Moving mountains to build islands on the Mississippi
The U.S. Fish and Wildlife Service's Jim Nissen heads toward an island under construction. It's one of the Upper Mississippi Wildlife Refuge's newest. Already, a great blue heron walks the shore. He points out a few others.
"There's a great egret right there, (and a) ring-billed gull," he says.
Back in 1939 this part of the river, called the Raft Channel, south of Brownsville had 625 acres of islands. That was a couple years after the Army Corps of Engineers built Lock and Dam No. 7, just to the north.
By 1989, only 129 acres of islands remained. Nissen says wind, high water and the wakes from barge traffic had worn most of them away.
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"The islands disappeared and the vegetation went with it. So if you were a fisherman, or somebody who wanted to observe wildlife, in 1997 you wouldn't have seen much. The islands were gone, the vegetation was gone," Nissen says.
Islands slow river currents, and provide vegetation for waterfowl and birds. They also provide cover for swans and habitat for creatures like muskrats and turtles.
This is not the first island built by the Fish and Wildlife Service. In the early 1990s the FWS, along with the Army Corps of Engineers and Minnesota and Wisconsin DNRs, started to restore this habitat through the federal Environmental Management Program.
Nissen pulls out a map of the old habitat. He says the idea is to recreate the clusters of islands that were once here. The 8,000 cubic yards of sand poured for this island is pressed against an existing thread of a willow and cattail-covered land.
"So we're trying to tie it in with an existing island. When we get around the corner you'll see that existing island starts to pull away. We get below where they are working right now and there really isn't any island left," he says.
In addition to this one, the Fish and Wildlife Service planted four seed islands. Seed islands are small berms of rock covered in sand that will grow over time with the current. Next year four more islands are planned in the channel.
Nissen gets out of the boat and walks along the sand. An Army Corps of Engineers crew is at work.
A dump truck and crane pile rock along the edge of the embankment and plow the sand. By November, the new strip of the island will be 40 feet wide. Nissen says they'll add six inches of topsoil and plant it with rye.
"We had to learn how to build islands. And we certainly have done that. Lake Onalaska, this horseshoe island, Stoddard Island and other islands above and below here," Nissen says.
Nissen says in previous projects, they built islands several feet above the 10-year flood mark to avoid erosion. The islands held up but looked unnatural. Vegetation didn't grow as well in some areas. Still, that was a step up from a 1983 project. Nissen says then, river managers tried to avoid erosion by using bound tires.
"What we have out here now is a breakwater built out of tires. So that was what they had. I think there are 1,500 tires out here. They tried to place it in the main channel, but it didn't hold," he says.
In the meantime, river managers discovered that if they made the islands lower, like this one, and added rock to protect them, the winds and waves shape them naturally. Sand builds up in some places, wears away in others. Sand and mud flats form for turtles and shore birds to nest.
Army Corps of Engineers wildlife biologist Randy Devendorf says they have learned to mimic the river when they build these islands.
"To help keep them in place, and make sure we don't have as much maintenance to have them there. So we're trying to restore those traditional rivering and flood plain processes in our design," he says.
Devendorf says the construction of these islands is part of a larger plan that's unfolded over the last 18 years. So far the $20 million project has restored 123 acres of islands in this region of the river.
Devendorf says no islands have failed yet.