1991 Bureau of Environmental Services Educational flier
BASIN FOCUS: COLUMBIA SLOUGH
City of Portland, Bureau of Environmental Services
Running nearly 18 miles from Fairview Lake to the Willamette River, the Columbia Slough remains one of the last vestiges of the shifting wetlands, lakes, and channels that once dominated the floodplain of the Columbia River and Challenged Lewis and Clark on their quest to the Pacific.
Yet while the slough retains remnants of its natural heritage, 150 years of logging, dikes and levees have transformed the slough from an interconnected network of lakes and wetlands into a slow-moving drainage canal.
Nonetheless, the slough still provides one of the City’s largest open space and wildlife habitat resources. Bobcat, coyote, and river otter live along the banks; cougar have been seen at the eastern end near Blue Lake. The riparian areas and wetlands provide cover and feed for over 120 species of birds. Black cottonwood, ash and willow offer a shady screen from nearby industrial areas.
Years of filling and diking have created two distinctly different sections of the slough. The lower slough extends from the Willamette River to the Peninsula Canal-about NE 13th Avenue.
One contiguous stretch, the lower slough offers high-quality canoe and kayak recreation to urban paddlers. Daily tidal influences may change water levels as much as three feet in this portion of the Columbia Slough.
The upper slough continues eastward to Fairview Lake, but consists of long, narrow pond-like segments separated by road crossings and connected only by culverts that restrict small boat traffic. Storm runoff and springs provide much of the flow for the upper reach.
Both sections of the slough face threats to water quality. Twelve combined sewer outfalls empty diluted, untreated sewage into the lower slough whenever heavy rainfall overloads the City’s sewer system. Storms also wash pollutants form nearby streets and industrial developments into the slough. The upper slough is further polluted by septic tank and cesspool effluent that enters the groundwater in mid-Multnomah County, emerging from the springs that feed the slough.
Interest in improving and managing slough land and water resources is building on a regional basis, as the public and agencies ranging from the Port of Portland to the Army Corps of Engineers reexamine their posture toward this valuable urban natural area.
And while the slough may never again be renewed each year by Columbia River floods, it remains an important link in Portland’s chain of urban natural areas and will grow in importance as a resource for recreation and wildlife habitat.
