concept development and preliminary project analysis...

CONCEPT DEVELOPMENT AND PRELIMINARY

PROJECT ANALYSIS AND DESIGN

HANSEN CREEK REACH 5 RESTORATION PROJECT

Prepared for Skagit County Public Works

Prepared by Herrera Environmental Consultants, Inc.

Note: Some pages in this document have been purposely skipped or blank pages inserted so that this document will copy correctly when duplexed.

CONCEPT DEVELOPMENT AND PRELIMINARY

PROJECT ANALYSIS AND DESIGN

HANSEN CREEK REACH 5 RESTORATION PROJECT

Prepared for

Skagit County Public Works

1800 Continental Place

Mount Vernon, Washington 98273

Prepared by

Herrera Environmental Consultants, Inc.

2200 Sixth Avenue, Suite 1100

Seattle, Washington 98121

Telephone: 206/441-9080

May 23, 2013

i

jr 10-04664-001 concept dev & prelim proj analysis & design

CONTENTS

Introduction ................................................................................................. 1

Background ............................................................................................. 1

Report Context and Project Status ................................................................. 1

Project Summary ........................................................................................... 3

Project Area Location ................................................................................ 3

Stakeholders ........................................................................................... 3

Project Goals .......................................................................................... 5

Previous Studies and Projects ....................................................................... 5

Hansen Creek Watershed Management Plan ............................................... 5

Hansen Creek Alluvial Fan and Wetland Restoration Project ............................ 5

Existing Conditions ......................................................................................... 7

Land Use ................................................................................................ 7

Geomorphology ........................................................................................ 7

Hydrologic Patterns and Flooding .................................................................. 10

Habitat ................................................................................................. 11

Cultural Resources ................................................................................... 12

Habitat Restoration and Conceptual Plan Development ............................................. 13

Planning Process...................................................................................... 13

Property Acquisition, Easements, and Utilities Coordination .................................. 14

Workshops ............................................................................................. 15

Workshop #1 ................................................................................... 15

Workshop #2 ................................................................................... 15

Workshop #3 ................................................................................... 16

Workshop #4 ................................................................................... 21

Workshop #5 ................................................................................... 21

Workshop Conclusions ........................................................................ 21

Preliminary Analyses ...................................................................................... 23

Hydrologic Updates .................................................................................. 23

Geomorphic Considerations ......................................................................... 24

Hydraulic Modeling ................................................................................... 25

Preliminary Plan for Phased Project Implementation ................................................ 45

Phase 1 - Near-Term Project ....................................................................... 45

Phase 2 - Medium-Term Project ................................................................... 46

Phase 3 - Long-Term Project ....................................................................... 50

Habitat Benefits ...................................................................................... 50

ii


References ................................................................................................. 53

Appendix A Basemap Survey

Appendix B Geomorphic Analysis Data

Appendix C Phase 1 Near-Term Drainage Improvements Project Drawings

Appendix D Phase 2 Medium-Term Project 30% Drawings

iii


TABLES

Table 1. Pebble Count Results from the Field Investigation. ..................................... 8

Table 2. Hansen Creek and Red Creek Sediment Flux Analysis Results (Syvitsky et al.

2005). ......................................................................................... 10

Table 3. Summary of Workshop Objectives and Conclusions. ................................... 17

Table 4. Flow Portion for Reach 5 of Hansen Creek Using Updated Contributing Basin

Areas of 7.49mi2 for Hansen Creek and 2.53 mi2 for Red Creek. ..................... 23

Table 5. Phase 2 Medium-Term Hansen Creek Reach 5 Project Habitat Gains –

Comparison of Existing and Proposed Conditions. ...................................... 51

Table 6. Hansen Creek Reach 5 Floodplain and Salmonid Accessibility Frequency

Matrix. ........................................................................................ 52

FIGURES

Figure 1. Vicinity Map for the Hansen Creek Reach 5 Restoration Project Area. ............... 4

Figure 2. Comparison of Monitoring Cross-Sections for Hansen Creek Reach 5, near

the Confluence with Red Creek. ........................................................... 9

Figure 3. 100-year Flood Depth Difference: Post-Project Near-Term Drainage

Improvements Minus Pre-Project Conditions. ........................................... 29

Figure 4. Existing 2-year Flood Depths Reflecting Near-Term Project Improvements. ....... 31

Figure 5. Existing 100-year Flood Depths Reflecting Near-Term Project

Improvements. ............................................................................... 33

Figure 6. 100-year Flood Depths for the Phase 2 Medium-Term Project Alternative 1. ...... 35

Figure 7. 100-year Flood Depths for the Phase 2 Medium-Term Project Alternative 2. ...... 37

Figure 8. 2-year Flood Depths for the Phase 2 Medium-Term Project Alternative 1. ......... 41

Figure 9. 2-year Flood Depths for the Phase 2 Medium-Term Project Alternative 2. ......... 43

Figure 10. Phased Channel and Floodplain Restoration Projects for Hansen Creek

Reach 5. ...................................................................................... 47

Figure 11. Phased Schedule for the Hansen Creek Reach 5 Restoration Project. ............... 49

May 2013

Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 1

INTRODUCTION

This report describes the concept development process and preliminary design analyses

performed for a phased series of restoration projects, collectively referred to as the Hansen

Creek Reach 5 Restoration project (the project). The report also presents the key features of

the preliminary project designs and outlines additional work needed to support final design

and permitting for the project. Herrera Environmental Consultants (Herrera) prepared this

report under contract, and in close coordination with, Skagit County Public Works.

Background

The project area is located along Reach 5 of Hansen Creek (Reach 5) in Skagit County,

approximately 1.5 miles east of Sedro Woolley, Washington. Hansen Creek historically

supported a number of salmon fish species that are now depressed or listed as threatened

under the Endangered Species Act. Between the 1930s and 1940s, a number of land use

changes collectively contributed to simplified channel and riparian habitat and the isolation

of Hansen Creek from its floodplain. These changes included clear-cut logging, the conversion

of riparian forests for agricultural land uses, and implementation of local hydromodifications,

such as channel straightening and levee construction along the banks of Reach 5. Sediment

inputs to the reach increased as landslides resulted from upstream logging practices. Without

access to its floodplain, the balance between sediment supply and sediment transport

capacity in Hansen Creek was offset. The natural decrease in channel bed gradient upstream

of and within Reach 5 made it susceptible to ongoing aggradation, which required the

property owners and the local Skagit County Flood Control District to dredge the channel

regularly to reduce flooding. Collectively, these changes reduced the ability of Reach 5 to

provide quality salmonid rearing habitat for the last 60 to 70 years (Miller 2002).

In 2010, Skagit County initiated a project in collaboration with several other stakeholders to

develop, design, and begin implementing a series of phased channel restoration and flood

mitigation projects along Reach 5. The County’s objectives for Reach 5 were to develop near-

term, medium-term, and long-term solutions for restoration and flood mitigation that

incorporate a holistic, reach-wide approach to restoring geomorphic and hydraulic processes

as a framework for improving biological habitat (e.g., improved fish spawning and rearing

habitat as well as wetland habitat).

Report Context and Project Status

The Hansen Creek Reach 5 Restoration project is being developed by the County in

collaboration with stakeholders, and involves a phased series of near-term, medium-term,

and long-term projects, all of which are discussed in this report. At the time of this report,

the Phase 1 near-term project has been completed (i.e., designed and constructed), a

preliminary design for the Phase 2 medium-term project has been prepared, and conceptual

development for the Phase 3 long-term project is underway.

May 2013

2 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project

The near-term project was completed between 2011 and 2012, and included both floodplain

revegetation to jump-start a riparian ecosystem within former pastures and agricultural

fields. It also included drainage improvements to prevent the exacerbation of flooding

conditions from subsequent future project efforts associated with the medium- and long-term

projects. These subsequent project efforts would be intended to improve floodplain, channel,

and wetland habitat, and hydrologic connectivity.

The preliminary medium-term project design seeks to maximize salmonid fish spawning,

rearing, and refuge habitat types within the project area, without increasing flooding of

adjacent private properties or public roadways.

The preliminary long-term design was conceptualized to improve the connectivity of reach-

wide hydraulic and geomorphic processes with the intention of creating a project that would

be eligible for grant funding for completion of design as well as for construction.

The remainder of this report includes the following:

An overview of the project that describes the history and goals of project

development to date

A discussion of existing conditions at the project area

A discussion of habitat restoration plan development, including alternatives that were

analyzed and used as a basis for selecting the preferred alternatives for preliminary

design

A summary of the technical analyses performed to support design development and

establish important information needed for project permitting and collaboration with

regulatory agencies and local Native American Indian tribes

A description of key aspects of the preliminary design plans

There are several appendices to this report that document important technical analyses

completed to date. Appendix A provides the basemap survey of existing conditions completed

in 2010 and used as the basis for depicting existing conditions for project design drawings.

Appendix B provides the field forms and notes from the geomorphic and ordinary high water

and wetland surveys completed for the project area in 2010. Appendix C includes the final

drawings for the near-term drainage improvements project that was completed in 2012.

Appendix D includes the preliminary medium-term project design drawings.

May 2013


PROJECT SUMMARY

Project Area Location

As previously stated, the project area is located in Skagit County, approximately 1.5 miles

east of Sedro Woolley, Washington. Reach 5 of Hansen Creek is located near the confluence

with Red Creek, bounded by State Route (SR) 20 to the north and Minkler Road to the south.

Hansen Creek is a tributary of the Skagit River and is situated within Washington State Water

Resources Inventory Area (WRIA) 3. Figure 1 provides a vicinity map for the project area.

Stakeholders

Several stakeholders are involved in restoring the channel, floodplain, and wetland habitat of

Reach 5 of Hansen Creek.

Skagit County Public Works is spearheading the majority of the design efforts, on behalf of

Skagit County.

The Skagit River System Cooperative (SRSC, often referred to as the “COOP”), has a vested

interest in restoring ecosystem processes in the Skagit River system, on behalf of the

Swinomish Indian Tribal Community, and has spearheaded the property acquisition efforts

for siting the Hansen Creek Reach 5 restoration projects.

The Upper Skagit Indian Tribe (USIT) also has a stake in restoring ecosystem processes in the

Skagit River system, and spearheaded the 2009 alluvial fan and wetland restoration project

within Reaches 3 and 4 of Hansen Creek as well as several projects to improve fish passage

and habitat along Red Creek. USIT also monitors fish and wildlife habitat use for Hansen Creek

and Red Creek.

The Skagit Fisheries Enhancement Group (SFEG) nonprofit organization is supporting

revegetation efforts within the Hansen Creek Reach 5 Restoration project area.

The Skagit Watershed Council is the organization of community partnership to which the

aforementioned stakeholders, including many others not specifically listed here, belong and

which coordinates salmon recovery planning efforts to promote sustainable salmon fisheries in

the Skagit Watershed.

The Washington State Department of Fish and Wildlife (WDFW) is the regulatory agency

that promotes self-sustaining alternatives to dredging for managing sedimentation problems

and restoring aquatic habitat. WDFW does so through grant funding and regulatory permit

review of projects requiring Hydraulic Project Approval (HPA) permits.

The National Marine Fisheries Service (NMFS), of the National Oceanic and Atmospheric

Administration (NOAA), is the federal agency responsible for the stewardship and

Skagit River

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Minkler Road

Old Oxbow Channel

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Figure 1. Vicinity Map for the Hansen Creek Reach 5 Restoration Project Area.

May 2013


management of salmon species and their habitat. NMFS is responsible for implementing the

Endangered Species Act, including the listing of salmon species as “threatened” or

“endangered” as well as the designation of Critical Habitat for these species.

Agricultural landowners in the project vicinity also have a stake in the project in relation to

effects on flooding of their lands and the conversion of potentially productive farmland to

another use of the land at the project area.

Utility companies, including Williams Northwest, Cascade Natural Gas, and the Bonneville

Power Administration, all have utility lines that cross a portion of the project area.

Project Goals

The overarching project goals include the following:

Improving and expanding salmonid habitat

Rehabilitating hydraulic and geomorphic processes

Restoring hydrologic connectivity between Hansen Creek, its floodplain, and adjacent

wetlands

Previous Studies and Projects

The development of the Hansen Creek Reach 5 Restoration project has been heavily

influenced by previous planning efforts and projects, the most significant of which are noted

here.

Hansen Creek Watershed Management Plan

In 2002, with early salmon recovery funding from the State (99-1647), Skagit County

sponsored the development of the Hansen Creek Watershed Management Plan (WMP) (Miller

2002). Several restoration projects originally identified by the WMP have since been

implemented. Log structures were installed within Reach 2 of Hansen Creek in 2007 to

provide roughness and trap sediment. In 2009, a large wetland and alluvial fan restoration

project, the Hansen Creek Alluvial Fan and Wetland Restoration project, was completed along

Reaches 3 and 4 (Herrera 2007).

The WMP was unable to identify a preferred alternative for Reach 5 because consensus on the

best course of action could not be reached among the private landowners. Nonetheless, the

series of Reach 5 channel restoration and flood mitigation projects discussed in this study

were developed to be consistent with goals established in the WMP, including reach-wide

improvements to fish habitat, sedimentation, and flooding problems, as well as to have

process-based integration with the restoration projects already constructed.

Hansen Creek Alluvial Fan and Wetland Restoration Project

As previously stated, the Hansen Creek Alluvial Fan and Wetland Restoration project was

constructed in 2009, sponsored by USIT with assistance from Skagit County, as well as several

May 2013


state and federal agencies’ grant and permitting programs. The project succeeded in

rehabilitating Reaches 3 and 4 to emulate their natural historic wetland and alluvial fan

functions, as originally recommended in the Hansen Creek Watershed Management Plan

(Miller 2002). The project area spanned 140 acres, and involved the following key elements:

Rehabilitation of 87 acres of riverine wetland

The removal of 60 acres of invasive reed canarygrass

The removal of 12 acres of invasive Himalayan blackberry

The removal of approximately 200,000 cubic yards of soils to notch and remove

confining levees, to provide storage for sediment deposition in the alluvial fan, and to

re-grade the alluvial fan and wetland area to drain toward the creek outlet and not

increase flooding in adjacent properties

The installation of 302 log structures to provide habitat complexity and grade control

in the main channel to encourage strategic channel avulsions into the floodplain

The installation of 105,000 native plants to enhance riparian and floodplain habitat

and reestablish riparian forest

As expected, the project has also had a profound influence on watershed geomorphic and

hydrologic processes as well as ecosystem functions. Perhaps most relevant to Reach 5, the

reactivated alluvial fan and wetland system now helps to regulate the flow of bedload and

suspended sediment as well as flood flows downstream, thus allowing Reach 5 to approximate

a better balance between the sediment supplied to the reach and sediment transport capacity

of the reach. The project impacts on the existing and pre-project conditions for Reach 5 are

discussed in more detail in the Existing Conditions section below.

May 2013


EXISTING CONDITIONS

Reach 5 extends approximately 6,540 feet in length, from SR 20 at the north end to Minkler

Road. This reach has been affected by historic hydromodifications and ongoing dredging

activities. These activities have resulted in a straightened channel with simplified physical

habitat and levees composed of dredge spoils that isolate the channel from its surrounding

floodplain. The Hansen Creek Reach 5 floodplain includes the confluence of Hansen Creek and

Red Creek.

Land Use

Reach 5 is surrounded by private properties dominated by agricultural land use practices

including farming and ranching, that have been in place since the 1940s. The Washington

State Department of Transportation (WSDOT) operates and maintains SR 20 at the northern

boundary of the reach. Immediately south (downstream) of SR 20, Hansen Creek intersects

the Cascade Trail, a regional bike and pedestrian trail that occupies the old railroad grade

that parallels SR 20. The upper watershed, including Lyman Hill, has been logged since the

early to mid-1900s and continues to support logging practices today. Residential development

of the upper watershed has increased since the 1980s, yet less than 1 percent of the Hansen

Creek watershed contributing to Reach 5 is covered by impervious surfaces (Herrera 2007).

Geomorphology

A field investigation of Hansen Creek Reach 5 and Reach 4 (which is the lower alluvial fan

area of this creek) was conducted by Herrera geomorphologists on April 28, 2010. The field

investigation included general geomorphic mapping, reach classification, and an evaluation

of sediment transport conditions, including pebble counts to qualify the sediment size

distribution.

The general gradient of Reach 5 is to the southwest, but the historical piling of dredge spoils

along the channel banks, and especially along the right bank downstream of SR 20, has

created an artificial ridge that significantly affects flow patterns along the natural southwest

gradient of the floodplain. The existing Hansen Creek channel is highly confined with leveed

banks. The historical straightening and dredging of Reach 5 has resulted in the channel

exhibiting plane-bed morphology. However, increased sediment loading from headwater

landslides and from upstream incision through the alluvial fan has historically exceeded the

transport capacity of the reach. As a result, Reach 5 had become a depositional reach,

requiring more frequent dredging to prevent flooding.

In order to understand the evolution Reach 5 has experienced over time, particularly that

resulting from the implementation of the Hansen Creek Alluvial Fan and Wetland Restoration

project (Reaches 3 and 4), a comparison between sediment conditions in Reaches 5 and 4

over time was warranted.

May 2013


Both surface and subsurface pebble counts were conducted during the April 2010 field

investigation to characterize potential bed armoring, to describe the bedload composition,

and to make inferences about the balance between sediment supply and sediment transport

capacity. The Reach 5 pebble counts were collected upstream of the Red Creek confluence.

The Reach 4 pebble counts were collected in the historical Reach 4 channel, approximately

100 feet upstream of the confluence with the east avulsion channel. The channel bed armor

ratio was calculated as a ratio of the surface median sediment size to the subsurface median

sediment size. An armor ratio greater than 1 would indicate the presence of an armor layer

coarser than the subsurface. Armoring is prevalent in mixed sediment sizes when the ability

of a river to transport sediment (transport capacity) exceeds the supply of various sediment

sizes. Table 1 summarizes the sediment size distribution and the armor ratio results for each

sample, and references the 2007 results (Herrera 2007) obtained prior to the Alluvial Fan

and Wetland Restoration project for comparison. Graphs of the pebble count results are in

Appendix B.

Table 1. Pebble Count Results from the Field Investigation.

Reach Year

Surface Sediment Size (mm) Subsurface Sediment Size (mm) Armoring

Ratio # Sand D16 D50 D84 D90 # Sand D16 D50 D84 D90

5 2007 9 7 15 30 38 31 5 11 23 27 1.33

5 2010 5 5 9 15 19 15 5 10 20 24 0.86

4 2007 8 8 14 29 33 21 5 9 9 21 1.61

4 2010 40 6 8 11 13 30 5 8 13 15 0.94

As can be seen in Table 1, sediment sampling in 2007 found the median gravel size in Reach 5

to be about the same as that in Reach 4 (Herrera 2007). The results for Reaches 4 and 5

were comparable again in 2010; however, unlike the 2007 results, the surface sediment size

significantly decreased for both reaches in 2010, and the subsurface sediment size remained

about the same between 2007 and 2010. Significant sediment-transporting events were

experienced during the winter of 2009/2010 after the Alluvial Fan and Wetland Restoration

project was completed (Rich et al. 2011; Skagit County 2012; Mostrenko et al. 2011). Thus,

the 2010 surface pebble count results indicate that the bedload sediment size of both

Reaches 5 and 4 appear to be becoming finer due to coarser bedload deposits occurring

further upstream in Reach 3. This is because the restored alluvial fan processes created

sediment storage capacity affecting the broader watershed.

The armor ratios for Reaches 4 and 5 in 2010 were very close to 1, indicating a potentially

better balance between sediment supply and sediment transport capacity in those reaches

than existed in 2007, when the armor ratios reflected supply-limited conditions. Skagit

County has been monitoring the channel geometry of Reach 5 of Hansen Creek since 2006,

when the channel was last dredged. Three cross-sections are surveyed annually including

one cross-section immediately downstream of the trail bridge, one near the confluence with

Red Creek, and a third upstream of the Breier Lane Bridge before Hansen Creek makes a

significant turn to the west. Figure 2 provides a comparison of the available cross-section

survey information for one of these cross-section locations, near the confluence with Red

May 2013


Creek (Skagit County 2011, Skagit County 2012). As the figure indicates, since the 2006

dredging, and prior to the completion of the Alluvial Fan and Wetland Restoration project

affecting Reaches 3 and 4 in 2009, the monitored cross-sections showed between 2.5 to

3 feet of sediment aggradation in the channel. Yet after construction of the Reaches 3 and 4

project, the Reach 5 channel bed has remained stable even after several significant floods

deposited more than the average annual bedload in the Reach 3 and 4 project area (Skagit

County 2012; Rich et al. 2011). Additional graphics presenting the cross-section monitoring

results between 2006 and 2012 are included in Appendix B.

Figure 2. Comparison of Monitoring Cross-Sections for Hansen Creek Reach 5, near the

Confluence with Red Creek.

These cross-section observations, combined with the observations of minor erosion of older

Reach 5 gravel bar deposits during the geomorphic field reconnaissance of April 2010,

indicate that the effect of the reactivated alluvial fan in regulating the sediment supply to

downstream reaches has resulted in a channel (Reach 5) that is currently approximating a

state of equilibrium between sediment supply and sediment transport capacity. This trend is

likely to persist into the future as long as the alluvial fan (Reach 3) and adjacent wetlands

(Reach 4) have capacity to trap bedload and provide some flood attenuation. Even though

significant volumes of suspended sediment deposits have also been observed within the

May 2013


reactivated alluvial fan, it is assumed that suspended sediment is still moving through the

existing confined Reach 5 channel since there is no evidence of increased sand deposition.

A Syvitski analysis (Syvitski et al. 2005) was completed in order to estimate the average

annual sediment (bedload and suspended load) inputs to the Hansen Creek and Red Creek

alluvial fans, and to compare the results with the patterns of sediment deposition observed

during the field reconnaissance to be reaching the project area. Project alternatives that

alter the channel geometry and the depositional environment of the reach would need to

account for the likelihood of increased deposition of suspended load within the project, and

acknowledge that the reach would be starved of coarse bedload sediment inputs until the

alluvial fan reaches its sediment storage capacity and approaches an equilibrium state. The

Syvitski analysis provides an estimation of the potential annual average sediment flux volumes

to the Reach 5 project area that should be considered in design development.

The Syvitski sediment flux analysis uses an empirical model of long-term, average annual

sediment flux in coastal streams based on basin area, maximum elevation, mean elevation,

precipitation, mean annual temperature, and latitude (Syvitski et al. 2005). GIS spatial

analyst tools were used to calculate the area weighted basin elevations for Hansen and Red

creeks. Annual air temperature data from the Hansen Creek flow gauge #03J100 maintained

by the Washington Department of Ecology were averaged and compared to the annual average

air temperature recorded by the NOAA weather station #127 for Sedro Woolley. The results of

the sediment flux analysis completed for the project using Syvitsky et al. (2005) are provided

in Table 2. The total average annual sediment flux (including bedload and suspended loads)

for Hansen Creek and Red Creek were estimated to be 39,700 cubic yards per year and

15,700 cubic yards per year, respectively.

Table 2. Hansen Creek and Red Creek Sediment Flux Analysis Results (Syvitsky et al. 2005).

Basin

Basin Area (km

2)

Total Annual Average

Sediment Input

(tons/year)


Sediment Input

(cy/year)


Bedload Flux (tons/year)


Bedload Flux (cy/year) Notes

Hansen 19.41 51,500 39,700 5,200 4,000 Bedload not observed to be reaching Hansen Reach 5

Red 6.55 20,400 15,700 2,100 1,600 Neither bedload nor suspended load appears to be

reaching Hansen Reach 5

km2 = square kilometers

tons/year = tons per year

cy/year = cubic yards per year

Hydrologic Patterns and Flooding

As previously discussed, the Hansen Creek Reach 5 floodplain includes the confluence of

Hansen Creek and Red Creek. The Hansen Creek watershed accounts for approximately

75 percent of the Reach 5 hydrology, and Red Creek accounts for approximately 25 percent.

May 2013


The Reach 5 floodplain is delineated upstream by SR 20 (north) and downstream by Minkler

Road (south). The Reach 5 floodplain is relatively flat with widespread shallow flooding, and

complex flow patterns. The general gradient of Reach 5 is to the southwest, but historical

hydromodifications have resulted in an artificial ridge significantly affecting flow patterns

along the natural southwest gradient of the floodplain. The existing Hansen Creek channel

is highly confined with leveed banks that only overtop during relatively high flood events,

significantly higher than the expected 1.5-year to 2-year recurrence “bankfull” flood event

for the Hansen Creek watershed. Decades of topographic modifications to the floodplain

combined with overbank deposition have resulted in a concave shaped floodplain. As such,

overbank floodwaters are typically isolated from the Hansen Creek channel until they re-

converge at the downstream Minkler Road crossings. Hence, floodplain connectivity from a

habitat perspective is significantly impaired.

The existing Red Creek channel has a lower gradient than Hansen Creek with lower banks.

Deposition in Hansen Creek has an overwhelming impact on the effective gradient of Red

Creek, which results in frequent overbank flows into the upstream Red Creek floodplain. In

fact, the difference in the bed elevations between the two channels combined with the low

Red Creek banks results in a significant portion (upwards of 25 percent) of the Hansen Creek

floodwaters backwatering up into the Red Creek floodplain and draining to the southeast

through agricultural fields (Good and Houston properties). These floodwaters drain to a

6-foot-diameter culvert under Minkler Road and eventually drain to the Skagit River through a

series of agricultural swales. This loss of hydraulic connectivity for small frequent events is a

significant impact to salmonid habitat and the natural geomorphology of the Hansen Creek

and Red Creek channels.

Habitat

The altered geomorphic and hydrologic conditions described in the previous sections limit

habitat creation and maintenance processes, and thereby salmonid fish presence in Reach 5.

The riparian corridor adjacent to Reach 5 of Hansen Creek is fairly narrow, with only about

10 to 20 feet of red alder and black cottonwood trees on each bank, and agricultural fields

or pastures occupying the majority of the floodplain. Within the narrow riparian corridor,

Himalayan blackberry outcompetes most native shrub species below the tree canopy. Prior

to any restoration activities, Red Creek had little to no riparian habitat in Reach 5. Recent

plantings through the Conservation Reserve Enhancement Program (CREP) program initiated

by the property owner (Martinez) and the SRSC have established a new diverse riparian

corridor for Red Creek.

From the fish habitat perspective, Reach 5 is characterized by a lack of channel complexity,

and very little instream and off-channel salmonid rearing habitats. The reach lacks large

woody debris and, therefore, is mostly devoid of pool habitat (both for adult holding as well

as for juvenile rearing). In addition, the reach lacks functional riparian vegetation, thus

limiting the potential for future recruitment of large woody debris. Salmonid spawning-size

gravel is present throughout the reach, though it is embedded with sand in some areas.

Confinement of about 80 percent of this reach by levees (mostly in the upper portion of this

reach) limits floodplain habitat connectivity. Under existing conditions, this reach provides

May 2013


spawning habitat, very limited rearing habitat, and is primarily a transportation corridor for

returning adults (on their way to spawn in Reach 2) and out-migrating juvenile salmonids

(originating in Reaches 2, 3, and 4). Historical map analyses and the gradient of the

reach suggest that the entire reach would have supported primarily rearing habitat with

predominately low gradient and highly connected floodplain forested wetlands (Collins 2000;

Collins and Sheik 2002; SRSC and WDFW 2005).

Cultural Resources

A cultural resources investigation was undertaken in 2011 during project planning for the

near-term and medium-term projects (Rosario Archaeology 2011). The investigation sought to

evaluate the potential cultural resources implications of the near-term alternative project

involving channel excavation and floodplain grading as well as riparian plantings planned

for within the former Knudsen property at the time. Thus, the geographic limits of the

investigation were focused on the left bank (east) floodplain. Archaeological investigations

have not yet been completed for the majority of the right bank (west) floodplain where the

medium-term and long-term projects are being planned.

The 2011 archaeological investigation did not identify any pre‐contact or historic cultural

resources within the near-term alternative Reach 5 project area (Rosario Archaeology 2011).

In their 2011 investigation, Rosario Archaeology recommended that a Determination of

No Historic Properties Affected be presented to the Washington State Historic Preservation

Officer for the proposed project with one caveat. The report recommended the avoidance

of two 8-meter-diameter areas within the central and southern portions of the east side of

the project area by ground-disturbing project activities. The archaeological investigation

discovered that those areas contained some features of unknown cultural affiliation and time

frame that were observable at the plow zone substratum interface. The areas were located

in the report, flagged for avoidance, and the report provided protocols to follow in the event

that cultural resources were inadvertently discovered during future project activities.

May 2013


HABITAT RESTORATION AND CONCEPTUAL PLAN

DEVELOPMENT

A conceptual plan for the Hansen Creek Reach 5 Restoration project was prepared; it includes

both restoration and flood mitigation actions. The development of the conceptual plan’s

project alternatives took into consideration the Skagit Chinook Recovery Plan (SRSC and

WDFW 2005) and was guided by the goals identified in the Hansen Creek Watershed

Management Plan (Miller 2002). It was further guided by the process-based restoration

principles outlined by Beechie et al. (2010). Together, these goals and guiding principles

intend to reestablish self-sustaining physical, chemical, and biological processes affecting

river and floodplain ecosystems to the maximum extent feasible while respecting adjacent

land uses, and without exacerbating flooding problems.

Planning Process

The concepts and preferred alternatives for the project were developed following close

coordination among Herrera, the County, and the stakeholders identified previously in this

report. The County hosted a series of five stakeholder workshops that each incorporated the

following key elements, particular to the stage of project development and planning:

Identification of specific project objectives

Outline of current project opportunities and constraints

Review of geomorphic and hydraulic analysis results

Identification of preferred alternative configurations for further analysis or design

development

Clarification of priorities and responsibilities for the next stage of analysis and design

development

The planning process included a phased approach given the size, scope, project costs, and

extent of potentially affected properties. The planning process was parsed into near-term,

medium-term, and long-term potential projects based on realistic project costs, available

project funding, permit requirements, and landowner coordination. Near-term project

alternatives were based on restoration work on the Swinomish property (formerly the Knudsen

property) and on County property to improve floodplain connectivity but also to alleviate

immediate flood issues. Near-term alternatives included those projects deemed potentially

feasible to construct within 1 to 2 years. Medium- and long-term project alternatives

were more focused on restoration efforts that required significant easements or property

acquisition within the limits of Reach 5 (south of SR 20 and north of Minkler Road). Long-term

alternatives referred to more holistic Reach 5 restoration efforts with respect to hydraulic

May 2013


and ecologic connectivity with the upstream subreach (north of SR 20) and downstream

subreach (south of Minkler Road). Long-term alternatives also include off-channel wetland

opportunities that would improve available off-channel juvenile rearing habitat.

A detailed two-dimensional hydraulic model of the Reach 5 floodplain was developed using

the FLO-2D software program (FLO-2D 2009) to assist in the planning and assessment of the

restoration alternatives. FLO-2D is a two-dimensional, finite-difference, dynamic flood

routing model that is well suited for application to conditions in the project reach. It provides

water surface elevation and velocity output based on an input flood flow hydrograph. FLO-2D

is approved by the Federal Emergency Management Agency for both riverine studies and

unconfined alluvial fans. The hydraulic model was initially developed as a screening tool

to assess the complex lateral floodplain flows and the potential hydraulic effects of the

alternatives evaluated in the workshops. The hydraulic model was modified and refined based

on the outcomes and feedback from the workshops as discussed in later sections of this

report.

Property Acquisition, Easements, and Utilities Coordination

At the onset of the project, the entire Reach 5 channel corridor was surrounded by private

properties, aside from road and trail crossings. Although one of the properties along Hansen

Creek, the former Knudsen property, has since been purchased by the Swinomish Indian

Tribe (through SRSC) to support the project’s restoration activities, most of these private

properties are farms or ranches that have been in operation for at least a generation,

and sometimes two or three generations. As such, many of these private property owners

supported the Hansen Creek sub-flood control zone district that previously handled the

frequent dredging of Hansen Creek to reduce flood impacts. The Hansen Creek sub-flood

control zone district was recently dissolved, and the Skagit County Drainage Utility assumed

responsibility for addressing flood concerns in the area. Despite the wishes of the private

landowners, the County has been hesitant to allow dredging of creeks like Hansen, due to the

negative habitat impacts and difficulty in obtaining permits to do so.

To exacerbate further potential strain between the Reach 5 project proponents and private

landowners, there has been a growing regional resentment by farmers and ranchers regarding

the conversion of agricultural land to a natural condition for restoration purposes. The

project would need to tread carefully across this issue, knowing that any project alternative

brought to construction would require property acquisition or restoration easements.

Similarly, there are several regional utilities that cross the project corridor, including regional

buried gas and power transmission lines. Various project alternatives would possibly involve

perimeter protection of these utilities using features such as perimeter berms, but could also

involve utility relocation, which may provide unique project opportunities, but which would

likely also be accompanied by a hefty price tag, and elongated planning and construction

schedule.

The outreach to both private landowners and utility companies was handled by Skagit County

Public Works. Both parties were encouraged to participate in project workshops. Private

May 2013


landowners frequently attended, whereas representatives from the utility companies met

with Skagit County independently from the workshops.

Workshops

Although project communication and coordination was important throughout the project

planning process, five primary workshops represented unique milestone iterations of the

conceptual plan development. These workshops were held on May 12, 2010; November 19,

2010; June 20, 2011; September 27, 2011; and December 13, 2012. Table 3 outlines the

specific objectives, description, results, conclusions, and project significance of each of these

workshops. A brief summary of the workshop outcomes follows.

Workshop #1

The November 19, 2010, workshop provided the first opportunity to gather the regulatory

stakeholders together to identify project goals, opportunities, and constraints. Attendees

included representatives from Skagit County, Herrera, SRSC, USIT, SFEG, Skagit Watershed

Council, and WDFW.

A detailed topographic surface was presented at the workshop utilizing lidar, an old survey of

the Red Creek channel and floodplain in the Martinez property, and new bathymetric survey

in the Hansen Creek Reach 5 channel. Channel profiles and cross-sections were used to

discuss drainage trends and issues. The primary issue discussed was related to the altered

concave nature of the floodplain and the fact that the current channel alignment followed an

artificial ridge though the floodplain. It was determined that the alternatives could be

generalized into three categories based on topography and property boundaries:

Scenario 1: alternatives east of the current channel alignment

Scenario 2: alternatives west of the current channel alignment

Scenario 3: alternatives using both sides of the floodplain

Extents and goals for the hydraulic modeling were established based on the extent of the

Reach 5 restoration project objectives. The hydraulic model was expected to be required for

the assessment of the alternatives for future workshops.

Workshop #2

The November 19, 2010, workshop was focused on near-term project development given the

opportunities for land acquisition at the Knudsen (now Swinomish) property and the concerns

for alleviating flooding problems of properties adjacent to the Hansen Creek and Red Creek

confluence. The workshop was hosted by Skagit County Public Works and attended by Skagit

County Planning and Development, USIT, WDFW, NMFS, SRSC, Herrera, and some of the

private landowners. Initial hydraulic analysis results discovered that a large portion of the

Hansen Creek floodwaters backwatered into Red Creek and flowed over agricultural fields

to the south and southeast. The results suggested that the Hansen Creek and Red Creek

confluence location was likely adjusted many decades ago and was not located in a

May 2013


geomorphically suitable location. Consensus in the workshop was that the confluence

should be shifted downstream to improve fish passage and the continuity of hydrologic and

geomorphic processes through the reach. The property owners advocated for Hansen Creek

dredging, but a review of the channel monitoring cross-sections indicated that Reach 5 of

Hansen Creek was no longer aggrading. Initial hydraulic modeling indicated that a realigned

Red Creek channel and a relocated Hansen Creek and Red Creek confluence would improve

flooding for the properties upstream and east of the confluence but increase flooding for the

downstream properties along Hansen Creek. However, several property owners felt the model

results reflected underestimated flows for Red Creek. Additional subbasin hydrologic revisions

and design revisions of the near-term alternative were determined to be necessary to ensure

additional flood attenuation could accompany conveyance improvements so that private

properties and roadways would not experience increased flooding after project construction.

With flow-monitoring assistance from USIT and subbasin boundary field truthing from Skagit

County Public Works and Herrera, the subbasin boundaries and portions of the total

hydrologic inputs from Red Creek and Hansen Creek, respectively, were updated.

Workshop #3

Two workshops were held at Skagit County offices on June 20, 2011. They are collectively

referred to as “Workshop #3” in this report. One meeting was held in the morning to convene

the regulatory stakeholders working on and supporting the project, including Skagit County

Public Works, Skagit County Planning and Development, USIT, WDFW, NMFS, SRSC, and

Herrera. Another meeting was held in the afternoon among Skagit County Public Works,

Herrera, and the private property owners representing the Good, Sorenson, and White

properties. Both of these meetings were focused on the near-term project development

within the properties that were likely to be acquired or obtain easements, although the

morning meeting emphasized habitat restoration, and the afternoon meeting emphasized

ameliorating flood problems.

At the time of the meeting, SRSC was about to close on the purchase of the Knudsen property

and was working closely with the Martinez property towards a restoration easement and

to retire a significant portion of the cattle pasture east of Hansen Creek through the

CREP. Herrera presented updated hydraulic modeling results for incremental changes to

combinations of the near-term (east floodplain) and long-term (west floodplain) alternatives.

The modeling results presented reflected the updated subbasin delineations and hydrologic

inputs determined to be necessary during the previous workshop.

The model results did not pinpoint a perfect near-term alternative. When near-term project

work in the east floodplain would reduce flooding for the properties to the east and

southeast, downstream properties to the west would experience increased flows. The

opposite effect also appeared to be true, yet the model results appeared close to achieving

project results that could be permitted by regulatory agencies. As a result, Herrera was

instructed to continue refining the near-term project elements in the model while continuing

to develop the core near-term alternative project alternatives into design.

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Table 3. Summary of Workshop Objectives and Conclusions.

Workshop/Iteration Date Objectives Description Results/Conclusions Significance and next steps

May 12, 2010 Identify project goals, opportunities, and constraints

Goals emphasized cooperation and finding mutual benefits for fish and neighboring property owners.

Knudsen was the only identified property owner that was known to be possibly amenable to potential easement or sale (opportunity)

Focus near term restoration efforts on Knudsen property

Constraints included a concave shaped floodplain Restoration efforts would likely result in the isolation of the opposite floodplain

Include separate alternatives for each side of the floodplain

Constraints to the east bank included only 2 property owners, but constraints to the west included 6 or more property owners.

Restoration and hydraulic reconnection to the west was more geomorphically feasible, but included significantly more property easements

or acquisition.

Initiate restoration concepts to both the east and west with emphasis on the east for the short term

and medium term project due to less property acquisition complication

November 19, 2010 Discuss restoration project opportunities and constraints

Knudsen property owner amenable to potential easement or sale for floodplain/wetland restoration project.

Near-term project alternatives focused within Knudsen property (east floodplain) providing opportunity for realigning Red Creek for a more

geomorphically natural equilibrium gradient and confluence with Hansen Creek

Emphasis on near-term restoration opportunities within Knudsen property and on east floodplain where the Red/Hansen Creek confluence could

be improved.

Review geomorphic analysis results for baseline and initial alternative

conditions

Field Observations confirm gravel bedload is depositing in reactivated wetland and alluvial fan (Reaches 3 and 4); Monitoring cross-sections

indicate a stable or slightly degrading channel in Reach 5.

Reactivation of the alluvial fan has reduced Reach 5 aggradation problem; suspended sediment likely continuing to move through existing Reach 5

channel

Reduced pressure to dredge Reach 5 Hansen below the equilibrium profile for flood reduction

benefits; Side channel design will need to account for suspended sediment (keeping it

suspended or allowing it to deposit strategically).

Review hydraulic analysis results for baseline and initial alternative

conditions

Properties within the Hansen Creek floodplain downstream of SR 20 are influenced by the Skagit River's 100-year floodplain (FEMA 1989) and are

unlikely to receive significant 100-year flood benefits.

Near-term project including Red Creek realignment through east floodplain significantly improves flooding for upstream and east floodplain properties but increases flood impacts to downstream and west floodplain properties;

Property owners suggest model underestimates Red Creek flows.

Flow monitoring and subbasin verification needed to confirm hydrologic inputs to hydraulic

model are accurate. More analysis needed before implementing a restoration project that

could potentially exacerbate flooding somewhere in the floodplain.

Identify preferred channel restoration and flood mitigation near-term and

long-term options to take into further analysis and design development

Pressure from agricultural landowners to dredge Reach 5 of Hansen Creek as the recently dissolved flood control district used to do every few

years over the last 60 years; Watershed management Plan and other watershed stakeholders hope to restore natural geomorphic and

biological processes and promote a self-sustaining channel and floodplain that would not require ongoing dredging or maintenance

More hydraulic analysis needed to verify near-term and long-term alternatives do not exacerbate flooding before completing alternative design

development.

More hydraulic analysis needed to verify near-term and long-term alternatives do not

exacerbate flooding before completing alternative design development; SFEG to move forward with

proposed near-term Red Creek channel realignment for delineation of near-term riparian

revegetation areas

June 20, 2011 - morning agency

workshop

Discuss restoration project opportunities and constraints

SRSC planning to purchase Knudsen property and is working with Martinez property for a restoration easement and to retire a significant

portion of the cattle pasture east of Hansen Creek through the Conservation Reserve Enhancement Program (CREP); USIT and SRSC recommend consideration of alternatives with multiple drainage pathways

for Red and Hansen Creeks to Skagit River

Near-term alternatives remain focused on the Red and Hansen Creek confluence area and the left-bank floodplain where property acquisition is

likely to occur

Significantly more investment and time would be needed to acquire the properties and easements necessary to restore multiple drainage pathways

to the Skagit River; scope determined beyond ability of this analysis

May 2013


Table 3 (continued). Summary of Workshop Objectives and Conclusions.

Workshop/Iteration Date Objectives Description Results/Conclusions Significance and next steps

Review updated hydraulic analysis results for baseline and initial

alternative conditions

Herrera updated the subbasin boundaries and hydrologic inputs to the hydraulic model using ground-truthing, and flow measurements and

observations from USIT and Skagit County

Herrera presented model results showing incremental flood impacts of individual changes to near-term alternative components, including berm

elevations, levee notching, side channel alignments, and the location of the Red and Hansen Creek confluence.

Model results appear close to being refined for avoiding flood impacts; Herrera plans to provide

additional modeling analysis to see how additional changes to the berm elevation or notch

locations could eliminate any flood increases

Identify preferred combinations of near-term and long-term options for

flood mitigation and Reach 5 Hansen channel restoration work

Near-term alternatives had focused on work in the left-bank (east) floodplain, and long-term alternatives focused on the right bank (west)

floodplain

near-term hydraulic results indicate perimeter berms would be needed to prevent increased flooding of adjacent properties

Alternatives involving berms would require a shoreline permit, and a 6-month local permit

review process

June 20, 2011 - afternoon property owner workshop

Discuss restoration project opportunities and constraints

SRSC planning to purchase Knudsen property and is working with Martinez property for a restoration easement and to retire a significant

portion of the cattle pasture east of Hansen Creek through the Conservation Reserve Enhancement Program (CREP)

Carl Sorenson offers to discuss property acquisition possibilities with neighbors, including Boettcher

Review updated hydraulic analysis results for baseline and initial

alternative conditions

Herrera updated the subbasin boundaries and hydrologic inputs to the hydraulic model using ground truthing, and flow measurements and

observations from USIT and Skagit County

Property owners indicate Minkler Road is a flow/sediment constriction Herrera will continue to adjust the near-term model results in order to show flood

improvements vs. impacts

Identify preferred combinations of near-term and long-term options for

flood mitigation and Reach 5 Hansen channel restoration work

Near-term alternatives had focused on work in the left-bank (east) floodplain, and long-term alternatives focused on the right bank (west)

floodplain

Property owners prefer a short-term alternative that includes dredging; property owners acknowledge the natural drainage pathway for Hansen

flood flows is toward the west (right-bank) floodplain

Herrera will develop altered long-term model alternatives that consider property acquisition and project work within the west (right-bank)

floodplain

September 27, 2011 Discuss restoration project opportunities and constraints

SRSC owns former Knudsen property and is collaborating with Martinez property for a 50-acre restoration easement (including the CREP area);

Riparian areas within near-term project vicinity already replanted by SFEG; SRSC completed a wetland survey and cultural resources/ archaeological

survey of the former Knudsen property

Herrera to proceed with design development and draft drawings for a near-term habitat

improvement project on the former Knudsen property and possibly including drainage

improvements along Minkler.

Review updated hydraulic analysis results for alternative conditions

Several alternatives (8, 9, 10) were thrown out because they resulted in significant downstream flooding impacts; model results do indicate some

channel constrictions in the profile upstream of Minkler Road

Alternative 11E represented the alternative with the most potential; if the constrictions in the channel upstream of Minkler Road were removed, the

model results would likely show that Minkler Road is a hydraulic constriction.

Herrera to proceed with model evaluation of drainage improvements along Minkler Road and

at the Minkler/Hansen crossing; Herrera to evaluate refined medium-term projects that

incorporate work in the west floodplain.

December 13, 2012 Discuss restoration project opportunities and constraints

Soldate and Boettcher properties interested in selling; SRSC is communicating with PSE and utility companies that have easements through properties; Nielsen, Burress, and White properties have also

expressed interest in selling

Medium-term projects involving channel work in the west floodplain have increased likelihood and viability with Nielsen property; Herrera to evaluate

two Hansen channel realignment alternatives dependent on whether relocation of the gas line (and thus utilization of the Soldate and Burress

properties) are possible.

Possibilities for additional property acquisition and easements open door for the most natural

and process-based alternative. Perimeter berms will likely not be necessary. Herrera begins initial concept development for a revised medium-term

project alternative.

May 2013


Workshop #4

The September 27, 2011, workshop was a telephone conference, but represented a key

milestone iteration of the model results and design progress to support the development of

the near-term project. Workshop #4 was attended by Skagit County Public Works, SRSC, and

Herrera. At the time of this telephone conference, the hydraulic model analysis had assessed

over 18 model geometry iterations of the near-term design alternatives and 4 different model

geometry iterations of the long-term design alternatives. SRSC had completed a wetland

survey and cultural resources/archaeological survey of the former Knudsen property, and

SFEG and WDFW had sponsored the revegetation of specific riparian areas identified for

vegetative enhancement within the property.

Although the hydraulic model results for the nearly optimized near-term alternative reduced

flood depths on all properties, it also indicated there would be some local increases in

floodwater surface elevations along the Hansen Creek channel downstream. Skagit County

planned to inform and coordinate with the property owners in those areas. To compensate for

this localized flooding increase and to provide advanced flood control benefits for a medium-

term alternative, the County directed Herrera to develop designs for improved drainage

conveyance along Minkler Road and at the Minkler Road Crossing with Hansen Creek. The

drainage improvement design would accompany the habitat restoration design for the near-

term alternative project work in the east floodplain.

Subsequent to Workshop #4, it was determined that any near-term alternative focused on the

east floodplain was likely to be associated with some localized flooding increases somewhere

in the floodplain. Even with the drainage improvements along Minkler Road, which would

provide significantly greater flood improvements, the County decided to postpone further

design development of the habitat portions until after the near-term drainage improvements

could be implemented and the benefits realized by the community. As a result, the County

constructed only the near-term drainage improvements along Minkler Road, and not the

previously modeled floodplain channel and habitat improvements, in 2012.

Workshop #5

The December 13, 2012, workshop was also a telephone conference with Skagit County Public

Works, SRSC, and Herrera. Workshop #5 focused on the recent developments with potential

property acquisition from various landowners as well as new collaboration successes regarding

the potential relocation of significant utilities underlying the natural drainage pathway for

Hansen Creek in the west floodplain. This renewed collaboration brought light to a medium-

term habitat project that had the potential to reconnect Hansen Creek with its surrounding

wetlands and floodplain. The project would also restore natural geomorphic and hydrologic

processes through the reach by allowing Hansen Creek to follow the natural floodplain

gradient and, at the same time, alleviate the backwater problem at the former confluence

with Red Creek.

Workshop Conclusions

In summary, the workshops were productive because they provided unique opportunities for

the various stakeholders to communicate and collaborate on conceptual project development.

May 2013


They also provided a means of documenting important milestones in the project’s design

development process. For Reach 5, the workshop outcomes that had the greatest bearing on

future restoration project design development were as follows:

Channel and floodplain restoration opportunities in the western floodplain have the

greatest potential to rehabilitate natural geomorphic and hydrologic processes to

serve as a framework for ecological habitat improvements without worsening flooding

and sedimentation problems for private landowners.

The natural gradient of the Hansen Creek floodplain was to the west floodplain.

Forcing channel realignment within the east floodplain would have required setback

berms and floodwater manipulation in order to achieve increased aquatic habitat area

without exacerbating flooding problems for private landowners.

The current confluence between Red Creek and Hansen Creek does not support the

continuity of natural hydrologic and geomorphic processes. Therefore, it should be

relocated as far downstream as possible to be consistent with an equilibrium channel

profile and to maximize potential aquatic habitat area. Floodwater connectivity

should still be allowed between the two channels. This would enable multiple

floodplain channels to develop, given a low probability of Hansen Creek avulsing into

its former channel, because of the natural floodplain gradient to the west. Similarly,

there is a low probability that the primary Red Creek channel would have the stream

energy to avulse into a realigned Hansen Creek channel in the west floodplain.

May 2013


PRELIMINARY ANALYSES

The following sections provide a brief summary of some of the preliminary analyses that

have been completed in support of the medium-term and long-term restoration projects for

Hansen Creek Reach 5. A comprehensive report summarizing the hydrologic, geomorphic, and

hydraulic analyses completed for these projects will be available later in 2013.

Hydrologic Updates

As described in the workshop section, communications with the property owners regarding

flood observations allowed for some important calibration of the modeling used for project

alternative analysis. The original Reach 5 models had been developed based on the previous

hydrologic and hydraulic information used for the Alluvial Fan and Wetland Restoration

project (Herrera 2007). Yet, both the subbasin boundaries and the proportion of the

Hansen/Red Creek watershed flow attributed to Red Creek were revised during the Hansen

Creek Reach 5 Restoration project.

During the 2010-2011 winter, USIT and SFEG conducted flow monitoring and both Skagit

County Public Works and Herrera completed field reconnaissance in order to verify

contributing subbasin areas. The contributing area for Red Creek was modified based on

these observations and by delineating the corresponding contributing areas using lidar

contours in GIS. It was determined that there was an additional 1.2 square miles of drainage

area contributing to the Red Creek subbasin that had previously been assumed to drain

toward the Coal Creek watershed (The next major creek watershed east of Red Creek). This

nearly doubled the size of the Red Creek subbasin to Hansen Creek and resulted in Red Creek

contributing approximately 25 percent of the total flow to Reach 5 of Hansen Creek. The

updated hydrologic inputs to be used in the FLO-2D modeling are outlined in Table 4.

Table 4. Flow Portion for Reach 5 of Hansen Creek Using Updated Contributing Basin Areas of 7.49mi2 for Hansen Creek and 2.53 mi2 for Red Creek.

Recurrence Interval (years)

Hansen Creek Flow (cfs)

Red Creek Flow (cfs)

100 698 235

50 644 217

25 578 195

10 495 167

5 413 139

2 314 106

cfs = cubic feet per second

May 2013


Geomorphic Considerations

The channel evolution process that has taken place within Reach 4 since the alluvial fan was

reactivated in 2009 provides a good example of what might be expected from reactivating

floodplain connectivity in Reach 5. Similar to Reach 4, the proposed Reach 5 restoration

design will also need to accommodate the altered sediment delivery patterns resulting from

the reactivated alluvial fan upstream. Removing (or notching) selected portions of the Hansen

Creek levee located along the right bank downstream of SR 20 will enable avulsions to the

realigned Hansen Creek channels in the west floodplain. It will also result in the shunting of

remaining sediment bedload and suspended load, first in the main channel and later in the

floodplain. This will take place as the encouragement of Hansen Creek flows toward the

west floodplain reduces stream energy to transport sediment in the main channel. Given the

probability that the fan (Reaches 3 and 4) will continue to trap the majority of the bedload

sediment for some time, it is likely that Reach 5 of Hansen Creek will be somewhat starved

of coarse bedload sediment(e.g., gravels). However, Hansen Creek is likely to have access to

adequate volumes of previously suspended and deposited sands to support the processes of

natural channel evolution (Simon and Rinaldi 2006).

Once Hansen Creek flow is introduced to the realigned floodplain channel, previously

suspended sands are likely to drop out of suspension and deposit because the channel gradient

will be significantly less than that of the existing Hansen Creek channel. The realigned Hansen

Creek channel will provide an initial preferential flow path for Hansen Creek, but, over time,

the creek flow will rework the deposited sands and develop self-forming shallow channels

within the overall floodway, similarly to what has occurred in Reach 3. The actual widths and

depths of these resulting low flow channels will be self-forming following moderate or greater

flood events, but it is likely that multiple perennial and ephemeral braided channels will

eventually develop within the broad, low-gradient floodplain. Test pit samples of the soil

material below the existing floodplain surface should be taken to enable further evaluation of

the likelihood of future floodplain channels to incise into the floodplain material as well as to

verify whether adequate alluvium source material is available on site or whether additional

gravel supplementation would be needed.

Log structures can be designed to provide localized physical habitat complexity, including

pool habitat, for juvenile salmonid species that occur in Hansen Creek. Log structures can

also be useful in slowing or even arresting channel incision by providing grade control and a

mechanism to retain sediment, lower stream energy, and increase water elevations to

promote reconnections between the stream and floodplain habitats. Reach 4 large woody

debris (LWD) and channel monitoring results can also be used in guiding the LWD placement

strategy for Reach 5. The Reach 3 and 4 restoration project installed LWD throughout the

floodplain to provide physical habitat complexity and to encourage sinuosity and diverse

microtopography in the event that avulsion channels accessed the floodplain prior to the

establishment of the project’s riparian plantings. The LWD monitoring results found that,

because the channel avulsions occurred before the riparian vegetation had a chance to

establish, many of the young plantings were lost as the channels carved new pathways and

migrated right into the rougher LWD structures, which were essential in encouraging sinuosity

(Rich et al. 2011; Mostrenko et al. 2011). The Reach 3 and 4 monitoring results suggest that

May 2013


revegetating the floodplain at least two years prior to introducing flow to the realigned

floodplain channels would better enable the floodplain vegetation to provide the habitat and

hydraulic complexity that would otherwise be offered by the LWD installed in the floodplain.

Providing roughness and complexity via vegetation, combined with microtopographic

variability (i.e., hummocks), will ensure that the geomorphic evolution of the site will be

more gradual, allowing LWD installations to be focused within the initial realigned floodplain

channels. Hence, the conceptual designs for the Reach 5 habitat restoration projects

(primarily the medium-term project) include complex log structures installed with higher

densities along the realigned Hansen Creek channels and with lower densities within the

floodplain.

In summary, the realigned Hansen Creek channel would be used to jump-start the channel

evolution process using a geometry based on the observed Reach 4 channel formation. If

desired and/or requested by regulatory agencies, the initial channel substrate could be

“dressed” with available salmonid spawning gravels, knowing that the reach is likely to be

somewhat starved of coarse bedload sediment and expecting that the log structures will serve

an important function in encouraging gravel retention and sorting. The channel realignment,

log installation, and floodplain replanting should occur at least 2 years before the notching of

the right bank levee in order to allow the replanted floodplain vegetation some time to

mature before being exposed to Hansen Creek flows.

Hydraulic Modeling

Hydraulic modeling was conducted to characterize the existing Reach 5 hydraulics and to

provide a tool for assessing the relative effects of floodplain restoration alternatives. A

wide variety of alternatives were developed and modeled from 2010 through 2012. These

alternatives included different combinations and scenarios for new and realigned creek

channels and floodplain grading associated with opportunities for property acquisition. Creek

habitat restoration scenarios were paired with other near-term alternatives for improving

drainage and conveyance of surface runoff from roads and private properties to improve

rather than exacerbate existing flooding problems. The primary objective of the alternatives

developed was to improve both fish habitat and flood inundation of surrounding properties

by increasing the flood frequency within the primary habitat area and decreasing flood

frequency along surrounding agricultural lands.

Given the project objectives, characterizing lateral flows within the restored channel and

floodplain is essential for assessing the hydraulic response to the project alternatives in the

context of the surrounding project area. The current Hansen Creek and Red Creek channels

have aggraded over the years to elevations exceeding the surrounding floodplain in many

places. As such, a two-dimensional hydraulic model, FLO-2D (FLO-2D 2009), was developed to

assess the complex lateral floodplain flows for various alternatives that included levee

breaching and removal. As previously stated, the FLO-2D model is well suited for application

to conditions in the project reach. It provides water surface elevation and velocity output

based on an input flood flow hydrograph.

May 2013


Model Setup and Development

Two-dimensional numerical models like FLO-2D require boundary conditions such as hydraulic

roughness values, topography transposed onto a geometric computational mesh, and a

discharge hydrographs that define the computational domain. The Manning’s roughness values

(n-values) were selected based on professional judgment for similar systems, several site

visits, and comparison to literature values as those included in Chow (1959). The n-values

used for the model varied between 0.03 to 0.04 for the channel and grass floodplain, and up

to 0.12 for the more heavily vegetated areas (forested). The computational grid was set up as

a combined one-dimensional (channel) and two-dimensional (floodplain) numerical model to

optimize the modeling process. A 30-foot grid was selected to provide the required resolution

for the surrounding topography with cross-sections for every grid along the channel corridor

(30-foot cross-section spacing). A topographic surface was imported onto the 30-foot grid

using a combined photogrammetry topographic surface from Skagit County (Skagit County

2010) and surveyed topographic surface (BRH 2010) to provide a very detailed representation

of the Hansen Creek and Red Creek floodplains.

Hydraulic boundary conditions consisted of several upstream hydrographs (transient state

input flows) and a downstream outflow boundary downstream of the 16-foot Minkler Road

culvert. The downstream FLO-2D boundary conditions included the simple designation of

outflow grid elements, which assumed a localized slope between adjacent elements and a

uniform flow approximation to calculate output flow rates from the output grid element (i.e.,

normal flow). The peak flows for the hydrographs are described above. Historical USGS gage

data was used to scale the peak flows into a 160-hour flood hydrograph. The last 48 hours of

the hydrograph was held at a steady flow equivalent to the average annual base flow to assess

the drainage characteristics after the occurrence of a flood. The upstream inflow hydrographs

were located as follows:

1. Hansen Creek channel at the SR 20 crossing

2. Red Creek channel at the SR 20 crossing

3. SR 20 ditch providing drainage flow down the west boundary of the project area (west

of the Nielsen and Snyder properties)

4. At the head of the old oxbow channel west of the White property near the Cook

property to represent Coal Creek overflow along the trail

5. In oxbow to saturate the oxbow prior to a flood event to represent local overland flow

6. Along the Minkler ditch to represent road and local overland flow

Two primary culverts convey water under Minkler Road including the main 16-foot, 7-inch

span pipe arch culvert at Hansen Creek and a smaller 72-inch-diameter culvert near the Good

property. A stage discharge rating curve was developed for each culvert and entered into the

FLO-2D model to provide a reliable and robust evaluation of the hydraulic performance of the

culverts and related effects with respect to flood conveyance.

May 2013


Past Modeling Results and Public Meetings

Modeling of alternatives has occurred from 2010 to 2013 and included 10 rounds of varying

alternatives presented at the five workshops discussed previously in this report. The modeling

findings informed the near-term project elements that were implemented between 2011

and 2012, including floodplain revegetation by the Swinomish Tribe and SFEG, as well as the

drainage improvements carried out by Skagit County. This memorandum includes a summary

of the details for the final round of results for the two remaining preferred alternatives for

the medium-term project.

In summary, the previous modeling results revealed the following key conclusions:

The aggradation and flooding issues were directly related to the location of the

Hansen Creek and Red Creek confluence. The confluence needed to move downstream

to a more natural location based on the elevations and gradients of the two channels.

Habitat values and flood control (depth and extent of flooding) benefits were marginal

for all alternatives with restoration on the east side of the channel. This is, because

the existing Hansen Creek channel starts flowing to the west and southwest at the

southern extent of the Swinomish Tribe property, forcing the revised east side Hansen

Creek/Red Creek confluence to occur on the Swinomish Tribe property (former

Knudsen property), which was still not far enough downstream.

Habitat values and floodplain hydraulics could be optimized for flow restoration

efforts concentrated to the west. The natural floodplain gradient downstream of SR 20

and the Nielsen properties conveys Hansen Creek flood flows generally toward the

southwest. Moving the Hansen Creek/Red Creek confluence nearly one-half mile

downstream provides more stream habitat and is more consistent with hydraulic and

geomorphic processes.

In addition to the preliminary hydraulic model results, new information about the possibilities

for floodplain acquisition for habitat restoration surfaced in late 2012. As a result, two

final alternatives for a medium-term habitat restoration project were selected that focus

restoration efforts to the west side of Hansen Creek. After presenting the modeling results

and potential habitat gains to the stakeholders, these two alternatives were selected as the

preferred medium-term project alternatives. Hansen Creek would be diverted to the west to

occupy its lower-elevation historical floodplain, and Red Creek would occupy the east side

floodplain and existing Hansen Creek channel. The two alternatives are based on available

property for the restoration effort (minimal property for Alternative 1, and maximum

property for Alternative 2).

Interpretation of Model Results Figures

Colored graphics are used to display the spatially detailed data generated by the FLO-2D

model of existing and proposed conditions. The graphic results are presented with color

schemes and gradations that are consistent between various model runs so that direct visual

comparisons between alternative scenarios can be made.

May 2013


Since it is difficult to see subtle changes in hydraulic characteristics in the project reach

under high flood flow conditions, “difference” plots are provided for the proposed conditions

output that show relative changes between the proposed and existing conditions. For

example, at the scale of the model output graphics it is difficult to see water surface changes

of 0.1 feet when the water depth is 10 feet, yet 0.1 feet can be important for floodplain

activation and, therefore, habitat connectivity. As such, proposed conditions (alternatives)

graphics for water depths are supplemented with difference plots.

The difference represented in the figures in the following discussion is always the proposed

condition minus the existing condition. Thus, a positive change indicates an increase in the

flow depth or flow velocity as a result of the channel and floodplain restoration construction.

Darker colors indicate larger differences. The color scheme for “no significant change” is

varied between the flow depth and flow velocity plots so that they are easily distinguishable

at first glance. For flow depths, a significant change is considered to be any water surface

elevation change greater than 0.02 (i.e., ±0.01-foot rise for difference).

Final Hydraulic Model Results

Drainage alterations were conducted along Minkler Road in the summer of 2012 to provide

short-term and long-term conveyance improvements. These improvements included new

culverts along Minkler Road and a new cross culvert to alleviate drainage back into Hansen

Creek. The cross culvert will also provide some short-term flood relief until the culvert

is replaced with a bridge as part of the long-term project plan. A difference plot for the

100-year flood is provided in Figure 3. The grey areas indicate no floodwater changes with the

green areas showing water surface decreases due to the 2012 drainage improvement project.

The existing conditions hydraulics model was updated in early 2013 to reflect the construction

of the near-term habitat and drainage improvements (2011 to 2012). The updated existing

2-year and 100-year floodwater depths are provided in Figures 4 and 5, respectively. These

results reflect the high existing levee restricting Hansen Creek flow to the west (with

eventual overflow) with a large portion of the flow at the confluence between the two creeks

being directed to the east over the Martinez, Good, and Houston properties. The flow split in

this area suggests that 100 percent of the Red Creek flow and over 25 percent of the Hansen

Creek flow spills to the east over the Good property toward the 72-inch culvert under Minkler

Road. The gradient at the confluence is significantly decreased, which accelerates sediment

aggradation. This increases flood flow and flood frequency to the east, which in turn has

progressively increased flood conveyance issues along Minkler Road. This pattern of flood flow

and sediment aggradation is also detrimental to fish habitat in that flows are directed more

frequently to agricultural pasture land and drainage ditches. The aggradation issue has not

increased since the alluvial fan restoration efforts in the upstream reach (Reach 4) north of

SR 20, but the current streambed elevations is directing, and will continue to direct, a large

portion of the Hansen Creek flood flows to the east.

Figures 6 and 7 show the 100-year hydraulic results for Alternatives 1 and 2, respectively.

Both alternatives show significant improvements as far as flooding to the east. However,

Alternative 1 shows increased flooding on the Burress property, which is outside the assumed

property acquisition area for Alternative 1. The frequency of flooding to the east into the

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Figure 3.100-year Flood Depth Difference:Post-Project Near-Term Drainage Improvements Minus Pre-ProjectConditions.

K:\Projects\10-04664-001\Project\modeling_output_round10.mxd (3/1/2013) Round 10

LegendStreamMinkler Ditch flow

100-year flood depth difference (ft)< -1-1 to -0.5-0.5 to -0.14-0.14 to -0.05-0.05 to -0.02-0.02 to 0.020.02 to 0.050.05 to 0.140.14 to 0.50.5 to 1> 1

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Existing 2-year flood depth (ft)< 11 to 22 to 33 to 44 to 55 to 66 to 7

Figure 4.Existing 2-year Flood DepthsReflecting Near-Term Improvements.

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LegendMinkler Ditch flowStream

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Figure 5.Existing 100-year Flood DepthsReflecting Near-Term Improvements.

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Figure 6.100-year Flood Depth for the Phase 2 Medium-TermProject Alternative 1.



100-year flood depth (ft)< 11 to 22 to 33 to 44 to 55 to 66 to 7

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May 2013


pasture land is also decreased, which will provide more flood flow within the restored habitat

area and increase the habitat value of either Alternative 1 or Alternative 2. Figures 8 and 9

illustrate the 2-year hydraulic results for Alternatives 1 and 2, respectively. The 2-year event

provides an important estimation of the wetland and floodplain habitat areas that would be

used more frequently than those areas overlapping the less frequently occurring 100-year

floodplain. A flood berm/levee or extensive flood easement may be required for Alternative 1

and will need to be assessed in final design once the final property acquisition details and

easement boundaries are confirmed. The model results displayed in the figures do not reflect

the inclusion of berms, only floodplain grading.

The 100-year event floodwaters in the east floodplain for both alternatives are primarily

composed of floodwater from Red Creek. A 100-year flood event would result in more flow

directed to the Hansen Creek floodplain and the main crossing under Minkler Road. The

results show that the increased flood elevations are contained upstream within the channel

and in the proposed restored floodplain. However, it appears that the existing culvert is

undersized and could be at risk from scour. A more detailed analysis would be required based

on the alternative chosen to assess the appropriate bridge opening size and to assess

downstream impacts.

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May 2013


PRELIMINARY PLAN FOR PHASED PROJECT

IMPLEMENTATION

The preceding sections have outlined the preliminary project analyses and workshop

outcomes that have provided the framework for the development of the proposed Hansen

Creek Reach Restoration project. This section describes the phased project implementation

approach that the County is proposing and has begun to execute. Figure 10 outlines the

general geographic boundaries anticipated for each of the phased projects. Figure 11 presents

a preliminary project schedule for phasing the near-term, medium-term, and long-term

project components.

Phase 1 - Near-Term Project

After four workshops and the completion of at least 18 modeling iterations for a potential

near-term project alternative, it was determined that any near-term alternative focused on

the east floodplain would require setback berms to contain the reactivated floodplain. The

alternative was still likely to be associated with localized flooding increases for some of the

private properties downstream due to the overall conveyance improvements associated with

relocating the Hansen Creek and Red Creek confluence. As a result, the County decided to

postpone further design development of the habitat portions of a near-term alternative until

after the drainage improvements could be implemented and the benefits realized by the

community. In summary, the Phase 1 near-term project evolved to include the following

elements, implemented between 2011 and 2012:

Riparian plantings spearheaded by the SFEG on the Swinomish (former Knudsen)

property

Riparian plantings spearheaded by the SRSC on the Martinez property

Removal of the culvert at the outlet of Red Creek at the confluence with Hansen

Creek, spearheaded by the SRSC and the Martinez property

Removal of the east-west berm along the property boundary between the Swinomish

property (former Knudsen) and the Martinez property, spearheaded by the SRSC and

the Martinez property

Improvements to ditch drainage along the north-south running ditch between the

Swinomish property (former Knudsen) and Good property, spearheaded by the SRSC

Drainage improvements along Minkler Road to provide near-term and long-term

conveyance improvements, spearheaded by Skagit County Public Works. These

drainage improvements included new culverts for the ditch along the north side of

Minkler Road and a new cross culvert installed above the ordinary high water level at

the Hansen Creek crossing, to provide near-term flood and backwater relief until the

culvert can be replaced by a bridge in the future.

May 2013


Final design drawings illustrating for the near-term drainage improvements are provided in

Appendix C.

Phase 2 - Medium-Term Project

After at least six different model iterations for a medium-term habitat improvement project,

recent developments for potential property acquisition within the west floodplain and

improved coordination with utility companies (as described in the Workshop #5 outcomes)

together provided a basis for developing a potential medium-term project that would

complement the natural geomorphic processes and drainage pathways through the west

floodplain. Two alternative options (Alternatives 1 and 2, as discussed previously in the

Hydraulic Modeling section description) for the medium-term project are still being

considered as the final boundaries are determined during negotiations with private property

owners and the utility companies. Both alternatives include the following key elements:

The diversion of Hansen Creek to the west to occupy its lower elevation historic

floodplain and to create additional channel aquatic habitat

Red Creek occupation of the existing Hansen Creek channel downstream of the

existing confluence

Relocation of the Hansen Creek and Red Creek confluence approximately 3,000 feet

downstream of the existing location

Floodplain grading along the high-elevation Boettcher property to provide additional

floodplain storage capacity and to avoid channel confinement

Floodplain grading throughout the project area to create microtopographic complexity

including high-elevation upland hummocks and low-elevation depressions, with overall

positive drainage back to channels

Restoration of hydrologic connectivity between the Hansen Creek channel and its

floodplain

Enhancement of existing depressional floodplain wetlands by improving hydrologic

connectivity to create riverine wetland habitat and through revegetation with native

wetland plants

Enhancement of physical complexity and aquatic habitat through the dense placement

of log structures along the realigned Hansen Creek channel and Red Creek channel

(former Hansen Creek channel) as well as placement of additional log structures in the

floodplain

Re-creation of a floodplain forest by revegetation with native plants

The Phase 2 medium-term project is currently at a 30 percent level of design and is awaiting

additional direction from the property acquisition and easement negotiation process before

proceeding further. The draft 30 percent design drawings are provided in Appendix D.

HansenCreek

RedCreek

Phase 3: Replace existing Minkler Roadculvert with a new bridge

Phase 0: Alluvial Fan and Wetland Restoration

Phase 2: Hansen Reach 5 FloodplainReconnection and Channel

Realignment

Phase 1: Drainage Improvements along Minkler Road from Breier Lane N to Hansen Creek

Phase 1: Riparian Revegetation within Hansen Reach 5and Red Creek confluence area

Alternative 2Alternative 1

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Aerial: Skagit County 2011, USDA (2009)Coordinates: WA State Plane North NAD 83 (feet)

Figure 10. Phased Channel and Floodplain Restoration Projects for Hansen Creek Reach 5.

Legend

K:\Projects\10-04664-001\Project\phased_channels_restoration.mxd (5/17/2013)

ParcelPhase 2 Hansen Creek RealignmentPhase 2 Red Creek Realignment

Project PhasesPhase 0 - Alluvial Fan and Wetland RestorationPhase 1 - Planting and Drainage ImprovementsPhase 2 - Alternative 1 Channel and FloodplainPhase 2 - Alternative 2 Channel and FloodplainPhase 3 - New Bridge

Figure 11. Phased Schedule for the Hansen Creek Reach 5 Restoration Project.

Project Phase

Project Component

Sprin

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Fall

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Channel and Floodplain Habitat

Field Evaluation (County, Herrera)

Construction (SRSC)

**

Drainage Improvements


Construction (County)

**

Riparian PlantingsField Evaluation (County, Herrera)

Design and Permitting (SFEG, SRSC)

**

West floodplain grading and revegetation


**

Introduce Hansen flow to west floodplain


**

Install wood in Red Creek (old Hansen Creek)


**

Replace Minkler Rd. Hansen Culvert with new Bridge


**

Floodplain grading and channel restoration


**

* * Denotes the completion of a particular project component.


Phase 1 ‐ Near‐Term Project

Construction (SFEG, SRSC)

Project Planning (All stakeholders)


Final Design and Permitting (County, Herrera)Final Design and Permitting (County, Herrera)

Preliminary (30%) Design (County, Herrera)


Final Design and Permitting (County, Herrera)

Final Design and Permitting (County, Herrera)


Project Planning (All stakeholders)Final Design and Permitting (County, Herrera)


2016


Design and Permitting (County, Herrera)

Design modifications

Design and Permitting (County, Herrera)

2015


2010 2011 2012 2013 2014


Floodplain Establishment Period

Floodplain Establishment Period



Preliminary (30%) Design (County, Preliminary (30%) Design (County,

Construction (County)Construction (County)

2018

Phase 3 ‐ Long‐Term Project

Phase 2 ‐ Medium‐Term Project

2017


May 2013


Phase 3 - Long-Term Project

Preliminary hydraulic modeling and geomorphic analysis suggest that the Hansen Creek

culvert crossing under Minkler Road may be undersized and is likely confining the continuity

of floodplain and geomorphic processes. A Phase 3 long-term project will further evaluate this

crossing and other barriers to reach-wide restoration of hydrologic and geomorphic processes.

Additional analyses would include a thorough hydraulic, geomorphic, and scour evaluation

of the current Minkler culvert opening as well as a downstream analysis to ensure that any

changes to the Hansen Creek crossing at Minkler Road would not trigger negative flood

impacts downstream. The Phase 3 long-term project is currently in the preliminary stages

of conceptual design development.

Habitat Benefits

The specific habitat benefits (improvements and area gains) described here are attributed

to the Phase 2 medium-term project, which will create the most direct habitat benefits by

reconnecting Hansen Creek with its floodplain and enhancing adjacent wetlands and riparian

forest. However, all the proposed projects are interrelated and important in establishing a

framework for self-sustaining watershed processes. Together, the proposed phased projects

will yield a substantial net gain in wetland function, floodplain reconnection, increased

aquatic habitat area, and improved habitat for fish and wildlife. Existing conditions for

Hansen Creek include very little floodplain connectivity. The only floodplain connectivity is

via overflows to Red Creek; however, the drainage of that connectivity is into agricultural

fields to the south that are only partially hydraulically connected to Hansen Creek via

drainage ditches.

Hansen Creek’s consistent baseflow of approximately 20 cubic feet per second (cfs) translates

to unique restoration opportunities for providing and improving year-round fish habitat. The

average annual flow for Hansen Creek is approximately 20 to 25 cfs, and it does tend to

experience relatively “flashy” flood flows. However, it is the high frequency (low magnitude)

flow events are critical for assessing habitat gains. Flows around 25 cfs (average annual and

baseflow) have resulted in local braiding (bars and split flows) in the predominant channel

in the restored Reach 3 fan area and some flooding and interaction in the Reach 4 wetland

area. The Phase 2 medium-term project’s proposed reactivated floodplain area is expected to

perform very similarly to the Reach 4 wetland area. Hydraulic modeling of lower-magnitude,

higher-frequency flows was conducted for the medium-term Reach 5 floodplain to assess the

frequency with which the floodplain is available to salmonids. Average annual flows of

approximately 25 cfs will likely result in flow in one main channel with some braiding (i.e.,

bar formation) with the possibility of a smaller anabranching side channel similar to the

response in the upstream Reach 4 restoration area. At 50 cfs, a flow which according to

historical flow data since 2005 (according to the Reach 3 Hansen Creek Ecology gage) occurs

approximately 20 percent of the time during the winter and spring months (Herrera 2007),

smaller anabranching side channels will develop. The values in Table 5 include estimated

quantities of available habitat gains in terms of linear feet of stream channel and acreage of

wetlands for flows between 25 and 50 cfs. Table 6 includes estimated temporal quantities of

available habitat compared to the frequency of salmonid usage of that habitat.

May 2013


Table 5. Phase 2 Medium-Term Hansen Creek Reach 5 Project Habitat Gains – Comparison of Existing and Proposed Conditions.

Habitat Type Units

Existing Proposed

Summary of Expected Conditions Quantity Quantity

Instream channel length

Linear Feet

8,000 13,000 An unconstrained channel allows potential for more channel sinuosity; spawning and complex rearing

habitat maintained through natural recruitment of wood after plant succession is achieved.

Instream side channels

Linear Feet

0 2,000 High-discharge (ephemeral) channels that convey sediment to the floodplain and active (perennial)

channels that provide spawning and rearing habitat.

Off channel floodplain habitat (connected for flows less than 50 cfs)

Acres 0 18 Excavation of some higher floodplain areas will allow for microtopographic variability that will provide frequent,

and even continuous, aquatic habitat providing valuable off channel habitat for juvenile coho and Chinook

salmonids.

Forested riverine flow through wetland

Acres 0 50-60 Excavation of floodplain will create channels and a mosaic of upland forest and forested riverine wetlands.

The Phase 2 medium-term project will create more unconfined perennial channels and will

promote the creation of high-discharge (ephemeral) channels that provide more in-channel

spawning and rearing habitat; increased floodplain connectivity will increase off-channel

rearing habitat. Additionally, complex channels and a mosaic of upland forest will enable

sediment aggradation to mimic historic patterns, thereby reducing the sediment volumes

transported to and deposited in lower gradient downstream reaches. Rehabilitating the

floodplain and removing the confined channel banks will also enable a complex physical

habitat that promotes the natural recruitment of wood, the activation of perennial and

ephemeral channels, and the reconnection of the stream channel to its floodplain and

adjacent wetland habitat. In particular, substantial restoration of channels and riverine

wetlands will dramatically increase the quantity and quality of habitat available to salmonids.

Forested riverine wetlands will be created and restored. Thus, the stream, wetland, and

floodplain design will result in increased off-channel habitat for both returning adult and

rearing juvenile salmonid species. Over time, once plant succession is achieved, spawning and

complex instream rearing habitat will be maintained through the natural recruitment of

wood.

Overall, the Phase 2 medium-term project for Reach 5 of Hansen Creek, with support and

connectivity to the reactivated alluvial fan and wetland restoration project upstream in

Reaches 3 and 4, as well as the Phase 1 near-term and Phase 3 long-term restoration projects

for Reach 5 of Hansen Creek, will substantially increase salmonid habitat and subsequent

production capacity. This will be achieved by providing complex habitat supportive of critical

biological needs and life history stages such as adult holding, spawning, egg-to-embryo

development, juvenile rearing and foraging, and refugia for adult and juvenile fish during

flooding conditions.

May 2013


Table 6. Hansen Creek Reach 5 Floodplain and Salmonid Accessibility Frequency Matrix.

Characteristics

Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Flow – mean (cfs) 42 31 30 25 20 18 8 8 10 14 25 25

Freq. flow >50 cfs (days) 12 7 4 2 3 3 3 9 5

Active Channel – Existing (feet)

8,000 8,000 8,000 8,000 8,000 8,000 8,000 8,000 8,000 8,000 8,000 8,000

Active Channel – Proposed Alt 1 (feet)

13,000 12,500 12,500 12,000 11,500 11,000 10,500 10,500 10,500 11,000 12,000 12,000

Active Channel – Proposed Alt 1 and 2 (feet)

15,000 14,000 14,000 14,000 13,500 13,000 12,000 12,000 12,500 13,000 14,000 14,000

Wetland access - Existing (acres)

0 0 0 0 0 0 0 0 0 0 0 0

Wetland access - Proposed Alt 1 (acres)

12 7 7 6 6 5 2 2 3 5 6 6

Wetland access – Proposed Alts 1 and 2 (acres)

18 13 13 12 10 9 3 3 4 9 12 12

Chinook (adult) X X X

Chinook (fry and yearlings) X X X X X X X X X X X X

Coho (adult) X X X

Coho (juvenile) X X X X X X X X X X X X

Steelhead (adult) X X X

Steelhead (juvenile) X X X X X X X X X X X X

X – Known fish use

X – Fish use based on anecdotal information from USIT monitoring of Hansen Creek Reach 4 wetland restoration area

May 2013


REFERENCES

Beechie, T.J., D.A. Sear, J.D. Olden, G.R. Pess, J.M. Buffington, H. Moir, P. Roni, and

M.M. Pollock. 2010. Process-based principles for restoring river ecosystems. BioScience

60(3):209-222.

BRH. 2010. Topographic Survey CAD files for the Hansen Creek Reach 5/Red Creek Confluence

Area. CAD datasets provided via ftp site from Dakin Bell, BRH to Ian Mostrenko, Herrera

Environmental Consultants, Ins., Seattle, Washington, on May 11, 2010.

Chow, V.T. 1959. Open channel hydraulics. McGraw Hill, New York, New York.

Collins, B. 2000. Mid-19th Century Stream Channels and Wetlands Interpreted from Archival

Sources for Three North Puget Sound Estuaries. Report prepared for Skagit System

Cooperative, Skagit Watershed Council, and The Bullitt Foundation, University of Washington,

Seattle.

Collins, B. and A. Sheik. 2002. Methods used to map the historical riverine landscape and

habitats of the Skagit River. Report to Skagit System Cooperative, LaConner, Washington.

FEMA. 1989. Flood Insurance Rate Map: Skagit County, Washington (Unincorporated Areas).

Flood Insurance Community-Panel Number 530151 0255 D. Federal Emergency Management

Agency, Washington, D.C.

FLO-2D. 2009. FLO-2D Reference Manual. FLO-2D, Inc., Nutrioso, Arizona.

Herrera. 2007. Conceptual Restoration Report – Hansen Creek Alluvial Fan and Wetland

Restoration Project. Prepared for the Upper Skagit Indian Tribe by Herrera Environmental

Consultants, Inc., Seattle, Washington. December 26, 2007.

Miller Consulting and Watershed Professionals Network. 2002. Hansen Creek Watershed

Management Plan. Prepared for the Skagit County Public Works Department by Miller

Consulting and Watershed Professionals Network.

Mostrenko, I., C. Avolio, C. Brummer, K. Lepine, and L. Rich. 2011. Hansen Creek Alluvial

Fan and Wetland Restoration Project: Hydrogeomorphic Changes of a Re-Activated Alluvial

Fan (Poster #1). Poster Presentation at the Salish Sea Conference, October 25-27, 2011,

Vancouver, British Columbia, Canada.

Rich, L., C. Gourley, and L. Hainey. 2011. Hansen Creek Alluvial Fan and Wetland Restoration

Project: Early Habitat Formation in a Restoring Floodplain (Poster #2). Poster Presentation at

the Salish Sea Conference, October 25-27, 2011, Vancouver, British Columbia, Canada.

Rosario Archaeology, LLC. 2011. Cultural Resource Assessment for 2011 Plantings at the

Lower Hansen Creek Restoration Project, Skagit County, Washington. Prepared for the Skagit

Fisheries Enhancement Group by Rosario Archaeology, LL C, Bellingham, Washington. April 5,

2011.

May 2013


Simon, A. and M. Rinaldi. 2006. Disturbance, stream incision, and channel evolution: The

roles of excess transport capacity and boundary materials in controlling channel response.

Geomorphology 79:361-383.

Skagit County. 2010. Photogrammetry Topographic Data X, Y, Z points Shapefile for the

Hansen Creek Reach 5/Red Creek Confluence Area. Dataset provided via ftp site from

Josh Greenberg, Skagit County, to Christina Avolio, Herrera Environmental Consultants, Inc.,

Seattle, Washington, on May 4, 2010.

Skagit County. 2011. 2011 Cross Section monitoring survey results for Hansen Creek Reach 5.

Pdf graphics of the surveyed cross-sections provided via email from Jan Flagan, Skagit

County, to Christina Avolio, Herrera Environmental Consultants, Inc., Seattle, Washington,

on September 9, 2011.

Skagit County. 2012. 2012 Cross Section monitoring survey results for Hansen Creek Reach 5.

Pdf graphics of the surveyed cross-sections provided via email from Jeff McGowan, Skagit

County, to Christina Avolio, Herrera Environmental Consultants, Inc., Seattle, Washington,

on November 2, 2012.

SRSC & WDFW. 2005. Skagit Chinook Recovery Plan. Prepared by Skagit River System

Cooperative (SRSC) and Washington Department of Fish and Wildlife (WDFW), LaConner,

Washington.

Syvitski, J.P.M., A.J. Kettner, S.D. Peckham, and S.J. Kao. 2005. Predicting the Flux of

Sediment to the Coastal Zone: Application to the Lanyang Watershed, Northern Taiwan.

Journal of Coastal Research 21(3):580-587.

APPENDIX A

Basemap Survey

APPENDIX B

Geomorphic Analysis Data

Pebble Count Calculator Armoring: 0.940525Chris Brummer, Christina Avolio gbn=grid by number (Wolman count)

Site: Hansen Reach 5 Project - Reach 4 Sample, GPS 15Location: Reach 4

Sample Date: April 28, 2010SURFACE

Sand: 40% Sand: 27.40

gbn gbn 16 50 84 90Ψ Di mm (frac finer) (frac) (count) (% finer) Ψ D16 (Ψ) D50 (Ψ) D84 (Ψ) D90 (Ψ)

1.5 2.83 0.0000 0.00000 0 0.0000 1.502 4.00 0.0283 0.02830 3 2.8302 2.00 2.498571

2.5 5.66 0.1604 0.13208 14 16.0377 2.50 2.953 8.00 0.5377 0.37736 40 53.7736 3.00

3.5 11.31 0.8396 0.30189 32 83.9623 3.50 3.50125 3.74 16.00 0.9906 0.15094 16 99.0566 4.00

4.5 22.63 1.0000 0.00943 1 100.0000 4.505 32.00 1.0000 0.00000 0 100.0000 5.00

5.5 45.25 1.0000 0.00000 0 100.0000 5.506 64.00 1.0000 0.00000 0 100.0000 6.00

6.5 90.51 1.0000 0.00000 0 100.0000 6.507 128.00 1.0000 0.00000 0 100.0000 7.00

7.5 181.02 1.0000 0.00000 0 100.0000 7.508 256.00 1.0000 0.00000 0 100.0000 8.00

8.5 362.04 1.0000 0.00000 0 100.0000 8.509 512.00 1.0000 0.00000 0 100.0000 9.00

9.5 724.08 1.0000 0.00000 0 100.0000 9.5010 1024.00 1.0000 0.00000 0 100.0000 10.00

10.5 1448.15 1.0000 0.00000 0 100.0000 10.5011 2048.00 1.0000 0.00000 0 100.0000 11.00

11.5 2896.31 1.0000 0.00000 0 100.0000 11.5012 4096.00 1.0000 0.00000 0 100.0000 12.00

D (mm) --> 5.651256 7.727491 11.32352 12.996041.00000 106 D16 (mm) D50 (mm) D84 (mm) D90 (mm)

SUBSURFACESand: 30

% Sand: 23.08gbn gbn

Ψ Di mm (frac finer) (frac) (count) (% finer) Ψ D16 (Ψ) D50 (Ψ) D84 (Ψ) D90 (Ψ)1.5 2.83 0.0000 0.00000 0 0.0000 1.50

2 4.00 0.0800 0.08000 8 8.0000 2.00 2.3076922.5 5.66 0.2100 0.13000 13 21.0000 2.50

3 8.00 0.4800 0.27000 27 48.0000 3.00 3.0384623.5 11.31 0.7400 0.26000 26 74.0000 3.50 3.727273 3.863636

4 16.00 0.9600 0.22000 22 96.0000 4.004.5 22.63 1.0000 0.04000 4 100.0000 4.50

5 32.00 1.0000 0.00000 0 100.0000 5.005.5 45.25 1.0000 0.00000 0 100.0000 5.50

6 64.00 1.0000 0.00000 0 100.0000 6.006.5 90.51 1.0000 0.00000 0 100.0000 6.50

7 128.00 1.0000 0.00000 0 100.0000 7.007.5 181.02 1.0000 0.00000 0 100.0000 7.50

8 256.00 1.0000 0.00000 0 100.0000 8.008.5 362.04 1.0000 0.00000 0 100.0000 8.50

9 512.00 1.0000 0.00000 0 100.0000 9.009.5 724.08 1.0000 0.00000 0 100.0000 9.5010 1024.00 1.0000 0.00000 0 100.0000 10.00

10.5 1448.15 1.0000 0.00000 0 100.0000 10.5011 2048.00 1.0000 0.00000 0 100.0000 11.00

11.5 2896.31 1.0000 0.00000 0 100.0000 11.5012 4096.00 1.0000 0.00000 0 100.0000 12.00


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Pebble Count Calculator Armoring: 0.857981Chris Brummer, Christina Avolio gbn=grid by number (Wolman count)

Site: Hansen Reach 5 Project - Reach 5 Sample, GPS 16Location: Reach 5

Sample Date: April 28, 2010SURFACE

Sand: 5% Sand: 4.39

gbn gbn 16 50 84 90Ψ Di mm (frac finer) (frac) (count) (% finer) Ψ D16 (Ψ) D50 (Ψ) D84 (Ψ) D90 (Ψ)

1.5 2.83 0.0000 0.00000 0 0.0000 1.502 4.00 0.0459 0.04587 5 4.5872 2.00 2.311

2.5 5.66 0.2294 0.18349 20 22.9358 2.503 8.00 0.4128 0.18349 20 41.2844 3.00 3.169643

3.5 11.31 0.6697 0.25688 28 66.9725 3.50 3.9419054 16.00 0.8624 0.19266 21 86.2385 4.00 4.227778

4.5 22.63 0.9450 0.08257 9 94.4954 4.505 32.00 1.0000 0.05505 6 100.0000 5.00

5.5 45.25 1.0000 0.00000 0 100.0000 5.506 64.00 1.0000 0.00000 0 100.0000 6.00

6.5 90.51 1.0000 0.00000 0 100.0000 6.507 128.00 1.0000 0.00000 0 100.0000 7.00

7.5 181.02 1.0000 0.00000 0 100.0000 7.508 256.00 1.0000 0.00000 0 100.0000 8.00

8.5 362.04 1.0000 0.00000 0 100.0000 8.509 512.00 1.0000 0.00000 0 100.0000 9.00

9.5 724.08 1.0000 0.00000 0 100.0000 9.5010 1024.00 1.0000 0.00000 0 100.0000 10.00

10.5 1448.15 1.0000 0.00000 0 100.0000 10.5011 2048.00 1.0000 0.00000 0 100.0000 11.00

11.5 2896.31 1.0000 0.00000 0 100.0000 11.5012 4096.00 1.0000 0.00000 0 100.0000 12.00


SUBSURFACESand: 15

% Sand: 12.93gbn gbn

Ψ Di mm (frac finer) (frac) (count) (% finer) Ψ D16 (Ψ) D50 (Ψ) D84 (Ψ) D90 (Ψ)1.5 2.83 0.0000 0.00000 0 0.0000 1.50

2 4.00 0.0693 0.06931 7 6.9307 2.00 2.3816672.5 5.66 0.1881 0.11881 12 18.8119 2.50

3 8.00 0.3762 0.18812 19 37.6238 3.00 3.3906253.5 11.31 0.5347 0.15842 16 53.4653 3.50

4 16.00 0.7723 0.23762 24 77.2277 4.00 4.3109094.5 22.63 0.8812 0.10891 11 88.1188 4.50 4.605556

5 32.00 0.9703 0.08911 9 97.0297 5.005.5 45.25 0.9802 0.00990 1 98.0198 5.50

6 64.00 0.9901 0.00990 1 99.0099 6.006.5 90.51 1.0000 0.00990 1 100.0000 6.50

7 128.00 1.0000 0.00000 0 100.0000 7.007.5 181.02 1.0000 0.00000 0 100.0000 7.50

8 256.00 1.0000 0.00000 0 100.0000 8.008.5 362.04 1.0000 0.00000 0 100.0000 8.50

9 512.00 1.0000 0.00000 0 100.0000 9.009.5 724.08 1.0000 0.00000 0 100.0000 9.5010 1024.00 1.0000 0.00000 0 100.0000 10.00

10.5 1448.15 1.0000 0.00000 0 100.0000 10.5011 2048.00 1.0000 0.00000 0 100.0000 11.00

11.5 2896.31 1.0000 0.00000 0 100.0000 11.5012 4096.00 1.0000 0.00000 0 100.0000 12.00


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APPENDIX D

Phase 2 Medium-Term Project

30% Drawings

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M. EWBANK

30% PERMIT SET - NOT FOR CONSTRUCTION

SKAGIT COUNTY

HANSEN CREEK/RED CREEK PHASE 2

MEDIUM-TERM HABITAT IMPROVEMENT PROJECT

SEDRO-WOOLLEY, WASHINGTON

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PROJECT

LOCATION

NOTE AND DETAIL/SECTION REFERENCING

DRAWING FROM WHICH DETAIL WAS TAKEN

DETAIL REFERENCE NUMBER

DRAWING FROM WHICH SECTION WAS TAKEN

SECTION REFERENCE LETTER

"-" INDICATES THAT THE DETAIL/SECTION IS SHOWN ON THE SAME SHEET

"TYP" INDICATES THAT THE DETAIL/SECTION IS UNIFORMLY TYPICAL

THROUGHOUT PROJECT EXCEPT WHERE OTHERWISE NOTED

"VAR" SPECIFIES THAT DETAIL/SECTION WAS TAKEN FROM SEVERAL DRAWINGS

DETAIL REFERENCE NUMBER

DRAWING ON WHICH SECTION IS SHOWN

SECTION REFERENCE LETTER

DRAWING ON WHICH DETAIL IS SHOWN

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VICINITY MAP

SKAGIT COUNTY

HANSEN CREEK/RED CREEK, PHASE 2 MEDIUM-TERM

HABITAT IMPROVEMENT PROJECT

SEDRO WOOLLEY, WASHINGTON

SCALE: N.T.S.

CONTACT INFORMATION:

JEFF MCGOWAN

SKAGIT COUNTY PUBLIC WORKS

1800 CONTINENTAL PLACE

MOUNT VERNON, WA 98273

(360) 419-3427

OWNER:

SKAGIT COUNTY PUBLIC WORKS

ENGINEER:

IAN MOSTRENKO, HERRERA

CHRISTINA AVOLIO, HERRERA

PROJECT MANAGER:

JEFF MCGOWAN, SKAGIT COUNTY

NAVD 88, NAD 83

PHASE 2 PROJECT

LOCATION

CALL 2 WORKING DAYS

BEFORE YOU DIG

1-800-424-5555

(UNDERGROUND UTILITY LOCATIONS ARE APPROX.)

SHEET INDEX

SHEET NO. DRAWING NO. SHEET DESCRIPTION

1 G-1 COVER SHEET

2 G-2 EXISTING CONDITIONS AND KEY MAP

3 C-1 PROPOSED PROJECT PLAN NORTH

4 C-2 PROPOSED PROJECT PLAN SOUTH

5 C-3 CHANNEL AND FLOODPLAIN SECTIONS AND DETAILS

6 C-4 LOG STRUCTURE DETAILS

7 P-1 PLANTING PLAN

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DRAWING NO:

SHEET NO: OF

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SKAGIT COUNTY




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E E

EXISTING CONDITIONS AND KEY MAP

0200 200

400

SCALE IN FEET

GENERAL NOTES:

1. PHASE 1 PROJECT ELEMENTS CONSTRUCTED IN 2011

AND 2012.

2. ADDITIONAL WETLAND DELINEATION NEEDED.

WETLANDS HAVE NOT BEEN DELINEATED OUTSIDE

PHASE 1 PROJECT AREA.

3. 2012 PHASE 1 DRAINAGE IMPROVEMENTS

INCREASED DITCH AND CULVERT CONVEYANCE

CAPACITY ALONG MINKLER ROAD.

4. PHASE 2 IMPROVEMENTS WILL INCLUDE

ALTERNATIVE 2 AREA IF PROPERTY ACQUISITION

POSSIBLE FROM BURRESS AND IF EASEMENTS AND

COLLABORATION GRANTED BY NORTHWEST GAS

PIPELINE. OTHERWISE PHASE 2 PROJECT LIMITED TO

ALTERNATIVE 1 AREA SHOWN. EXACT LOCATIONS

OF UTILITIES TO BE VERIFIED.

5. THE FUTURE PHASE 3 PROJECT WILL REPLACE THE

EXISTING HANSEN CREEK CULVERT UNDER MINKLER

ROAD TO REDUCE CHANNEL CONFINEMENT AND

IMPROVE THE CONTINUITY OF THE HYDROLOGIC

AND GEOMORPHIC PROCESSES BENEATH THE

CROSSING.

LEGEND:

EXISTING MAJOR CONTOUR

EXISTING MINOR CONTOUR

OVERHEAD UTILITIES

EXISTING WETLANDS

PHASE 2 PROJECT LIMITS

(WITH ALT 2)


2011 REVEGETATION AREA


(ALT 1 ONLY)


P POVERHEAD POWER

G GBURIED GAS LINES

PARCEL BOUNDARY

NORTHWEST GAS

PIPELINE, SEE NOTE 4

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PROPOSED PROJECT PLAN NORTH

NOTES:

1. NOTCH EXISTING RIGHT BANK LEVEE OF HANSEN CREEK TO

ENCOURAGE HANSEN CREEK FLOW AND SEDIMENT TRANSPORT

TOWARD RIGHT BANK (WEST) FLOODPLAIN.

2. MAINTAIN SEVERAL HIGH ELEVATION UPLAND LOCATIONS TO

ENCOURAGE FLOODPLAIN FLOW INUNDATION, AND VEGETATION

DIVERSITY. INCLUDE MICROTOPOGRAPHY COMPLEXITY AND

DEPRESSIONS. THAT POSITIVELY DRAIN BACK TO CHANNEL.

3. EXACT LOCATIONS AND NUMBERS OF LOG STRUCTURES TO BE

DETERMINED.

1000

100200

SCALE IN FEET

NOTCH LEVEE BETWEEN DENSE TREES

FOR NEW HANSEN CREEK CHANNEL

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ll rights reserved.

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DESIGNED:

DESIGNED:

DESIGNED:

SCALE:

DRAWN:

DRAWN:

CHECKED:

APPROVED:

DATE:

PROJECT NO:

DRAWING NO:

SHEET NO: OF

MAY 2013

10-04664-004

7

C. AVOLIO

I. MOSTRENKO

-

AS NOTED

T. PRESCOTT

-

I. MOSTRENKO

M. EWBANK


SKAGIT COUNTY




D

R

A

F

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MA

TC

HL

IN

E S

EE

S

HE

ET

C

-2

LEGEND:



EXISTING CREEK CENTERLINE

PARCEL BOUNDARY

EXISTING WETLANDS

PROJECT LIMTS

0+00 1+00

PROPOSED CHANNEL ALIGNMENT

FLOODPLAIN LOWERING

GRADING ZONE (ALT 1 ONLY)

PROPOSED HANSEN CREEK

CHANNEL AND WETLAND ZONE

RED CREEK OCCUPIES OLD

(EXISTING) HANSEN CREEK CHANNEL

ENCOURAGE FLOODPLAIN

HYDROLOGIC CONNECTIVITY TO

CHANNEL WITH GRADING, SEE

A

C-3

EXCAVATE NEW HANSEN CREEK

CHANNEL AND FLOODPLAIN, SEE

1

C-3

BANK LOG STRUCTURES

(SEE NOTE 3)

ROOTWAD LOG STRUCTURES

(SEE NOTE 3)

SEE NOTE 1

SEE NOTE 1

RAPTOR PERCH (SNAG)

RIGHT BANK LEVEE NOTCH


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PROPOSED PROJECT PLAN SOUTH

1000

100200

SCALE IN FEET

RED CREEK OCCUPIES

OLD (EXISTING ) HANSEN

CREEK CHANNEL

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O:\proj\Y

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Todd P

rescott

© 2013 H

errera E

nvironm

ental, Inc. A

ll rights reserved.

Cad U

ser:

Path:

Plot D

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DESIGNED:

DESIGNED:

DESIGNED:

SCALE:

DRAWN:

DRAWN:

CHECKED:

APPROVED:

DATE:

PROJECT NO:

DRAWING NO:

SHEET NO: OF

MAY 2013

10-04664-004

7

C. AVOLIO

I. MOSTRENKO

-

AS NOTED

T. PRESCOTT

-

I. MOSTRENKO

M. EWBANK


SKAGIT COUNTY




D

R

A

F

T


MA

TC

HL

IN

E S

EE

S

HE

ET

C

-1

LEGEND:




PARCEL BOUNDARY

PROJECT LIMTS

0+00 1+00

PROPOSED CHANNEL ALIGNMENT

PROPOSED CHANNEL AND

WETLAND ZONE

FLOODPLAIN LOWERING

GRADING ZONE (WITH ALT 2)



FLOODPLAIN LOWERING

GRADING ZONE (ALT 1 ONLY)

HIGH ELEVATION UPLAND

HUMMOCK

BANK LOG STRUCTURES

(SEE NOTE 3)

ROOTWAD LOG STRUCTURES

(SEE NOTE 3)

ALTERNATIVE 1 NEW CONFLUENCE

OF HANSEN AND RED CREEKS

ALTERNATIVE 2 NEW CONFLUENCE

OF HANSEN AND RED CREEKS

EXCAVATE NEW

HANSEN CREEK

CHANNEL AND

FLOODPLAIN, SEE

1

C-3

GENERAL NOTES:

1. PHASE 2 IMPROVEMENTS WILL INCLUDE

ALTERNATIVE 2 AREA IF PROPERTY ACQUISITION

POSSIBLE FROM BURRESS AND IF EASEMENTS AND

COLLABORATION GRANTED BY NORTHWEST GAS

PIPELINE. OTHERWISE PHASE 2 PROJECT LIMITED TO

ALTERNATIVE 1 AREA SHOWN.

2. MAINTAIN SEVERAL HIGH ELEVATION UPLAND

LOCATIONS, AS SHOWN TO ENCOURAGE

FLOODPLAIN FLOW INUNDATION, AND VEGETATION

DIVERSITY. INCLUDE MICROTOPOGRAPHY

COMPLEXITY AND DEPRESSIONS. THAT POSITIVELY

DRAIN BACK TO CHANNEL.

3. EXACT LOCATIONS AND NUMBERS OF LOG

STRUCTURES TO BE DETERMINED.

4. EXACT LOCATIONS OF UTILITIES TO BE VERIFIED.

ENCOURAGE FLOODPLAIN

HYDROLOGIC CONNECTIVITY TO

CHANNEL WITH GRADING, SEE

A

C-3

A

C-3

THIS CHANNEL SEGMENT NOT

CONSTRUCTED UNDER ALTERNATIVE 1

RAPTOR PERCH (SNAP)

E EOVERHEAD UTILITIES

P POVERHEAD POWER

G GBURIED GAS LINES

NORTHWEST GAS

PIPELINE, SEE NOTE 4

1

5

2

4

5

:1

2

:

1

1

:1

3

:

1

3

1

5

3

2

4

2

:

1

3

:

1

1

2

1:1

1

:

1

3

4

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LOG STRUCTURE DETAILS

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O:\proj\Y

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Todd P

rescott

© 2013 H

errera E

nvironm

ental, Inc. A

ll rights reserved.

Cad U

ser:

Path:

Plot D

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DESIGNED:

DESIGNED:

DESIGNED:

SCALE:

DRAWN:

DRAWN:

CHECKED:

APPROVED:

DATE:

PROJECT NO:

DRAWING NO:

SHEET NO: OF

MAY 2013

10-04664-004

7

C. AVOLIO

I. MOSTRENKO

-

AS NOTED

T. PRESCOTT

-

I. MOSTRENKO

M. EWBANK


SKAGIT COUNTY




D

R

A

F

T


LEGEND:

A

-

FLOW

FLOW

N

O

S

L

O

P

E

SURVEY CONTROL POINT

AT CENTER OF CHANNEL

SURVEY CONTROL POINT AT CENTER

OF LOW FLOW CHANNEL

FLOW

PARTIALLY

EMBEDDED LOG

EXPOSED EMBEDDED

LOG #

LOG

CATEGORY

DIAMETER

(IN)

LENGTH (FT)

ROOTWAD

1 1 18 30 YES

2 2 18 30 NO

3 2 18 30 NO

4 2 18 30 NO

5 9 18 15 NO

TABLE - BANK LOG STRUCTURE LOG SCHEDULE

LOG #

LOG

CATEGORY

DIAMETER

(IN)

LENGTH

(FT)

ROOTWAD

1 3 18 25 YES

2 4 18 25 NO

3 3 18 25 YES

4 4 18 25 NO

TABLE - ROOTWAD LOG STRUCTURE LOG SCHEDULE


EXISTING SUBGRADE

1

LOG IDENTIFICATION NUMBER

6.5' (MIN)

SCALE:

PLAN - BANK LOG STRUCTURE 1

-

NTS SCALE:

PLAN - ROOTWAD LOG STRUCTURE 2

-

NTS

SCALE:

SECTION - BANK LOG STRUCTURE A

-

NTS

54

64

0+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00

62

60

58

56

66

9+00 10+00 11+00 12+00

54

64

62

60

58

56

66

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CHANNEL AND FLOODPLAIN

SECTIONS AND DETAILS

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Todd P

rescott

© 2013 H

errera E

nvironm

ental, Inc. A

ll rights reserved.

Cad U

ser:

Path:

Plot D

ate:


DESIGNED:

DESIGNED:

DESIGNED:

SCALE:

DRAWN:

DRAWN:

CHECKED:

APPROVED:

DATE:

PROJECT NO:

DRAWING NO:

SHEET NO: OF

MAY 2013

10-04664-004

7

C. AVOLIO

I. MOSTRENKO

-

AS NOTED

T. PRESCOTT

-

I. MOSTRENKO

M. EWBANK


SKAGIT COUNTY




D

R

A

F

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HORIZ. SCALE:

VERT. SCALE:

SECTION A

C-2

1"=80'

1"=8'

SCALE IN FEET

40 0 40 80

SCALE IN FEET

4 0 4 8

HORIZONTAL SCALE

VERTICAL SCALE

NEW HANSEN CREEK

CHANNEL, SEE

NOTES:

1. CROSS SECTIONS ARE LOOKING DOWNSTREAM - TO THE SOUTH.

2. GRADE FLOODPLAIN AT 0.5% SLOPE (APPROX.) TOWARD CHANNEL.

3. MAINTAIN SEVERAL HIGH ELEVATION UPLAND LOCATIONS, AS SHOWN TO ENCOURAGE FLOODPLAIN FLOW INUNDATION, AND

VEGETATION DIVERSITY. INCLUDE MICROTOPOGRAPHY COMPLEXITY AND DEPRESSIONS.

4. LOG STRUCTURES TO BE PLACED ALONG CHANNEL AND FLOODPLAIN. SEE DWGS C-1 AND C-2 FOR APPROXIMATE LOCATION

AND DETAILS ON DWG C-4.

1

-

EXISTING SUBGRADE

EMBANKMENT

LEGEND:

TOPSOIL TYPE B

STREAMBED GRAVEL


MAINTAIN EXISTING GRADE TO

PRESERVE EXISTING TREES

NEW ALTERNATIVE 2

HANSEN CREEK CHANNEL

ALTERNATIVE 1 FLOODPLAIN

LOWER TO ELEV. 59.5' (TYP)

NEW ALTERNATIVE 1

HANSEN CREEK CHANNEL

OLD (EXISTING) HANSEN CREEK

CHANNEL, NEW RED CREEK CHANNEL

℄1 (TYP)

2

REMOVE 1' (MIN) AND REPLACE WITH SALVAGED GRAVEL

SCALE:

DETAIL - NEW HANSEN CREEK CHANNEL1

VAR

1" = 10'

VARIES (80' - 500') STAGE 1 FLOODPLAIN

10' LOW FLOW

CHANNEL. SEE

NOTE 1

WETLAND BENCH, SEE NOTE 1

REPLACE OVEREXCAVATED

AREAS WITH NATIVE SOIL

80' (MIN) STAGE 2 FLOODPLAIN

SCALE IN FEET

5 0 5 10

EXISTING GRADE

PROPOSED GRADE

SEE NOTE 2 SEE NOTE 2

SEE

NOTE 2SEE NOTE 2

GRADE BACK AT 2H:1V (MAX) TO MATCH

BOETTCHER PROPERTY LINE

1'

1'-2' VARIES

0' - 3' VARIES, SEE NOTE 2

NEW HANSEN CREEK

CHANNEL, SEE

1

-

SEE NOTE 4

ALTERNATIVE 2 FLOODPLAIN

LOWER TO ELEV. 59.5' (TYP)

30'

STAGE 1 FLOODPLAIN

NOTES:

1. LOW FLOW CHANNEL AND WETLAND BENCH LOCATION MAY VARY WITHIN OVERALL

FLOODPLAIN.

2. HEIGHT BETWEEN STAGE 1 AND STAGE 2 FLOODPLAIN VARIES. HEIGHT IS ZERO AT

SOUTHERN EXTENT OF PROJECT AREA WHERE FLOODPLAIN GRADING OCCURS, SEE

STAGE 2 FLOODPLAIN

STAGE 3 FLOODPLAIN

STAGE 1 FLOODPLAIN

A

-

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PLANTING PLAN

0200 200

400

SCALE IN FEET

SEE DWG C-2 FOR ALTERNATIVE

CHANNEL ALIGNMENTS; PLANT RIPARIAN

WETLAND FOREST WHERE ALTERNATIVE

CHANNEL NOT CONSTRUCTED

5/23/2013 12:14 P

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O:\proj\Y

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AD

\D

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-1.dw

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Todd P

rescott

© 2013 H

errera E

nvironm

ental, Inc. A

ll rights reserved.

Cad U

ser:

Path:

Plot D

ate:


DESIGNED:

DESIGNED:

DESIGNED:

SCALE:

DRAWN:

DRAWN:

CHECKED:

APPROVED:

DATE:

PROJECT NO:

DRAWING NO:

SHEET NO: OF

MAY 2013

10-04664-004

7

C. AVOLIO

I. MOSTRENKO

-

AS NOTED

T. PRESCOTT

-

I. MOSTRENKO

M. EWBANK


SKAGIT COUNTY




D

R

A

F

T


NAVD 88, NAD 83

GENERAL NOTES:

1. ADDITIONAL WETLAND DELINEATION NEEDED.

WETLANDS HAVE NOT BEEN DELINEATED OUTSIDE

THE PHASE 1 PROJECT AREA.

LEGEND:




PARCEL BOUNDARY

EXISTING WETLANDS

PROJECT LIMITS

PHASE 1 PLANTING ZONES

RIPARIAN WETLAND FOREST

PLANTING ZONE

UPLAND HUMMOCK FOREST

PLANTING ZONE

SHRUB AND EMERGENT WETLAND

PLANTING ZONES

concept development and preliminary project analysis...

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