Natural River and Floodplain Function Goal of Design

A team of engineers, ecologists, hydrologists, geomorphologists, and biologists assembled by the State of Montana collaborate to restore the Clark Fork.

Goal of Restoration: Restoring Natural River and Floodplain Function

The restoration design emphasizes restoring natural river and floodplain function based on local conditions. These objectives were developed collaboratively by the Site Natural Resource Trustees: State of Montana, US Fish and Wildlife Service, and the Confederated Salish and Kootenai Tribes.

Milltown Dam was removed in stages between 2007 and 2009. The Environmental Protection Agency and the State of Montana coordinated remediation and restoration projects. The remedial work led by EPA focuses on removing contaminated mining sediments that had accumulated behind the dam since 1908.

What are specific restoration goals? (1) Maintain water quality by reducing the erosion of contaminated sediments; (2) Provide channel and floodplains that will accommodate sediment transport and channel dynamics appropriate for the geomorphic setting; (3) Provide high quality habitat for all native fishes and other trout species, including continuous upstream and downstream migration while minimizing habitats that will promote undesirable fish species; (4) Provide functional wetlands and riparian communities, where feasible. These communities will also provide improved riparian and wildlife habitat within the restored area; (5) Improve visual and aesthetic values through natural river channel design, revegetation and the use of native plants and materials; and (6) Provide safe recreational opportunities compatible with other restoration goals including channel and floodplain stability, sediment transport, and fish habitat.

The restoration area includes the former Milltown Dam and its reservoir and the Clark Fork and Blackfoot Rivers upstream of the former Milltown Dam location.

Revegetation is a significant component of restoration. The revegetation plan focuses on creating conditions that will support riparian plant community development in a natural way. The revegetation plan includes some planting and seeding, but many surfaces are being designed to promote natural vegetation recruitment. The design was possible through a unique collaboration between engineers, ecologists, hydrologists, geomorphologists, and biologists assembled by the State of Montana.

The team includes River Design Group, Inc. of Whitefish, Montana; WestWater Consultants of Corvallis, Montana; and Geum Environmental Consulting, Inc. of Hamilton, Montana. The Natural Resource Damage Program and Montana Department of Fish, Wildlife and Parks also participated as technical team members and provided leadership that made an interdisciplinary approach possible.

The plan developed features grading criteria and includes micro-swales, wetland features, and woody debris as components of the final graded floodplain surface. Revegetation activities include weed management, seeding, planting containerized plants and wetland plugs, installation of pre-vegetated coir mats and logs, bioengineering structures such as vegetated soil lifts and sod brush trenches along river banks, and variation of substrate and topography.

The desired future condition for vegetation in the streamside and floodplain restoration area is a diverse, native plant community that supports the many natural ecosystem functions in the river corridor. The planting scheme accounts for the ecological niches that one finds near a river – including streambanks, backwater wetlands, and drier upland areas. The idea is to re-create the setting that likely existed before the dam was built. The restoration plan acknowledges that over time, the river itself, through floods and other events, will ultimately determine where and how vegetation grows, but the restoration efforts will set the trajectory for this natural process.

Implementation of the restoration plan began in Summer 2008 and restoration work will continue through 2012. A monitoring plan was also developed to evaluate the effectiveness of restoration actions. Monitoring began in 2009 and will continue for several years. Project progress can be followed at http://www.clarkfork.org and http://www.doj.mt.gov/lands/naturalresource/milltowndam.asp.

Excerpted from a publication by Tom Parker, Geum Environmental Consulting, Inc. Thanks also to Chris Brick, Clark Fork Coalition