River Island Channel

In 1996 a 100-year rain-on-snow flood event caused the mainstem Clackamas River to breach a levee and flow through this active gravel mining operation. Inter-Fluve developed design plans and oversaw construction for the property including rebuilding riparian-forested wetlands at the gravel mine site, and reconnecting Goose Creek – a Clackamas River tributary – to the Clackamas River mainstem to provide 3,500 feet of rearing habitat for juvenile salmonids. This $4 million project was completed in 2016.

GreenWorks PC designed this birds-eye concept-level image representing the River Island project in 20+ years. This image was used in meetings with the public to convey preliminary designs.

In 1996 a 100-year rain-on-snow event caused the mainstem Clackamas River to breach a levee and flow through this active gravel mining operation. Photo: Metro Parks & Nature

Over 40 acres of floodplain were lowered and rebuilt, 3,500 feet of perennially active channel was re-sized and reconnected to the mainstem Clackamas, and over 1,700 logs were placed to provide cover and refuge to native salmonids. Photo: Metro Parks & Nature

Prior to construction, in summer months, Goose Creek’s relatively low discharge could no longer reach the Clackamas. This resulted in ponding and elevated temperatures lethal to salmonids. Photo: Metro Parks & Nature

Goose Creek was re-sized and its profile was re-shaped to provide salmonids access at all but extreme low flows. Nearly 1,000 logs were placed along its length to provide cover at a range of flows. Photo: Metro Parks & Nature

Prior to construction, much of the site’s floodplain was disconnected or composed of warm water pools. Photo: Metro Parks & Nature

Portions of the property were preserved for open water/emergent habitat to provide habitat for birds and stillwater species, including turtles. Photo: Metro Parks & Nature

Emily Alcott (project manager) and Mike Brunfelt onsite during construction observation.

Western Pond Turtle.

La Center Wetlands

Inter-Fluve supported the Lower Columbia Estuary Partnership in identifying restoration opportunities, designing and constructing this large-scale floodplain reconnection project. Project design elements included breaching existing levees to reconnect surface water from the East Fork Lewis River to adjacent floodplains to enhance off-channel habitat for ESA-listed salmonids and native aquatic species. The project improved off-channel rearing and winter refugia for juvenile salmonids, removed two fish passage barriers, installed habitat large woody material, created riparian buffers, and naturalized a drainage canal. A roughened channel improved fish access to an existing wetland while still maintaining water levels within the wetlands. A 2D model was used to evaluate the impacts of project design elements, including on adjacent private and public landowners.

The La Center restoration project reconnected 453 acres of floodplain to Washington’s East Fork Lewis River. Photo: Lower Columbia Estuary Partnership

Estuary Partnership staff at one of three future levee breaches.

Because the levee is used as a recreational trail, bridges were installed over the three levee breach channels.

A quarter-mile long agricultural drainage ditch was naturalized and improved for salmonid habitat.

Horsetail Creek

Located on the Columbia River floodplain, the 180-acre Horsetail Creek project area was dramatically impacted by construction of Interstate 1-84 and resulting diversions of the creek, as well as a pea gravel mine. Despite this legacy of disturbance, intact portions of Horsetail and Oneonta Creeks were still providing key rearing habitat for local and out-migrating upriver mainstem populations of ESA-listed salmon and steelhead.

Inter-Fluve assisted the Lower Columbia Estuary Partnership in a baseline assessment, fish passage evaluation, habitat and fish passage restoration feasibility study, conceptual and detailed restoration design, development of construction documents, and assistance through project solicitation and implementation. The project was constructed 2013 with aid of a Chinook helicopter for transporting and placing large wood.

Portland General Electric (PGE) and Inter-Fluve received an American Council of Engineering Companies (ACEC) Engineering Excellence Honor Award in spring 2016 for the project.

A Chinook helicopter transports large wood at the Horsetail site. Over 700 logs were used.

Bill Norris, PE, aids in placement of logs.

Enhanced channel segment in lower Oneonta Creek at high water.

The enhanced channel segment 16 months later at low water.

Complex construction sequencing involved the US Forest Service, ODOT, Cascade Locks Electric, Union Pacific railroad, and many regulatory entities with jurisdiction over the area.

The project is a model for implementing complex floodplain and stream restoration in an area that was heavily impacted by both construction of an interstate and railroad.