North Creek Drainage Needs Report - Snohomish County

North Creek
Drainage Needs Report
DNR No. 10
DECEMBER 2002
Snohomish County
Public Works
Surface Water Management Division
2731 Wetmore Avenue, 2nd Floor
Everett, WA 98201
425-388-3464

Responsible County Officials
The Drainage Needs Report (DNR) Project is an innovative 2-year project that was
initiated by the Snohomish County Council in 2001. The project was completed under
the direction of the following Snohomish County government officials:
2002 Snohomish County Council:
• John Koster, Council District 1
• Kirke Sievers, Council District 2
• Gary Nelson, Council District 3, Council Chair
• Dave Gossett, Council District 4
• Jeff Sax, Council District 5
Snohomish County Executive:
• Bob Drewel
Snohomish County Public Works:
• Public Works Director: Peter Hahn
• Public Works, Surface Water Management (SWM) Division Director: Joan Lee, P.E.
• DNR Project Director: Loren Sand, P.E.
• DNR Technical Manager and SWM Coordinator: Gregg Farris, P.E.
• Snohomish County SWM Drainage Supervisor: Karen Kerwin, P.E.
Responsible County Officials
NORTH CREEK ACKNOWLEDGMENTS_FINAL.DOC ii DECEMBER 2002

Acknowledgments
This North Creek Drainage Needs Report (DNR) was prepared in coordination with
Snohomish County Public Works, Surface Water Management (SCSWM) Division, by a
consultant team consisting of CH2M HILL, Tetra Tech/KCM, Aqua Terra Consultants,
Otak, GeoEngineers, TerraLogic GIS, and R.W. Beck. Technical support was provided
by a separate consultant team consisting of R.W. Beck, Entranco, Herrera
Environmental Consultants, Northwest Hydraulic Consultants, and Parametrix.
The preparation of this report was shared between multiple firms, with Tetra Tech/KCM
leading the Penny Creek, Silver Creek, Middle 2 and South North Creek subbasins, and
CH2M HILL leading the North and Middle 1 North Creek subbasins. This report was
prepared and reviewed by the following lead staff:
Team Project Manager John Rogers, P.E., CH2M HILL
DNR Lead Tony Melone, P.E., Tetra Tech/KCM
Teresa Platin, P.E., CH2M HILL
Gregg Farris, P.E., SWM DNR Lead Reviewer
Hydraulic Modeling Greg Gaasland, P.E., Tetra Tech/KCM
Tom Spangenberg, P.E., Tetra Tech/KCM
Jerry Scheller, P.E., CH2M HILL
Tawni Hoang, CH2M HILL
Gregg Farris, P.E., SWM DNR Hydraulic Lead
Hydrologic Modeling Joe Brascher, Aqua Terra
Doug Beyerlein, P.E., Aqua Terra
Gregg Farris, P.E., SWM DNR Hydrologic Lead
Drainage Inventory Bill Lawrence, P.L.S., Otak
Mike McGuiness, SWM GIS/GPS Resource Manager
Habitat Analysis Hans Ehlert, Wetlands/Riparian Lead, CH2M HILL
Randy Whitman, Aquatic Habitat Lead, CH2M HILL
Caroline Barnes, P.E., Tetra Tech/KCM
Darrell Smith, SWM DNR Habitat Lead
Water Quality Analysis Harry Gibbons, Tetra Tech/KCM
Reid Adams, P.E., CH2M HILL
Geomorphology Analysis Mary Ann Reinhart, P.G., P.E.G., GeoEngineers
Acknowledgments
NORTH CREEK ACKNOWLEDGMENTS_FINAL.DOC iii DECEMBER 2002

Capital Improvement Greg Gaasland, P.E., Tetra Tech/KCM
Program (CIP) Project Teresa Platin, P.E., CH2M HILL
Development Dennis Galinato, CH2M HILL
Gregg Farris, P.E., SWM DNR Lead Reviewer
Darrell Smith, SWM DNR Habitat Lead
Geographic Information Jane Cassady, TerraLogic GIS
System (GIS) Analysis Levon Yengoyan, TerraLogic GIS
Scott Corwin, R.W. Beck
Christine Coats, SWM DNR GIS Lead
Acknowledgments
NORTH CREEK ACKNOWLEDGMENTS_FINAL.DOC iv DECEMBER 2002

Contents
Page
Responsible County Officials ........................................................................................ ii
Acknowledgments ......................................................................................................... iii
Acronyms and Abbreviations ...................................................................................... xv
Executive Summary.................................................................................................. ES-1
1.0 Introduction .........................................................................................................1-1
1.1 Purpose .....................................................................................................1-1
1.2 North Creek Study Area ............................................................................1-1
1.3 Report Organization ..................................................................................1-2
2.0 Basin Characteristics..........................................................................................2-1
2.1 Hydrologic Characteristics.........................................................................2-1
2.1.1 General Basin Description ..........................................................2-1
2.1.2 Soils and Geology.......................................................................2-2
2.1.3 Groundwater ...............................................................................2-3
2.1.4 Topography and Slope ...............................................................2-4
2.1.5 Land Use and Cover...................................................................2-4
2.2 Conveyance Systems..............................................................................2-30
2.2.1 Streams ....................................................................................2-30
2.2.2 Drainage Systems ....................................................................2-32
2.3 Stream and Wetland Habitat ...................................................................2-33
2.3.1 Stream Habitat..........................................................................2-33
2.3.2 Wetland Habitat ........................................................................2-34
2.4 Water Quality...........................................................................................2-34
2.5 Stream Channel Erosion .........................................................................2-35
3.0 Hydrologic and Hydraulic Modeling ..................................................................3-1
3.1 Introduction................................................................................................3-1
3.2 Hydrologic Model Selection.......................................................................3-1
3.3 HSPF Hydrologic Model Development and Results ..................................3-1
3.3.1 Data Collection ...........................................................................3-2
3.3.2 HSPF Model Set-Up ...................................................................3-2
3.3.3 HSPF Model Results ..................................................................3-5
3.4 Hydraulic Model Selection.........................................................................3-6
3.4.1 Penny Creek Subbasin .............................................................3-10
3.4.2 Silver Creek Subbasin ..............................................................3-10
3.4.3 North North Creek Subbasin.....................................................3-10
3.4.4 Middle 1 North Creek Subbasin................................................3-12
3.4.5 Middle 2 North Creek Subbasin................................................3-13
3.4.6 South North Creek Subbasin ....................................................3-13
Contents
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North Creek Drainage Needs Report
3.5 Hydraulic Model Data Collection .............................................................3-13
3.6 Hydraulic Model Development and Results: Penny Creek
Subbasin..................................................................................................3-13
3.6.1 Introduction ...............................................................................3-13
3.6.2 HEC-RAS Model Set-Up...........................................................3-14
3.6.3 HEC-RAS Model Results..........................................................3-27
3.6.4 SWMM Model Set-Up ...............................................................3-27
3.6.5 SWMM Model Results ..............................................................3-31
3.7 Hydraulic Model Development and Results: Silver Creek
Subbasin..................................................................................................3-35
3.7.1 Introduction ...............................................................................3-35
3.7.2 HEC-RAS Model Set-Up...........................................................3-35
3.7.3 HEC-RAS Model Results..........................................................3-35
3.7.4 SWMM Model Set-Up ...............................................................3-36
3.7.5 SWMM Model Results ..............................................................3-36
3.8 Hydraulic Model Development and Results: North North Creek
Subbasin..................................................................................................3-37
3.8.1 Introduction ...............................................................................3-37
3.8.2 HEC-RAS Model Set-Up...........................................................3-37
3.8.3 HEC-RAS Model Results..........................................................3-41
3.8.4 SWMM Model Set-Up ...............................................................3-41
3.8.5 SWMM Model Results ..............................................................3-46
3.8.6 HY-8 and KCBW Model Development......................................3-51
3.8.7 KCBW Model Results ...............................................................3-52
3.9 Hydraulic Model Development and Results: Middle 1 North
Creek Subbasin.......................................................................................3-52
3.9.1 Introduction..................................................................................3-52
3.9.2 HEC-RAS Model Set-Up ............................................................3-52
3.9.3 HEC-RAS Model Results............................................................3-54
3.9.4 SWMM Model Set-Up.................................................................3-55
3.9.5 SWMM Model Results ................................................................3-58
3.9.6 Other Model Development...........................................................3-59
3.10 Hydraulic Model Development and Results: Middle 2 North
Creek Subbasin.......................................................................................3-59
3.10.1 Introduction ...............................................................................3-59
3.10.2 HEC-RAS Model Set-Up...........................................................3-59
3.10.3 HEC-RAS Model Results..........................................................3-63
3.10.4 SWMM Model Set-Up ...............................................................3-63
3.10.5 SWMM Model Results ..............................................................3-64
3.11 Hydraulic Model Development: South North Creek Subbasin.................3-64
3.11.1 Introduction ...............................................................................3-64
3.11.2 HEC-RAS Model Set-Up...........................................................3-64
3.11.3 HEC-RAS Model Results..........................................................3-66
3.11.4 SWMM Model Set-Up ...............................................................3-66
3.11.5 SWMM Model Results ..............................................................3-66
4.0 Habitat Assessment............................................................................................4-1
4.1 Introduction................................................................................................4-1
4.1.1 Scope of Assessment .................................................................4-1
4.1.2 Fish Habitat and Use ..................................................................4-1
4.2 Background ...............................................................................................4-2
Contents
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North Creek Drainage Needs Report
4.2.1 Instream Habitat .........................................................................4-2
4.2.2 Biotic Integrity ...........................................................................4-17
4.2.3 Fish Passage ............................................................................4-17
4.2.4 Riparian Habitat ........................................................................4-18
4.2.5 Wetlands...................................................................................4-18
4.3 Methods...................................................................................................4-19
4.3.1 Selection of Assessment Sites .................................................4-19
4.3.2 Instream Habitat .......................................................................4-20
4.3.3 Biotic Integrity ...........................................................................4-21
4.3.4 Fish Passage ............................................................................4-21
4.3.5 Riparian Habitat ........................................................................4-21
4.3.6 Wetland Habitat ........................................................................4-22
4.3.7 Analysis ....................................................................................4-22
4.3.8 Assessment Criteria..................................................................4-22
4.4 Results and Discussion ...........................................................................4-23
4.4.1 Instream Habitat .......................................................................4-23
4.4.2 Biotic Integrity ...........................................................................4-25
4.4.3 Fish Passage ............................................................................4-25
4.4.4 Riparian Habitat ........................................................................4-25
4.4.5 Wetlands Habitat ......................................................................4-26
5.0 Water Quality Assessment.................................................................................5-1
5.1 Introduction................................................................................................5-1
5.2 Land Use Patterns Affecting Water Quality ...............................................5-1
5.3 Summary of Available Water Quality Information......................................5-3
5.4 Water Quality Analysis Methods................................................................5-4
5.5 Existing Water Quality ...............................................................................5-4
5.5.1 Fecal Coliform.............................................................................5-8
5.5.2 Dissolved Oxygen.......................................................................5-9
5.5.3 Temperature ...............................................................................5-9
5.5.4 Nutrients ...................................................................................5-10
5.5.5 Total Suspended Solids and Turbidity ......................................5-10
5.5.6 Heavy Metals ............................................................................5-11
5.5.7 Summary ..................................................................................5-11
5.6 Future Water Quality ...............................................................................5-12
6.0 Channel Erosion Assessment............................................................................6-1
6.1 Introduction................................................................................................6-1
6.2 Channel Erosion Assessment Methods.....................................................6-2
6.3 Channel Erosion and Sediment Conditions...............................................6-2
7.0 CIP Design Guidelines........................................................................................7-1
7.1 Introduction................................................................................................7-1
7.2 Flooding and Drainage Design Guidelines................................................7-1
7.2.1 Problem Definition Criteria..........................................................7-1
7.2.2 Design Guidelines.......................................................................7-2
7.3 Aquatic Habitat Design Guidelines............................................................7-4
7.3.1 Problem Definition Criteria..........................................................7-4
7.3.2 Design Guidelines.......................................................................7-6
7.4 Water Quality Design Guidelines...............................................................7-7
7.4.1 Problem Definition Criteria..........................................................7-7
Contents
NORTH CREEK CONTENTS_FINAL.DOC vii DECEMBER 2002

North Creek Drainage Needs Report
7.4.2 Design Guidelines.......................................................................7-7
7.5 Channel Erosion Design Guidelines..........................................................7-7
7.5.1 Problem Definition Criteria..........................................................7-7
7.5.2 Design Guidelines.......................................................................7-7
8.0 Existing and Future Problems ...........................................................................8-1
8.1 Introduction................................................................................................8-1
8.2 Flooding and Maintenance Problems........................................................8-1
8.2.1 Flooding Problems......................................................................8-2
8.2.2 Maintenance Problems .............................................................8-62
8.3 Habitat Problems.....................................................................................8-63
8.3.1 Fish Passage Barriers ..............................................................8-63
8.3.2 Excessive Fine Sediment .........................................................8-85
8.3.3 Limited Instream LWD ..............................................................8-85
8.3.4 Excessive Bedload Movement..................................................8-86
8.3.5 Areas Lacking LWD Recruitment, Shade, and/or
Riparian Width ..........................................................................8-86
8.3.6 Substantial Wetland Loss .........................................................8-87
8.4 Water Quality Problems...........................................................................8-87
8.4.1 Pollution Generated by Residential Development ....................8-87
8.4.2 Point and Nonpoint Source Pollution from Impervious
Surfaces....................................................................................8-88
8.4.3 Pollution Generated by Pasture and Agricultural Lands ...........8-92
8.4.4 Pollution Generated by Commercial and Light Industrial
Uses..........................................................................................8-95
8.5 Erosion and Sedimentation Problems .....................................................8-96
9.0 CIP Development, Alternatives Analysis, and Recommended
Solutions..............................................................................................................9-1
9.1 Problem Selection for CIP Modeling..........................................................9-1
9.2 Modeling Alternatives ..............................................................................9-10
9.2.1 CIP Modeling Alternative 1 .......................................................9-11
9.2.2 CIP Modeling Alternative 2 .......................................................9-12
9.2.3 Penny Creek Subbasin Modeling Alternatives..........................9-12
9.2.4 Silver Creek Subbasin Modeling Alternatives...........................9-35
9.2.5 North North Creek Subbasin Modeling Alternatives .................9-38
9.2.6 Middle 1 North Creek Subbasin Modeling Alternatives ............9-46
9.2.7 Middle 2 North Creek Subbasin Modeling Alternatives ............9-51
9.2.8 South North Creek Subbasin Modeling Alternatives.................9-52
9.2.9 Basin Wide Alternative Summary Results ................................9-59
9.3 Other Habitat, Water Quality, and Erosion CIP Projects .........................9-60
9.3.1 Habitat CIP Projects .................................................................9-61
9.3.2 Water Quality CIP Projects .......................................................9-78
9.3.3 Erosion CIP Projects.................................................................9-83
10.0 Recommended Plan..........................................................................................10-1
10.1 Introduction..............................................................................................10-1
10.2 Project Selection Criteria and Methodology ............................................10-1
10.2.1 Evaluation Criteria ....................................................................10-2
10.3 Recommended CIP Projects ...................................................................10-5
Contents
NORTH CREEK CONTENTS_FINAL.DOC viii DECEMBER 2002

North Creek Drainage Needs Report
10.3.1 Responsibility for Implementation (Public/Private and
Unincorporated/Incorporated)...................................................10-5
10.3.2 Project Sequencing.................................................................10-49
10.3.3 Funding...................................................................................10-49
10.3.4 Permits....................................................................................10-49
10.3.5 Early Action Projects...............................................................10-50
10.4 Other Recommendations.......................................................................10-50
10.4.1 Maintenance ...........................................................................10-51
10.4.2 Additional Studies ...................................................................10-51
10.4.3 Potential Mitigation Projects ...................................................10-56
10.4.4 Detention Pond Retrofits.........................................................10-56
10.4.5 Ditch Retrofits .........................................................................10-57
10.4.6 Coordination with Cities of Bothell, Mill Creek and
Everett to Implement Water Quality Improvements ................10-57
10.4.7 Small Farm Best Management Practices ...............................10-57
10.4.8 Sweeping of Public Parking Lots ............................................10-58
10.4.9 Cleaning of Catch Basins in Targeted Areas..........................10-58
11.0 References.........................................................................................................11-1
Appendices
A Hydrologic Model Development and Application
B1 Hydraulic Model Development and Application for Penny Creek
B2 Hydraulic Model Development and Application for Silver/Nickel Creeks
B3 Hydraulic Model Development and Application for North North Creek
B4 Hydraulic Model Development and Application for Middle 1 North Creek
B5 Hydraulic Model Development and Application for Middle 2 North Creek
B6 Hydraulic Model Development and Application for South North Creek
C Habitat Surveys, Data Analysis, and Results
D Water Quality Data and Results
E Geomorphic Channel Evaluation
F Project Summaries and Cost Estimates
Contents
NORTH CREEK CONTENTS_FINAL.DOC ix DECEMBER 2002

Figures
North Creek Drainage Needs Report
1-1
Page
County DNR Areas ...........................................................................................1-3
1-2 North Creek Basin DNR Study Area.................................................................1-5
2-1a Penny Creek Subbasin Existing Land Use .......................................................2-5
2-1b Silver Creek Subbasin Existing Land Use ........................................................2-7
2-1c North North Creek Subbasin Existing Land Use ..............................................2-9
2-1d Middle 1 North Creek Subbasin Existing Land Use........................................2-11
2-1e Middle 2 North Creek Subbasin Existing Land Use........................................2-13
2-1f South North Creek Subbasin Existing Land Use ............................................2-15
2-2a Penny Creek Subbasin Future Land Use .......................................................2-17
2-2b Silver Creek Subbasin Future Land Use.........................................................2-19
2-2c North North Creek Subbasin Future Land Use...............................................2-21
2-2d Middle 1 North Creek Subbasin Future Land Use ..........................................2-23
2-2e Middle 2 North Creek Subbasin Future Land Use ..........................................2-25
2-2f South North Creek Subbasin Future Land Use ..............................................2-27
3-1a Penny Creek Subbasin Hydrologic and Hydraulic Modeling
Locations ........................................................................................................3-15
3-1b Silver Creek Subbasin Hydrologic and Hydraulic Modeling
Locations ........................................................................................................3-17
3-1c North North Creek Subbasin Hydrologic and Hydraulic Modeling
Locations ........................................................................................................3-19
3-1d Middle 1 North Creek Subbasin Hydrologic and Hydraulic Modeling
Locations ........................................................................................................3-21
3-1e Middle 2 North Creek Subbasin Hydrologic and Hydraulic Modeling
Locations ........................................................................................................3-23
3-1f South North Creek Subbasin Hydrologic and Hydraulic Modeling
Locations ........................................................................................................3-25
4-1a Penny Creek Subbasin Instream Habitats........................................................4-3
4-1b Silver Creek Subbasin Instream Habitats ........................................................4-5
4-1c North North Creek Subbasin Instream Habitats................................................4-7
4-1d Middle 1 North Creek Subbasin Instream Habitats...........................................4-9
4-1e Middle 2 North Creek Subbasin Instream Habitats.........................................4-11
4-1f South North Creek Subbasin Instream Habitats.............................................4-13
4-2a Penny Creek Subbasin Wetlands and Riparian Corridors..............................4-27
4-2b Silver Creek Subbasin Wetlands and Riparian Corridors ...............................4-29
4-2c North North Creek Subbasin Wetlands and Riparian Corridors......................4-31
4-2d Middle 1 North Creek Subbasin Wetlands and Riparian Corridors.................4-33
4-2e Middle 2 North Creek Subbasin Wetlands and Riparian Corridors.................4-35
4-2f South North Creek Subbasin Wetlands and Riparian Corridors.....................4-37
5-1 Water Quality Monitoring and Outfall Screening Locations ..............................5-5
8-1a Penny Creek Subbasin Flooding Problem Locations......................................8-37
8-1b Silver Creek Subbasin Flooding Problem Locations.......................................8-39
8-1c North North Creek Subbasin Flooding Problem Locations .............................8-41
Contents
NORTH CREEK CONTENTS_FINAL.DOC xi DECEMBER 2002

North Creek Drainage Needs Report
8-1d Middle 1 North Creek Subbasin Flooding Problem Locations ........................8-43
8-1e Middle 2 North Creek Subbasin Flooding Problem Locations ........................8-45
8-1f South North Creek Subbasin Flooding Problem Locations.............................8-47
8-2a Penny Creek Subbasin Habitat Problem Locations........................................8-73
8-2b Silver Creek Subbasin Habitat Problem Locations .........................................8-75
8-2c North North Creek Subbasin Habitat Problem Locations................................8-77
8-2d Middle 1 North Creek Subbasin Habitat Problem Locations...........................8-79
8-2e Middle 2 North Creek Subbasin Habitat Problem Locations...........................8-81
8-2f South North Creek Subbasin Habitat Problem Locations...............................8-83
8-3 Water Quality Problem Locations ...................................................................8-93
9-1a Penny Creek Subbasin Modeling Alternative CIP Projects.............................9-25
9-1b Silver Creek Subbasin Modeling Alternative CIP Projects..............................9-39
9-1c North North Creek Subbasin Modeling Alternative CIP Projects….................9-41
9-1d Middle 1 North Creek Subbasin Modeling Alternative CIP Projects ...............9-49
9-1e Middle 2 North Creek Subbasin Modeling Alternative CIP Projects ...............9-53
9-1f South North Creek Subbasin Modeling Alternative CIP Projects....................9-57
9-2a Penny Creek Subbasin Additional Habitat and Water Quality CIP Projects ...9-65
9-2b Silver Creek Subbasin Additional Habitat and Water Quality CIP Projects ....9-67
9-2c North North Creek Subbasin Additional Habitat and Water Quality
CIP Projects....................................................................................................9-69
9-2d Middle 1 North Creek Subbasin Additional Habitat and Water Quality CIP
Projects...........................................................................................................9-71
9-2e Middle 2 North Creek Subbasin Additional Habitat and Water Quality CIP
Projects...........................................................................................................9-73
9-2f South North Creek Subbasin Additional Habitat and Water Quality CIP
Projects...........................................................................................................9-75
10-1a Penny Creek Subbasin Recommended CIP Projects...................................10-37
10-1b Silver Creek Subbasin Recommended CIP Projects....................................10-39
10-1c North North Creek Subbasin Recommended CIP Projects ..........................10-41
10-1d Middle 1 North Creek Subbasin Recommended CIP Projects......................10-43
10-1e Middle 2 North Creek Subbasin Recommended CIP Projects......................10-45
10-1f South North Creek Subbasin Recommended CIP Projects..........................10-47
Contents
NORTH CREEK CONTENTS_FINAL.DOC xii DECEMBER 2002

Tables
North Creek Drainage Needs Report
Page
3-1 Existing and Future Flood Frequencies..............................................................3-7
3-2 Hydraulic Models Used for Conveyance Systems ...........................................3-11
3-3 HEC-RAS Hydraulic Model Results for Penny Creek Subbasin in Unincorporated
UGA, Existing System with Existing and Future Land Use Conditions ....3-28
3-4 SWMM Hydraulic Model Results for Penny Creek Subbasin, Existing
System with Existing and Future Land Use Conditions....................................3-32
3-5 SWMM Hydraulic Model Results for Silver Creek Subbasin, Existing System
with Existing and Future Land Use Conditions.................................................3-38
3-6 HEC-RAS Hydraulic Model Results for North North Creek Subbasin in
Unincorporated UGA, Existing System with Existing and Future Land Use
Conditions ........................................................................................................3-42
3-7 SWMM Hydraulic Modeling Results Summary for North North Creek
Subbasin, Existing System with Existing and Future Land Use Conditions .....3-47
3-8 KCBW Hydraulic Modeling Results Summary for North North Creek Subbasin,
Existing System with Existing and Future Land Use Conditions ......................3-53
3-9 HEC-RAS Hydraulic Model Results for Middle 1 North Creek Subbasin in
Unincorporated UGA, Existing System with Existing and Future Land Use
Conditions ........................................................................................................3-55
3-10 SWMM Hydraulic Modeling Results Summary for Middle 1 North Creek
Subbasin, Existing System with Existing and Future Land Use Conditions .....3-60
3-11 SWMM Hydraulic Model Results for Middle 2 North Creek Subbasin,
Existing System with Existing and Future Land Use Conditions ......................3-65
3-12 SWMM Hydraulic Model Results for South North Creek Subbasin, Existing
System with Existing and Future Land Use Conditions....................................3-67
4-1 Rosgen Channel Types....................................................................................4-20
4-2 Instream Habitat Survey Results for Selected Attributes .................................4-24
5-1 Percent Coverage by Water Quality Land Use Categories in the
North Creek DNR Study Area ............................................................................5-3
7-1 Selected Drainage Design Criteria from EDDS..................................................7-3
7-2 Instream Habitat Condition Criteria ....................................................................7-5
7-3 Habitat Condition Criteria for Riparian Areas .....................................................7-5
8-1a Flooding Problems for Existing and Future Land Use Conditions
Penny Creek Subbasin.......................................................................................8-3
8-1b Flooding Problems for Existing and Future Land Use Conditions
Silver Creek Subbasin........................................................................................8-9
8-1c Flooding Problems for Existing and Future Land Use Conditions
North North Creek Subbasin ............................................................................8-12
8-1d Flooding Problems for Existing and Future Land Use Conditions
Middle 1 North Creek Subbasin .......................................................................8-23
8-1e Flooding Problems for Existing and Future Land Use Conditions
Middle 2 North Creek Subbasin .......................................................................8-31
8-1f Flooding Problems for Existing and Future Land Use Conditions
South North Creek Subbasin............................................................................8-33
Contents
NORTH CREEK CONTENTS_FINAL.DOC xiii DECEMBER 2002

North Creek Drainage Needs Report
8-2 Existing Habitat Problems ................................................................................8-34
8-3 Existing Water Quality Problems......................................................................8-89
8-4 North Creek Erosion Problems ........................................................................8-97
9-1 Summary of Problems Selected for Hydraulic and Hydrologic Modeling ...........9-2
9-2 Modeled CIP Projects.......................................................................................9-13
9-3 Modeled Flow Results for CIP Modeling Alternatives 1 and 2 .........................9-27
9-4 Estimated Costs for Modeling Alternatives 1 and 2..........................................9-32
9-5 Summary of Estimated Costs for CIP Modeling Alternatives by Subbasin .....9-60
9-6 Habitat CIP Projects Not Modeled....................................................................9-63
9-7 Habitat Problems Eliminated from Consideration in North Creek DNR Area ...9-77
9-8 Summary of Riparian Revegetation Project Information by Subbasin ............9-77
9-9 Water Quality CIP Projects ..............................................................................9-81
10-1 CIP Project Evaluation .....................................................................................10-3
10-2 Recommended Flooding Projects ....................................................................10-7
10-3 Recommended Habitat Projects.....................................................................10-19
10-4 Recommended Water Quality Projects ..........................................................10-25
10-5 Recommended Flooding/Habitat Projects......................................................10-27
10-6 Recommended Flooding/ Water Quality Projects ..........................................10-35
10-7 Recommended Additional Studies/Analysis...................................................10-54
Contents
NORTH CREEK CONTENTS_FINAL.DOC xiv DECEMBER 2002

Acronyms and Abbreviations
AAS Adopt-A-Stream Foundation
AES Associated Earth Services
bgs below the ground surface
B-IBI benthic index of biological indicators
BFW bankfull width
BMP best management practice
°C degrees Celsius
cfs cubic feet per second
CIP Capital Improvement Program
CMP corrugated metal pipe
DNMA Dairy Nutrient Management Act
DNR drainage needs report
DO dissolved oxygen
DRI Drainage Rehabilitation and Investigation
Ecology Washington Sate Department of Ecology
EDDS Engineering Design and Development Standards
EIA effective impervious area
ESA Endangered Species Act
Extran U.S. EPA SWMM Extended Transport
FEMA Federal Emergency Management Agency
FHWA Federal Highway Administration
GIS geographic information system
gpm gallons per minute
GPP General Policy Plan
HEC-RAS Hydrologic Engineering Center River Analysis System
HPA Hydraulic Project Approval
HSPF Hydrologic Simulation Program–FORTRAN
I Interstate
IQR interquartile range
KCBW King County Backwater
LWD large woody debris
mg/L milligrams per liter
Acronyms and Abbreviations
NORTH CREEK ACRONYMS_FINAL.DOC xv DECEMBER 2002

NAVD North American Vertical Datum
NHC Northwest Hydraulics Consultants
NOAA National Oceanic and Atmospheric Administration
NMFS National Marine Fisheries Service
NWI National Wetland Inventory
PEM palustrine emergent
PERLND pervious land
PFMC Pacific Fishery Management Council
PFO palustrine forested
PSS palustrine scrub/shrub
POW palustrine open water
RCH-RES reach/reservoir
RM river mile
RU riparian unit
QA/QC quality assurance/quality control
North Creek Drainage Needs Report
SC Snohomish County
SCC Snohomish County Code
SR state route
SCSWM Snohomish County Public Works, Surface Water Management Division
SWMM Storm Water Management Model
TIA total impervious area
TMDL total maximum daily load
UGA urban growth area
USACOE United States Army Corps of Engineers
USFS U.S. Forest Service
USGS U.S. Geology Survey
USFWS U.S. Fish and Wildlife Service
WAC Washington Administrative Code
WDFW Washington Department of Fish and Wildlife
WDNR Washington Department of Natural Resources
WFPB Washington Forest Practices Board
WRIA water resource inventory area
WSDOT Washington Department of Transportation
WSEL Water surface elevation
Acronyms and Abbreviations
NORTH CREEK ACRONYMS_FINAL.DOC xvi SEPTEMBER 2002 DRAFT