About Zackuse Creek
Zackuse (also spelled Zaccuse) Creek drains a 240-acre watershed into Lake Sammamish. It is one of the four primary creeks used by endangered kokanee of Lake Sammamish. The creek descends from the Plateau through mature forest to what was previously farmland.
In the 1800s, the area was deforested and much was converted to farmland. The Seattle Lakeshore & Eastern Railroad crossed Zackuse Creek approximately 500 feet upstream of Lake Sammamish, and a lumber mill was located on the shoreline within one mile to the north. Since the 1980s, significant residential development has taken place in the upper watershed.
Features of the 2018 Zackuse Creek restoration project:
- Replaced pipe culvert barriers with fish-friendly box culverts. The new culverts provide wide, unobstructed fish passage, designed to emulate a natural stream bed. Locations:
- East Lake Sammamish Parkway (ELSP)
- East Lake Sammamish Trail
- East Lake Sammamish Shore Lane NE
- Realigned (relocated) and restored 400 feet of creek:
- Away from: 1) where it was choked by invasives, which had trapped fines and sands and destroyed spawning habitat; and 2) where the channel was straight and provided no habitat.
- Inline with the new box culvert at ELSP.
- Design goals:
- Enable the creek to sort gravel and sediments to maintain good spawning material for kokanee.
- Prevent sedimentation of the creek channel by allowing fines and sands to flush through to Lake Sammamish and outside of the creek channel to the wetlands.
- Prevent the stream channel from migrating within the alluvial plain in order to maintain alignment with the culvert at ELSP.
- Establish riparian growth with the goal of longterm stream diversity.
- Design features:
- NEED HELP HERE BECAUSE THE ACTUAL DESIGN DIFFERS FROM THE PLAN.
Challenges of an alluvial plain
The plateau above the project area is characterized by glacial deposition and, during storm events, Zackuse Creek carries a high load of sediment and gravel. The project area is, in fact, historically an alluvial plain — where sediment drops off as flow fans out. Typically, within such an environment, the creek would naturally migrate and braid, and this presents a challenge for longterm alignment with permanent structures — in this case, the culvert under East Lake Sammamish Parkway.
The new section of creek was designed to maintain a defined channel, with some room for the creek to migrate within the channel. The ongoing challenge will be how to preserve its alignment with the culvert while not creating sediment deposition buildup within the channel.
As of February, 2021, the new box channel culvert has accumulated significant sediment and will need to be monitored and possibly modified to ensure sediment flows through to Lake Sammamish, as intended, rather than create flooding problems.
Significant issues remain upstream
Immediately upstream of the project area (Reaches 5 & 6 in the gallery) is an area of transition to mature forest. These reaches should demonstrate what recovery looks like. Instead, they show the effects of surging stormwater runoff from residential development in the upper watershed. Paved surfaces and roofs (impervious surfaces) have altered the flow of the creek. Storm drains, which convey rain water to the creek quickly rather than allow it to percolate into the groundwater table, overload Zackuse Creek during storm events, scouring the creek bed and eroding natural features of the channel. More than that, all creeks rely on groundwater for flow during dry periods, and development in the upper watershed has blocked a significant portion of that recharge for Zackuse Creek.
Evidence A in Zackuse Creek: in 2012, stream surveyors documented a __-foot long incised channel in Reach 5 (see gallery). They concluded that this incision in the creek channel is a result of the creek not being able to naturally withstand the new volume of storm water flow from developments upstream.
Evidence B in Zackuse Creek: at the upstream end of this incision — at the time — was a 5-foot high waterfall. When the surveyors returned in 2015, the waterfall had receded over 150 feet upstream (extending the incised channel). It is most likely that this incision has eroded further upstream since that time.
This creekbed incision & recession was responsible for much of the sediment deposition in the lower reaches prior to the realignment of the creek in 2018. The new, realigned channel has been designed to compensate for this sediment overload, but the continuing erosion, incision and recession of this upstream reach will destroy further habitat upstream until it is addressed.
Special Note: Collaboration
This restoration project was initiated in 2012 when Wally Pereyra, a private landowner and kokanee advocate, contracted an environmental-engineering firm to evaluate conditions on Zackuse Creek from the mouth of the creek to the east portion of his property (over 1,300 feet total). Mr. Pereyra funded a second study in 2015, all with the intent of jumpstarting a formal review process for the creek. His efforts led to a restoration partnership of the following agencies and groups:
- City of Sammamish
- King County Parks
- Kokanee Work Group
- Snoqualmie Tribe
- Trout Unlimited
- Washington State Fish and Wildlife
- Private property owners.