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
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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
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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
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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
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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.
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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.
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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 3
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
Sedro-Woolley
Hanse
nCr
eekRed
Creek
Minkler Road
Old Oxbow Channel
Coal Creek
UV9
UV20
K:\Projects\10-04664-001\Project\vicinity_map.mxd (5/23/2013)
0 3,000 6,0001,500Feet
LegendStreamProject areaProperty boundaryCity boundary
PACI
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OREGON
WASHINGTON
BRITISH COLUMBIA
Area ofmap detail
Aerial: USDA (2009)
Figure 1. Vicinity Map for the Hansen Creek Reach 5 Restoration Project Area.
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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 5
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
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6 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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.
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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 7
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.
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8 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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
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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 9
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
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10 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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)
Total Annual Average
Sediment Input
(cy/year)
Total Annual Average
Bedload Flux (tons/year)
Total Annual Average
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.
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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 11
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
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12 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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.
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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 13
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
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14 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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
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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 15
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
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16 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 17
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
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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 19
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.
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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 21
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.
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22 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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.
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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 23
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
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24 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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
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Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 25
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.
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26 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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
Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 27
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
28 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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
Hansen
Creek
Red Cr
eek
Old Oxbow Channel
Minkler Road Ditch
Martinez
Good
Nielsen
Boettcher
Snyder
Hudson
Burress
Swinomish Tribe,formely Knudsen
Breier
Soldate
Harris
Sorensen
Houston
Frank
Kauf
man
Cedar LanePark
Van Puttenand Taylor
Tung
ley
DannoWhite
Cook Cook
Cook
ElkProperties
Stovall Howland
Hankins DooborskyKnapp
Peterson
Tillman
Good
Sorensen
Draper Valley
Haberly
Minkler Road E
Fruit
dale
Road
N
State Route 20 E
Burmaster Road E
Soren
Roa
d N
Chase Road E
Breie
r Lan
e N
Helm
ick R
oad E
Mcgarigle R
oad E
Wicker Road E
Marlene Way E
Diane Lane E
1306500
1306500
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1307250
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1308750
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0 750 1,500375Feet
Aerial: Skagit County 2011, USDA (2009)Coordinates: WA State Plane North
NAD 83 (feet)
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
Hansen
Creek
Red Cr
eek
Old Oxbow Channel
Minkler Road Ditch
Martinez
Good
Nielsen
Boettcher
Snyder
Hudson
Burress
Swinomish Tribe,formely Knudsen
Breier
Soldate
Harris
Sorensen
Houston
Frank
Kauf
man
Cedar LanePark
Van Puttenand Taylor
Tung
ley
DannoWhite
Cook Cook
Cook
ElkProperties
Stovall Howland
Hankins DooborskyKnapp
Peterson
Tillman
Good
Sorensen
Draper Valley
Haberly
Minkler Road E
Fruit
dale
Road
N
State Route 20 E
Burmaster Road E
Soren
Roa
d N
Chase Road E
Breie
r Lan
e N
Helm
ick R
oad E
Mcgarigle R
oad E
Wicker Road E
Marlene Way E
Diane Lane E
1306500
1306500
1307250
1307250
1308000
1308000
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1308750
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1309500
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NAD 83 (feet)K:\Projects\10-04664-001\Project\modeling_output_round10.mxd (3/1/2013) Round 10
LegendStreamMinkler Ditch flow
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.
Hansen
Creek
Red Cr
eek
Old Oxbow Channel
Minkler Road Ditch
Martinez
Good
Nielsen
Boettcher
Snyder
Hudson
Burress
Swinomish Tribe,formely Knudsen
Breier
Soldate
Harris
Sorensen
Houston
Frank
Kauf
man
Cedar LanePark
Van Puttenand Taylor
Tung
ley
DannoWhite
Cook Cook
Cook
ElkProperties
Stovall Howland
Hankins DooborskyKnapp
Peterson
Tillman
Good
Sorensen
Draper Valley
Haberly
Minkler Road E
Fruit
dale
Road
N
State Route 20 E
Burmaster Road E
Soren
Roa
d N
Chase Road E
Breie
r Lan
e N
Helm
ick R
oad E
Mcgarigle R
oad E
Wicker Road E
Marlene Way E
Diane Lane E
1306500
1306500
1307250
1307250
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1308000
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1308750
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1309500
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50
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0 750 1,500375Feet
Aerial: Skagit County 2011, USDA (2009)Coordinates: WA State Plane North
NAD 83 (feet)K:\Projects\10-04664-001\Project\modeling_output_round10.mxd (3/1/2013) Round 10
LegendMinkler Ditch flowStream
Existing 100-year flood depth (ft)< 11 to 22 to 33 to 44 to 55 to 66 to 7
Figure 5.Existing 100-year Flood DepthsReflecting Near-Term Improvements.
Hansen
Creek
Red Cr
eek
Old Oxbow Channel
Minkler Road Ditch
Martinez
Good
Nielsen
Boettcher
Snyder
Hudson
Burress
Swinomish Tribe,formely Knudsen
Breier
Soldate
Harris
Sorensen
Houston
Frank
Kauf
man
Cedar LanePark
Van Puttenand Taylor
Tung
ley
DannoWhite
Cook Cook
Cook
ElkProperties
Stovall Howland
Hankins DooborskyKnapp
Peterson
Tillman
Good
Sorensen
Draper Valley
Haberly
Minkler Road E
Fruit
dale
Road
N
State Route 20 E
Burmaster Road E
Soren
Roa
d N
Chase Road E
Breie
r Lan
e N
Helm
ick R
oad E
Mcgarigle R
oad E
Wicker Road E
Marlene Way E
Diane Lane E
1306500
1306500
1307250
1307250
1308000
1308000
1308750
1308750
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1309500
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5580
00
5587
50
5587
50
0 750 1,500375Feet
Aerial: Skagit County 2011, USDA (2009)Coordinates: WA State Plane North
NAD 83 (feet)
Figure 6.100-year Flood Depth for the Phase 2 Medium-TermProject Alternative 1.
K:\Projects\10-04664-001\Project\modeling_output_round10.mxd (3/1/2013) Round 10
LegendStreamMinkler Ditch flow
100-year flood depth (ft)< 11 to 22 to 33 to 44 to 55 to 66 to 7
Hansen
Creek
Red Cr
eek
Old Oxbow Channel
Minkler Road Ditch
Martinez
Good
Nielsen
Boettcher
Snyder
Hudson
Burress
Swinomish Tribe,formely Knudsen
Breier
Soldate
Harris
Sorensen
Houston
Frank
Kauf
man
Cedar LanePark
Van Puttenand Taylor
Tung
ley
DannoWhite
Cook Cook
Cook
ElkProperties
Stovall Howland
Hankins DooborskyKnapp
Peterson
Tillman
Good
Sorensen
Draper Valley
Haberly
Minkler Road E
Fruit
dale
Road
N
State Route 20 E
Burmaster Road E
Soren
Roa
d N
Chase Road E
Breie
r Lan
e N
Helm
ick R
oad E
Mcgarigle R
oad E
Wicker Road E
Marlene Way E
Diane Lane E
1306500
1306500
1307250
1307250
1308000
1308000
1308750
1308750
1309500
1309500
1310250
1310250
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1311000
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NAD 83 (feet)K:\Projects\10-04664-001\Project\modeling_output_round10.mxd (3/1/2013) Round 10
LegendStreamMinkler Ditch flow
100-year flood depth (ft)< 11 to 22 to 33 to 44 to 55 to 66 to 7
Figure 7.100-year Flood Depth for the Phase 2 Medium-TermProject Alternative 2.
May 2013
Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 39
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.
Hansen
Creek
Red Cr
eek
Old Oxbow Channel
Minkler Road Ditch
Martinez
Good
Nielsen
Boettcher
Snyder
Hudson
Burress
Swinomish Tribe,formely Knudsen
Breier
Soldate
Harris
Sorensen
Houston
Frank
Kauf
man
Cedar LanePark
Van Puttenand Taylor
Tung
ley
DannoWhite
Cook Cook
Cook
ElkProperties
Stovall Howland
Hankins DooborskyKnapp
Peterson
Tillman
Good
Sorensen
Draper Valley
Haberly
Minkler Road E
Fruit
dale
Road
N
State Route 20 E
Burmaster Road E
Soren
Roa
d N
Chase Road E
Breie
r Lan
e N
Helm
ick R
oad E
Mcgarigle R
oad E
Wicker Road E
Marlene Way E
Diane Lane E
1306500
1306500
1307250
1307250
1308000
1308000
1308750
1308750
1309500
1309500
1310250
1310250
1311000
1311000
1311750
1311750
1312500
1312500
1313250
1313250
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1314000
1314750
1314750
1315500
1315500
5527
50
5527
50
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00
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00
5542
50
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50
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00
5572
50
5572
50
5580
00
5580
00
5587
50
5587
50
0 750 1,500375Feet
Aerial: Skagit County 2011, USDA (2009)Coordinates: WA State Plane North
NAD 83 (feet)
Figure 8.2-year Flood Depth for the Phase 2 Medium-TermProject Alternative 1.
K:\Projects\10-04664-001\Project\modeling_output_round10.mxd (3/1/2013) Round 10
LegendStreamMinkler Ditch flow
2-year flood depth (ft)< 11 to 22 to 33 to 44 to 55 to 66 to 7
Hansen
Creek
Red Cr
eek
Old Oxbow Channel
Minkler Road Ditch
Martinez
Good
Nielsen
Boettcher
Snyder
Hudson
Burress
Swinomish Tribe,formely Knudsen
Breier
Soldate
Harris
Sorensen
Houston
Frank
Kauf
man
Cedar LanePark
Van Puttenand Taylor
Tung
ley
DannoWhite
Cook Cook
Cook
ElkProperties
Stovall Howland
Hankins DooborskyKnapp
Peterson
Tillman
Good
Sorensen
Draper Valley
Haberly
Minkler Road E
Fruit
dale
Road
N
State Route 20 E
Burmaster Road E
Soren
Roa
d N
Chase Road E
Breie
r Lan
e N
Helm
ick R
oad E
Mcgarigle R
oad E
Wicker Road E
Marlene Way E
Diane Lane E
1306500
1306500
1307250
1307250
1308000
1308000
1308750
1308750
1309500
1309500
1310250
1310250
1311000
1311000
1311750
1311750
1312500
1312500
1313250
1313250
1314000
1314000
1314750
1314750
1315500
1315500
5527
50
5527
50
5535
00
5535
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5542
50
5542
50
5550
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5550
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5557
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5565
00
5572
50
5572
50
5580
00
5580
00
5587
50
5587
50
0 750 1,500375Feet
Aerial: Skagit County 2011, USDA (2009)Coordinates: WA State Plane North
NAD 83 (feet)
Figure 9.2-year Flood Depth for the Phase 2 Medium-TermProject Alternative 2.
K:\Projects\10-04664-001\Project\modeling_output_round10.mxd (3/1/2013) Round 10
LegendStreamMinkler Ditch flow
2-year flood depth (ft)< 11 to 22 to 33 to 44 to 55 to 66 to 7
May 2013
Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 45
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
46 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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
Martinez
Good
Nielsen
Boettcher
Snyder
Hudson
Burress
Swinomish Tribe,formely Knudsen
Breier
Soldate
Harris
Sorensen
Houston
Frank
Kauf
man
Cedar LanePark
Van Puttenand Taylor
Tung
ley
DannoWhite
Cook Cook
Cook
ElkProperties
Stovall Howland
Hankins DooborskyKnapp
Peterson
Tillman
Good
Sorensen
Draper Valley
Haberly
Minkler Road E
Fruit
dale
Road
N
State Route 20 E
Burmaster Road E
Soren
Roa
d N
Chase Road E
Breie
r Lan
e N
Helm
ick R
oad E
Mcgarigle R
oad E
Wicker Road E
Marlene Way E
Diane Lane E
1306500
1306500
1307250
1307250
1308000
1308000
1308750
1308750
1309500
1309500
1310250
1310250
1311000
1311000
1311750
1311750
1312500
1312500
1313250
1313250
1314000
1314000
1314750
1314750
1315500
1315500
5527
50
5527
50
5535
00
5535
00
5542
50
5542
50
5550
00
5550
00
5557
50
5557
50
5565
00
5565
00
5572
50
5572
50
5580
00
5580
00
5587
50
5587
50
0 750 1,500375Feet
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
g
Summer
Fall
Winter
Sprin
g
Summer
Fall
Winter
Sprin
g
Summer
Fall
Winter
Sprin
g
Summer
Fall
Winter
Sprin
g
Summer
Fall
Winter
Sprin
g
Summer
Fall
Winter
Sprin
g
Summer
Fall
Winter
Sprin
g
Summer
Fall
Winter
Sprin
g
Summer
Fall
Channel and Floodplain Habitat
Field Evaluation (County, Herrera)
Construction (SRSC)
**
Drainage Improvements
Field Evaluation (County, Herrera)
Construction (County)
**
Riparian PlantingsField Evaluation (County, Herrera)
Design and Permitting (SFEG, SRSC)
**
West floodplain grading and revegetation
Field Evaluation (County, Herrera)
**
Introduce Hansen flow to west floodplain
Field Evaluation (County, Herrera)
**
Install wood in Red Creek (old Hansen Creek)
Field Evaluation (County, Herrera)
**
Replace Minkler Rd. Hansen Culvert with new Bridge
Field Evaluation (County, Herrera)
**
Floodplain grading and channel restoration
Field Evaluation (County, Herrera)
**
* * Denotes the completion of a particular project component.
Construction (County)
Phase 1 ‐ Near‐Term Project
Construction (SFEG, SRSC)
Project Planning (All stakeholders)
Project Planning (All stakeholders)
Final Design and Permitting (County, Herrera)Final Design and Permitting (County, Herrera)
Preliminary (30%) Design (County, Herrera)
Preliminary (30%) Design (County, Herrera)
Final Design and Permitting (County, Herrera)
Final Design and Permitting (County, Herrera)
Project Planning (All stakeholders)
Project Planning (All stakeholders)Final Design and Permitting (County, Herrera)
Preliminary (30%) Design (County, Herrera)
2016
Project Planning (All stakeholders)
Design and Permitting (County, Herrera)
Design modifications
Design and Permitting (County, Herrera)
2015
Project Planning (All stakeholders)
2010 2011 2012 2013 2014
Construction (County)
Floodplain Establishment Period
Floodplain Establishment Period
Project Planning (All stakeholders)
Project Planning (All stakeholders)
Preliminary (30%) Design (County, Preliminary (30%) Design (County,
Construction (County)Construction (County)
2018
Phase 3 ‐ Long‐Term Project
Phase 2 ‐ Medium‐Term Project
2017
Construction (County)
May 2013
50 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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
Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 51
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
52 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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
Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project 53
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
54 Draft Concept Development and Preliminary Project Analysis and Design – Hansen Creek Reach 5 Restoration Project
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
D (mm) --> 4.950905 8.216144 13.24405 14.556951.00000 100 D16 (mm) D50 (mm) D84 (mm) D90 (mm)
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1015202530354045
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O:\proj\Y2010\10-04664-001\Data\Geomorphic analysis\Pebble Counts\Hansen_Reach5_PebbleCounts_4-28-10.xlsReach 4_GPS 15 5/23/2013
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
D (mm) --> 4.962269 8.99824 15.3685 18.736481.00000 109 D16 (mm) D50 (mm) D84 (mm) D90 (mm)
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
D (mm) --> 5.211384 10.48769 19.84783 24.345031.00000 101 D16 (mm) D50 (mm) D84 (mm) D90 (mm)
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O:\proj\Y2010\10-04664-001\Data\Geomorphic analysis\Pebble Counts\Hansen_Reach5_PebbleCounts_4-28-10.xlsReach 5_GPS 16 5/23/2013
APPENDIX D
Phase 2 Medium-Term Project
30% Drawings
Herrera.ctb
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No. REVISION BY APP'D DATE
DESIGNED:
DESIGNED:
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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
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I. MOSTRENKO
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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ALL DRAWINGS - REVEGETATION AREAS TP CA 5/15/131
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
1
C-3
SCALE:
DETAIL 1
C-1
NTS
A
C-4
SCALE:
SECTIONA
C-2
NTS
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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Todd P
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errera E
nvironm
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ll rights reserved.
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Path:
Plot D
ate:
No. REVISION BY APP'D DATE
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
30% PERMIT SET - NOT FOR CONSTRUCTION
SKAGIT COUNTY
HANSEN CREEK/RED CREEK PHASE 2
MEDIUM-TERM HABITAT IMPROVEMENT PROJECT
SEDRO-WOOLLEY, WASHINGTON
D
R
A
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ALL DRAWINGS - REVEGETATION AREAS TP CA 5/15/131
NAVD 88, NAD 83
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)
PHASE 1 PROJECT LIMITS
2011 REVEGETATION AREA
PHASE 2 PROJECT LIMITS
(ALT 1 ONLY)
PHASE 3 PROJECT LIMITS
P POVERHEAD POWER
G GBURIED GAS LINES
PARCEL BOUNDARY
NORTHWEST GAS
PIPELINE, SEE NOTE 4
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C-1
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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Todd P
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© 2013 H
errera E
nvironm
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ll rights reserved.
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Path:
Plot D
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No. REVISION BY APP'D DATE
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
30% PERMIT SET - NOT FOR CONSTRUCTION
SKAGIT COUNTY
HANSEN CREEK/RED CREEK PHASE 2
MEDIUM-TERM HABITAT IMPROVEMENT PROJECT
SEDRO-WOOLLEY, WASHINGTON
D
R
A
F
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ALL DRAWINGS - REVEGETATION AREAS TP CA 5/15/131
MA
TC
HL
IN
E S
EE
S
HE
ET
C
-2
LEGEND:
EXISTING MAJOR CONTOUR
EXISTING MINOR CONTOUR
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
2011 REVEGETATION AREA
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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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Todd P
rescott
© 2013 H
errera E
nvironm
ental, Inc. A
ll rights reserved.
Cad U
ser:
Path:
Plot D
ate:
No. REVISION BY APP'D DATE
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
30% PERMIT SET - NOT FOR CONSTRUCTION
SKAGIT COUNTY
HANSEN CREEK/RED CREEK PHASE 2
MEDIUM-TERM HABITAT IMPROVEMENT PROJECT
SEDRO-WOOLLEY, WASHINGTON
D
R
A
F
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ALL DRAWINGS - REVEGETATION AREAS TP CA 5/15/131
MA
TC
HL
IN
E S
EE
S
HE
ET
C
-1
LEGEND:
EXISTING MAJOR CONTOUR
EXISTING MINOR CONTOUR
EXISTING CREEK CENTERLINE
PARCEL BOUNDARY
PROJECT LIMTS
0+00 1+00
PROPOSED CHANNEL ALIGNMENT
PROPOSED CHANNEL AND
WETLAND ZONE
FLOODPLAIN LOWERING
GRADING ZONE (WITH ALT 2)
PHASE 1 PROJECT LIMITS
2011 REVEGETATION AREA
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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Todd P
rescott
© 2013 H
errera E
nvironm
ental, Inc. A
ll rights reserved.
Cad U
ser:
Path:
Plot D
ate:
No. REVISION BY APP'D DATE
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
30% PERMIT SET - NOT FOR CONSTRUCTION
SKAGIT COUNTY
HANSEN CREEK/RED CREEK PHASE 2
MEDIUM-TERM HABITAT IMPROVEMENT PROJECT
SEDRO-WOOLLEY, WASHINGTON
D
R
A
F
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ALL DRAWINGS - REVEGETATION AREAS TP CA 5/15/131
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
SURVEY CONTROL POINT
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
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© 2013 H
errera E
nvironm
ental, Inc. A
ll rights reserved.
Cad U
ser:
Path:
Plot D
ate:
No. REVISION BY APP'D DATE
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
30% PERMIT SET - NOT FOR CONSTRUCTION
SKAGIT COUNTY
HANSEN CREEK/RED CREEK PHASE 2
MEDIUM-TERM HABITAT IMPROVEMENT PROJECT
SEDRO-WOOLLEY, WASHINGTON
D
R
A
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ALL DRAWINGS - REVEGETATION AREAS TP CA 5/15/131
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
SURVEY CONTROL POINT
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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2010\10-04664-004\C
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\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:
No. REVISION BY APP'D DATE
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
30% PERMIT SET - NOT FOR CONSTRUCTION
SKAGIT COUNTY
HANSEN CREEK/RED CREEK PHASE 2
MEDIUM-TERM HABITAT IMPROVEMENT PROJECT
SEDRO-WOOLLEY, WASHINGTON
D
R
A
F
T
ALL DRAWINGS - REVEGETATION AREAS TP CA 5/15/131
NAVD 88, NAD 83
GENERAL NOTES:
1. ADDITIONAL WETLAND DELINEATION NEEDED.
WETLANDS HAVE NOT BEEN DELINEATED OUTSIDE
THE PHASE 1 PROJECT AREA.
LEGEND:
EXISTING MAJOR CONTOUR
EXISTING MINOR CONTOUR
EXISTING CREEK CENTERLINE
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
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