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State proposes raising dike around Wiley Slough to prevent flooding

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In the south Skagit River delta, the state Department of Fish and Wildlife is proposing to again reshape the landscape around Wiley Slough.

The slough is one of several freshwater ribbons that pull away from the Skagit River on Fir Island and fan into Skagit Bay.

WDFW Headquarters Unit aerial. Photo WDFW.jpg

To the right of the snaking Freshwater Slough, adjoining pools of water mark the 160-acre Wiley Slough site that was restored in 2009. This aerial photo was taken in August 2013.

More than a decade ago, Fish and Wildlife undertook a project to restore the reach of the bay’s tides to about 160 acres of land around Wiley Slough that had previously been closed in by dikes and used as farmland. The project was a compromise between Skagit River salmon and Skagit Valley farming.

The problem is that while successful for fish, a new diking system built at the site has proven problematic for neighboring farms and for flood protection.

“Overtopping events have occurred four times in the last five years and have resulted in damages to the dike ... and flooding of neighboring properties,” Fish and Wildlife Puget Sound Region Communications Manager Chase Gunnell said. “If not remediated, future overtopping could result in a dike breach, which could flood hundreds of acres of farms, homes and roads.”

Fish and Wildlife is now proposing to spend about $7.3 million to fix the problem.

Gunnell said the funding has been earmarked through the state’s Estuary and Salmon Restoration Program, in Fish and Wildlife’s 2020 capital budget, and in the state’s 2021-2023 capital budget.


As early as 2003, Fish and Wildlife began planning a fish habitat project at Wiley Slough. A few years later, agreements were reached with fish, farm and hunting stakeholders, and construction began in 2008.

2005 design graphic.png

In 2008 and 2009, Fish and Wildlife built a new segment of dike and removed the dike shown in yellow, opening about 160 acres of estuary for fish.

The project involved building about 5,000 feet of new dike inland of the old dike, installing a tide gate on the new dike and breaching the old dike.

The idea was that as the land transformed back into an estuary — where salt water and fresh water meet — more young salmon migrating out of the Skagit River would find refuge where they could rest, eat and grow before heading out to sea.

In that respect, the project worked.

For chinook salmon, an Endangered Species Act-protected fish in the Skagit River and throughout Puget Sound, the new habitat has the capacity for up to 367,000 young fish, according to a Fish and Wildlife fact sheet.

The Skagit Watershed Council wrote in a 2020 letter about Wiley Slough that it has been the most successful habitat restoration project for young Skagit River salmon.

Gunnell said the new habitat also supports more than 20 other types of fish as well as shorebirds, herons, waterfowl and other wildlife.

“This is important progress, and a valuable component of regional estuary restoration efforts,” Gunnell said. “However, further action is needed to ensure the project’s flood protection and drainage objectives are being met.”


Wiley Slough_overtopping photos 2016.jpg

A series of photos shows flooding and damage when the Wiley Slough dike and tidegate were overtopped in 2016.

The project has been unsuccessful in flood protection, which Fish and Wildlife had agreed to provide using the new dike and tide gate system.

That system has repeatedly failed, flooding neighboring fields despite attempted remedies including replacing the tide gate after its first failure and installing a pump house between 2013 and 2015.

According to project documents, the dike and tide gate system has since been overtopped several times, the most severe of which occurred in March 2016 and the most recent of which came in November.

“While significant ecological and salmon benefits have been realized as a result of the project, deficiencies in the design and operational functionality of the setback levee continue to pose a significant risk to farms, homes and roads on Fir Island,” a June 2020 letter from Skagitonians to Preserve Farmland states.

Fish and Wildlife is now proposing to raise the dike and tide gate system by several feet as a permanent repair.

“A longer or more severe overtopping event has the potential to cause a dike breach, which could result in damages to property and risk to human health and safety,” states a permit application recently submitted to the Army Corps of Engineers and the state Department of Ecology. “This project proposes to raise the dike ... to prevent future overtopping.”


The plan is to add about 3 feet in height to the 5,000 feet of dike built as part of the earlier project, bringing it to a height of 16.75 feet, according to permit applications.


The latest proposal for Wiley Slough would raise the dikes shown in orange to 16.75 feet. The dashed red line marks where dikes were removed in 2009 to restore estuary habitat for fish.

Gunnell said how much to add to the dike was determined by data that has become available in recent years on river flooding, coastal storms and sea level rise.

“As we’ve seen recently, coastal storms and river flood events are increasing in frequency, significantly impacting Northwest Washington and the Skagit watershed,” he said.

According to project documents, the dike needs to be raised to at least 16.5 feet to meet Army Corps of Engineers standards.

In addition to raising the height of the dike, the proposal includes reinforcing segments of the dike with new riprap, or rock, to help it withstand high tides, and rerouting a segment around a parking area, according to a permit application.

The proposal also includes adjustments for parking, restroom and boat launch facilities as needed at the site, which is at the Headquarters Unit of Fish and Wildlife’s Skagit Wildlife Area.

In 2019, Fish and Wildlife began seeking grant funding for the repairs, which have support from Skagit County and from agricultural interests.


According to Fish and Wildlife and local stakeholders, maintaining a dike system at Wiley Slough is important to help protect hundreds of acres of neighboring properties from flooding, as well as to enable access to public land for recreation including hunting and birdwatching.

Wiley Slough is one of several sites within the Skagit Wildlife Area where the Fish & Wildlife has sought that balance.

The Skagit Wildlife Area is a collection of properties that Fish and Wildlife manages as wildlife habitat open to the public for recreation.

Several other fish habitat restoration projects have been completed or are planned on those properties, including a major dike setback done at the Fir Island Farms Unit in 2016 and estuary restoration being considered for the Island Unit that neighbors Wiley Slough.


Fish and Wildlife recently began applying for permits for the Wiley Slough work.

The applications estimate construction will cost $4.5 million and take more than two years — potentially from May 2022 to October 2024 if permits are approved quickly — to complete.

Because the work will take place in and around water, it requires permits from the Army Corps of Engineers and Ecology under the federal Clean Water Act. The project also requires a Shorelines Substantial Development Permit from Skagit County.

Skagit County received a permit application for the project in November.

Leah Forbes of Skagit County Planning and Development Services said the department is reviewing the application and will eventually schedule a public comment period and public hearing for the proposal.

Ecology and the Army Corps of Engineers received a joint permit application in October and are accepting public comment through Dec. 24.

— Reporter Kimberly Cauvel: 360-416-2199,, Twitter: @Kimberly_SVH,

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