About Confluence Park
Located in the heart of downtown Issaquah at the confluence of the main stem and North Fork of Issaquah Creek, Confluence Park is a gem in the City of Issaquah park system, and took 20 years of acquisition, planning and execution to realize. It is an example of the City’s ongoing effort to acquire property along Issaquah Creek for preservation and conservation of salmon habitat. With Confluence Park, the City restored sections of the East and main forks of Issaquah Creek, and converted the 15.5 acre property into a park for the community, complete with a covered picnic structure, community garden, walking trails, a pedestrian bridge over Issaquah Creek, and a restroom facility. The restoration portion of the project included 14,000 feet of stream and 2.3 acres of riparian habitat.
The East Fork of Issaquah Creek flows from West Tiger Mountain, down the I-90 corridor and into the City of Issaquah where it joins the main stem of Issaquah Creek.
Issues with the Creek:
Creek bank “armoring” prevented regrowth and destroyed habitat. Beginning in the 1800s, Issaquah experienced widespread deforestation, mining, and conversion of flatlands to farmland. Armoring (re-enforcing the creek channel with riprap and/or concrete) was a common practice to prevent creek bed erosion, but it also prevented re-growth. Armoring disrupted the natural forces in the stream, including the accumulation of stream bed gravel, flushing of sediments, and development of pools, side channels and other “hydraulic diversity” that salmon need. As a result, the creek bed lacked spawning gravel and was heavy in sediment. Stream side (riparian) vegetation is important for providing shade to maintain cool water temperatures. Moreover, over time, a developing forest contributes woody debris to the stream, creating pools, side channels, a healthy variation of gravel types, holding areas for adult returning salmon, and cover for rearing juveniles.
The Restoration Plan
- Remove the armoring and re-grade the creek banks to a gentler slope to reconnect the creek to the floodplain.
- Add Large Woody Debris (LWD) and Large Woody Debris structures to the channel to create diverse in-stream habitat — including pools, rearing habitat, and spawning beds.
- Install “roughness elements” in the stream channel to reduce the hydraulic forces during storm events in order to help the creek bed retain spawning gravels.
- Excavate gravel from the confluence and redistribute it upstream to encourage Chinook and kokanee spawning.
- Improve access for salmon to the East Fork, particularly during low flows.
- Remove invasive plant species; plant native riparian species on the banks, which will eventually contribute wood to the stream system as it matures.
Also added nearby: Salmon Run Nature Park
Restoration completed: 2016
Description: 3.7 acre nature park along Issaquah Creek with walking trails, benches and overlooks of the creek. Located just 300 yards downstream of Confluence park.
The City restored the creek channel and eroding shoreline, opened up a backchannel for water to go instead of flooding local businesses, and installed a stormwater vault to treat urban runoff before it enters the creek. The City worked with the Mountains to Sound Greenway Trust to remove invasive blackberries and old orchard trees, and plant native plants and mulch.