South Dakota is using the bridge at I-29 exit 4 in South Dakota to build a levee across the interstate and try to save North Sioux City from flooding.
There are two different detours in place. One goes through the northeast corner of Nebraska and Vermillion, while another MUCH longer one uses I-90, I-35, and I-80. I-35 was used as a detour for I-29 in 2011, too, when floods hit western Iowa.
The Sioux Falls Argus Leader asked about the long detour, and got a response that all interstates “must be connected”.