The flood of 2019 set record levels for 45 river gages, including five on the Missouri River.  Sixteen federal levees were overtopped and breached, an additional nine federal levees were overtopped sustaining significant damages but did not breach, and four non-federal levees were overtopped and breached.

A bomb cyclone storm dumped up to 2.25 inches of rainfall on a heavy wet snowpack across the region between Tuesday, March 12 and Thursday, March 14. The rain fell on a plains snowpack that held 3 or more inches of snow water equivalent in Nebraska and Iowa with even higher amounts in eastern South Dakota. In north central South Dakota and North Dakota that snowmelt is forecast to occur in the coming weeks. Waters from this flood event came from unregulated tributaries that enter the Missouri River below the large main stem storage reservoirs.

Water remains on the floodplain limiting access to assess damages to levees along the Missouri River. Two levee breaches along the Platte River have initial closures in place that stopped water from flowing through the breaches. Contracts have been awarded for initial closures on the Missouri River to return the river to the channel.

In response to this record setting event, the Omaha District commander established the Omaha Systems Restoration Team as a special execution cell to focus the vast skills and abilities of the district to engage in time-sensitive rehabilitation of flood controls structures in the Missouri River Basin. 

Q. Why did so many levees fail? The ‘bomb cyclone’ storm impacted the unregulated Elkhorn River, eastern Nebraska Platte River, and lower Missouri River basins and overwhelmed the design capacity of the levee systems in the region. The storm followed one of the wettest winters on record for this region, and a cold February. The ground was frozen, snow covered, with numerous ice jams on the tributaries. The storm dropped 1.5”-3” of rain across six states BELOW the main stem dams, and the ensuing runoff was unregulated/uncontrolled. The volume of water overtopped levees and breaches occurred. Kansas River project releases were limited to mitigate the Missouri River crest downstream from the confluence.

Q. How long until the waters recede? Unregulated runoff from the rapid snowmelt is already passing through the basins and the water is beginning to recede. The Corps' number one priority in its operations is life safety. Our current focus is to protect life, mitigate risks to flooding events, and repair damages due to the recent events in the Basin.

Q. Why did this particular event happen so quickly? On March 13, a heavy rainfall event totaling 2 to 4 inches of precipitation fell over Nebraska, South Dakota and Iowa on top of a snowpack containing 2 to 3 inches of liquid content. Due to the frozen and saturated soils, very little of the rainfall and snowmelt infiltrated into the soil. Rather, it became direct runoff into streams and rivers throughout Nebraska and Iowa resulting in record high flows on many of the unregulated streams and rivers in the lower Missouri River basin.

Q. Why didn’t the Corps give more warning or communicate more ahead of the flood? The National Weather Service is the official forecast and warning entity. This event developed very rapidly. On Tuesday, 3/12, the Omaha District held flood fight training for the levee sponsors, County Emergency Managers, and State Emergency Managers in which the upcoming forecast was discussed. Before this event began and since, Corps has been in constant contact with state and local emergency management offices. We continue to proactively inform the public of the impacts of the runoff to the federal system and our efforts to support local flood fighters. We will continue to do so through the duration of this event and well after. The Corps also began hosting daily CODEL calls March 13.

Q. What could the Corps have done to prevent this flood? Most of the inflows were from unregulated tributaries. The Corps helped mitigate the risks of flooding, by reduced Fort Randall releases to 0 cfs to lessen inflow into the Gavins Point reservoir. However, the Gavins Point project, which is a re-regulation project used to smooth out fluctuating releases from upstream projects, contains only a minimal amount (about 100,000 acre-feet, see Figure 1) of the Mainstem System’s flood control storage (less than 1%). Thus, the minimal Gavins Point reservoir’s available flood control storage was quickly filled. All 14 Gavins Point spillway gates were used to increase the reservoir storage, a practice referred to as surcharging. Even by surcharging the pool to 1212.3 feet, 2.3 above the top of the Exclusive Flood Control Zone, the Corps needed to increase Gavins Point releases to 100,000 cfs for 6 hours so that the gates would not be overtopped.

Q. Is this flood event bigger than the 2011 flood? All floods are different. The 2019 flood is meteorologically, hydrologically, and geographically different.

Q. Why are you repairing some levees before you repair others? The District is currently focused on stopping the flow into the entry breaches. After these are temporarily closed, work will begin to bring the levee system up to its’ original design capacity.