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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Water Quality and Ecology Research » Research » Publications at this Location » Publication #81127

Title: THE MISSOURI RIVER BELOW FORT PECK DAM, MONTANA: TO FIX THE RIVER OR THE BANKS?

Author
item BERNARD, J
item MUNSEY, T
item Shields Jr, Fletcher
item STEFFEN, L

Submitted to: Management of Landscapes Disturbed by Channel Incision Stabilization Rehabi
Publication Type: Proceedings
Publication Acceptance Date: 5/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: River bank erosion on the Missouri River below Fort Peck Dam, Montana, averages about 9.3 ft per year, leading to a loss of about 0.5 acres of land per river mile per year. Physical impacts are the loss of agricultural land, irrigation pumping stations and pipelines, damage to roads and bridges, and downstream sedimentation in Lake Sakakawea. Bank erosion and associated deposition is creating a lower floodplain within the river channel that is of lower soil quality for agricultural uses than the floodplains created prior to Fort Peck Dam. These recently deposited soils are coarser in texture and lower in natural nutrients than the older pre-dam deposits. A coordinated resource management group was formed, including local and federal stakeholders, to seek ways to address the problems. Federal agencies, state agencies, tribes, and local landowners are collaborating through the group to help develop solutions to the resource problems. This project provides a model for others working with streambank erosion problems along large rivers and for those working with resource management in riverine corridors with multiple stakeholders.

Technical Abstract: Bank erosion on the Missouri River between Fort Peck Dam, Montana, and the North Dakota state line averages about 9.3 ft per year, leading to a loss of about 0.5 acres of land per river mile per year. About 57 percent of the banks along the 180-mile reach are eroding through mass wasting processes. Critical bank heights vary from 3 feet to 30 feet. Prior to impoundment, erosion rates were about three times higher than post-impoundment. Physical impacts of erosion are the loss of agricultural land, irrigation pumping stations and pipelines, damage to roads and bridges, and downstream sedimentation in Lake Sakakawea. Land lost to bank erosion is partially replaced through deposition, but due to the peak stage and sediment load reductions associated with the dam, the newly formed surface is of lower soil quality for agricultural uses than the older floodplains. A coordinated resource management group was formed, including Federal agencies, state agencies, tribes, and local landowners to seek ways to address these problems. are collaborating through the group to help develop solutions to the resource problems. This project provides a model for others working with streambank erosion problems along large rivers and for those working with resource management in riverine corridors with multiple stakeholders. Solutions to the bank erosion problems along the Missouri River below Fort Peck Dam should be planned and implemented in the context of a comprehensive system plan that addresses multiple goals.