Geomorphic Characteristics of Drainage Ditches in Southern Minnesota

John Nieber, Professor
Bruce Wilson, Professor
Gary Sands, Associate Professor
Bradley Hansen, Assistant Scientist
Joseph Magner, Minnesota Pollution Control Agency
Gregory Johnson, Minnesota Pollution Control Agency

Funding Source

Minnesota Pollution Control Agency

Objective

Investigate the relationship between the geomorphic characteristics of natural stream channels and man-made drainage channels and their associated watersheds for locations in southern Minnesota. The goal is to begin to develop criteria for new channel designs.

Need or Impact

The periodic maintenance of drainage ditches costs local units of government and private landowners hundreds of thousands of dollars a year in Minnesota. In addition, drainage channels can have a detrimental impact on downstream water quality because of the lack of any self-cleaning mechanism in conventionally designed channels. There is a need to improve designs of drainage channels to make them more self-sustainable so that the cost of maintenance can be reduced and the impact on water quality and in-stream biological health can be reduced.

Project Status

Morphology data from man-made channels and natural stream channels at a number of locations within the Minnesota River basin was collected. The data have been analyzed to determine the relationships that link channel morphology to contributing watershed characteristics. A drainage channel located in Lincoln County is being redesigned because it currently threatens an adjacent road. The channel will be moved laterally and reconstructed using a two-stage design using information gained from this project. The new channel will consist of a meandering channel that will convey the mean annual peak discharge, contained within a larger channel that will convey the design peak discharge. After construction, this channel will be monitored to assess the adequacy of the two-stage design.