

4.3.3 Sediment removal

In a developing landscape, one of the most important and often cited functions of a riparian buffer is the removal of fine sediment from overland flow. Even in natural conditions, particularly in headwater streams where natural disturbances are prevalent (e.g., landslides), the retention of sediment by riparian areas is critical as the cumulative impacts of sediment input from many small streams can significantly impact downstream receiving waters (Knutson and Naef, 1997; May et al., 1997; Naiman et al., 2000).

Research on the effectiveness of various buffer widths on sediment removal points to a broad range of values. Importantly, the diversity of recommended widths stems in large part from fundamentally different approaches to answering the question. For example, while some studies have tested the sediment removal effectiveness of natural riparian areas, the multitude of research has involved the use of engineered or cultivated solutions, such as vegetated filter strips (VFS) (May, 2003). Moreover, some studies measure gross sediment quantities while others monitor indicator measures such as water turbidity of total suspended solids (TSS) (Desbonnet et al., 1994). Also, most studies are of the short-term variety, e.g., studies designed to evaluate the effectiveness of VFS in controlling construction-related runoff. Few long-term studies have been completed (May, 2003). The results of three long-term studies suggest that long-term sediment retention requires significantly wider buffers, and that effectiveness is highly dependent on soil type, slope and vegetation conditions (Lowrance et al., 1986; Lowrance et al., 1988; Cooper et al., 1987).

VFS and biofiltration swales can be very effective in the removal of fine sediment, and effectiveness generally increases with buffer width or treatment length and decreases with slope (Horner and Mar, 1982; May, 2003). These Best Management Practices (BMP) serve an important purpose, but they have substantial limitations. For example, single, episodic events or prolonged sediment inputs can significantly reduce effectiveness (May, 2003). Moreover, periodic inspection and maintenance is required (Horner, 1996), particularly when associated with high-intensity land uses.

Perhaps the most significant limitation of VFS is that they are strictly limited to providing sediment and pollutant removal, and do not provide any of the other functions associated with natural riparian areas (May, 2003). For this reason, the use of VFS alone is insufficient to protect stream, riparian or wetland values.

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Research on VFS effectiveness predictably produces a broad range of recommendations, due to differences in study design cited above and other factors. Results range from 53-66% removal of fine sediment by VFS measuring only 5 m (16.4 ft) (Dillaha et al., 1988; Magette et al., 1989), to 95% removal for VFS measuring 61 m (200 ft) (Wong and McCuen, 1982). While VFS measuring 30 m (100 ft) appear to capture a significant percentage of fine sediment according to many studies, the application of these engineered BMPs may best be accomplished on a case-by-case basis.

Studies investigating the effectiveness of natural riparian vegetation in trapping sediment (which of course also provide other functions and values) also suggest a broad range of recommended widths, from 30 m to achieve 80% removal (Erman et al., 1977) to a buffer of 88 m to achieve only 50% removal (Gilliam and Skaggs, 1988). Buffers measuring 50 m are likely necessary for the effectiveness of long-term sediment removal, particularly in areas of substantial input or moderate slopes.

4.3.4 LWD recruitment

The importance of LWD to aquatic ecosystems in the PNW cannot be overstated. LWD is a key structural element of the ecosystem that affects stream hydraulics and channel form, stabilizes streambanks, and strongly influences the routing of water and sediment. Moreover LWD, provides shelter from predation and low energy refugia from high flows to salmonids and other aquatic organisms.

LWD enters streams in a variety of ways, including toppling of dead trees, wind-throw, debris avalanches, streambank erosion and via stream transport from upstream areas (Naiman et al., 2000). The characteristics of the riparian corridor - such as species composition, soil type, maturity, slope, etc – determine the rate of LWD recruitment to the stream. Species composition is important in that different trees mature and die at different sizes, and the persistence of LWD in the stream varies by the type of tree. For example, conifers are known to decompose more slowly than hardwoods and therefore have a greater ability to create and maintain structural features over time (Naiman et al., 200).

The width of forested riparian buffers required to produce natural rates of LWD recruitment varies from values as low as 30 m (Murphy and Koski, 1989) to one or more site potential tree heights (SPTH) depending on site conditions (FEMAT, 1993; Spence et al., 1996), with several studies recommending roughly 50 m as a minimum width for LWD recruitment (Robinson and Beschta, 1990; Van Sickle and Gregory, 1990; Thomas et al., 1993).

The quality of the buffer is of course critical to LWD recruitment. In restoration projects, while deciduous trees can provide a suite of important functions during earlier stages of reestablishment, long-term plans should seek to foster the development of coniferous, forested conditions over the long-term to ensure more natural LWD quality and recruitment rates in the future (i.e., 50-100 year time scale).

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4.3.5 Nutrient and pollutant removal

Riparian vegetation traps pollutants from stormwater runoff through trapping of overland flow containing agricultural and industrial chemicals, as well pesticides and herbicides used by residential homeowners. Riparian vegetation takes up nutrients for plant growth and store it as woody (long-term) and non-woody (short-term) material (May, 2003). Microbial processes may also contribute to nutrient reduction through immobilization of nutrients, denitrification of nitrate and degradation of organic pollutants (Palone and Todd, 1997). Pollutants may occur in particulate or dissolved form, though the particulate form is more common (May, 2003). As a result, removal of sediment and organic matter often also removes a large percentage of pollutants as well (Karr and Schlosser, 1977; Osborne and Kovacic, 1993).

Nutrient pollution can result in the eutrophication of receiving waters, which results in rapid increases in algal biomass which may consist of toxic and non-toxic algae (Welch, 1992). When these algae “blooms” die-off, decomposition processes can reduce dissolved oxygen to lethal levels for other stream organisms. Phosphorous is the “limiting factor” in most PNW streams, meaning that it controls levels of primary production, and represents the greatest concern for freshwater systems (May, 2003).

The effectiveness of forested buffers and VFS in controlling nutrient pollution has been extensively studies, while effects on chemical pollutants have received far less attention. Particulate phosphorus in sediment can be effectively trapped by VFS, but they are not effective in removing soluble phosphorous or in providing long-term storage (Peterjohn and Correll, 1984; Lowrance et al., 1997). Moreover, riparian buffers or VFS can become saturated with phosphorous once all binding sites are filled (May, 2003). Phosphorous can also leach into the groundwater table and enter surface water streams through that route as well (Osborne and Kovacic, 1993; Omernik et al., 1981; Mander, 1997). Nitrogen uptake by riparian vegetation tends to be more effective than phosphorous removal largely due to natural uptake and denitrification (Lowrance, 1985).

The range of experimentally derived buffer widths for nutrient and other pollutant removal is quite broad, ranging from less than 10 m for 90-96% removal of nitrogen and phosphorus using VFS (Madison et al., 1992), to greater than 200 m for 80% nutrient removal on a 4% slope (Vanderholm and Dickey, 1978). Numerous studies point to buffer widths ranging from 16-30 m (50-100 ft) for substantial rates of nutrient removal, as well as fecal coliform bacteria (Jacobs and Gilliam, 1985; Osborne and Kovacic, 1993; Wenger, 1999; Jones et al., 1988; Terrell and Perfetti, 1989).

The best, cheapest and easiest approach to dealing with nutrient and chemical pollution is to apply BMPs to control generation at the source rather than after they have entered the runoff stream (Binford and Buchenau, 1993; Barling and Moore, 1994; May et al., 1997; May, 2003).

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4.3.6 Streambank stabilization

The riparian corridor protects streambanks from erosion through several mechanisms. Simply by providing physical structure to the riparian area, water velocity and energy is reduced. Moreover, the root systems of woody vegetation in particular tend to be quite dense and serve to stabilize soils in the riparian area (Naiman et al., 2000). Also, in floodplain areas, the slowed movement of water through the riparian corridor promotes sediment deposition, which not only reduces sediment loads in the stream but also promotes streambank building over time (May, 2003).

As described above, bank stability is particularly important in headwater areas prone to natural disturbances. However, even in mainstem river areas, bank stability is important not only for instream habitat values but also for the protection of properties and municipal infrastructure, such as bridges and utility lines.

May (2000) suggests that a 30 m (100 ft) forested buffer attains roughly 80% protection of streambank stability. Spence et al. (1996) and FEMAT (1993) found that 50 m (165 ft) of riparian forest is required for bank stabilization.

5 CITY OF BOTHELL SUB-BASIN SUMMARIES

Rivers and streams within the city of Bothell (City) include the Sammamish River (River), its major tributaries North, Horse, and Swamp creeks, and multiple unnamed independent tributaries.

The Sammamish River is approximately 13.8 miles in length (Mobrand 2003) and drains a watershed of approximately 240 square miles (Kerwin 2001). It originates at the north end of Lake Sammamish in King County and stretches 13.8 miles to connect the north end of Lake Sammamish to the north end of Lake Washington. A 3.23-mile reach of the River falls within the City boundary, and together with several key tributaries, is encompassed within the subject area of this report. The River’s major tributaries lie to the north within the City limits, with headwaters extending into unincorporated Snohomish County and the cities of Mill Creek and Everett. Several unnamed independent tributaries drain from the south side of the River providing good sources of cold water, but are not known to be important salmon bearing streams (Kerwin 2001).

5.1 Sammamish River Mainstem

5.1.1 Land Use

The primary designated land uses within the Sammamish River corridor include residential, open space, recreational, urban, commercial, and agriculture (Kerwin 2001).

5.1.2 Fish Utilization

The Sammamish River supports Chinook, coho, and sockeye/kokanee salmon, as well as steelhead/rainbow, and coastal cutthroat trout (Kerwin 2001). The U.S. Fish and Wildlife

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Service has also identified the river as potential foraging habitat for bull trout based on the assumption that they are found in the Sammamish watershed (Kerwin 2001).

The WRIA 8 Ecosystem Diagnosis and Treatment (EDT) Model Project (Mobrand 2003) suggests that habitat quantity and habitat diversity are the highest priority restoration attributes for Chinook salmon in the Sammamish River mainstem. High priorities for restoration include shallow edge and off-channel habitats used by migrating juvenile salmon and complex pool habitats with cool groundwater sources, which are important to migrating adult salmon as well as some juveniles. (WRIA 8 2004)

5.1.3 Habitat Conditions

Waterways in the Lake Washington basin, in which the Sammamish River is located, are among some of the most altered streams in the Puget Sound Region (Kerwin 2001). Alterations to the Sammamish River include, but are not limited to, rates of sediment transport, riparian processes, channelization, discharge rates, temperature, and water quality.

Sediment loads and alteration in the sediment transport regime have had substantial adverse affect on salmonid habitat in the Sammamish River. A 1999 habitat assessment of the Sammamish River found that silt and clay were the dominant substrate in 82 of 97 measured units along the River (R2 Resource Consultants 1999; as cited in Kerwin 2001). The area immediately downstream of the confluence with Little Bear Creek was the only section of the mainstem with substrate dominated by gravel. The plowing of land, stripping of turf, and excavation and maintenance of drainage channels surrounding areas during the wet season also result in a major influx of silt (Clayton 2001; as cited in Kerwin 2001). Additionally, erosion of the streambeds and banks of tributaries has increased the amount of fine sediment reaching the mainstem of the River (Lackey 2000; as cited in Kerwin 2001).

Channelization and hardened banks are another major problem in the River. The U.S. Corps of Engineers dredged and channelized the river in the 1960s, which resulted in the removal of large woody debris from the channel and all natural vegetation from the riverbanks. Continued clearing to maintain channel conveyance has largely eliminated any recruitment of new woody debris. Furthermore, rip-rap and dredging spoils that were used to harden the riverbanks has drastically reduced the capacity of the river to scour its bed and banks, a process that normally creates and maintains channel complexity and recruits sand and gravel into the channel (Kerwin 2001). Tetra Tech (2002) reported that mainstem Sammamish channelization has led to the development of a homogenous stream channel comprised of 98% glide habitat, 1.4% riffle habitat, and only two pools. This loss of riffle and pool habitat significantly reduces key salmonid rearing habitat and prey organisms.

The Sammamish River Corridor Action Plan (Tetra Tech 2002) reported that vegetated riparian buffers along the Sammamish River mainstem remain less than 50 feet in width and contain very few trees. Much of the River’s riparian area is dominated by invasive, nonnative Himalayan blackberry and reed canary grass (Kerwin 2001). The lack of native riparian species and natural riparian characteristics contribute to the loss of channel complexity; increased temperatures and bank erosion; poor cover, forage, refugia, and large woody debris recruitment potential. In recent years, the City of Bothell has undertaken

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substantial bank revegetation projects along the Sammamish, mostly along the south bank of the river. These restoration efforts increase shading and sediment retention, while also providing habitat benefits to smaller avian and terrestrial species.

Low summer flows have been identified in the Sammamish mainstem due to water withdrawals and land uses that reduce groundwater recharge throughout its watershed. Dredging and channelization of the river also lowered the water table of the river and disconnected it from its floodplain, reducing groundwater inflows (Tetra Tech 2002).

The Sammamish River can exhibit extremely high water temperatures during the summer and early fall during adult chinook and sockeye migration. Stress and mortality of migrating adult salmon due to high water temperatures has been documented (Mattila 1998; as cited in Kerwin 2001). The River is on the Washington Department of Ecology (WDOE) 303(d) list for violations of water temperature standards. The warmest reach of the river has been found above Bear Creek. This stretch has recorded temperatures as warm as 27°C (81°F) in late July 1998 (Martz et al 1999; as cited in Kerwin 2001). Temperatures exceeding 25°C are lethal to salmon (Martz et al 1999; as cited in Kerwin 2001). High water temperature conditions also contribute to other water quality problems, such as decreased dissolved oxygen (Boyle’s Law). Temperature stress has also been found to increase the susceptibility of salmon to fish pathogens (disease), cause advancements in sexual maturation, and alter spawning times. However, the river is at its coolest in the reach within the City of Bothell (Tetra Tech 2002). This is partly due to a general trend in cooling that begins at the mouth of Bear Creek, as cooler surface and ground water flows into the river, joining the warm water from the upper layer of Lake Sammamish that forms the beginning of the river. The river begins to heat up again downstream of Bothell, largely because of backwater effects from Lake Washington. However, the relatively high levels of shade from Blyth Park and other forested areas along the river within Bothell, along with cool surface and ground water inflows (particularly from areas within the City south of the river), also contribute to the cooler temperatures in this reach (Tetra Tech 2002).

Lastly, the Sammamish River has been known to reach critical dissolved oxygen levels which may exceed the lower threshold for oxygen requirements necessary for safe salmonid passage and rearing. The River is on WDOE's 303(d) list for violations of dissolved oxygen standards (Kerwin 2001).

5.2 North Creek

North Creek is a Sammamish River tributary that originates in Snohomish County, flows southward into King County, and joins the Sammamish River (River Mile 4.4) near Campus Way in the city of Bothell.

5.2.1 Land Use

General land uses in North Creek include residential, open space/recreational, urban, commercial, and some agriculture. Approximately 98% of the basin is within the regional Urban Growth Area, but some reaches and tributaries are still relatively undeveloped.

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5.2.2 Fish Utilization

North Creek supports runs of Chinook, coho, and sockeye/kokanee salmon, as well as steelhead/rainbow, and coastal cutthroat trout.

The WRIA 8 Ecosystem Diagnosis and Treatment (EDT) Model Project (Mobrand 2003) found that North Creek has the greatest production potential for chinook of any North Lake Washington tributary apart from Bear Creek. It is therefore key to WRIA 8’s goal of expanding the geographic distribution of North Lake Washington chinook beyond its current concentration in Bear Creek (WRIA 8 2004).. Key restoration priorities suggested to improve Chinook salmon productivity in the North Creek watershed include restoring habitat diversity and key habitat quantity; and reducing sediment load, as well as harassment and poaching.

North Creek is one of the major coho producing tributaries in the North Lake Washington watershed (Mobrand 2003). The WRIA 8 EDT model also found that North Creek was the second most important North Lake Washington tributary for coho salmon, again behind Bear Creek (Mobrand 2003). Ludwa et al (1997) found that “coho were present in high numbers” in North, Little Bear and Swamp Creeks, “relative to other intensely urbanized systems” in the Lake Washington watershed surveyed in 1996. The report suggested that “relatively intact riparian zones and wetlands in Swamp and North creeks help support a more robust biota than would otherwise be expected for intensely urbanized basins.” According to the , key restoration priorities to improve coho salmon productivity in the North Creek watershed include restoring natural flows, habitat diversity, channel stability, and key habitat quantity; while reducing sediment loads, chemical inputs, obstructions, and harassment/poaching.

5.2.3 Habitat Conditions

North Creek is reported as having slightly better ecological conditions than the mainstem Sammamish River but are still considered degraded (Tetra Tech 2002). Residential and commercial development activities have resulted in significant bank armoring along much of North Creek. Development activities have reduced in-stream habitat quality in North Creek by increasing and altering sediment loads; reducing channel complexity and connectivity; degrading riparian conditions and large woody debris recruitment; altering flows; increasing temperatures and levels of biological and heavy metal pollutants; and constructing fish passage barriers (Kerwin 2001). However, high quality fish habitat still exists in North Creek within the upper watershed upstream of 240th Streeet SE; the best habitat is found between 240th Street SE and 228th Street SE. These sections of the stream contain a significant riparian canopy, multiple riffle/pool complexes, large woody debris, good spawning gravels, and reduced fine sediment levels (City of Bothell Fitzgerald 2004).

Although much of the lower North Creek watershed’s wetlands have been developed, dredged, and diked, fifty-three acres of good quality and intact wetlands remain (City of Bothell 2004). A recent large-scale stream and wetland restoration project at the lower end of North Creek near the University of Washington Bothell campus marks a substantial improvement to this historically altered and re-routed portion of the stream. The multi- million dollar project features reconnection of the stream corridor with its historical

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floodplain, in addition to a high-flow auxiliary channel designed to reduce flood impacts on the main channel. Mound and depression topography has been recreated, coupled with extensive native revegetation, as well as strategic large wood placement to provide bank stability and nurse log functions.

Upstream of the UW restoration project, North Creek passes through an extensive business park complex and is flanked by levees. Substantial revegetation has been performed within the levee-bound sections and salmon are known to spawn occasionally within this reach. However, extensive sediment input from upstream sources as well as extremely high velocity flood flows significantly reduce the current spawning suitability of the area.

Just upstream of the business park area, North Creek is fed by numerous, small spring-fed tributaries that flow east to west from Bloomberg Hill along the eastern boundary of the drainage, between 236th and 240th St. SE. The hillside features several, small forested wetlands that likely provide a critical, perennial source of cold water to the lower mainstem of North Creek.

Tributaries to North Creek include (in order from downstream) Coal, Palm, Penny, Queensborough, Joco, and Filbert creeks, as well as the Royal Anne tributaries.

5.3 North Creek Tributaries

5.3.1 Coal Creek

Coal Creek (a.k.a. Woods Creek) is a relatively high quality perennial stream that drains into North Creek from the east. The headwaters of Coal Creek begin in unincorporated Snohomish County and are fed by a complex of forested wetlands at its source. From its source, Coal Creek flows through an 18-acre forested wetland (Pentec Environmental 2004) before tumbling through a more confined segment downstream of 228th Street SE. Downstream of the 35th Street SE crossing, the stream once again enters a low gradient, large wetland complex before emptying into North Creek about a quarter-mile upstream of 240th Street SE. Overall, Coal Creek is relatively undeveloped, with good to excellent riparian areas and adequate buffers between the stream and adjoining land uses. Coal Creek overstory riparian vegetation consists of multiple cohorts of broadleaf deciduous trees, including red alder and big leaf maple, as well as coniferous trees, including western red cedar, western hemlock, and Douglas fir. Understory vegetation consists of salmonberry, Oregon grape, elderberry, sword fern, as well as other native herbs and shrubs. Low-flow wetted widths range from approximately 2 to 6 feet, with substrates ranging from fine sand and silt to medium gravel and cobble.

Currently, four fish passage barriers exist in the Coal Creek watershed, including two downstream of 35th Street SE and two upstream. Coal Creek supports populations of resident cutthroat trout (Pentec Environmental 2004) and would likely support spawning runs of coho salmon and steelhead, and to a lesser extent Chinook and sockeye salmon, if barriers to fish

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passage were removed. The low-gradient reaches of Coal Creek would also provide excellent refugia and rearing habitat for juvenile salmonids with barrier removal.

5.3.2 Palm Creek

Palm Creek is the primary stream within the Canyon Creek Sub-Area. Along with Coal Creek, Palm Creek contributes an essential supply of cool, clean water to North Creek throughout the year Palm and Coal creeks are estimated to contribute 28-41 percent of the fall/winter flow and 37-56 percent of the summer flow to North Creek (Pentec Environmental 2004).

Palm Creek is a perennial stream that drains into North Creek from the east approximately one-mile upstream of the Coal Creek confluence. The Palm Creek watershed, like Coal Creek, is relatively unaltered. However, recent development activities near the source of the creek in unincorporated Snohomish County are beginning to encroach upon the stream. Once it enters the City west of 35th Street SE, Palm Creek flows in a southwesterly direction through a fairly confined canyon before draining into North Creek just south of 228th Street SE. This canyon section contains a number of groundwater seeps that supply coldwater year- round, providing excellent potential fish habitat for both resident and anadromous salmonids. Riparian zones in this deep ravine are intact and contain much of the same riparian vegetation as Coal Creek. The stream contains healthy amounts of large woody debris, leading to excellent plunge and lateral scour pool habitat. Substrates range from coarse sand to cobble throughout Palm Creek with limited mass wasting due to healthy riparian vegetation and relatively few impervious surfaces (Pentec Environmental 2004).

At least four fish passage barriers limit upstream salmonid migration in the Palm Creek watershed, including a series of man-made weirs just upstream of 228th Street SE; however, resident cutthroat trout are prevalent throughout the creek (Pentec Environmental 2004). Removal of the barriers would result in restoration of excellent adult spawning and juvenile rearing habitat for all anadromous salmonids in the North Creek drainage.

5.3.3 Perry Creek

Perry Creek is a perennial right bank tributary that flows north and drains into North Creek just north of 228th Street SE. The creek is unique in that is originates from a set of three lakes just north of 242nd Street SE. A manual release gate on the lowest of the three lakes adjusts Perry Creek flow downstream of the lakes. A private individual who lives near the lowest lake opens the release gate just before and during storm events to ensure stormwater capacity of the lakes. Downstream of the lakes, the stream flows through a confined ravine with good vegetative buffers and very little development. As a result of the stormwater releases from the lakes, severe scouring and mass wasting occurs in the confined stream reach downstream of the lakes. Moreover, groundwater seepage in the lower portion of the Perry Creek watershed contribute to the flooding problem in the residential neighborhood near the mouth of the stream.

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Juvenile salmonids have been sighted in the lower portion of Perry Creek and fish passage barriers are nonexistent in the watershed up to the manual release gate location at the mouth of the lowermost lake.

5.3.4 Queensborough Creek

Queensborough Creek is a small right bank tributary of North Creek that originates west of Interstate 405 and SR 527 in a residential area between 216th Street SW and 224th Street SW and drains into North Creek just west of 17th Avenue SE. This stream drains a residential area west of I-405 and SR 527 and flows through a business park before its confluence with North Creek. There are currently vegetated buffers ranging between 10-25 feet throughout the business park reach. Queensborough Creek contains excessive amounts of sediment downstream of SR 527 due to mass wasting in the upper watershed. The creek also conveys significant flows from groundwater seeps that originate from the portion of the watershed just west of I-405.

The culvert crossing at SR 527 is currently a passage barrier to upstream fish passage. Fish use in Queensborough Creek remains unknown.

5.3.5 Joco Creek

Joco Creek is a perennial stream that drains the largest forested wetland complex within the City of Bothell before emptying into North Creek just south of SR 527. The majority of Joco Creek flows through excellent forested riparian habitat containing groundwater sources of year-round flow before entering the more developed lower reaches. The lower portion of Joco Creek flows through a business park and proposed business park lots and has been rerouted to facilitate development opportunities.

A partial fish passage barrier may exist near the mouth of Joco Creek; however, coho salmon are know to spawn in the lower reaches of Joco Creek and juvenile salmonids utilize the stream for rearing and refugia up to 23rd Avenue SE.

5.3.6 Royal Anne Tributaries

Four independent tributary streams comprise the Royal Anne tributaries. These perennial tributaries arise from sources west of I-405 and join together east of I-405 just before joining Filbert Creek and emptying into North Creek north of 214th Street SE. The Royal Anne tributaries currently flow through undeveloped forested open space and wetland habitats with significant groundwater seeps east of I-405; however, residential or commercial land use is proposed for this area. Current riparian areas are well vegetated with native broadleaf deciduous species (e.g., red alder and big leaf maple) and various native herbs and shrubs (e.g., sword fern and salmonberry).

Shortly after the tributary streams join, they flow through a man-made pond that represents a barrier to upstream fish passage. Resident trout presence in the Royal Anne tributaries is assumed. City staff suggest that the owner of the man-made pond is willing to work to remove the barrier and allow anadromous use of the tributaries.

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5.3.7 Filbert Creek

Filbert Creek is a small, perennial stream that flows southeast through Thrashers Park and into North Creek just north of 214th Street SE. Thrashers Park is permanent open space with potential for North Creek floodplain reconnection. Filbert Creek is a well-buffered stream with dense vegetation on both banks. Coarse substrate and pool/riffle sequences in Thrashers Park south of 208th Street SE provide excellent habitat for all salmonid species present in the watershed. Juvenile salmonids have been sighted up to the northern City boundary at 208th Street SE.

5.4 Horse Creek

Horse Creek is a tributary to the Sammamish River that originates in Lake Pleasant near 240th St SE just east of Bothell-Everett Highway (SR 527). The stream flows south into downtown Bothell before discharging into the Sammamish near Bothell Landing.

5.4.1 Land Use

The upper reaches of Horse Creek pass through low and high density residential areas before reaching the Bothell urban core. Just north of NE 190 St., Horse Creek enters a culvert that passes underneath several blocks of commercial and light-industrial areas. The stream reemerges approximately 100 ft before joining the river just downstream of SR 522 (NE Bothell Way).

5.4.2 Fish Utilization

Coho and occasionally other salmonids are regularly sighted within the lowest reach of Horse Creek up to the known barrier at SR 522. Recent restoration efforts have reestablished a riparian canopy over this highly confined reach downstream of the culvert outfall. Salmon are not known to pass through the pipe that extends for roughly 10 city blocks. Resident trout are presumed to utilize the upper reaches of the stream.

5.4.3 Habitat Conditions

The upper reaches of Horse Creek are of variable quality. The stream is well shaded by riparian vegetation throughout, but passes through very confined, armored reaches between SR 527 and adjacent apartment complexes. According to Bothell City staff, water quality is relatively high in the upper area. The middle reach of the stream flows through an extensive delineated wetland complex along the west side of SR 527, bordered by low-density residential properties. Just prior to reaching downtown Bothell, the stream enters a pipe that passes beneath several blocks of retail businesses, a school bus maintenance depot and other commercial properties. Stormwater from numerous properties is directed into the pipe. After passing through the pipe, water quality is extremely poor, with persistent traces of oil and a perceptible foul odor. As a result of City investigations, some potential sources of contaminants have been addressed, but the problem continues. An oil boom is maintained at the mouth of the stream along the edge of the Sammamish River. Notably, this section of Bothell marks the intersection of two important State Routes (522 and 527) that served the

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local area prior to the construction of interstate highways. Decades old photographs reveal an intense concentration of filling stations and car dealerships that were likely accompanied by numerous underground storage tanks that may still be contributing to current conditions (Jon Morrow, City of Bothell, personal communication).

5.5 Swamp Creek

Swamp Creek is a tributary of the Sammamish River with tributaries and headwaters extending into the City of Bothell. Swamp Creek flows south from Snohomish County to King County before joining the Sammamish River at 80th Ave NE and Bothell Way near River Mile 0.6 in Kenmore. Little Swamp Creek, a tributary to the mainstem, originates in the western portion of the Bothell Planning Area before entering Kenmore at approximately the Snohomish/King County line.

5.5.1 Land Use

The Swamp Creek basin is entirely within the regional Urban Growth Area, though only a small portion falls within the City’s planning area boundary, primarily within the Little Swamp Creek tributary drainage. The upper reaches of Little Swamp Creek are primarily marked by medium density residential areas, as well as a series of forested and non-forested wetlands that border the stream course.

5.5.2 Fish Utilization

Swamp Creek supports runs of sockeye, kokanee, and coho salmon and steelhead and coastal cutthroat trout. It has historically supported chinook salmon, but recent volunteer spawner surveys have found no evidence of chinook. The level of recent fish utilization in Swamp Creek has been assessed from time to time by King County. In 1997 coho, sockeye, and kokanee were sighted in Swamp Creek reaches by King County Volunteer Salmon Watchers (King County WLRD, 2000). Fewer observations were made in 1998 and 1999 by volunteers and no spawning salmonids were observed (King County WLRD, 2001b). In 1999 coho and cutthroat trout were observed spawning in an area not covered by volunteer watchers (King County WLRD, 1999. Unpublished data). Chinook redds were not found in Swamp Creek during the 1999 King County assessment (King County WLRD, 2000a); however, juvenile salmonids, including coho and cutthroat, were observed in many segments during the 1999 habitat surveys (King County WLRD. 2001a). The level of fish use in the Bothell planning area is not clear at this time.

5.5.3 Habitat Conditions

Conditions affecting habitat quality in Swamp Creek include fish passage barriers, increased sedimentation and altered sediment transport, degradation of riparian condition, loss of channel complexity and connectivity, increased temperature, and decreased water quality.

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5.6 Sammamish Independent Tributaries

Several small, independent, unnamed tributaries flow into the Sammamish River from the south. The landform is marked by adjacent, steep hills separated by Interstate 405.

5.6.1 Land Use

Land use around these independent tributaries is almost exclusively residential, with the exception of light industrial and commercial uses and an abandoned railroad grade along sections of the Sammamish River shoreline. The lower reaches of the westernmost tributary flow through the Wayne Golf Course before discharging into the Sammamish River.

5.6.2 Fish Utilization

Fish utilization is nonexistent in all but the westernmost tributary. Not only are the streams quite steep, but their connection to the Sammamish has been severely altered through the construction of levees and roads along the river. The streams (with the exception of the golf course tributary) discharge from elevated outlets onto rip rap pads before joining the river. The tributary that flows through Wayne Golf Course has some fish utilization, primarily by coho salmon, along the flat, lower reaches before entering steep, confined hillside canyons. There is a known fish barrier on the golf course tributary at the Waynita Way NE crossing.

5.6.3 Habitat Conditions

All of the independent tributaries originate in steep-sided ravines that are generally well vegetated with a combination of deciduous trees and conifers, as well as ferns, salmonberry and a relatively dense understory. However, residential and some commercial development at the top of the hills, combined with inadequate stormwater detention, has left these streams extremely vulnerable to erosion during high flows. The slopes are geologically prone to landslides and the streams are known to transport massive amounts of sediment from upland areas. One very small tributary alone transports roughly 100 cubic yards of fine sand annually into a roadside ditch just prior to entering the Sammamish River (City of Bothell Public Works staff, personal communication). The tributary is the recipient of stormwater from an expanding hilltop development that is permitted to manage stormwater to pre-1992 standards pursuant to a site Master Plan (City of Bothell Public Works staff, personal communication).

Though small, these groundwater-fed perennial streams are an important source of year- round cool water to the often overheated Sammamish River. In fact, the section of the Sammamish within the City of Bothell is the coolest segment along its entire length. During high flows, discharge in a few of these tributaries greatly exceeds the capacity of the altered lower portions of the stream channels and on occasion threatens properties along Riverside Drive.

The sole fish-bearing tributary originates in similar, steep terrain before passing through several intensive residential developments on its way down to the valley floor. Inadequate and poorly maintained detention ponds associated with these developments exacerbate high

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flows in the fish-bearing lower sections of the stream. Habitat quality in the lower section is relatively poor as the stream passes in a severely confined channel through manicured golf course fairways and residential properties. While some salmon may spawn in this reach, high flows and accompanying sediment likely have a pronounced impact on egg survival. Moreover, the lack of sufficient instream structure and riparian cover make this tributary relatively poor as a rearing area.

5.7 Unique watershed characteristics

From a broad, watershed-based perspective, perhaps one of the more unique characteristics of the planning area is the combination of topography and hydrogeology. Both the south and north sides of the Sammamish River are marked by considerable relief in the form of hills reaching elevations of roughly 350-400 ft. On the south side of the river, the hills slope steeply down into the river valley with tributaries flowing primarily from south to north. On the north side of the river, North Creek flows in a southerly direction through a valley between Beckstrom Hill and Bloomberg Hill.

Throughout the watershed, perched groundwater aquifers within the hillslopes supply perennial flow to a vast network of tributary streams and seeps. Areas of forested wetland can be found on benched portions of relatively steep slopes, such as those described along the west flank of Bloomberg Hill in Section 4.2.3. These ample sources of cool surface water are critical to the suitability of North Creek, the Sammamish River and numerous tributaries for all lifestages of salmonids, and for overall water quality in the basin. Groundwater resources are dramatically impacted by urbanization in particular, largely due to the effects of impervious surfaces and soil compaction on groundwater recharge. Moreover, stormwater management policies and practices that emphasize discharge into surface waters not only create high-flow related impacts to streams and surrounding riparian areas, but further reduce groundwater recharge.

Many of the primary seeps and tributaries spring out of slopes that are geologically hazardous and thus unsuitable for development. However, this is not the case in all instances, and much of the remaining undeveloped land in the planning area is along hilly terrain. Also, these aquifers likely extend well into the hills and are thus influenced by groundwater recharge (or lack thereof) from a considerable distance. Coupled with improved stormwater management policies, riparian protection and other restoration activities, the identification and protection of these areas is critical to the long-term health of not just the salmon-bearing streams but also the broader watershed.

As part of the City’s Comprehensive Plan Update, the planning area has been divided into 13 sub-areas. While high-value habitat is located in several sub-areas, two of these stand out as having unique potential for providing core habitat for all four species of salmonids: the Fitzgerald sub-area and the Canyon Creek sub-area [a broader discussion will be included in the next draft]. The Canyon Creek sub-area encompasses Palm Creek, described above in Section 5.3.2.

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6 SYNTHESIS OF BEST AVAILABLE SCIENCE AND LOCAL CONDITIONS

[Note: This section will be developed substantially following review and discussion with City staff regarding the approach, level of detail of recommendations, relationship between document 1 and document 2.]

Within the City of Bothell planning area there are a variety of habitat types representing a broad suite of habitat functions and values with both localized and broader, downstream importance. North Creek represents a core area from a fish-use perspective, and features a mix of both heavily impacted reaches as well as portions of very high quality habitat worthy of substantial levels of protection. Tributaries to North Creek are of highly variable quality, but all have significant impacts (positive and negative) on habitat quality in core areas of North Creek. Other independent tributaries – particularly those on the south side of the Sammamish – perform critical functions for downstream areas, despite the absence of direct fish utilization. The purpose of this section is to couple the best available science regarding riparian functions and values with the specific characteristics of sub-basins within the planning area.

6.1 Sammamish river mainstem

The Sammamish River mainstem is highly altered environment in terms of channel form, riparian condition, floodplain connectivity, surrounding land-use, and many other factors. Instream habitat complexity is very low, sediment and temperature problems are prevalent, and the opportunities for substantial restoration are limited by channel confinement and alteration.

Tributaries from within the planning area provide a substantial amount of cold water (good) and fine sediment (bad) to the mainstem Sammamish. Protection of these cold water sources and the reduction of sediment delivery are key priorities for surrounding tributaries. These issues are discussed further in the appropriate sub-section, below.

While the ability of riparian areas to lower stream temperatures by shading is more limited in larger streams, the Sammamish is by no means a large river and can certainly benefit from improved riparian conditions for purposes of thermal regulation. Wherever possible given surrounding land uses, riparian restoration should seek to provide adequate shade to produce thermal benefits, particularly on the south bank of the river. While narrow bands of mature trees (primarily deciduous cottonwood) are present along much of the bank, the width and density of mature vegetation should be increased over time to the extent possible. Existing revegetation efforts along the streambanks should be continued as they will provide more than simply thermal benefits at maturity.

Where undeveloped open spaces remain, it is critically important to maintain substantial vegetated buffers on both banks to improve water quality via the filtration of sediment and pollutants.

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While off-channel habitat creation would be highly desirable in the mainstem Sammamish, opportunities for restoring connectivity in this highly channelized system are unfortunately extremely limited.

6.2 North Creek

Portions of North Creek contain substantial blocks of currently intact habitat that can and do provide many of the most important functions of riparian corridors. The most significant block of this type is likely the Fitzgerald sub-area, between SE 228th St. and SE 240th St. In rapidly urbanizing watersheds, stream reaches of this quality are quite rare and equally important to preserve. They cannot be re-created once they have been developed and fragmented, nor can their functions and values be recaptured elsewhere through restoration. The highest levels of protection should be afforded to these areas in an effort to protect the full suite of riparian functions, including the needs of terrestrial wildlife.

These core areas are nonetheless threatened by conditions in upstream areas in North Creek itself as well as in tributaries. Inadequate stormwater management measures in upstream areas create magnified high flows that destroy instream habitat and damage properties as well as infrastructure. Late summer low flow reductions in headwater streams due to reduced groundwater recharge (i.e., primarily due to impervious surfaces and soil compaction) elevate temperatures and reduce rearing and spawning habitat. Coupled with low flows, high water temperatures due to inadequate shading decrease water quality and can create lethal risks for aquatic organisms. Elevated levels of sediment bury salmon redds, reduce invertebrate production and increase turbidity to levels that pose substantial harm to juvenile salmonids as well as other species. Pollutants from upstream areas, particularly nutrients, create unhealthy conditions for numerous species, including highly sensitive invertebrates that are a key component of the salmonid food chain.

As a primary tributary that receives input from numerous smaller streams, the habitat quality in North Creek is also reduced by the prevalence of fish passage barriers in tributary streams. This is not only an issue for fish residing in tributaries, but denies critical rearing habitat and high-flow refuge areas to fish rearing in or migrating through the mainstem of North Creek. Restoration of physical connectivity throughout the watershed is a very high priority for anadromous salmonids.

Establishment of riparian buffers particularly upstream of the core areas should focus on reducing sediment input, reducing high flows, protecting base flows, providing adequate shade for thermal regulation, and filtering pollutants from surrounding areas of residential, agricultural and industrial activities.

6.3 North Creek tributaries

One of the highest priorities in the tributaries to North Creek is the removal of fish passage barriers. Particularly in areas of high quality habitat (e.g., Palm Creek in Canyon Creek Sub- Area; Coal/Woods Creek), streams should be protected as if fish currently utilize the area, i.e., to protect the full suite of riparian functions to support instream values.

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As tributaries to a very important fish-bearing stream, even those tributaries that have little possibility of providing fish habitat have a critical role through their influence on downstream conditions. As described above, these tributaries are largely responsible for the amount of sediment entering North Creek, water temperature, high flow magnitude, low flow and the amount of nutrients and other pollutants.

While many of these tributaries are highly fragmented with respect to habitat quality and riparian continuity, remaining areas of good riparian conditions should be well protected to achieve high levels of riparian function. Even in fragmented sections of these streams from a habitat perspective, restoration should focus on retention of sediment and pollutants, shading for temperature regulation, and stormwater management practices that reduce the magnitude of flood peak flows. Moreover, by increasing instream roughness (e.g., through LWD placement), the velocity of stormflows can be reduced, as well as the accompanying sediment load that is transported downstream.

One of the distinct characteristics of tributaries to North Creek is the prevalence of seeps and groundwater influence in general. Most of these tributaries are perennial sources of cool water which is invaluable to nearly all aquatic species, particularly during the summer months. Just as it is most important to control pollutants at the source, these sources of cool water should be protected to the maximum extent practicable, to ensure sources of cold water to North Creek in perpetuity. The source areas of these tributaries, as well as other associated areas with seeps and springs, should be mapped and carefully protected from the encroachment of impervious areas and loss of vegetation.

6.4 Horse Creek

Due to the substantial and largely irreversible modification of the lower portions of Horse Creek, the prospect for returning upper sections of the stream to habitat for anadromous fish is rather bleak. However, much as the south side tributaries to the Sammamish River and other tributaries in the planning area, Horse Creek has a definite role to play in the reduction of flood flows, water temperature, sediment input and other functions.

Due to the highly constrained nature of the lower, piped portions of the stream, protecting wetlands in the upper portion of the watershed is critical not only for resident fish species and downstream reaches, but also for flood protection in the downtown core. Moreover, riparian areas in the upstream reaches should be maintained and restored as necessary to reduce stream temperature to the extent possible.

6.5 Swamp Creek

[Synthesis for portions of Swamp Creek pending discussion with City re how best to handle the small portions of the watershed within planning area. JK]

6.6 Sammamish independent tributaries

One of the primary functions of the independent tributaries on the south bank of the Sammamish is the supply of perennial, cool water to the Sammamish River. This is largely a

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function of the well-shaded, southerly aspect of the hillslopes, as well as an apparently abundant supply of perched groundwater aquifers coupled with a rich network of seeps and springs. To protect these functions, impacts to the groundwater table should be strictly limited, particularly in the upper reaches. Impervious surfaces should be minimized, and where possible, stormwater management should emphasize infiltration.

The ravines that the tributaries flow through are currently well vegetated and must remain so for both the protection of thermal benefits and the retention of sediment on these steep, slide- prone slopes. Native, forested vegetation should be protected from land clearing and development throughout the area.

These tributaries supply a large amount of fine sediment to the Sammamish River, largely during episodic high-flow events that erode streambanks. Flows in these tributaries are exacerbated by highly inadequate stormwater detention facilities in upland areas. Addressing the sediment problem requires protection of existing vegetation, stormwater management practices that emphasize infiltration where possible and adequate detention where necessary, and possibly the placement of LWD in headwater areas to trap sediment and slow the movement of flood flows.

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7 REFERENCES

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WRIA 8. 2004. WRIA 8 Chinook Salmon Conservation Plan: June 30, 2004 Draft Work Product. WRIA 8 Service Provider Team, for WRIA 8 Steering Committee and Puget Sound Shared Strategy. Seattle, Washington.

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