Restoration work to prevent river flooding at Minnesota Valley National Wildlife Refuge

Just a few miles south of Minneapolis, along the final bends of the Minnesota River, large sections of a national wildlife refuge are under water.

The old and failing culverts in the Minnesota Valley National Wildlife Refuge can no longer keep up with the increasing rainfall, erosion and intensive draining systems that have caused the river to flow at twice its historical strength. The floods are drowning out native plants and habitats needed by birds and migrating waterfowl, as well as closing some of the hiking trails and bird-watching and hunting land used by about 300,000 visitors a year.

The U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service will begin a $4.1 million project this summer to build and replace a series of culverts and structures to lower water levels in the refuge.

The work, which will take about two years to complete, will help restore a wide variety of vegetation critical to migrating birds in a chain of ponds near Shakopee, Eden Prairie and Bloomington, said Eric Mruz, deputy refuge manager.

"Basically, we have lost the ability to manage water levels at several of these ponds and I honestly think that the flooding here is only going to get worse," Mruz said.

The refuge, which was created in the 1970s, is one of only a handful in the country located so close to a major urban area. It stretches along the last 70 miles or so of the Minnesota, from the city of Henderson to Bloomington, just before the river empties into the Mississippi River. It offers one of the rare spots in the Twin Cities where hikers can make it deep into the stillness of a marsh, or walk through one of the last remaining pockets of oak savanna in the state.

More than 50,000 ducks and geese stop in the refuge during spring and fall migrations, according to Audubon Minnesota, which lists the preserve as one of the state's most important bird areas. It's home to more than 260 different species of birds, at least 100 of which are known to nest there, according to the conservation group.

It's a marvel that such a sanctuary exists so close to the more than 4 million people who live in the area, said Robert Petzel, volunteer and president of the Minnesota Valley Refuge Friends organization.

It's home to miles of deep hiking and biking trails, rare trumpeter swans, tundra swans, bluebirds and flickers, he said.

"It's a wonderful place to get away from everything else might that might be going on," Petzel said.

Since the state largely shut down this spring because of the COVID-19 pandemic, the wildlife refuge has also become a refuge for families and hikers from across the metro area and the 14 counties the federal land touches.

What has long been more of a hidden gem is now receiving perhaps the most attention it has ever gotten from the public, Mruz said. In the months since the first cases of COVID-19 were found in Minnesota, the refuge has received about five times as many daily visitors as it had had in previous years.

But the increase in visitors comes as the hydrology of the Minnesota River has changed, according to the Army Corps and a number of federal and state studies.

The river's flow has more than doubled over the past decade, meaning water is rushing through with twice the force it did on average from 1950 to 2010. That's largely because the state is receiving more intense storms and rainfall than it has before, including last year, which went down as the wettest in Minnesota's history.

And over the past several decades, landowners in western and central Minnesota have drained more acres for row crops, funneling that water into the river and its tributaries.

The soft soil the Minnesota cuts through has always been prone to erosion. Now with the river's increased strength, the water is rapidly eating away its shoreline, doubling the width of the river in some segments and washing away homes and other structures.

The new drainage and water flow systems in the refuge were designed with the changing hydrology in mind, Mruz said.

"These structures are going to be big enough, we think, to handle that extra load of water," he said.