Water Resources Research Act Program

Details for Project ID 2008MT168B

Evolution of channel morphology and aquatic habitat in the Middle Clark Fork River following removal of Milltown Dam

Institute: Montana
Year Established: 2008 Start Date: 2008-03-01 End Date: 2010-02-28
Total Federal Funds: $31,636 Total Non-Federal Funds: $63,512

Principal Investigators: Andrew Wilcox, Andrew Wilcox

Project Summary: Removal of Milltown Dam on the Clark Fork River (CFR), MT, will increase sediment supply to downstream reaches of the CFR, including the potential downstream transport of approximately 3 million m3 of unexcavated reservoir sediments (sand, silt, and gravel), some of which may be contaminated with metals, downstream transport of uncontaminated fine sediment (sand and silt) out of the lower Blackfoot River, where the backwater effect of Milltown reservoir has built a wedge of fine sediment, and restoration of long-term sediment supplies from upstream contributing areas in the upper CFR and Blackfoot River basins This increase in sediment supply may cause a range of changes in channel conditions and aquatic habitat in the middle CFR, which extends from the present dam site to the confluence with the Flathead River, with associated potential effects on fish and macroinvertebrates.

I propose to conduct a detailed study of sediment transport and deposition, fine sediment infiltration, changes in channel morphology, and changes in aquatic habitat in the middle CFR following removal of Milltown Dam. This study is urgently needed both to understand the sedimentation and habitat impacts of removing Milltown Dam specific to the CFR, an issue of importance in its own right, and to take advantage of the fantastic research opportunity this dam removal and sediment release presents for improving our understanding of fluvial processes and habitat responses to sediment pulses in large gravel-bed rivers. The proposed research will allow for field-scale testing of emerging, lab-derived theories about fine sediment infiltration into coarse river beds, with important implications for understanding how sediment supply affects river processes and for improving planning for future dam removals. The proposed research will be a multi-year study of substantial state, regional, and national importance as well as broader scientific significance. Seed grant funds will allow us to take advantage of this opportunity, primarily by providing funding for students to begin data collection on the CFR in 2008.