Posted on September 17, 2026
OMAHA, Neb. — The U.S. Army Corps of Engineers, Omaha District, in partnership with Union County, South Dakota have signed a federal cost share agreement that formally begins a flood risk management feasibility study focused along the lower Big Sioux River in southeastern South Dakota and northwest Iowa to explore potential ways to better protect the people, homes, businesses, infrastructure, and agricultural land in the area from flooding. Union County initially requested the partnership in 2025 and will be serving as a non-federal sponsor, with local support from the cities of North Sioux City, South Dakota, and the Dakota Dunes Community Improvement District. The study is expected to take approximately three years to complete.
Communities along the lower Big Sioux River have experienced increasingly frequent and severe flooding in recent decades, including record flooding in June 2024 that caused severe erosion and significant damage to infrastructure and property.
“This study gives us an opportunity to partner with the local communities to look at the flood challenges facing the lower Big Sioux River as a whole and evaluate what may be possible moving forward,” said Jen Gitt, USACE Omaha District project manager. “We are at the very beginning of that process. Community input will be an important part of helping us understand the problems and potential solutions.”
The study area includes the lower Big Sioux River watershed starting where the river valley opens up onto the Missouri River floodplain near Richland, South Dakota downstream to the confluence with the Missouri River. Approximately 12,000 people are present in the area during the day, along with more than 4,000 residential, commercial, and public structures. The area includes major transportation routes including Interstate 29 and the BNSF Railway as well as tens of thousands of acres of cropland.
What happens next?
Over the coming months, the study team will work to better understand existing flood risks and develop a range of potential measures that could help reduce those risks. Those measures will then be evaluated and refined as the study progresses.
Potential solutions have not yet been determined. The study will consider improvements to the existing federal Big Sioux River Flood and Erosion Control Project as well as other measures that could reduce future flood risk.
The existing federal project includes two levee systems and a flood risk management channel. It was originally authorized in 1968, and construction was completed in 1981. The new study is being conducted under Section 216 of the Flood Control Act of 1970, which allows USACE to evaluate whether completed federal projects should be modified to better meet current needs.
The feasibility study does not mean a construction project has been selected or approved. The study is intended to identify flood-related problems, evaluate possible solutions, and determine if there is a technically feasible, environmentally compliant, and economically justified project that can be recommended for construction. Any future construction recommendation would require additional congressional authorization and funding.
Community involvement:
Public involvement is an important part of the study. As the study progresses, USACE and its partners will provide opportunities for the public to learn more, ask questions, and share input. The first public open house will be held in North Sioux City in late October.
Questions and comments about the Lower Big Sioux River Flood Risk Management Feasibility Study may be submitted to CENWO-CW-PlanningOutreach@usace.army.mil or to local study partner Jeff Dooley, City Administrator of North Sioux City, at jeff.dooley@northsiouxcity-sd.gov.
For Additional study information and future updates, please visit the U.S. Army Corps of Engineers project website: https://www.nwo.usace.army.mil/Missions/Civil-Works/Planning/Planning-Projects/Lower-Big-Sioux-River-Flood-Risk-Management-Study/
