Snohomish Delta

River Delta

River delta sites occur at 16 locations where large river floodplains meet the sea

Most Recent Edits

• File:Multi-scale benefits of estuary restoration for PS Chinook salmon ESRP webinar Final.pdf

Salish Sea References

• Watershed Characterization Mapper
• The Encyclopedia of Puget Sound
• PRISM Project Search
• Washington Coastal Atlas
• WDFW's Salmonscape Map

Wiki Rules

• Wiki text does not reflect the policy or opinion of any agency or organization
• Please adhere to our Social Contract and Style Guide
• Complain here, and be nice.

The Snohomish is one of the largest river delta sites in Puget Sound. Recovery of historical wetland area is a target of Salmon Recovery in the Snohomish Watershed. Portions of the Estuary are in the City of Everett but most are in Snohomish County. It is in usual and accustomed harvest areas of the Tulalip Tribes of Washington with portions within the tribal reservation. The lower delta is being modified under a series of large scale restoration projects including Qwuloolt Restoration, Smith Island Restoration, and Blue Heron Mitigation Bank among others. These projects are reestablishing a large area of tidal inundation in the saline mixing zone, and when complete will be the largest estuary restoration by area in Puget Sound. Upstream, freshwater tidal lands are in agricultural production, divided into diking districts such as Marshlands and Ebey Island, and depend on diking and pumping to lower water tables. There is controversy over the loss of agricultural lands as Snohomish County works to increase Snohomish Agricultural Resilience. Sea Level Rise effects may be important to long term planning. The Estuary is a study area of the Snohomish Sustainable Lands Strategy.

Chronology

For sites with lots of ecosystem management activity, maintaining a chronology with links is a great way to organize information:

• 1990's - Snohomish County starts acquisition of estuary parcels allowing future work.
• 1994 - The initial Spencer Island Restoration in 1994 and the smaller Marysville Mitigation Site (17 acres) provides early restoration examples.
• 1994 - Formation of the Tulalip Landfill Natural Resource Trustees (NOAA,USFWS,Tulalip Tribes,WDOE to pursue damages for the period where the illegal Tulalip Landfill was leaching hazardous substances into Snohomish Estuary.
• 1999 - Tulalip Landfill Natural Resource Trustees propose settlement for damages, and beginning of acquisition to support the future Qwuloolt Restoration
• 2001 - Publication of File:City of Everett 2001 snohomish estuary wetland salmon overlay.pdf identifies and prioritizes salmon recovery opportunities in the delta. Project funded by NOAA through GSRO with technical assistance by E. Stockdale Ecology who later joins Snohomish County staff during Smith Island restoration. Identifies all sites mentioned below.
• 2001 - Initiation of Puget Sound Nearshore Ecosystem Restoration Project between USACE and WDFW to identify large scale restoration opportunities in Puget Sound. This orients USACE CAP resources towards large delta restoration.
• 2001 - Snohomish County acquires north tip of Ebey Island for anticipated North Ebey Island Restoration
• 2003 - On July 26 a section of dike on the North end of South Spencer Island caught on fire. Over a week the fire had spread to 800' of dike and was still smoldering until WDFW breached the dike to extinguish the fire.Pcereghino (talk)
• 2005 - Publication of Snohomish Recovery plan (SBSRF 2005) sets Snohomish Delta restoration target of 1,237 acres of restoration by 2015.
• 2005 - Construction of Port of Everett's Union Slough Mitigation with Pentec Environmental leading.
• 2007 - Cereghino 2007 documents wetlands conditions as part of Qwuloolt Restoration feasibility.
• 2011 - File:Rice 2011 DRAFT qwuloolt monitoring plan.pdf establishes strategy of coordination among restoration projects to use project funding to support coordinated monitoring between NOAA, Tulalip Tribes, and Snohomish County, with support from NOAA CRP funding.
• 2012 - City of Everett and USACE collaborate on the Union Slough Restoration (93 acres) providing city mitigation, and using USACE funds to expand the project area.
• 2014 - Initial excavation of channels at Qwuloolt Restoration in anticipation of future breach.
• 2015 - First Tides at Qwuloolt Restoration (354 acres, not including the 17 acre Marysville Mitigation) with a final push using a USACE agreement with Tulalip Tribes
• 2015 - Agreement between Snohomish County and City of Everett (File:Snohomish County 2015 diking district 6 maintenance.pdf) over continued maintenance of failed Diking District 6
• 2016 - Publication of PSNERP final feasibility report identifies Spencer Island North Restoration, Everett Riverfront Wetland Restoration, and Quilceda Estuary Restoration as early target for USACE CAP efforts, and defers Everett Marshlands and the Snohomish Estuary Distributary Reconnection for future investigation.
• 2016 - Untimely death of Casey Rice, the NOAA Scientist who championed coordinated restoration monitoring.
• 2018 - First tide at Smith Island Restoration (315 acres, with an additional 18 acres developed for BNSF mitigation) and enhancement of natural breach at Mid-spencer Island Restoration (added to Smith Island construction through reallocation of NOAA funding to complete design). This was the first project to be redesigned using Greg Hood's Tidal Channel Reference Model
• 2018 - Port Gardner Natural Resource Trustees and USDOJ announce a $4M NRDA settlement with Jeld-Wen Inc, Kimberly Clark Corp., and Weyerhaeuser that will partially fund the Blue Heron Mitigation Bank
• 2019 - The US Navy and Port of Everett also reach settlement by contribution to Blue Heron.
• 2019 - Publication of File:Hall et al 2019 DRAFT snohomish monitoring plan.pdf documenting coordinated monitoring approach for delta.
• 2019 - NOAA begins funding WDFW to complete feasibility analysis in the vicinity of Ebey Island, including Spencer Island North Restoration, North Ebey Island Restoration and Diking District 6 Restoration.
• 2021 - USACE appropriated funds to complete work at Spencer Island North Restoration, owned by WDFW focused on increased connectivity similar to Mid-spencer Island Restoration, to improve tidal connectivity partially restored in 2003.
• 2022 - Planned first tides at Blue Heron Slough Mitigation Bank (354 acres) with support from the Port of Everett's NRDA Settlement, led by Wildlands, Inc., a for profit mitigation banker.

Notes

• Ecology TMDL for ammonia and BOD. The estuary has been listed as impaired for water quality violations. The study included load allocations for Quilceda, Allen, Woods Creek, and the Sultan and Pilchuck River watersheds, which drain into the mainstem Snohomish River, as well as four drainage systems controlled by pumping stations: French Creek, the Marshland, Deadwater Slough, and Swan Trail Slough.
• French Creek Watershed, Pilchuck River Watershed, and Marshlands systems all drain into the freshwater tidal zone of the delta.
• Quilceda Creek Watershed and the Jones and Allen Creek Watershed are the largest creeks flowing into the lower estuary from the north.
• SBSRF 2005 defines salmon recovery goals, including a 10 year objective for estuary restoration.
• The Delta was an area identified by SLS and NOAA in promoting large scale restoration national under the Snohomish Coordinated Investment Network.
• A 1884-85 topographic sheet of the historical estuary is available from the River History Project.

Nearshore Strategies Data Report

Cereghino et al 2012 completed a soundwide analysis to identify and describe river delta sites in Puget Sounds as part of a nearshore ecosystem restoration strategy (using remote sensing data c. 2000-2006). The following narrative of this delta site was developed to support distribution and use of analysis results:

The Snohomish Delta in the Whidbey sub-basin historically contained 18,706 acres of vegetated wetland along a 95 km shoreline. The delta receives flow from a 465,216 square kilometer watershed. These characteristics make this system the 2nd largest delta out of 16 systems in Puget Sound.

Simenstad et al 2011 found that this system had lost 90% of its vegetated tidal wetlands, and 37% of its shoreline length. Of the remaining shoreline, 87% shows some evidence of infrastructure development. In the surrounding uplands, 55% of land is estimated to have greater than 10% impervious surface. Across the watershed, 32% of land is estimated to have greater than 10% impervious surface. Based on these paramters, the site was given a degradation score of 54 out of 100, making it the 4th most degraded delta in Puget Sound. It faces a medium risk of future development locally, and a low risk of development across the watershed. Approximately 53 percent of the watershed is currently impounded behind dams.

Pages Beamer et al 2024 landscape determinants of estuary habitat use chinook salmon Blue Heron Mitigation Bank Coastal Blue Carbon Project File:Delta marsh recruitment.JPG File:Delta tree recruitment.JPG Diking District 6 Ebey Island Effects of Exposed Tidal Flats on Water Temperature in the Snohomish Estuary File:Estuary salmon recovery.png Evaluating Salmon Rearing Limitations in River Deltas Everett Marshlands Restoration Everett Riverfront Wetlands Marysville Mitigation Site Maulsby Mudflat Reconnection and Restoration Mid-spencer Island Restoration North Ebey Island Restoration Predicting Sea Level Rise Impacts on Ag Production File:Qwuloolt first flood.jpg File:Qwuloolt first flood.png Qwuloolt Restoration File:Smith island aerial 2011 NAIP NIR.png File:Smith island dike removal.jpg Smith Island Restoration Snohomish Agricultural Resilience Snohomish Agriculture Resilience Plan File:Snohomish delta after.jpg Snohomish Delta Ecosystem Monitoring and Evaluation Snohomish Estuary Restoration Effects on Temperature, Salinity, and Tides File:SnohomishTSheet.tif Spencer Island Restoration Steamboat Slough Mitigation Site The Marshlands Tulalip Landfill Cleanup Union Slough Mitigation Union Slough Restoration

Files File:USACE 2011 qwuloolt environmental assessment.pdf File:Wright 2021 integrated floodplain management puget sound.pdf File:Yang & Khangaonkar 2007.pdf