Clackamas River Basin, Oregon

In 1877, Livingston Stone, employed by the U.S. Fish Commission to explore potential hatchery sites throughout the Columbia River Basin, professed that “probably no tributary of the Columbia has abounded so profusely with salmon in past years as this river (the Clackamas).” Unfortunately, over the next 150 years, salmon populations in the Clackamas plummeted as a result of overfishing, dams, logging, mining and habitat destruction.

Since 1996, Inter-Fluve has completed 22 projects on the mainstem Clackamas River and its tributaries aimed at recovering lost salmonid habitat. Projects have included a flood damage assessment following the 1996 100-year-flood, the $4 million dollar River Island Channel & Floodplain Restoration project, the design and construction of a 700-foot-long side channel and a groundwater-fed backwater channel at Milo McIver State Park, and development and implementation of a side channel monitoring plan. Below are examples of some of the work we’ve done throughout the Clackamas watershed.

In 1889, after a day of steelhead fishing on the Clackamas River, Rudyard Kipling proclaimed: “I have lived! The American continent may now sink under the sea, for I have taken the best of it, and the best was neither dollars, love, nor real estate.”  Photo: Fishing at the mouth of the Clackamas River circa 1937. Credit: Courtesy of Old Oregon Photos (Original from Clackamas County Historical Society)

We developed design plans and oversaw construction for the River Island Channel & Floodplain Restoration project. It involved rebuilding riparian-forested floodplain (right side of photo), reclaiming alcove habitat, and reconnecting Goose Creek (left side of photo) to the Clackamas River mainstem.

Looking downstream at Goose Creek and the Clackamas River.

Pre-project photo of a historical side channel at Milo McIver State Park. In 2015, in this location, a 200-foot-long perforated pipe underground collects hyporheic flow (water moving through gravel bars) and delivers it into a 700-foot-long backwater channel.

Post-construction photo. Excavated along a historical channel alignment, hyporheic flow now mixes with groundwater, and provides salmonids cool water in the summer and warm water in the winter.

Five years after construction, riparian habitat along the Milo McIver side channel has matured.

In 2020, we surveyed and developed concept-level designs for the Kingfisher site.

One year post-construction, vegetation begins to re-establish along the Clackamas Parson’s project.

Juvenile salmonid observed utilizing large wood placed as part of the Milo McIver project.