Tributary dams help provide flood risk reduction, saving millions in damages

OMAHA, Neb. – Many people will visit popular lakes across the Midwest this summer for recreation without ever knowing the reservoirs provide several other benefits.

These benefits include irrigation, water supply for domestic use, and habitats for fish and wildlife. One of their primary purposes, however, is to provide critical flood risk reduction.

Each year, the reservoir systems help save downstream communities from the potential loss of life and millions of dollars in flood damage. The reservoirs work together to collect and store water during high-water events and then release it once downstream flood risks have subsided.

The U.S. Army Corps of Engineers, Omaha District, currently manages 35 tributary reservoirs with federally authorized flood control storage across several Upper Midwest and western states, including projects owned by USACE, the U.S. Bureau of Reclamation and local authorities.

“We are monitoring weather, reservoir, and runoff conditions every day,” said Katie Seefus, a hydraulic engineer with the Omaha District. “During a major storm event, engineers use reservoir inflow forecasts to simulate maximum reservoir pool elevations and then determine a reservoir release schedule that maximizes project benefits.”

Seefus said the last 30 years of data prove these projects have worked together to significantly reduce flood risk. As a result, millions of dollars in damages are avoided every year.

Analysis shows that North Dakota’s Pipestem and Jamestown dams reduced flood damage by an estimated $6.5 million in 2025. Nebraska’s Papillion Creek and Salt Creek dams prevented nearly $4.4 million in damage. In Wyoming, Boysen and Yellowtail dams reduced flood losses by about $2 million, while Montana’s Canyon Ferry and Tiber dams prevented nearly $4 million in damages.

“Without these reservoirs, surrounding communities would have been prone to flooding at a significant cost,” Seefus said.

The flood protection benefits become even more apparent during wetter years. Seefus pointed to 2009, 2010 and 2011 as exceptionally heavy runoff years that required extensive use of flood control storage throughout the basin.

More recently, the reservoir system significantly reduced damages during widespread flooding in 2015 and 2019. The Salt Creek dam system in Nebraska alone reduced flood damage by more than $75 million in 2015 and more than $23 million in 2019, according to USACE analysis.

Even with these successful outcomes, predicting storage levels and releases during high-water events can be challenging.

“Every runoff event is different just like every reservoir project and priority is different,” said Kellie Bergman, chief of the Omaha District’s Hydrologic Engineering Branch. “Balancing flood control with other reservoir purposes such as recreation and water supply remains a constant challenge because flood protection depends on maintaining enough empty storage space to absorb incoming runoff.”

Bergman said a key benefit of the reservoirs is preventing flooding before rivers ever rise downstream.

“It is easy to take these projects for granted because flooding does not typically strike a community every year,” Bergman said. “When heavy rain or significant snowmelt does occur, some of the flood water is captured by these reservoirs and therefore reduces the downstream impact of the flood.”

Reservoir operations are guided by detailed water control plans developed for each project in coordination with local stakeholders and communities. Operating plans are reviewed often, and dams are inspected routinely to help ensure their safe and reliable operation for communities throughout the Missouri River Basin.

Officials emphasized that while dams help reduce flood risk, no dam can eliminate all flooding. For more information on our nation’s dams or to view flood inundation maps for your community, visit the National Inventory of Dams at: https://nid.sec.usace.army.mil/.