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Habitat Limiting Factors and Reconnaissance Assessment ReportGreen/Duwamish and Central Puget Sound Watersheds(Water Resource Inventory Area 9 and Vashon Island)

December 2000

ExecutiveSummary

Habitat Limiting Factors and Reconnaissance Report Executive Summary 3

KING COUNTY

PIERCE COUNTY

KITSAPCOUNTY

KITTITASCOUNTY

SNOHOMISH COUNTY

STUDY AREA

I. INTRODUCTION

Many stocks of the wild salmonid populations in thePuget Sound ecoregion have declined. In March 1999,the National Marine Fisheries Service (NMFS) listedPuget Sound chinook salmon as a Threatenedspecies under the Endangered Species Act (ESA). InNovember 1999, the U.S. Fish and Wildlife Service(USFWS) listed bull trout as a Threatened speciesunder the ESA. Other populations and species areunder consideration for listing as Threatened orEndangered under ESA.

The Habitat Limiting Factors andReconnaissance ReportAs a first step in the long-term commitment tosalmonid recovery in Water Resource InventoryArea 9 (WRIA 9) and Vashon-Maury Islands, staff andrepresentatives from the Washington ConservationCommission and the WRIA 9 Steering Committeeworked together to develop the Habitat LimitingFactors and Reconnaissance Assessment Report. Thepurpose of this report is to provide a current snapshotin time of the existing salmonid species and thehabitat conditions that limit the natural production of

salmonids in the Green/Duwamish River watershed,the independent drainages to Puget Sound from ElliottBay south to the Puyallup watershed, the drainages onVashon-Maury Islands, and the nearshore. This area iscollectively termed WRIA˚9 for the purposes of thisreport. This report:

Provides a summary of what is known about currentand past salmonid species and habitat conditions inthe WRIA for future reference;

Provides baseline information for the WRIA (basedon currently available data) for use in theimplementation of an adaptive managementprogram;

Identifies habitat limiting factors in the WRIA, keyfindings, and associated data gaps that will be usedto build the WRIA 9 Salmonid Conservation Plan;and

Provides preliminary guidance for policy makers todetermine next steps and direct resources for therecovery process.

Focus on Habitat Limiting FactorsWhile the causes of declining salmonid populationscan be attributed to many factors, this report focuseson human-controlled modification or destruction ofsaltwater nearshore and freshwater habitats and thechanges to ecological processes that affect thosehabitats in WRIA 9.

4 Habitat Limiting Factors and Reconnaissance Report Executive Summary

II. WATERSHED OVERVIEW

Physical DescriptionThe Green/Duwamish River is the largest freshwatercomponent of WRIA 9. The Green/Duwamishmainstem is responsible for producing the eight majorspecies of anadromous and resident salmonids presentin the watershed. The Green/Duwamish Riverwatershed begins in the Cascade Mountains about 30miles northeast of Mount Rainier and flows for over93 miles to Puget Sound at Elliott Bay in Seattle. It isbounded on the north by the Lake Washingtonwatershed (WRIA 8) and to the south by the Puyallupwatershed (WRIA 10). Historically, the White, Green,and Cedar (via the Black) Rivers flowed into theDuwamish River, and the system drained an area ofover 1,600 square miles. Because of the diversion ofthe White River in 1911 and the Cedar River in 1916,the Green/Duwamish drainage area has been reducedto 556 square miles.

To help us better understand the Green/Duwamishwatershed and WRIA 9, we have divided it into sixgeographic areas as shown in the corresponding map(see centerfold map on pages 8-9):

Upper Green River Sub-watershed (River Mile 64.5to 93+, Howard Hanson Dam to headwaters)

Middle Green River Sub-watershed (River Mile 32.0to 64.5, Highway 18 to Howard Hanson Dam)

Lower Green River Sub-watershed (River Mile 11.0to 32.0, Black River to Highway 18)

Green/Duwamish River Estuary Sub-watershed(River Mile 0.0 to 11.0, Elliott Bay/Harbor Island toBlack River)

Nearshore Sub-watershed (independent tributaries toPuget Sound and Vashon-Maury Islands)

Nearshore Sub-watershed (estuarine/marine watersand habitats)

These divisions make sense because of natural and/oranthropogenic landscape features. However, the sub-watersheds are all linked together as part of the largerecosystem and by the processes necessary to supportnaturally produced salmonids.

Land Uses and HistoryLand uses differ considerably across the watershedand there are few watersheds in the Puget Sound basinthat match the extremes evident in WRIA 9. In theUpper Green River Sub-watershed, land is devotedalmost entirely to forest production. The Middle GreenRiver Sub-watershed is characterized by a mix ofresidential, commercial forestry, and agricultural landuses. Residential, industrial, and commercial usesprevail in the Lower Green River Sub-watershed. TheGreen/Duwamish River Sub-watershed is splitbetween residential and industrial uses. Independenttributaries to Puget Sound, including Vashon-MauryIslands, are primarily residential with small areas ofcommercial development and mining.

These land uses have emerged over the last 150 years,which have seen a number of other fundamentalchanges to the WRIA. Some of these major historicalchanges include:

1851 European settlement begins in the DuwamishRiver.

1880-1910 Logging occurs across much of thewatershed and in the lower river valley; agriculturalland use expands.

1911 White River is diverted from Green River toPuyallup River for flood control, reducing watershedarea by 30 percent.

1913 City of Tacoma begins diverting water fromGreen River to provide water for homes andindustry. Anadromous salmonids are blocked fromUpper Green River Sub-watershed.

1916 Black and Cedar Rivers are diverted fromDuwamish River to Lake Washington to improvenavigation, further reducing watershed area by 40percent from its original size.


1900-1940 Duwamish estuary tidelands are filled,drained, and dredged to support growing industrialand port activities.

1895-1980 The Green/Duwamish River ischannelized and diked for navigation and floodcontrol.

1945-2000 Residential, commercial, and industrialland uses expand, largely replacing farmlands andforests in the western half of the WRIA.

1962 Howard Hanson Dam is completed for floodcontrol purposes.

Fish StatusEvery species of anadromous salmonid that is nativeto the west coast of North America (coho, chinook,chum, sockeye, and pink salmon and coastal cutthroat,steelhead, and bull trout/Dolly Varden char) as well as

one non-native (Atlantic salmon) recently have beenfound in the Green/Duwamish watershed.

During the period 1968-1997, the Green/DuwamishRiver supported an average yearly total run (fishreturning to the river and those caught in the fisheries)of about 41,000 adult chinook salmon. It has beenestimated that on average 5,700 chinook annuallyreturned to the river to spawn naturally and 8,200returned to the Soos Creek hatchery during the sametime interval (Figure˚1). The Green River has notexperienced the same decline in naturally spawningadult chinook that has occurred in other Puget Soundstreams but these numbers may be masked by a highhatchery chinook stray rate onto the spawninggrounds. Research is needed to better understand thecontribution of strays to the wild chinook stocks inthe Green/Duwamish watershed.

680

5000

10000

15000

20000

70 72 74 76 78 80 82 84 86 88 90 92 94 96

Spawning Ground Mean

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Time series of chinook salmon returning to the spawning grounds and to the hatcheries, 1968-1997. Spawning ground estimates include an unknown number of stray hatchery salmon. Mean values are shown. Data source: WDFW 1998.

Figure 1Returning Chinook Salmon to the Spawning Grounds and Hatcheries 1968-1997


Anadromous fish access to the upper reaches of theGreen/Duwamish River has been blocked at RiverMile (RM) 61 since 1911 when the City of Tacomastarted construction on a water diversion dam( Headworks ). While the City of Tacoma has limitedpublic access in a portion of the upper sub-watershedto protect the potable water supply, commercial timberharvest has occurred throughout this portion of thewatershed. This activity has altered many of theecological processes and degraded much of thehabitat. Roads and a railroad also have had an impacton the mainstem as described below. Currently, onlythe resident form of coastal cutthroat and someanadromous salmonids that have been transportedaround the dams (juvenile steelhead trout, chinook andcoho salmon, and adult winter steelhead trout) use thisportion of the watershed.

In 1962, Howard Hanson Dam (HHD), a flood controldam, was completed at RM 64.5, which is thedownstream boundary of this sub-watershed. HHDalso is a complete barrier to upstream and downstreamadult migration. The large flood control dam andassociated reservoir interrupts the natural flow ofsediments and large woody debris to lower mainstemreaches of the Green River. It also chronically floodsupstream habitat.

Habitat Limiting Factors and Impacts

Mainstem Green River:

While the two dams block upstream passage andseverely hamper downstream passage, some salmonidsdo reside in this reach and are affected by existinghabitat conditions. If passage is improved in the future,existing habitat conditions will affect salmonids that arereintroduced to the area. These limiting habitat factorsinclude:

The placement of roads and a railroad immediatelyadjacent to rivers and streams resulting in:

Reduction and degradation of riparian habitat functionssuch as shade and large woody debris; and

Limited lateral channel migration and limited creation ofnew habitat.

A reservoir pool that is:

Reducing spawning habitat and riparian functions dueto periodic inundation of 4.5 miles of the Green Rivermainstem and 3.0 miles of tributaries; and

Delaying juvenile outmigration.

Tributaries:

Logging practices resulting in:

Reduced riparian habitat functions such as shade andinstream large woody debris;

Fish passage barriers;

Excessive sedimentation, especially of fine sediments;

Decreased water quality; and

Altered stream hydrology.

Human population: 1

Primary designated land uses: forest production (nearly100˚percent), municipal water supply, and recreation

Mean annual flow: about 1,300 cubic feet per second at RiverMile 64.5

Recently documented salmonid species present: residentcoastal cutthroat, transported juvenile steelhead, transportedjuvenile chinook, transported juvenile coho, and transportedsteelhead adults

Additional salmonid fish species historically present: chinook,coho, and bull trout (possible but not likely)

III. INDIVIDUAL SUB-WATERSHED SYNOPSES

Upper Green River Sub-watershed(RM 64.5 to headwaters)


Middle Green River Sub-watershed(RM 32.0 to 64.5)

In the Middle Green River Sub-watershed (RM 64.5 to32.0), the construction and operation of HowardHanson Dam has reduced the recruitment of sedimentsto a level where the river is in places gravel-starvedand incising. Because HHD serves to limit floods, thenatural flow regime of the mainstem Geen River hasbeen altered, harming habitat as described below. TheTacoma Headworks also block upstream passage of allsalmonids. Currently chinook, steelhead, coastalcutthroat, coho, and chum utilize this reach up to theHeadworks for spawning and rearing. There arelimited numbers of pink and sockeye salmon as wellan occasional observation of Atlantic salmon adults.All species, with the exception of Atlantic salmon, usethis reach of the mainstem for migration and feeding.



Dams, revetments, and residential and agricultural landuses that are:

Changing the natural flow regime in ways that haveharmed salmonids;

Causing gravel starvation and scouring;

Reducing the amount and size of large woody debriswith a consequent reduction of channel complexity;

Reducing side-channel and other off-channel habitats;and

Reducing and degrading riparian habitat functions.

Tributaries:

Residential, agricultural, and some urban developmentthat are:

Reducing and degrading wetland and riparianfunctions;

Reducing forest cover and increasing impervioussurfaces leading to hydrologic disruption to stream flow,channel degradation, increased sedimentation, anddecreased water quality;

Rechanneling streams and limiting their lateralmigration to facilitate roads and protect property;

Reducing the amount and size of large woody debris;

Creating barriers to fish passage; and

Introducing non-native plant and animal species.

Human population: 112,000

Primary designated land uses: residential (50 percent),commercial forestry (27 percent), agriculture (12 percent)

Mean annual flow: 1,300 to 2,000 cubic feet per second

Recently documented salmonid species present: chinook,coho, chum, pink, sockeye, steelhead, coastal cutthroat trout,and occasionally Atlantic salmon

Additional salmonid fish species historically present: bulltrout (possible but not likely)


Green/Duwamish

Estuary Sub-watershed

Lower

Green River

Sub-watershed

Middle

Green River

Sub-watershed

Nearshore

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Nearshore

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G R E E NR I V E R

Howard HansonReservoir

HowardHansonDam

TacomaHeadworks

Major Road

River/Stream

Sub-watershed Boundary

King County WRIA 9 Boundary

Open Water

WRIA 9 Watershed


Lower Green River Sub-watershed(RM 11.0 to 32.0)

In the Lower Green River Sub-watershed (RM 32.0 to11.0), the diversion of the White River in 1911 has ledto a decrease in flow and sediment and a lowering ofthe floodplain. Howard Hanson Dam operations andwater withdrawal at the Tacoma Headworks have ledto an unnatural flow regime (reduction in flood flowsand lower summer flows). One of the most significanthabitat alterations has been the construction of a seriesof revetments that has resulted in the disconnection ofoff- and side-channel habitats such as sloughs andadjacent wetlands. Currently this reach is utilized forthe upstream and downstream migration and rearingfor all native anadromous salmonid species. Itprovides some chinook, pink, sockeye, and chumsalmon and steelhead spawning habitat.


Primary designated land uses: residential (50 percent),industrial (17 percent), and commercial (10 percent)

Mean annual discharge: over 2,000 cubic feet per second

Recently documented salmonid species present: chinook,coho, chum, pink, sockeye, steelhead, coastal cutthroat trout, andoccasionally Atlantic salmon

Additional salmonid fish species historically present:bull trout (possible but not likely)



Urbanization, water diversions, and revetments that are:

Lowering the floodplain and disconnecting off-channelhabitats such as sloughs and adjacent wetlands;

Reducing large woody debris and associated instreamcomplexity, such as pools and riffles;

Creating some adult salmon migration problems due tolow flows;

Causing chronic water quality problems; and

Severely reducing riparian habitats and associatedfunctions.

Tributaries:

Intense urbanization and infrastructure that are:

Reducing forest cover and increasing impervioussurfaces leading to hydrologic disruptions to streamflow, channel degradation, increased sedimentation,and decreased water quality;

Channelizing streams to facilitate land use practices;

Creating barriers to fish passage; and

Introducing non-native plant and animal species.


Green/Duwamish Estuary Sub-watershed(RM 0.0 to 11.0)

The Duwamish River is that portion of the GreenRiver downstream of the historic confluence with theBlack River. With the diversion of the Cedar River in1916, the Black River was left almost dry. Today, theonly flow in the Black River comes from the tributarystreams that drain from the eastern bluffs of the lowerGreen River valley.

The urbanization and industrialization of this portionof the Green River watershed has resulted in anextensive system of filled tidelands and flood controlrevetments that have eliminated connectivity to thehistoric floodplain, stream channel complexity,functioning riparian zones, and floodplain habitats. Inthe Duwamish estuary, over 97 percent of the historicestuarine mudflats, marshes, and forested riparianswamps have been eliminated by channelstraightening, draining, dredging, and filling. All(100˚percent) of the tidal swamps bordering theDuwamish were filled by 1940. The remainingshortened channel has been simplified and suffersfrom polluted sediments along with stormwater andwastewater effluent. Currently all salmonid speciesmigrate, rear, and acclimate in this transitional areabetween river and marine waters. Juvenile chinookand chum salmon are most dependent on this type ofhabitat. Small numbers of char (bull trout/DollyVarden char) have been consistently documented asusing this reach.


Primary designated land uses: industrial (43 percent) andresidential (39 percent)

Mean annual discharge: tidally influenced reach although morethan 2,000 cubic feet per second of freshwater

Recently documented salmonid species present: chinook,coho, chum, pink, sockeye, steelhead, coastal cutthroat, adult bulltrout/Dolly Varden char, and occasionally Atlantic salmon

There are numerous small- and medium-sizedtributary streams that drain into this reach. All haveseen aggressive development that in turn has mademany of them inaccessible and inhospitable forsalmonids. Many of these streams have high levels ofimpervious surfaces that have degraded and altered thehistoric hydrologic regime. Most of the small patchesof remaining marginal habitat are disconnected andheavily impacted by stormwater-associated flows andpoor water quality. Functional riparian areas have beeneliminated or fragmented into a few undevelopedareas, often in the high gradient reaches where thecreeks cascade down the valley walls. The potentialsalmonid production of these creeks is expected tocontinue to be limited due to current land usepractices.


Mainstem Duwamish River/Waterway:

Urban and industrial land use practices that have:

Dredged, channelized, and filled 97 percent of theestuarine mudflats, marshes, and forested riparianswamps that formerly comprised the estuary;

Simplified the remaining channel and severely reducedriparian function; and

Polluted the remnant, shortened channel withstormwater and wastewater effluent.

Tributaries:

Development that is:

Creating fish passage barriers;

Leaving small patches of disconnected marginalhabitat;

Altering hydrology and channel stability due tostormwater-associated flows; and

Reducing water quality.


Nearshore Sub-watershed(Independent Tributaries to Puget Sound and Vashon-Maury Islands)

A number of independent streams in WRIA 9 draindirectly into Puget Sound. Among the largest areMiller and Des Moines Creeks on the mainland.Vashon-Maury Islands also host a number of directdrainages. With the exception of a few streams, mosthave small drainage areas and corresponding flows.

While a few of these streams are relatively intact andsupport small populations of salmonids, most areheavily impacted by urbanization and no longerfunction well to support salmonids.


Primary designated land uses: on mainland: residential(68˚percent), industrial (10 percent); on Vashon-Maury Islands:residential (90 percent)

Recently documented salmonid species present: chinook,coho, chum, and coastal cutthroat

Additional salmonid fish species historically present:unknown


Urban and industrial land use practices that are:

Creating fish passage barriers;

Reducing the amount of large woody debris andchannel complexity;

Causing chronic water quality problems; and

Simplifying the remaining channel and severelyreducing riparian functions.


The nearshore — the boundary between saltwater andland that stretches from beach bluffs out into theshallows of Puget Sound — provides an important linkin the life history of salmonids. All anadromoussalmonids use the nearshore for physiologicaltransition, feeding, refuge, and as a migration route toand from the ocean. Most salmonid species aredependent upon the nearshore for juvenile rearing.Much of the greater Puget Sound estuary shoreline hasbeen filled, armored, and developed. Extensive areashave been dredged to maintain navigation along piersand within marinas. The supply of beach sediment hasbeen curtailed and water quality problems stemmingfrom upland land use practices have affected nearshorehabitats. It is estimated that marine riparian vegetationexists along only 11 percent of the WRIA 9 shoreline(excluding Vashon-Maury Islands). This affects notonly salmonids produced in WRIA 9 watersheds butalso those produced in other Puget Sound watershedsthat use WRIA 9 shorelines for support duringmigration.

All migratory juvenile salmonids are dependent onhealthy estuarine and nearshore environments. Somespecies, such as chinook, chum, and pink salmon, aremore dependent on a healthy estuary environment forphysiological transition and rearing prior to theirocean migration. Nearshore habitats produceimportant food items for all life stages of salmonids.Especially important are the forage fish (e.g., sandlance, surf smelt, and herring) that require this area tospawn and rear.

Human population: see Nearshore Sub-watershed (page 12)

Primary designated land uses: see Nearshore Sub-watershed(page 12)

Recently documented fish species present: all species ofjuvenile and adult salmonids


Urban and industrial land use practices that are:

Altering or destroying significant amounts of nearshorehabitat;

Interrupting critical habitat-forming processes;

Fragmenting or destroying marine riparian corridors;and

Contributing toxic chemicals and harmful organiccompounds to nearshore waters and sediments.

Nearshore Sub-watershed(Estuarine/Marine Waters and Habitats)


IV. RECOVERY STRATEGY FOR THE GREEN/DUWAMISH WATERSHED

A multi-species salmonid recovery strategy wasdeveloped for the Green/Duwamish watershed usingthe information collected for this report. The strategyrelies heavily upon opening the currently untappedpotential for salmonid recovery in the Upper GreenRiver Sub-watershed. Dams have blocked access to106 lineal miles of stream habitat and about half of thewatershed acreage. The Upper Sub-watershed is largeenough and the habitat forming processes are stillrelatively intact or in a process of recovery to allowthis area to function as salmonid refugia. This refugiacan seed the downstream habitat, with a potential to

greatly increase natural salmonid production,especially for coho, chinook, steelhead, and cutthroatsalmonids. Implementation of the strategy relies ontwo critical or key actions: (1) restoration ofefficient upstream and downstream fish passage at thedams; and (2) ensuring that the juveniles produced inthe Upper Green River Sub-watershed are providedwith essential habitat functions in the downstreamareas of WRIA 9. In addition, it is essential to protectintact habitats and properly functioning processes thatare currently supporting existing salmonid populationsthroughout the WRIA.

V. NEXT STEPS

The Habitat Limiting Factors and ReconnaissanceAssessment Report is the first coordinated step towardsalmonid recovery in WRIA 9. It lays the groundworkfor a comprehensive conservation planning effort overthe next five years. This multi-species effort focuses onhabitat issues affecting the decline of salmonids andother species. The planning effort will unfold in fourstages over the next five years. Following the HabitatLimiting Factors and Reconnaissance AssessmentReport, a Near-term Action Agenda is expected to becompleted in 2001. This Agenda will guide interim and

immediate actions. Also in 2001, a Strategic Assess-ment will begin. This will culminate in a report inmid-2003 that will help fill important data gaps. TheComprehensive Conservation Plan is the ultimateproduct of the WRIA 9 planning process. It will guidelong-term salmonid conservation and recovery actionsin the watershed. The goal is to have theComprehensive Conservation Plan approved by theNational Marine Fisheries Service and the U.S. Fishand Wildlife Service by June 2005.

Produced by: GIS/Visual Communications UnitKing County Department of Natural Resources, Water & Land Resources DivisionFile Name: 0012 WRIA 9 Recon Report/0101 W9 ExecSumBook IMP.p65 LP

This material will be provided inalternative formats for individualswith disabilities upon request.

Voice: 206-296-6519 Jennifer Rice TTY: 1-800-833-6388

Published January 2001

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