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The U.S. Army Corps of Engineers has released a flood risk management study for the city of Watertown that suggests lowering the level of Lake Kampeska each autumn, widening the Big Sioux River channel and building levees along the river.
A public meeting will be held from 5:30 to 7:30 p.m. on Tuesday, Sept. 17, at the Ramkota Event Center, 1901 9th Ave. SW. The public meeting will include a short presentation on the proposal.
The purpose of the Corps’ project is to address flood risk management along the Big Sioux River in and around Watertown. The Corps aimed to develop and review flood risk management alternatives to identify a feasible and economically justified plan.
The Watertown area has experienced 11 major floods since 1943, averaging a major flood approximately once a decade. Watertown’s susceptibility to flood damage has increased over time as the city has grown and development has increased around nearby Lake Kampeska and Pelican Lake.
The Corps’ 109-page report presents 12 different options for reducing flood risk in the area, plus an option of taking no action. The option being recommended by the Corps would lower Lake Kampeska’s elevation to 1,718 feet above sea level each autumn, which is 0.8 feet below what is considered full. Corps engineers said this would create room for about 3,300 acre feet of floodwater storage in the lake.
As a comparison, the major flood of 1997 added more than 100,000 acre feet of water to Lake Kampeska.
The plan would also require the construction of a 4,435-foot levee along the river from West Kemp Avenue to just north of U.S. Highway 212.
The final aspect of the proposal would be to widen the Big Sioux River channel 50 feet on each side river from just north of 14th Avenue and continuing south past U.S. Highway 212.
Col. Robert J. Newbauer of the Corps of Engineers said the plan was one of several alternatives identified by engineers.
“These alternatives were evaluated for engineering feasibility, economic viability and environmental, tribal and public acceptability. … I find that the tentatively selected plan would lower flood risk by increasing the level of protection against different flood events.”
The estimated cost of the flood-control project is about $26.7 million, with the city paying about $9.3 million and the federal government covering the rest.
Each of the Corps’ 12 suggested plans would lower Lake Kampeska’s elevation to 1,718 feet. Each plan features combinations of left- and/or right-bank levees, channel-widening, and adding closing structures to the Big Sioux River.
A Corps of Engineers schedule calls for refining the plan after input from the public with final Corps approval set for May 2026.
