Louisiana’s coast is starved for river sand; Wisconsin has it

Most of the Mississippi River’s land-building ingredients never make it to the marsh
Published: Jul. 7, 2021 at 8:49 PM CDT|Updated: Jul. 7, 2021 at 10:33 PM CDT
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NEW ORLEANS (WVUE) - Chad Baker takes his recreation boat into a tiny cove on the east bank of the Mississippi, downriver from La Crosse, Wisconsin.

Here, at Crater Island, the U.S. Army Corps of Engineers has deposited river sand and created a weekend hot spot in the summer months.

“Locally famous, for sure,” Baker said of Crater Island, which he and others have been visiting for 30 years.

“It’s a big party cove, basically. Everybody comes out and parks the boats and hangs out on the sand bars.”

This is not the mighty Mississippi that New Orleanians know. Visitors are more likely to see small watercraft.

However, contractors for the Corps dredge the river for barge traffic to a depth of 11 feet.

Much of that sand gets piled at Crater Island and at a larger site across the state line in Brownsville, Minnesota.

“We’ve got about 200,000 cubic yards of sand here,” said George Stringham, a spokesman for the Corps.

Each year, the Army Corps St. Paul District alone dredges about one million cubic yards of material, or a Superdome worth of sand every four-and-a-half-years or so.

The Brownsville site is one of eight large storage areas in the district.

“Places like Crater Island, there are about 30 more of those,” Stringham said.

River sand is the other gold in Louisiana’s drive to restore its wetlands, a critical but mostly missing ingredient, in the river’s land-building process.

One LSU study found the river in South Louisiana contains less than half its historic sediment load, due in part to modern farming techniques that reduce the amount of soil erosion in midwestern states.

Dozens of locks and dams on the Mississippi and its tributaries also serve to trap millions of tons of sediment.

While the river seems level to the casual observer, it actually drops hundreds of feet in elevation as it makes its journey from Lake Itasca, Minnesota to the Gulf of Mexico.

“What the locks do is they stair-step the river off, which makes it easier for navigation,” said Chris McLindon, a geologist active in coastal issues. “But each one of those steps is, effectively, a sediment trap.”

Not all of this valuable material goes to waste.

Over the last decade, the Corps has captured much of the sediment from dredging near the mouth of the river, where it is piped into nearby wetlands in the Birdsfoot Delta.

The large sand pile in Brownsville will be put to use, adding elevation to 60 acres at a riverfront development project in La Crosse.

However, the cost of transporting some of the millions of tons of dredged material on the Upper Mississippi appears prohibitive.

“At least for the federal government, it’s not economically feasible to barge it all down there,” Stringham said.

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