Feb 12, 2020

Erosion Damage Expands Minnesota River

The Minnesota River is expanding much faster over the past 20 years than it ever has due to erosion.

erosion control

Stretches of Minnesota River's eastern bend have more than doubled in size since the 1940s. 

The homes built more than 50 feet from its banks or its main tributaries have collapsed or been demolished before they could be washed away by the encroaching waters, reported the Star Tribune

Cities in the river’s path are asking the state for funding to raise roads, reinforce bluffs and move needed infrastructure farther away from its banks, according to the Star Tribune

The only way to address the erosion of the river long term is to increase the storage capabilities around it and to provide enough space for water in order to reduce the river’s historically high flows, according to Karen Gran, professor of earth and environmental sciences at the University of Minnesota Duluth

“There is just a lot more water going into the river right now,” said Gran. “If we’re serious about alleviating these issues, it means we need to start holding more water back on the landscape.”

The creation of smaller temporary storage systems such as drainage ditches and holding ponds could also cut down erosion. 

The amount of sediment is now 10 times higher than it was in the 1800s, reported the Star Tribune. The Minnesota River’s flow has more than doubled over the past decade, meaning that water is rushing through at twice the force that it did on average from 1950 to 2010, according to a 2017 study by researchers with Utah State University.

Several studies have shown that the river has gotten stronger because of two major changes: The state is getting more intense storms and more rainfall than and over the past several decades, western and central Minnesota have become extensively drained by landowners who are converting acres into row crops.

The cost of adding enough storage systems to reduce the river’s flow is currently undetermined.

Summer 2018, the Minnesota Pollution Control Agency (MPCA) found that the river was still so thick with erosion and runoff that sediment levels would need to be cut by at least 50% just to make the water safe for fish, vegetation and human use. Along with other cleanup efforts, mitigation efforts could cost about $360 million over the next 25 years, reported the Star Tribune.

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