Background on Lower Big Sioux River Study 2026-2029

The U.S. Army Corps of Engineers (USACE) and Union County, South Dakota, are conducting a feasibility study to evaluate flood risk along the lower Big Sioux River in partnership with North Sioux City, South Dakota, Sioux City, Iowa, and the Dakota Dunes Community Improvement District, South Dakota. 

The study will examine whether improvements to the existing federal flood risk management system or other flood risk reduction measures could better protect people, homes, businesses, transportation routes, and other critical infrastructure from flooding. 

The existing federal flood control project was constructed between 1977 and 1981 and has generally performed as intended. However, recent flooding events have highlighted changing conditions and new challenges that warrant further evaluation. 

Public Open House Meeting - Lower Big Sioux River Flood Risk Management Study

•  Location: North Sioux City Community Hall, 205 Sodrac Drive, North Sioux City, South Dakota
• Date & Time: October 22, 2026 6:00 pm - 7:00 pm
• Details: Please click here to view Public Open House Flyer for location details.

Below is a link the US Army Corps of Engineers project website for the Lower Big Sioux River Flood Risk Management Study.

Click here -project website view the  more information regarding this study.

Click here to view news release regarding this study.