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CHAPTER 1.INTRODUCTION

1.1 PURPOSE AND PROJECT DESCRIPTION

In 1999, King County expanded the service area of its surface water utility to much of the rural area of theCounty. The County is committed to providing a comprehensive surface water program to these newareas. This rapid rural reconnaissance report provides a general overview of the existing conditions,problems, and identifies high priority capital improvements and opportunities related to surface water,groundwater, and nearshore habitat on Vashon-Maury Island (VMI).

1.2 STUDY AREA

A detail investigation of all of Vashon-Maury Island could not be made at this time because of budgetaryconstraints. Judd Creek and Shinglemill Creek basins were selected for a detail investigation because theyare the largest basins on the island and are experiencing the most growth problems.

The Judd Creek Basin covers 3,292 acres (5.1 square miles) or approximately 14% of VMI and is locatedin the middle of Vashon Island. Judd Creek, which discharges into Puget Sound through QuartermasterHarbor, is 3.0 miles long. The elevation of the Judd Creek Basin varies from sea level in the south to over440 feet in the north. Soil types in the watershed are approximately 69 percent till, 30 percent outwashand about 1 percent wetland. Under existing (2001) land use conditions, 2.2 percent of the basin isestimated to be impervious as shown in Table 2-10.

The Shinglemill Creek Basin covers 1,846 acres (2.9 square miles) or approximately 8% of VMI and islocated in the northern portion of Vashon Island. Shinglemill Creek, which discharges into Puget Soundnear the northwest corner of the island, is 2.7 miles long. The elevation of the Shinglemill Creek Basinvaries from sea level to about 420 feet at its southern end. Soil types in the watershed are approximately98 percent till, 1.5 percent outwash and 0.5 percent wetland. Under existing (2001) land use conditions,2.0 percent of the basin is estimated to be impervious.

Washington Trout identified 75 drainage basins on Vashon and Maury Island including the Judd Creekand Shinglemill Creek basins. Details of the Washington Trout report can be reviewed on their websitehttp://www.washingtontrout.org/vashon/vashon2001/ vashon Title.shtml. The drainage areas of the 73other basins range from 14 to 1,117 acres. Analysis of these basins did not include modeling and reliedheavily on existing information with only limited field investigation to determine existing needs.

The groundwater and nearshore habitat study area is island-wide. The Vashon-Maury Island nearshoreaccounts for 51 miles of shoreline. Figure 1-1 shows a map of the island and basin delineations.

1.3 PROJECT GOALS

The Vashon-Maury Island rapid rural reconnaissance report has two goals:

• Characterization—To produce a rapid, systematic inventory and ecological analysis ofstream conditions and drainage systems for both the Judd Creek and Shinglemill Creekdrainage basins, covering resources and problems under both current and future landuses. Each subbasin within these two basins was ranked, classified as “impacted,”“sensitive,” or “not supporting,” and identified as “restorable” or not, using definitions

KING COUNTY RAPID RURAL RECONNAISSANCE

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VASHON ISLAND - CREEK BASINS DELINEATIONS

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Figure 1-1

Vashon-Maury Island Rapid Rural Reconnaissance Report…

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from Watershed Vulnerability Analysis (Center for Watershed Protection 2002). Acomplete description of the watershed Vulnerability Analysis is included in Appendix G.

• Action Plan—To identify high-priority management needs in the study area and torecommend projects, studies, regulations, and programs for surface-water,groundwater, and habitat management.

1.4 PROJECT APPROACH

1.4.1 Characterization

The intent of the rapid rural reconnaissance is to describe ecological stream basin conditions through athorough analysis of all available data for both the Judd Creek and Shinglemill Creek basins. Usingmethods outlined in Watershed Vulnerability Analysis, the characterization analysis describes thehydrologic, geomorphic, and ecological processes that affect habitat and create surface water problems ineach subbasin. The characterization identifies significant resource areas that contribute to ecosystemhealth, including open space and other highly functioning ecological areas. The characterization identifiessignificant flooding, water quality, erosion and aquatic resource problems. It also attempts to project thelikely future conditions of the basin. For the Judd Creek and Shinglemill Creek basins, thecharacterization used available information and a limited amount of newly collected additional data.Table 1-1 summarizes the main elements of 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 Quality Data

Published Reports Interviews

County staff, other Agencies,Citizens

§ Conduct hydrologic analysis

§ Calculate impervious surface areas

§ Analyze existing data

§ Review published reports

§ Analyze remote and field data

§ Analyze existing reports and data onmajor private and public developmentprojects

§ Analyze complaint records

§ Conduct air photo analysis of land useand habitat conditions.

§ Conduct targeted field inspections oflikely aquatic habitat and surface waterproblems.

• Description of importanthydrologic, geomorphic andecological processes affectingbasin

• 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 projects for inclusion in a comprehensive 6-year capital improvement program(CIP) that will reduce risks posed by surface water and groundwater problems to human health and safety,rural infrastructure, personal property, and aquatic resources. The projects resolve surface water,groundwater, and nearshore problems in a way that either maintains or improves aquatic habitats. Table1-2 describes the general types of activities included in the action plan.

…1. INTRODUCTION

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1.5 REPORT CONTENTS

This report represents a reconnaissance level plan for both the Judd and Shinglemill Creek drainagebasins. It characterizes the existing stream and basin conditions of these two streams and describes capitalimprovements needed to reduce existing flooding, protect or improve water quality, protect or improvehabitat, and improve the overall health of these two basins. The report also identifies other island-widesurface water, groundwater, and habitat needs.

Chapter 2 discusses land cover characteristics in the Judd Creek and Shinglemill Creek basins and theireffects on hydrology and habitat. Chapter 3 analyzes basin hydrology for pre-development, existing(2001), and future conditions. Chapters 4, 5, 6, and 9 discusses the island’s groundwater, geomorphology,water quality, and drainage impacts and needs. Chapter 7 contains stream habitat analysis for Judd andShinglemill Creeks and a general discussion of island-wide habitat needs. Chapter 8 summarizesconditions of the island’s nearshore areas. Chapter 10 summarizes the findings in Chapters 4 through 9and contains the results of watershed vulnerability analyses for the Judd Creek and Shinglemill Creekbasins. Chapter 11 discusses the actions that have been identified and provides a recommended actionplan.

1.6 PUBLIC INVOLVEMENT

The County and the consultant performing this study met with the Vashon-Maury Island GroundwaterProtection Committee and leadership from the Vashon-Maury Island Land Trust and other watershedgroups on April 3, 2003.

The purpose of the meeting was to introduce the design team, describe the scope of work, present aninitial screening of projects, discuss a draft prioritization process, and discuss how to solicit input fromthe broader Vashon-Maury Island community. Input from the attendees was used to complete the draftreport and plan a community-wide meeting scheduled for early 2004.

Vashon-Maury Island Rapid Rural Reconnaissance Report…

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TABLE 1-2.TYPICAL ACTIVITIES INCLUDED IN ACTION PLAN

Description Purpose Typical Examples

Restoreecosystemprocesses

Restore natural flows andsediment regimes toalleviate downstreamproblems and improvesystem-wide habitatconditions.

§ Protect or acquire significant open space contributing to ecosystemhealth (e.g. headwater wetlands, groundwater recharge areas,estuarine salt marsh areas, riparian areas).

§ Reduce impervious surfaces and cleared, compacted lands e.g.gravel parking areas.

§ Increase natural forest cover and soil 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 passage andhabitat throughreconnection ofisolated/fragmentedenvironments.

§ Retrofit undersized or perched culverts, weirs, dams, etc.

§ Restore riparian buffers.

§ Prioritize levee removals.

§ Remove structures from within floodplains, alluvial fans andchannel migration areas.

§ Restore side channels.

Addressproblems wherethey areexpressed on thelandscape

Alleviate significant healthand safety or aquatichabitat problems withsubstantial impact on thecommunity.

§ Stabilize or restore stream banks.

§ Install or upgrade culverts.

§ Construct conveyance improvements.

§ Retrofit facilities for retention and detention.

§ Install storm drain lines.

Evaluation Analyze the effectivenessof identified actions