Numerical Simulation of Post Dam Removal Sediment Dynamics along the Kalamazoo River Between Otsego and Plainwell, Michigan

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 17.7-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 erosion of 3,350 T/y for the study reach, with net transport (suspended and bed load) of 5,010 T/y passing the downstream boundary. For the Dams Out case, net erosion jumps to 41,600 T/y with net transport of 59,200 T/y passing the downstream boundary. For the Design case, net erosion was 3,870 T/y with transport of 20,100 T/y passing the downstream boundary. The most significant findings were: (1) removal of the low-head dams will cause erosion in the study reach and increased sediment loads passing the downstream boundary, (2) bed erosion is the major source of eroded sediment, and (3) the Plainwell reach is the greatest contributor of total sediment and fine-grained sediment.