Ontonagon River (Michigan)

Project Status: modeling is complete

River Basin Characteristics
The Ontonagon River is a tributary to Lake Superior in the western portion of Michigan's Upper Peninsula, and discharges at Ontonagon Harbor  through a federally-maintained deep-draft navigation channel. The Ontonagon River watershed covers 1,384 square miles and is split between Ontonagon, Houghton, Gogebic, and Iron counties in Michigan, and Wisconsin's Vilas County.

The watershed's landuse is predominantly forest and wetland, but contains small areas of agricultural and urban land uses with small population densities.
Watershed soils in the headwaters and "lakes" area consist of end moraines and coarse-textured till; whereas, the remainder of the watershed is predominantly lacustrine clay and silt with significant valley incision and with flat upland terraces and steep valley walls. Sources of sediment are believed to include the natural erosion of valley walls and river banks over time, as well as logging practices during the late 19th and early 20th century.

Dredging occurs in the Ontonagon Navigation Channel for navigation purposes, with an average of 59,000 cubic yards of sediment dredged from the channel each year.

		Sediment deposition in the navigation channel is significant Dreding is conducted on the channel annually Watershed is 74% forested with the Ottawa National Forest covering approximately 57% or 790 square miles Much of the sediment in the channel originates from valley mass wasting and river bank erosion (natural, geologic processes)

Modeling Approach
Due to unstable valley walls and river banks in many locations, upland mitigation techniques are likely not feasible for the purpose of reducing sediment loadings downstream. As an alternative to a spatially distributed sediment yield model designed to site Best Management Practices for upland mitigation, the Corps developed and calibrated a HEC-RAS sediment transport model of the Ontonagon River through the Village of Ontonagon, and the federal navigation channel and harbor. In addition, a modern sediment budget and historic sediment yield were calculated to determine the natural sediment load to Lake Superior. To address downstream management of sediment, a sediment transport model of the lower 2.5 miles of the Ontonagon River was also developed.

Modeling for the Ontonagon River project was completed in August 2010, along with a training workshop for state and local partners to learn to utilize the modeling tool for various planning scenarios.

Use and Applications
The sediment transport model may be used to identify impacts associated with harbor modifications, or determine sedimentation rates based on various dredging
management scenarios. In addition, the model may be used to analyze proposed sediment trap efficiencies, as well as determine impacts to dredging requirements if there is a change in the watershed hydrology as a result of reservoir management or climate change.

Project Partners
U.S. Forest Service

Ontonagon River Watershed Council

Ontonagon County Road Commission

Ontonagon Soil Conservation District
Michigan Department of Natural Resources (Fisheries)

James P. Selegean, P.E., Ph.D.
Great Lakes Hydraulics and Hydrology Office
U.S. Army Corps of Engineers
Detroit District
477 Michigan Avenue
Detroit, MI 48226
Office: (313) 226-6791
Fax: (313) 226-2398
James.P.Selegean@usace.army.mil

Calvin T. Creech, PE, LEED AP, CFM

Great Lakes Hydraulics and Hydrology Office
U.S. Army Corps of Engineers
Detroit District
477 Michigan Avenue
Detroit, MI 48226
Office: (313) 226-3002

Calvin.T.Creech@usace.army.mil