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The Sammamish River is characterized by a uniform trapezoidal channel with
a silty/sandy bottom, low diversity riparian vegetation, and impaired water quality.
Lack of channel bottom, low diversity (such as low velocity pools for resting and cover from predation; gravel and cobble surfaces for food sources)
reduces resident fish use and limits river use for salmon and trout to a short-term
migration corridor. Lack of habitat diversity and native vegetation precludes
wildlife use for native species, while allowing introduced and invasive plants and animals
to thrive. Lack of shade along the river corridor allows summer water temperatures
to approach a critically high range for cold-water fish species, such as salmon and
trout.
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RiverWalk
Habitat Enhancement Project No. 1 (HEP 1) represents the City of Redmond's first undertaking to
restore the riparian habitat of the Sammamish River. The project, which is 300 feet
long, is constructed immediately north of the NE 85th Street bridge, west of the City Hall
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The
primary goal of this project was to enhance the river's environment for outmigrating
juvenile salmon. It was designed to be a pilot (or repeatable) project, coordinate
with other river uses including flood flow conveyance, and provide an aesthetically
pleasing area.
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Principle features of HEP 1 include:
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- Grading shaped the west bank into a series of
earth "benches". The top of the bank was moved back from the river about
fifty feet at its maximum point. The benches, stepping up from the water level,
provide the potential for different habitat zones and for trees which will help shade the
river as they grow taller. This grading provides spaces for plantings in the channel
while maintaining flood flow capacity.
- Both the newly reshaped west bank and
existing east bank were extensively planted with native, habitat-orientated vegetation to
support the river system (including its fish), to provide wildlife habitat, and to provide
future shade.
- In-stream work included an area about twenty
feet long where a mix of boulders, cobbles and gravel were installed in the channel
bottom, held in place against the current by a log placed across the channel bottom.
Other logs were added to the east bank, to help shape the grading and accelerate the river
velocity slightly over the rock mix to minimize the deposit of sediment. The rock
mixture provides a length of habitat change from the current slow silty river
bottom.
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This particular effort was a pilot project
and quickly showed signs of success. In September 1998, the U.S. Fish and Wildlife
Service studied the behavior of Chinook Salmon in Lake Washington and the waterways
connected to it. Although the HEP1 site was only monitored for one day, 10 Chinook
salmon and 90 Sockeye were counted in the "holding pool" created along the west
bank.
The City's HEP1 project team thanks the
prime design consultant, Parametrix, Inc., the landscape consultant, Steve Worthy &
Associates, and those in other agencies who helped with the design and permitting.
Agencies include King County Parks Department, King County Department of Natural
Resources, King County Property Services Division, State Department of Natural Resources,
State Department of Fish and Wildlife, State Department of Ecology, and US Army Corps of
Engineers.
Project sponsors either via cash or in-kind
service contributions include Group Health Credit Union, Puget Sound Energy, and
CarrAmerica.
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RiverWalk Habitat Enhancement
Project No. 2 (HEP 2) lies immediately north of HEP1. This project targets habitat
enhancement of 650 feet of the channelized Sammamish River and its banks for aquatic and
terretsrial wildlife. A main project design goal is to make the river look, flow,
and act more like a natural river. With this in mind, and lessons learned from HEP1,
grading and excavation of the channel and river banks has occurred to provide a more
natural topography, flow conditions, and diversity of aquatic .
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In-stream
features include:
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- placement of large woody
debris (LWD) in the form of fallen trees, root wads, and log jams;
- creation of gravel bars along
the water's edge on both river banks; and
- location of boulders and rock
outcroppings, mainly on the east .
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All of these features enhance the fisheries habitat of the river through
this reach.
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The river channel has been shifted a channel width to the west. Non-native and
invasive vegetation were replaced and both banks were densely planted with
native northwest riparian plant material. |
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RiverWalk Habitat Enhancement Project No 3
(HEP3) includes approximately 700 feet of the Sammamish River from the Redmond
Way Bridge to the railroad bridge, including both banks and the area under the
bridges. The goal of this project is to promote a major shift in the habitat
value of the river by meeting the following specific project objectives:
- Enhancement of the river substrate (in-channel bottom material);
- Diversification of the flow patterns;
- Enhancement of in-river general habitat and refuge habitat;
- Improvement of the function of the stormwater management facility (the
biofilters on the west side of the river);
- Control of exotic species (the non-native species of plants);
- Integration of project elements into the existing natural setting;
- Allowance for public opportunities to enjoy and observe wildlife (view
corridors); and
- Improvement of trail safety (where trail needs to be located further from
the river to provide space for habitat improvements).
The project is designed to improve habitat for migrating adult and juvenile
salmonids. In-river grading will occur to enhance form and function of the river
substrate and add variability to the flow regime. This grading will involve
placement of cobbles and gravelly material in the river bottom and formation of
a gravel bar island to split river flow during low-flow periods. It also
includes construction of gravel benches on either bank adjacent to the island.
Large woody debris will be placed in the river to mimic a natural stream system.
The plant communities on both banks will be restored to a native northwest
riparian system.
This project has been awarded a $150,000 King Conservation District Grant.
The city anticipates project construction in the summer of 2004.
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