The Plan
The Similk estuary restoration project is located to the north of Similk Bay, which is at the north end of Skagit Bay in the Whidbey Basin. This pocket estuary project has been a high priority for Chinook recovery since it was initially identified by the Skagit Chinook Recovery Plan in 2005 (p. 218). The Swinomish Tribe and the Skagit River System Cooperative (SRSC) are working together on this project to create 17 acres of juvenile Chinook rearing habitat.
We will accomplish this by reconnecting tidal influence to the wetland behind Similk Beach by excavating a tidal channel through the beach berm and road and a branching channel network inland. This will create a pocket estuary for juvenile Chinook salmon as they outmigrate from the Skagit River to the sea.
We hired Blue Coast Engineering to help us design the physical features of the site to best mimic natural conditions while also assessing and avoiding impacts to neighbors and surrounding areas. We’ve undertaken significant hydraulic and groundwater studies as part of years of feasibility work. We are still assessing effects on groundwater and septic systems, which will be fully undertaken during this final design process, and are committed to avoiding harm to neighbors.
Skagit County has partnered with us to complete this project. Satterlee Road is an important transportation and safety corridor for Skagit County, and the current failing pumphouse is an ongoing and expensive liability and maintenance headache for County government. To maintain the road, it will need to be elevated above the high tide elevation and a bridge constructed over the tidal inlet. The failure-prone drainage pump will no longer be necessary as the area drains naturally with the tide. This design also accommodates 2ft sea level rise projections through 2100, building climate resilience into civil infrastructure. The County Commissioners have given their full official support to the project and its benefit to the fish, the Tribe, and the County.
More concept illustrations HERE
What is a pocket estuary?
Pocket estuaries are shallow nearshore embayments that are not directly connected to natal streams where salmon spawn and juvenile salmon originate. These places are salmon nurseries when juvenile fish bypass natal estuaries like the Skagit River delta. Similk was historically a pocket estuary that was isolated by a beach berm and road and drained with a ditch network and pump to Similk Bay. Nearby Lone Tree Lagoon and Turners Bay Lagoon are examples of a functioning and connected pocket estuaries. Turners Bay was a very similar project that SRSC completed in 2012 to reconnect a historic estuary to tidal influence. It is now functioning as intended as juvenile Chinook habitat. Once the Similk Restoration project is complete the resulting lagoon it will be at least partially inundated by the tide twice every 24 hours.
There are many pocket estuaries throughout the Whidbey Basin (Figure 3.3), most of which have been modified or completely eliminated by people. Like the Skagit River delta, these low lying wet and flat areas were viewed by settlers as attractive for agriculture. They were often drained, filled, and disconnected from marine and tidal influence. The Skagit Chinook Recovery Plan (SRSC & WDFW 2005) identified 12 degraded pocket estuaries within a single day’s migration for Juvenile Chinook from the Skagit River Delta. Similk is one of these (Figure 7.2).
Why are pocket estuaries important to Chinook recovery?
Decades of research in Skagit Bay and the Skagit River delta has established pocket estuaries as important rearing habitat for juvenile Chinook. After these baby fish emerge from their redds in the river, they move downstream toward the estuary. They have a preference for estuary habitat, which provides growth advantages over both upriver and marine habitat. Estuaries are productive environments and serve as nurseries for growing baby Chinook. Food is abundant, water is warmer and more conducive to rapid growth, there are many places to hide from predators, and they lie at the transition between fresh and salt water, which eases stress on the physiological transitions freshwater juvenile Chinook must make to become a salt water smolts. These habitats make juvenile fish bigger and stronger, and better able to survive to adulthood in the salt water.
Figure 3.1 compares the Loss of historic Skagit River delta/estuary habitat since the 1860s. Over 86% of historic estuary habitat that juvenile Chinook depend on has been lost to diking, draining, and filling. This loss of habitat means that juvenile Chinook accumulate in the limited estuary habitats and become over crowded. Flooding can also push them out of the river. This forces growing juvenile Chinook to move into the marine areas before they are ready. This is the primary bottleneck to Chinook survival and recovery identified by decades of research. Due to rearing habitat limitations, even if more Chinook returned to spawn (such as if fishing were stopped), there is not enough estuary habitat to support increases in their offspring. This is why a fishing moratorium cannot lead to recovery.
Once undersized juvenile chinook enter marine waters they traverse shallow nearshore habitats, and when they find pocket estuaries, they accumulate in them. Pocket estuaries provide many of the same benefits as the natal delta habitat they would usually prefer. In this way pocket estuaries serve as a back up estuary, or a second chance for juvenile Chinook to find rearing habitat, that would otherwise be unlikely to survive, improving their chances of survival to adulthood.
Next Steps
We have completed the preliminary design where we have chosen an alternative based on transportation and habitat needs and surrounding effects and developed preliminary drawings. We’ve undertaken significant modeling and assessment work, including years of feasibility studies. The next stage is to develop final designs. These are “permit level” designs that require significant engineering and finalized modeling. Swinomish and SRSC have partnered with Skagit County to rebuild the road and bridge. As part of this final design stage, we are reaching out to the community to ensure locals are informed about the project, and to hear about concerns and answer questions. Often communities know their neighboring lands well, and can provide valuable insights that can improve designs.
We are hosting a virtual open house via Zoom on May 10th, 2022 (link on the home page). This is a first opportunity for the community to meet with the project sponsors and engineers. There will be ongoing opportunities as the project develops toward construction, which is likely to take a few more years. Please contact us using the form on the contact page, and let us know who you are, whereabouts you live, if and how the project might affect you, and sign up for email updates.