Flint River Restoration: A Unique Synthesis of Design Approaches to Meet Multiple Objectives
Jonathan Scheibly, PE PWS CERP
Stantec
Lexington, KY
Authors: Scheibly, Jonathan, Sendelbach, Michael, Cochrane, Jacob
The Flint River Restoration is a key component in a long‐term project to the revitalize the riverfront in downtown Flint, Michigan combining riverbank park improvements, greenway connectivity, and in‐river naturalization that will become the recently announced Flint State Park. Naturalization of the river will improve habitat and access along nearly 2 miles of the channel, address impairments from damming, channelization, dredging, and urban development, and improve access and recreational opportunities for city residents. The lynchpin was removal of the Hamilton Dam, which opened nearly 25 miles of streams to lake sturgeon and walleye and reconnected the upstream reaches to Saginaw Bay for the first time in over a century.
Hamilton Dam was removed from the Michigan high-hazard dam list by stabilization work in 2018; however, the remaining weir was a substantial barrier to fish passage and a hazard to river users with a hydraulic height of seven feet. The restoration included demolition of the remaining weir, foundation, and stilling basin, and construction of a series of naturalized riffle structures to transition the water elevation differential up- and downstream of the dam. This work had to provide fish passage, improve instream habitat, and accommodate boat travel while tying into an existing contaminated sediment remediation structure, not increasing increase flood risk to existing structures, and supporting park improvements.
Meeting multiple, and sometimes conflicting, objectives the project required innovative use of both natural channel design elements and traditional civil engineering approaches. Constructed riffles were designed as high width-depth ratio Rosgen Type B channels based on Flint River reference reaches, and individual cross-sections and profiles were optimized based on 1-dimensional hydraulic modeling to meet no-rise and meeting upstream constraints. Fish passage structures were designed using 2-dimensional modeling to confirm critical flow velocity and depth met target species biological criteria. More traditional approaches for dam stability analysis, contaminant risk assessment, shear stress, and sediment transport were used to address concerns with adjacent structures and potentially contaminated sediments. Construction was completed in autumn 2024, and upcoming geomorphic and biological monitoring in collaboration with University of Michigan Flint will demonstrate its efficacy in coming years.
About Jonathan Scheibly, PE PWS CERP
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