Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/15/2005
Publication Date: 4/3/2006
Citation: Langendoen, E.J., Wells, R.R. 2006. Numerical simulation of channel adjustment of the kalamazoo river following the removal of two low-head dams between Otsego and Plainwell, Michigan. In: Proceedings of the 8th Federal Interagency Sedimentation Conference, April 2-6, 2006, Reno, Nevada. CDROM.
Interpretive Summary: The state of Michigan is interested in removing four dams along the Kalamazoo River between Plainwell and Allagan. Sediment deposits behind the dams are contaminated with PCBs due to industrial waste materials. Concerns over the fate of PCB-laden channel sediments after dam removal resulted in the U.S. Geological Survey (USGS) supporting a study to evaluate the erosion, transport, and deposition of sediments in the Kalamazoo River between Plainwell and Otsego City, Michigan. Computer simulations were carried out over a 38-year period of record to determine the response of the Kalamazoo River between the cities of Otsego and Plainwell to: (1) removal of the Plainwell and Otsego City Dams (scenario A), and (2) a newly designed channel geometry without these dams (scenario B). Bank and bed erosion increased significantly for scenario A. The average-annual sediment load downstream of the Otsego City dam increased 3 times, with the largest increases occurring within the first three years after removal of the dams. For scenario B, average-annual sediment load is similar to that observed currently with the dams in place. This study shows that construction of a new channel through the reservoirs behind the dams greatly reduces the amount of fine-grained material eroded from the channel bed and streambanks.
Technical Abstract: The state of Michigan is interested in removing two low-head dams in an 8.8 km reach of the Kalamazoo River between Plainwell and Otsego, Michigan while minimizing impacts to the study reach and downstream reaches. The study was designed to evaluate the erosion, transport, and deposition of sediments over a 38-year period using the channel evolution model CONCEPTS for three simulation scenarios: Dams In, Dams Out, and Design. The total mass of sediment emanating from the channel boundary, for the Dams In case, shows net deposition of 8,760 T/y for the study reach, with net transport (suspended and bed load) of 10,500 T/y passing the downstream boundary. For the Dams Out case, there is net erosion of 9,180 T/y with net transport of 30,100 T/y passing the downstream boundary. For the Design case, net deposition was 9,070 T/y with transport of 14,200 T/y passing the downstream boundary. The most significant finding is that removal of the low-head dams will cause significant erosion of PCB-contaminated bed and bank material upstream of the dams.