The Lower Brule Sioux Reservation gets a little smaller every year.

Winter wind pushes heavy ice onto the western bank of the Missouri River, which forms the eastern boundary of the tribe’s reservation in central South Dakota.

The ice grinds against the shoreline and rips up sod.

After the ice melts each spring, waves wash over the exposed soil and carry it into the river.

At one spot where the erosion is especially bad, the shoreline recedes by 7 to 40 feet per year.

That spot is near the sewage lagoons that serve the 600 residents of the town of Lower Brule. Erosion has brought the shoreline within 70 feet of the closest lagoon.

“This lagoon is likely to breach within the next 2 to 3 years,” says the blunt assessment of an Army Corps of Engineers report on the problem.

To prevent a breach of the lagoon, the Corps plans to halt the shoreline erosion by building an $8.08 million breakwater in the river. The federal government would provide $7.43 million, assuming Congress provides the funding in a pending appropriations bill. The tribe would cover the remaining $645,364.

The breakwater would consist of a mile-long, 50-foot-wide, stone-and-earthen peninsula, most of which would run parallel with the shore. Waves would hit the breakwater and dissipate before they could cause further shoreline erosion.

To mimic conditions that predated the construction of dams on the river, a wetland would be created between the shore and the peninsula, and the peninsula would be planted with cottonwood and willow trees and other native vegetation.

A recreation area with a swim beach, boat ramp, vault toilets, picnic shelters and a fish-cleaning station would be built onshore near the breakwater. The new recreation area would replace an existing one that has been falling into the river as the land erodes underneath it.

Tribal officials have said they hope the recreation area will help connect reservation children to the river.

“Many have never been on the river in a boat, on the shore to fish nor in the river to swim because access to the water is not safely provided,” says an Army Corps of Engineers report.

The tribe’s reservation was created in an 1865 treaty with the United States. The federal government has reduced the size of the reservation several times, most recently during the 1940s, ’50s and ’60s while the Fort Randall and Big Bend dams were constructed.

The swollen river segments behind the dams — named Lake Francis Case and Lake Sharpe — inundated 40 square miles of the tribe’s bottomland and required the town of Lower Brule to be moved to higher ground.

Shoreline erosion has nibbled at the tribe’s shrunken land base since then. One estimate says the reservation has lost 6 square miles of land to the problem.

The tribe built a breakwater pilot project in 2007 about 15 miles upstream from the proposed new breakwater. That existing breakwater has performed as intended and now serves as inspiration for the proposed project near Lower Brule.

If funding is made available in a congressional spending bill this fall, the Corps of Engineers hopes to have the breakwater constructed by 2021.

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Contact Seth Tupper at seth.tupper@rapidcityjournal.com

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