1-1

CHAPTER 1.INTRODUCTION

1.1 PURPOSE AND PROJECT DESCRIPTION

King County recently expanded the service area of its surface water utility to much of therural area of the County. The County is committed to providing a comprehensive surfacewater program in these new areas. This rapid rural reconnaissance report provides ageneral overview of the existing stream and basin conditions, problems, and identifies highpriority capital improvements and opportunities related to surface water in the Boise Creekdrainage basin.

1.2 STUDY AREA

The Boise Creek Basin covers 9,861 acres (15.4 square miles) in southeast King County,Washington. It includes a portion of the City of Enumclaw and areas to the east, as shownin Figure 1-1. Boise Creek (WRIA #10.0057) is approximately 12.2 miles long and flows intoright bank of the White River (WRIA #10.0031) at river mile (RM) 23.3 south of Enumclaw.The White River becomes the Puyallup River (WRIA #10.0021) and flows into Puget Soundat Commencement Bay in the City of Tacoma.

The elevation of the Boise Creek Basin varies from about 630 feet in the west to over3,900 feet in the east. Under existing (2001) land use conditions, the basin is 35 percent till,23 percent bedrock, 35 percent outwash, and 7 percent impervious surface.

1.3 PROJECT GOALS

The Boise Creek rapid rural reconnaissance report has two goals:

• Characterization—To produce a rapid, systematic inventory and analysis ofstream conditions and drainage systems, covering resources and problemsunder both current and future land uses. Each subbasin is to be ranked,classified as “impacted,” “sensitive,” or “not supporting (cannot support adiverse stream community),” and identified as “restorable” or not, usingdefinitions from Watershed Vulnerability Analysis (Center for WatershedProtection 2002). A complete description of the Vulnerability Analysis isincluded in Appendix E.

• Action Plan—To identify high-priority management needs in the study areaand to recommend programs for surface-water and habitat management.

1.4 PROJECT APPROACH

1.4.1 Characterization

The intent of the rapid rural reconnaissance is to describe ecological stream basinconditions through a thorough analysis of all available data for the basin. Using methodsoutlined in Watershed Vulnerability Analysis, the characterization analysis describes the

KING COUNTY RAPID RURAL RECONNAISSANCE

SR 410

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Roosevelt Ave E

284

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SE 416th St

Har

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Warner Ave

SE 432nd St

Kibler Ave

Bla

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SE 456th St

SE 456th Way

Wat

son

St

NW

ashington Ave

Div

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244

th A

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SR 4

10

Griffin Ave

284

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Roosevelt Ave E

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St

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SE 448th St

Battersby Ave

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2300

2300

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30003000

27002700

38003800

2500

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3400

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18001800

3700

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2000

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31003100

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Boise Creek

Boise

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White River White River

Lake Little704ODFLake Little704ODF

First Lake089WLCFirst Lake089WLC

134ACC134ACC

765NON765NON

Third Lake438LLTThird Lake438LLT

Second Lake455DBYSecond Lake455DBY

737NSB737NSB

339SWC339SWC

017IVF017IVF

874SSD874SSD

374OHH374OHH

135ONX135ONX

091BJK091BJK

138SYM138SYM

210UGJ210UGJ

723XHC723XHC

758ALZ758ALZ

644FGT644FGT

453WHB453WHB

717GRL717GRL380VFX380VFX

025CPD025CPD

997OOT997OOT

670PBD670PBD

44214421

44514451

66376637

44144414

44224422

66446644

66476647

6610066100

66486648

66296629

66546654

66256625

66586658

66456645

66576657

66406640

6635B6635B

4449444944744474

44234423

6610566105

66426642

6631B6631B

4452B4452B

6643B6643B

6636B6636B

6634B6634B

4457B4457B

4450B4450B

4455B4455B

66566656

66536653

4447B4447B

4440B4440B

6633B6633B

6627B6627B

4434B4434B

6617B6617B

6646B6646B

6641B6641B

66556655

6632B6632B

6638B6638B

6639B6639B

4453B4453B

4428B4428B

BOISE CREEK DRAINAGE BASIN

SeattleSeattle

SammamishSammamishBellevueBellevue

KirklandKirkland

KentKent

Federal WayFederal WayAuburnAuburn

RentonRenton

Lake Washington

Puget Sound

File Name: FIG_1-1.pdf

0 10.5Miles

0 2,000 4,000Feet

Date Last Revised: 05/04/04

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SUB-BASIN 6SUB-BASIN 6SUB-BASIN 4SUB-BASIN 4

SUB-BASIN 7SUB-BASIN 7

SUB-BASIN 3SUB-BASIN 3

SUB-BASIN 1SUB-BASIN 1

SUB-BASIN 2SUB-BASIN 2

SUB-BASIN 5SUB-BASIN 5

979979

LegendBoise Creek Class 1

Boise Creek Unclassified

Watercourses Class 1

Watercourses Class 2

Watercourses Unclassified

Roads

100' Contours

20' Contours

Boise Creek Basin Boundary

Boise Creek Sub-Basin Boundaries

Wetlands (KC SAO)

Waterbodies

Parcels

Source: King County GIS, 2002; WSDOT 2002; WDNR

Figure 1-1Figure 1-1

Boise Creek Basin Rapid Rural Reconnaissance Report…

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hydrologic, geomorphic, and ecological processes that affect habitat and create surfacewater problems in each subbasin. The characterization identifies significant resource areasthat contribute to ecosystem health, including open space and other highly functioningecological areas. The characterization identifies significant flooding, water quality, erosionand aquatic resource problems. It also attempts to project the likely future conditions of thebasin. For the Boise Creek Basin, the characterization used available information and alimited amount of newly collected additional data. Table 1-1 summarizes the main elementsof the characterization process.

TABLE 1-1.MAIN ELEMENTS OF THE BASIN CHARACTERIZATION PROCESS

Compile Existing Data Analyze and Interpret Data Develop Report

Remote DataAerial photographyGIS Data setsClassified Land CoverPublic LandsSensitive Areas Mapping

Field DataStream TypingRain Gage DataStream Gage DataComplaint RecordsAmbient Water QualityData

Published Reports

Interviewed County staff,other Agencies, Citizens

§ Conduct hydrologic analysis

§ Calculate impervious surfaceareas

§ Analyze existing data

§ Review published reports

§ Analyze remote and field data

§ Analyze existing reports and dataon major private and publicdevelopment projects

§ Analyze complaint records

§ Conduct air photo analysis of landuse and habitat conditions.

§ Conduct targeted field inspectionsof likely aquatic habitat andsurface water problems.

• Description of importanthydrologic, geomorphicand ecological processesaffecting basin

• Description of significantresource areas and habitatfunctions warrantingprotection

• Description of significantsurface water problemswarranting remediation

• Description of likely futurebasin conditions

1.4.2 Action Plan

The action plan identifies capital projects that will reduce risks posed by surface waterproblems to human health and safety, rural infrastructure, personal property, and aquaticresources. The projects resolve surface water problems in a way that either maintains orimproves aquatic habitats. Table 1-2 describes the general types of activities included in theaction plan.

1.5 REPORT CONTENTS

This report is a reconnaissance level plan for the Boise Creek Basin. It characterizes theexisting stream and basin conditions and describes capital improvements needed to reduceexisting flooding, protect or improve water quality, protect or improve habitat, and improvethe overall health of the basin.

Chapter 2 discusses land cover characteristics in the Boise Creek drainage basin and theireffects on hydrology and habitat. Chapter 3 analyzes basin hydrology for pre-development,existing (2001), and future conditions. Chapters 4, 5, 6, and 7 discussed the basin’s

…1. INTRODUCTION

1-3

geomorphology, water quality, stream habitat, and drainage/erosion impacts and needs.Chapter 8 discusses the hydrology, geomorphology, and ecological processes affecting theBoise Creek Basin and likely future impacts. Chapter 9 discusses the projects that havebeen identified and provides a recommended action plan.

TABLE 1-2.TYPICAL ACTIVITIES INCLUDED IN ACTION PLAN

Description Purpose Typical Examples

Restoreecosystemprocesses

Restore natural flowsand sediment regimesto alleviatedownstream problemsand improve system-wide habitatconditions.

§ Protect or acquire significant open space contributing toecosystem health (e.g., headwater wetlands, groundwaterrecharge areas, and riparian areas).

§ Reduce impervious surfaces and cleared, compacted lands.

§ Protect and restore natural forest cover and topsoil depths.

§ Improve infiltration of surrounding soils to mimic naturalconditions by planting and other vegetation.

§ Construct retention and detention ponds that correctwater quality and flooding problems .

§ Allow natural formation of alluvial fans.

Restoreecologicalconnectivity

Restore fish passageand habitat throughreconnection ofisolated/fragmentedenvironments.

§ Remove or retrofit undersized or perched culverts, weirs,dams, etc.

§ Restore riparian buffers.

§ Prioritize levee removals

§ Remove structures from within floodplains, alluvial fansand channel migration areas.

§ Restore or create side channels.

Addressproblemswhere theyare expressedon thelandscape

Alleviate significanthealth and safety oraquatic habitatproblems withsubstantial impact onthe community.

§ Stabilize or restore stream banks.

§ Install or upgrade culverts

§ Construct conveyance improvements.

§ Retrofit facilities for retention and detention.

§ Install storm drain lines.

Evaluation Analyze theeffectiveness ofidentified actions