Officials with the U.S. Army Corps of Engineers will hold an open house tonight at the Effigy Mounds National Monument Visitor Center in Harpers Ferry to discuss plans to protect the area from flooding and erosion.

The prehistoric burial mounds that comprise Iowa's only national monument have stood for centuries, but the Corps' Jill Bathke says they're now under immediate threat.

"Construction of the locks and dams on the Mississippi River and climate change has altered the hydrology that has increased erosion of the shorelines," Bathke says, "and that's really eroded a lot of the irreplaceable Native American burial and ceremonial mounds and that cultural landscape."

The protected area of northeast Iowa is home to some 200 earthen mounds that are believed to have been built during the first millennium. Many mounds are shaped like animals, including bears and birds. About 100 mounds are in a low-lying area known as the Sny-Magill unit, and she says that's the section being placed at risk by the river.

"Right now, out on public notice is our tentatively selected plan which would protect the Sny-Magill unit with a 2,000 foot linear berm," Bathke says. "On top of that berm, there would be an access trail where people and tribal nations could views the mounds and appreciate their context in the cultural landscape."

The monument is managed by the National Park Service, and the area east of the Sny Magill unit is part of the Upper Mississippi River National Wildlife and Fish Refuge, which is managed by the U.S. Fish and Wildlife Service. Bathke says coordination and consultation with tribal nations about the proposed protection plan is ongoing.

Another element in the mix, she says an endangered species of mussel has been found in the area. "A lot of the work in the last year has been done to find ways to minimize impacts to those endangered species while also protecting this really important cultural resource," Bathke says. "We've done consultation with over 19 tribal nations that are culturally or traditionally affiliated with the park, and so that also has taken time."

If the project is approved, the boat launch at Sny-Magill would be temporally closed in spring and summer of 2026 for construction.

"Generally, we found that there's a lot of support for this project," Bathke says. "We are proposing to have tribal monitors on site during all active construction activities to ensure that we're doing this in a way that's appropriate. And if there's any significant findings that we would coordinate that appropriately with tribal nations."