SR 530 Riverbank stabilization and erosion control
Assessing flood impacts on transportation and the environment
River flooding has eroded the shoulder of SR 530 in Skagit County. |
The flooding events this winter serve as a reminder of how much we depend on our state’s transportation system. Frequent flooding and erosion of the riverbank can result in:
- severed transportation links
- negative impacts on fish and fish habitat
A recent project on State Route (SR) 530, near Rockport in Skagit County, is an example of how the Washington State Department of Transportation protects our investment in highways, while protecting fish habitats at the same time. SR 530 is adjacent to the Sauk River:
- Sauk River is designated a “Wild and Scenic River Corridor"
- it serves as home to nearly every species of salmon listed under the Endangered Species Act
- repeated flooding moved the Sauk River to a side channel, which began undermining the SR 530 shoulder
- WSDOT needed to quickly find an environmentally-friendly fix or risk losing the highway - an important transportation link between I-5 and the North Cascades Highway.
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Involving others in developing a solution
To help expedite this Sauk River project, WSDOT brought together a design team that included:
- Washington Department of Fish & Wildlife (WDFW)
- U.S. Forest Service
- tribes
- local officials
- project stakeholders
Together the team developed a two-part project:
This team approach resulted in finding a solution and plan for a bank stabilization design called a “log crib wall.”
- the design has been used successfully on the Nooksak River
- the consultant who designed the Nooksak project was part of this design team
- adopting and modifying an existing design saved valuable time and reduced costs
“Having the resource agencies at the table from the very start was a key to moving the project along very quickly,” said WSDOT’s Senior Hydrologist Jim Park. “We were able to fast-track the permitting process since many potential issues had already been considered and resolved, and everyone understood the project and what we were trying to accomplish.”
The project's permitting process was completed by the Multi-Agency Permitting Team (MAP Team), a partnership between five agencies that work out of the same office to permit transportation projects. Within 20 day, the MAP Team has secured permits from the Corps of Engineers, and the departments of Ecology and Fish and Wildlife.
As a result, design, permitting, and construction of the project was completed between July and October, 2008 – an astonishingly short amount of time for this type of work. Stage two design work begins in early 2009.
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Working to benefit people and fish
Crews add steel piles along the riverbank to help hold the bank and highway shoulder in place. |
The log crib wall is constructed of 112 steel pilings, large trees and rock to build a buffer between the riverbank and the highway. The design has many benefits for both transportation and the river environment. These benefits include:
- the log crib wall is narrow in profile and can be used in areas where space is limited between the river and highway
- since the materials used to build the crib wall are fish-friendly, we avoid mitigation costs for the project
- the woody debris slows the flow of the river and reduces the erosive force of water
- the woody debris provides protective cover for fish and a resting area for them
- the wood invites insects and provides a feeding area for fish
- plantings along the top of the riverbank help to stabilize the bank and provide shade for fish
Rocks and timber are added to slow the water flow and provide a more natural area for fish. |
The wall was put to the test in November 2008 and January 2009 and performed as it was intended to withstand flood flows.
“There are dozens of sites all over the state that can benefit from our experience with this project,” said Park. “By using a team approach everyone was aware of the challenges and participated in working through them. We have a design that is tested, works well in environmentally sensitive areas, improves fish habitat, and protects the highway. We can now focus on the long-term needs of the highway corridor.”
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Addressing locations that experience frequent erosion repairs
The completed "log crib wall" along SR 530 has withstood the test of the November 2008 and January 2009 floods. |
WSDOT's Chronic Environmental Deficiencies program corrects situations that cause repeated environmental damage like SR 530. Working with WDFW, we're moving away from costly, repetitive repairs toward long-term solutions that benefit fish habitat and address transportation needs:
- we began the program five years ago with $53 million available
- we've identified 44 projects as eligible for the funding, with an estimated cost of $241 million.
Eligible projects for this type of funding include:
- projects that have required repairs three times within 10 years
- involve maintenance work that impacts fish and/or fish habitat
- Rivers that provide habitat to endangered species of fish receive the highest priority
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Contact information:
Jim Park, Environmental Service Office, senior hydrologist, (360) 705-7415
Karen Zirkle, Chronic Environmental Deficiencies program manager, (360) 705-7402