Salmon season is upon us, and it’s a great time to look at some of the projects Environmental Services has been working on to improve salmon habitat. Portland’s rivers and streams support several species of fish protected under the Endangered Species Act. Projects like the Crystal Springs Creek Restoration have shown excellent results and contributed to Portland’s designation as a Salmon-Safe city. Environmental Services is continuing work on other habitat restoration and protection projects throughout the city. One common element of these project is culvert removal or replacement, which can remove barriers to fish passage and habitat access.
What are culverts?
Culverts are pipe segments that take above ground stream flows underground. They are often found at road crossings as they pipe the steam under the roadway. Culverts can present several challenges. First, water flows faster through smooth pipes than it does in a natural streambed, which increases the potential for erosion and adds sediment in the water. Also, culverts tend to be hard for fish and other wildlife to pass through, and can increase the risk of flooding.
Catkin Marsh culvert removal
Two culverts were removed in September 2017 from a Columbia Slough channel within a 54-acre natural area with multiple wetlands known as Catkin Marsh The wetlands collect surface water from surrounding land and direct it to the Lower Columbia Slough, which is a designated Critical Habitat for salmon. The wetlands filter sediments and pollutants from surface water; cycle nutrients and contribute to the food web; moderate air and water temperatures; and provide connectivity to the Columbia Slough. To date, Environmental Services has planted over 17,000 native trees and shrubs throughout the site’s wetlands and uplands.
Culvert removal at Catkin Marsh in September 2017
The removal of the two unnecessary culverts improves stream connectivity, allowing the water and organisms to move freely through the channel. The Multnomah County Drainage District partnered with the City and performed the in-water work. Environmental Services will plant native vegetation along the slough channel, to help improve habitat and water quality by shading the waterways and lowering water temperatures.
To find out more about projects in the Columbia Slough: https://www.portlandoregon.gov/bes/32202
Fanno Creek culvert replacement at SW 45th Ave
Across town, crews replaced another undersized culvert that blocked fish passage much of the year where SW 45th crosses Fanno Creek, just north of Beaverton-Hillsdale Highway. Fanno Creek is a tributary to the Tualatin River, which flows to the Willamette, and provides important habitat for fish, birds and pollinators. Fanno Creek is also an important part of the stormwater management system in SW Portland, where much of the stormwater stays on the surface and flows through ditches and culverts into streams such as Fanno.
A new constructed streambed culvert getting installed at SW 45th and Fanno Creek
The new culvert under SW 45th will serve two main functions. First, its constructed streambank will consist of a mix of gravel and boulders to simulate a natural stream bottom, which will slow down the flow of water and make the culvert passable for fish and other river-dwelling critters. Second, the larger culvert opening will help manage large stream flows in the rainy season and reduce the potential for flooding. The project also includes the installation of native vegetation and removal of invasive plants. Native plants, which will be installed near the river after the project is complete, help to stabilize stream banks, resist erosion, keep invasives at bay, and provide quality habitat.
Construction is underway, and will be completed this fall. For more project information: https://www.portlandoregon.gov/bes/article/573861.
To find out more about projects in the Fanno Creek Watershed: www.portlandoregon.gov/bes/fannocreek
Forest Park culvert replacement on Leif Erikson Drive
Environmental Services and Portland Parks & Recreation (PP&R) are working on another culvert replacement project along Leif Erikson Drive in Forest Park. Several of the culverts under the roadway are degraded and failing. They are also not passable for fish or other wildlife since there is a drop between the bottom of the pipe and the streambed (see photo) and the fact that the pipes are steep and have smooth bottoms. They are also contributing to erosion and downcutting of stream banks, which impacts the natural movement of the streams. The project will replace the culverts with pipes that have small dams in them to accumulate small amounts of gravel and sediment to make the stream passable for wildlife even as the stream goes underground. Construction is scheduled to begin next year.
Existing culvert and fish passage barrier along Leif Erikson Drive in Forest Park
Culvert removal and replacement projects are tools that help the City of Portland improve watershed health. For more information, the Watershed Health Report Cards are a great way to track our progress.