Flooding in South Dakota
On this page you learn what types of flooding are typical in South Dakota and how to you protect yourself, your family and your home. You will also find out more about significant South Dakota floods. Finally, you'll find links to NWS offices that provide forecast and safety information for South Dakota as well as links to our partners who play a significant role in keeping you safe.
|Significant South Dakota
Black Hills Flood of 1972
On the evening of June 9, 1972, heavy thunderstorms caused devastating flash flooding throughout Rapid City and the eastern foothills of the Black Hills, destroying homes, vehicles, businesses and bridges, and claiming 238 lives. Two areas of thunderstorms developed over the Black Hills during the afternoon as the approaching disturbance made the atmosphere more unstable. Rain over the northeastern corner of the Black Hills spread southward toward the Nemo area. Showers over the southern Black Hills and southeast of Rapid City moved northwest and intensified over the central Black Hills. By 6 p.m., a nearly continuous line of thunderstorms covered the eastern Black Hills. The strong easterly winds along the ground and light winds above the hills kept the storms anchored in place. The steep canyons channeled the high volumes of water that rushed toward the plains. Flood water from Deer Creek, Victoria Creek, Prairie Creek, and smaller drainages emptied into Rapid Creek above Rapid City, swelling the stream to over 300 times its normal volume. Data from the stream gauge on Rapid Creek above Canyon Lake indicated from 9:15 pm until 11:15 pm, the water level rose approximately 12 feet in 2 hours. Flooding also occurred along Bear Butte, Elk, Box Elder, Spring and Battle Creeks from Sturgis to Hermosa.
Around 12:30 am, June 10, the storms began to dissipate and move slowly to the east over the plains with no precipitation indicated by the Ellsworth Air Force Base weather radar by 6:30 am.Below are some statistics:
- As much as 15 inches of rain fell near Nemo and Sheridan Lake, with an average of 10 inches over 60 square miles.
- The heaviest rainfall in Rapid City occurred between 10:30 pm on June 9 and 1:00 am June 10.
- Peak flow on Rapid Creek 50,600 cubic feet per second, more than 10 times greater than the previous flood of record.
- During the flood, water rose as fast as 3.5 feet in 15 minutes.
- Flood debris clogged the Canyon Lake spillway and temporarily raised the pool 11 to 12 feet deeper than normal.
- 238 people were killed; 8 of the deaths in Keystone.
- 3,000 people were injured.
- 1,335 homes were destroyed.
- 5,000 automobiles were destroyed.
- $160 million damage (1972 dollars, $644 million in 2002 dollars)
- 15 of the 23 bridges over Rapid Creek were destroyed.
- 754 acres were developed as a floodway.
Flood damage on East Blvd. at Omaha St. in Rapid City, June 10, 1972. Photo courtesy of the Rapid City Journal.
Eastern South Dakota Snowmelt Flood of 1969
Following a wet autumn in 1968 when much of the eastern part of the state received from 150 percent to over 300 percent of normal rainfall, the winter of 1968-1969 saw the James, Vermillion, and Big Sioux river basins receive record snowfall of 60 to over 90 inches from December 1968 through March 1969 (300 to 400 percent of normal). The snow came along with temperatures that were 4 to 6 degrees below normal through the heart of the winter. The water equivalent of the snow pack by early March 1969 was between 4 to 8 inches across nearly all of eastern South Dakota. Little of the snow melted in March because temperatures remained below normal, but in early April, a rapid warm-up occurred with high temperatures reaching into the 50s and 60s and low temperatures remaining near to above freezing at night.
On the James River, backwater from ice and high tributary flows north of Huron kept the stage from reaching the record levels of the 1881 flood, but peak discharge from the snowmelt was as much as 1.5 times the previous maximum discharge. Major flooding affected the entire river basin, and flood damages exceeded $16 million across the basin.
The Vermillion River also saw major flooding, but not near any record levels. Flood damages in the Vermillion Basin exceeded $1 million.
The Big Sioux River from Watertown through Sioux Falls to Sioux City also saw major to record flooding in early to mid-April as the deep and wet snowpack quickly melted. More than 100 families were evacuated along the river from Watertown to north of Sioux Falls, including all 50 residents of the town of Renner. The U.S. Army Corps of Engineers flood prevention works in and around Sioux Falls, which include a bypass channel and extensive dikes and levees, protected the state's largest city from any major damages even though peak discharges were about 1.5 times the previous peak flood.
Downstream of Sioux Falls to Sioux City, roughly 50 homes were evacuated and suffered damage. The entire population of North Sioux City (800 people at the time) was evacuated. Total estimates of the number of people evacuated were around 4,000 in South Dakota. Over 150 National Guard troops were called out to help with the flood emergency in southeastern South Dakota. Total flood damages in the Big Sioux River Basin were greater than $15 million.
Flooding along the Big Sioux River in North Sioux City, courtesy of Sioux City Journal
Missouri River Flood of 2011
The 2011 Missouri River flood was the largest on record for the entire basin in terms of volume of water. Record peak flows were also experienced in some reaches. River stages and peak flows are difficult to summarize because stages vary with channel conditions and flows are different in historical and post-regulation time frames. In summary, the unprecedented runoff occurred from record rainfall over portions of the upper basin, along with plains and mountain snowmelt, led to the following record peak releases from the System dams:
- 65,000 ft 3/s at Fort Peck
- 150,000 ft3/s at Garrison
- 160,000 ft3/s at Oahe
- 166,000 ft3/s at Big Bend
- 160,000 ft3/s at Fort Randall
- 160,000 ft3/s at Gavins Point
During 2011, the annual runoff into the Missouri River Reservoir System, upstream of Sioux City, IA, was estimated at 60.8 million acre-feet (MAF). In comparison, the previous greatest annual runoff volumes were 49 million acre-feet in 1997 and about 50 MAF in 1881. During 2011, the March-July runoff was 48.7 MAF, greatly exceeding the previous record of 36.6 MAF in 1997.
The Missouri River mainstem reservoir system, authorized by the 1944 Flood Control Act (Missouri River Authorized Purposes Study, 2010), consists of six dams and reservoirs constructed on the Missouri River: Fort Peck Dam (Fort Peck Lake), Garrison Dam (Lake Sakakawea), Oahe Dam (Lake Oahe), Big Bend Dam (Lake Sharpe), Fort Randall Dam (Lake Francis Case), and Gavins Point Dam (Lewis and Clark Lake). The combined storage of all six system reservoirs is reported to be 73.1 MAF.
Downstream from Oahe Dam, at Pierre, SD, the river stage reached an average daily level of 1,433.98 feet at a streamflow rate of about 160,000 feet 3/s on June 21, 2011. This was the highest stage since the dam was completed in 1958. Although the 2011 flood is the largest flood of record in overall volume, earlier floods have had higher peak flow rates and stage levels. Prior to construction of Garrison and Oahe Dams, the Missouri River at Pierre reached a peak stage of 1439.6 feet on April 6, 1952 at a streamflow rate of 440,000 ft. 3/s.
Downstream of Gavins Point Dam, the peak flood stage at Sioux City, IA, was the highest since construction of the dams. The stage on July 21, 2011, was 35.25 feet, or over 4 feet higher than the next highest, which occurred in 1984 (Figure 5). Prior to regulation, the stage at Sioux City reached 44.26 feet at a streamflow of 441,000 ft. 3/s.
On June 1, nearly 3,000 people in Pierre and Fort Pierre were evacuated. On June 3, South Dakota governor Dennis Daugaard urged residents in the Country Club section of Dakota Dunes (which is below Gavins Point Dam) to evacuate. He noted that it might be 2 months before they could return.
On June 21, South Dakota reported its first flood fatalities when two women drowned in Lyman County after they drove their car down a washed out road. On the same day Pierre officials estimated costs from the flood would be $13.2 million for that community. High water damaged 42 of the 130 state parks and recreation areas in 2011, ultimately causing about $9 million in damage. The flooding on the Missouri River persisted into September 2011, leaving many areas under water for 3 to 4 months.
The floods of the Missouri River Basin caused approximately $85 million in direct damages, claimed 5 lives and led FEMA to issue disaster declarations in each state along the Missouri River. Two of these flood deaths were vehicle related and occurred directly on or near the main-stem Missouri River.
Gavins Point Dam
Flood waters from the Missouri River flood Griffin Park in Pierre, S.D., AP Photo
Levee construction continues along the Missouri River in this aerial photograph taken over the Spanish Bay addition in Dakota Dunes, S.D., Tuesday, June 7, 2011, AP Photo/The Sioux City Journal
Southeastern South Dakota Floods of June 1984
October 1983 through March 1984 saw greater than normal precipitation across most of southeastern South Dakota. Most sites reported over 200 percent of normal precipitation for this period. That precipitation was followed by a wet April with southeastern South Dakota averaging between 250-300 percent of normal. May 1984 had near normal rainfall, but the ground remained saturated with higher than normal river levels heading into June. June 1984 then set a record (at the time) for wetness, and the James, Vermillion, and Big Sioux Rivers all saw widespread and damaging flooding from June 11-26.
The first heavy rains of June occurred on the 4th-5th, causing lowland flooding on the Vermillion and Big Sioux rivers. Then, from the 7th-11th, the area measured additional rains of up to 5 inches, causing flash flooding on the smaller tributaries and eventually more significant flooding on the three rivers, with many roads and bridges damaged. Another 1-4 inches of rain fell over the same areas on the 14th-17th, followed by up to 7 inches of rain on the 19th-22nd.
Roads, bridges and culverts were washed out, basements collapsed, and stock dams were washed out. Some streets were under 5 feet of water, and many homes had 3 to 4 feet of water in them. In total, it was estimated that on June 21-22 alone, 1,000 miles of roads and over 1 million acres of crop land were inundated, and over 40 homes were evacuated. Damage estimates in 16 counties in southeastern South Dakota were placed at $300 million, most of which was to agriculture.
Eastern South Dakota Snowmelt Flood of March 2010
Major to record flooding occurred on the James, Vermillion and Big Sioux Rivers in eastern South Dakota in March 2010 following an excessively wet fall and winter. The Glacial Lakes in northeastern South Dakota also reached record high levels. October 2009 saw 200 percent to over 300 percent of normal rainfall across all of eastern South Dakota. Then, after a dry to normal November, the winter (December 2009 through February 2010) saw precipitation amounts of 1 to 3 inches above normal and snowfall totals of 40 to 60 inches, along with much below normal temperatures. Snowpack depths of 10 to 25 inches were common by late winter, with the water equivalent of that snowpack ranging from 4 to 8 inches. Temperature in March 2010 remained cool for the first half of the month, with highs in the 30s to lower 40s and lows in the mid 20s to mid 30s. That changed quickly around the 15th when a rapid warm-up occurred in the region with high temperatures into the 50s and lows above freezing for the next 2 weeks. In the last several days of the month, temperatures soared into the 70s and 80s, melting the snowpack completely. With the rapid warm-up and snow melt on top of frozen ground, major flooding became widespread across eastern South Dakota. Luckily, there was little additional precipitation after March 10, and little to none after the snowpack began melting. Five USGS gauging locations in the James, Vermillion and Big Sioux basins set new record high stages in March 2010, with many others in the top five.
The glacial lakes in the northeastern part of South Dakota also filled to record high levels, only to be surpassed in 2011, that spring after several years of declining lake levels. Many homes around Waubay Lake were inundated, as were one around Lake Poinsett and some near Lake Kampeska in Watertown.
Ice Jams on the Vermillion River, courtesty SD Public Broadcasting
This is the flood pool sitting just north of Lake Kampeska. Much of this water is headed into Lake Kampeska until the lake elevation rises enough to force it downstream through Watertown. The outline of winding ice is the normal river channel, Watertown Public Opinion
The Big Sioux River swallows up farm land near Castlewood, Watertown Public Opinion
Flash flooding is a rapid and extreme flow of high water into a normally dry area, or a rapid water level rise in a stream or creek above a predetermined flood level, beginning within six hours of the causative event (i.e.,
intense rainfall, dam failure, ice jam). More information...
River flooding occurs when river levels rise and overflow their banks or the edges of their main channel and inundate areas that are normally dry. More information...
When heavy rain falls over extremely dry land, the water rushes towards low-lying areas, which may include dried up canyon or river beds. This can quickly turn a dry channel into a raging river.More information...
A back-up of water into surrounding areas can occur when a river or stream is blocked by a build-up of ice or other debris. Debris Jam: A back-up of water into surrounding areas can occur when a river or stream is blocked by a build-up of debris. More information...
Flooding due to snowmelt most often occurs in the spring when rapidly warming temperatures quickly melt the snow. The water runs off the already saturated ground into nearby streams and rivers, causing them to rapidly rise and, in some cases, overflow their banks.More information...
Dam Breaks/Levee Failure
A break or failure can occur with little to no warning. Most often they are caused by water overtopping the structure, excessive seepage through the surrounding ground, or a structural failure. More information...
Burn Scars/Debris Flows
Wildfires burn away the vegetation of an area, leaving behind bare ground that tends to repel water. When rain falls, it runs off a burn scar towards a low lying area, sometimes carrying branches, soil and other debris along with it. Without vegetation to hold the soil in place, flooding can produce mud and debris flows. More information...
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