High flows are contributing to the collapse of bluffs along the Le Sueur River in south-central Minnesota. The erosion sends tons of sediment into the river and downstream waters.
Flooding. Collapsing banks and bluffs. Murky water. A short canoe ride down the Le Sueur River shows all the symptoms of a suffering river system.
Putting in canoes and kayaks in the river at the Red Jacket Park in Mankato, paddlers see the new trail trestle that replaces the one wiped out by the 2010 flood. A bluff downstream provides a beautiful scene and an alarming one as it’s sliding into the river, bringing tons of sediment with it. The river is too murky to see the bottom, even when an aluminum canoe scrapes noisily over rocks in shallow water.
After flowing through gently rolling landscape, most of it farmland, the Le Sueur cuts down through high bluffs to join the Blue Earth River. The confluence looks like an immense cauldron of simmering mud.
Leaving the river at the County Highway 90 bridge and looking upstream, a paddler notes she didn’t see one fish jump along the 1.75-mile route.
The group of 15 paddlers heads back to the park, where many more citizens join them for a potluck supper and discussion on how to heal the Le Sueur River.
Paddlers on the Le Sueur River head for the confluence of the Blue Earth River near Mankato as part of effort to learn about the river and ways to restore it.
At one table, residents are concerned about trees falling into the river. Paul Davis, watershed project manager with the Minnesota Pollution Control Agency explains that the trees are a symptom of bigger problem that dates back to the 1800s when settlers arrived to farm the area. They drained the land, creating some of the most productive farmland in the world. But they drained 89% of the wetlands, eliminating nature's way of retaining and filtering water. And they built an extensive drainage system, converting streams into ditch channels and connecting the ditches to rivers, bringing more water into the system.
At the same time, people built cities, roads, and bridges. These changes in the landscape also altered the river system.
Crops and buildings replaced floodplains, nature’s overflow system. The river once flowed into floodplains at high levels; now it has nowhere to go. Over decades, the river channel has widened and deepened, putting more pressure on its banks and bluffs, which collapse under the pressure.
Climate change is another factor. Minnesota experiences more frequent storms and resulting bursts of water into the river system.
The result is a huge increase in the amount of sediment in the river, hurting fish populations and recreational opportunities. The huge increase in water in the river system also takes it toll with flooding, which poses risks to people and infrastructures.
A hydrograph is one way to depict the water levels in a stream. A natural stream – one that hasn’t been straightened, widened or deepened to facilitate drainage – will show a slow rise in water levels on a hydrograph as the stream finds its way to floodplains. An altered stream will flash, showing a sharp rise in the hydrograph.
“We can’t put it back the way it was. So now what?” Davis asked.
Landowners, state agency staff, and other interested citizens discuss problems in the Le Sueur River and ways to address them.
People at this gathering had some ideas. One landowner talked to a conservationist about restoring a wetland. Another sought advice on fixing ravines. A farmer noted she and her husband are renewing their contract for their acres in the Conservation Reserve Program.
This gathering was organized by the Clean Up the River Environment (CURE) and the Water Resources Center of Minnesota State University-Mankato. The two organizations are seeking citizens to lead the Le Sueur River Watershed project, which will include identifying areas for protection and restoration.
This project will entail some hard work and hard decisions. The MPCA intensely studied the water quality of the Le Sueur watershed from 2008-2011, examining fish populations, bug populations, and water chemistry. The scientists found few stream sections in healthy condition.
As people at the May gathering in Red Jacket Park moved from table to table, learning about river life and the watershed project, one participant looked around and asked, “Where’s the table where they’re going to talk about how to clean it up?”
Citizens will get to that question at later gatherings. Call CURE at 1-877-269-2873 for more information.