Gov. Dennis Daugaard warned residents of Pierre and Fort Pierre on Thursday that some level of flooding is imminent in their communities because of rising water levels on the Missouri River.
Record flows into the river from Montana through South Dakota are forcing the Army Corps of Engineers to increase releases from the mainstem dams. Those increased releases will raise water levels.
- For questions about the situation, or information about flood preparation:
Note: This release is based on projections and the most current information from the Army Corps of Engineers. This is a rapidly-evolving situation that may change as more information because available.
Who is threatened?
In the following areas, flooding is projected begin on Saturday, May 28, and will worsen on June 4-6. Property owners in this area should plan to evacuate without delay over the next 48 hours.
- In Ft. Pierre: For the area south of the Missouri River bridge and north of Cedar Avenue, everything between the Missouri River and Highway 83. North of the Missouri River bridge and south of Echo Point, everything between the River and Marion Pastures.
- In Pierre: The residences on either side of Marina Drive. The southeast Pierre area. Everything that is both east of Washington Street, which is near St. Mary’s Hospital, and south of Missouri Avenue.
When will this begin and for how long will it last?
Water levels will begin to rise late this week, and the water levels could remain at this flood stage into July. Property owners should plan to evacuate their property by this weekend and may not be able to return until mid-summer.
The Corps plans to increase the water release beginning on Saturday. Water levels are expected to stay the same until Saturday, then they will begin to go up.
The current elevation of the Missouri River at Pierre and Ft. Pierre is 1,430 feet above sea level. That could increase as much as four feet as water flows increase.
On Saturday, May 28, the Corps will increase water flow from the Oahe Dam to 85,000 cubic feet per second (CFS). Subsequent flows will later increase as follows:
- 90,000 CFS on Saturday, June 4.
- 95,000 CFS on Sunday, June 5.
- 100,000 CFS on Monday, June 6.
As the snowmelt continues into late June and early July, the water flow will increase to 110,000 CFS and may reach 120,000 CFS.
How are we responding?
State and local officials are currently coordinating plans for shelter and assessing the potential impact on utilities and other infrastructure. Officials are also working to obtain additional flood-fighting and sheltering supplies.
The public will receive updates on these plans as they are available.
How will flooding impact other river communities in South Dakota?
At this time, the primary area of concern is Pierre and Ft. Pierre. However, this flooding will impact other communities, and that information will be released as it is available.
Explanation of the cause
Last night, the Army Corps of Engineers dramatically increased their calculation of water release required from the mainstem dams on the Missouri River. The Corps believes that this increased water release is necessary to avoid overtopping of the spillways.
Huge rainfalls in Wyoming, Montana, and western North Dakota and South Dakota over the past month have exceeded rainfall in a normal year. This used the reservoir capacity that had been reserved to accommodate the snowmelt. In addition, mountain snowpack is 135 percent to 140 percent of normal, and it is melting at a later time. As a result, all the moisture will require the Corps to increase water flows to unprecedented levels.
Source: office of Governor Daugaard