Project Description

River Island Channel & Floodplain Restoration

Metro, a regional government body, contracted Inter-Fluve to restore an abandoned gravel mine on the Clackamas River. 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. Goals of the project included: to strategically implement restoration actions in areas where existing processes are insufficient to create or maintain highly functioning habitats, restoring perennially hydrologic connectivity to tributary habitats, and supporting multiple values including salmonids, stillwater species, and wildlife habitat, riparian and floodplain forests, water quality and recreation.

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. Because of its location within the Portland Metro Area, stakeholder and public outreach and communication were a critical component of the project efforts. The two phases of construction were completed in 2015 and 2016, totaling over $4 million dollars of habitat restoration.

Inter-Fluve received a 2018 Engineering Excellence Award from the American Council of Engineering Companies (ACEC) Oregon for our work on the River Island Restoration project.

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. The avulsion initiated rapid channel incision, leaving behind a disconnected floodplain and remnant warm-water gravel ponds.  Photo: Metro Parks & Nature

Project construction included lowering and rebuilding of 40+ acres of floodplain, re-sizing and reconnecting of over 3,500 feet of perennially active channel to adapt to the river’s current incised condition and hydrologic regime, and placement of over 1,700 logs to provide cover and refuge to native salmonids. Photo: Metro Parks & Nature

Channel incision related to the 1996 levee breach had disconnected Goose Creek, a tributary historically important for salmonid spawning and rearing. 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

Over 40 acres of floodplain was reconnected to be active at regular high-water events. 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.