| The Minnesota River flows through a 95% agricultural watershed, yet it has been ranked among the 20 most polluted rivers in the U.S. The river flows through a relatively flat landscape, but is fed by tributaries that are incised with steep and unstable stream banks. It is not clear what proportion of the sediment and nutrient pollution in the Minnesota River is from upland erosion vis-à-vis stream bank collapse. This study is designed to determine the feasibility of using a helicopter- mounted scanning laser to estimate riverbank erosion. Specifically, this research group is measuring bank erosion along the Blue Earth River in southern Minnesota; this river contributes 55% of the sediment load to the Minnesota River at Mankato. The procedure involves two laser scans, taken one year apart, of the Blue Earth River valley. The difference in the elevations between scans quantifies the extent of banks that may have eroded or sloughed during that time period.
In April 2001, the research group made the first scan of a 35-mile length of the Blue Earth River from Amboy to Rapidan Dam. They have constructed the digital elevation model of the river and have also made an animation of the river valley. The figure shows an example of the raw elevation data for two riverbanks along the Blue Earth River. The group will make a second scan of the riverbanks in Spring 2002. They will use the difference in elevations between the two scans to estimate bank erosion during the last year. They have also made bulk density measurements on the riverbanks and will be using these to convert volume change into sediment loads. |
 Laser scan of two riverbanks on the Blue Earth River. |
Marin Bauer, Faculty Collaborator
David Thoma, Graduate Student Researcher
This information is available in alternative formats upon request by
individuals with disabilities. Please send email to
alt-format@msi.umn.edu
or call 612-624-0528.
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