Big Sioux River

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Big Sioux River
The falls of the Big Sioux River at Sioux Falls, South Dakota
The course and watershed of the Big Sioux River.
EtymologyLakota people (Sioux Natives)
Native nameTehankasandata (Lakota)
CountryUnited States
StateSouth Dakota, Iowa
Physical characteristics
SourceCoteau des Prairies
 • locationRoberts County, South Dakota
MouthMissouri River
 • location
Sioux City, Iowa
 • coordinates
42°29′27″N 96°26′44″W / 42.490805°N 96.445490°W / 42.490805; -96.445490
Length419 mi (674 km)
Basin size9,006 sq mi (23,330 km2) [1]
Basin features
Progressiongenerally southwardly
 • leftSkunk Creek
 • rightRock River, Broken Kettle Creek

The Big Sioux River is a tributary of the Missouri River in eastern South Dakota and northwestern Iowa in the United States.[2] It flows generally southwardly for 419 mi (674 km),[3] and its watershed is 9,006 sq mi (23,330 km2).[1] The United States Board on Geographic Names settled on "Big Sioux River" as the stream's name in 1931.[4] The river was named after the Lakota people (Sioux Natives)[5] which was known by them as Tehankasandata, or Thick Wooded River.[6]

The Big Sioux River rises in Roberts County, South Dakota[4] on a low plateau known as the Coteau des Prairies and flows generally southwardly through Grant, Codington, Hamlin, Brookings, Moody, and Minnehaha counties, past the communities of Watertown, Castlewood, Bruce, Flandreau, Egan, Trent, Dell Rapids, and Baltic to Sioux Falls, where it passes over a waterfall in Falls Park, which gives that city its name. Downstream of Sioux Falls and the community of Brandon, the Big Sioux defines the boundary between South Dakota and Iowa, flowing along the eastern borders of Lincoln and Union counties in South Dakota, and the western borders of Lyon, Sioux and Plymouth counties in Iowa, past the communities of Canton, Fairview, Hudson, Hawarden, North Sioux City, and Dakota Dunes in South Dakota and Beloit, Hawarden and Akron in Iowa. It joins the Missouri River from the north at Sioux City, Iowa.[7][8]

This excerpt from the Lewis and Clark map of 1814 shows the rivers of western Iowa and eastern South Dakota. The Big Sioux River ("Sioux") is seen near the center of the map.

The Big Sioux River, at the USGS station in Sioux City, Iowa, has a mean annual discharge of approximately 3,793 cubic feet per second.[9]


The Big Sioux River collects the Rock River from the northeast in Sioux County, Iowa.[7] A minor headwaters tributary of the Big Sioux in Grant County, South Dakota, is known as the Indian River.[8][10] Broken Kettle Creek has its confluence with the Big Sioux in Plymouth County, Iowa.


The Big Sioux is South Dakota's most populated river basin. Agriculture is the primary use of land along most of the river's course. To comply with the Clean Water Act, the state monitors water quality of its rivers. Most of the Big Sioux north of Sioux Falls was scored well in 2012. Portions near Lake Kampeska and between Willow and Stray Horse Creeks (Codington and Hamlin counties) exceeded federally allowable levels of E. coli and fecal coliform bacteria. However, the Big Sioux south of Sioux Falls is much more polluted with E. coli, fecal coliform, and suspended solids. Several portions heavily restrict fishing or human contact, and swimming is banned.[11]

Flood control[edit]

Between 1955 and 1961, an extensive flood control system was constructed by the U.S. Army Corps of Engineers along the Big Sioux and some of its tributaries in Sioux Falls to protect the city from a 100-year flood event.[12] Features of the system include 29 miles (47 km) of levees, a floodwall in downtown, and a 15,000 feet (4,600 m) diversion channel with a dam at one end and a 118-foot (36 m) spillway at the other.[12] The diversion channel connects two ends of the Big Sioux's natural loop around central Sioux Falls in an effort to channel floodwater away from the city.[12] The levees then act to contain any floodwater either remaining in the natural channel or originating from Skunk Creek (whose mouth is downriver of the diversion dam).[12][13] Additionally, a greenway covers much of the river's floodplain in southern and eastern Sioux Falls, further mitigating any property damage from high water.


The Big Sioux River experienced record-breaking flooding during the 2019 Midwestern U.S. floods.[14]

The Big Sioux River Flood Information System was used to model flooding during the March 2019 bomb cyclone event.[15]

The river overflowed its banks between September 12–15, 2019, flooding three blocks of Dell Rapids, South Dakota, and damaging up to a dozen homes.[16] Interstate 90 was shut down between Mitchell and Sioux Falls.[14]

See also[edit]


  1. ^ a b Frank D. Amundson and Neil C. Koch (1985). "Drainage areas in the Big Sioux River basin in eastern South Dakota". USGS. p. plate 1. doi:10.3133/ofr85348. Retrieved 2021-09-08.
  2. ^ "Columbia Gazetteer of North America entry". Archived from the original on 2006-02-25. Retrieved 2006-06-06.
  3. ^ U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. The National Map Archived 2012-03-29 at the Wayback Machine, accessed March 30, 2011
  4. ^ a b U.S. Geological Survey Geographic Names Information System: Big Sioux River
  5. ^ Federal Writers' Project (1940). South Dakota place-names, v.3. University of South Dakota. p. 4.
  6. ^ State Department of History (1924). South Dakota Historical Collections Volume XII. Pierre, South Dakota: Hipple Printing Company. p. 304. Retrieved 1 July 2020.
  7. ^ a b DeLorme (1998). Iowa Atlas & Gazetteer. Yarmouth, Maine: DeLorme. ISBN 0-89933-214-5
  8. ^ a b DeLorme (2001). South Dakota Atlas & Gazetteer. Yarmouth, Maine: DeLorme. ISBN 0-89933-330-3
  9. ^ USGS station
  10. ^ U.S. Geological Survey Geographic Names Information System: Indian River
  11. ^ Andrews, John (March 2013). "Can We Save the Big Sioux?". South Dakota Magazine. Archived from the original on 2018-09-04. Retrieved 2020-02-04.
  12. ^ a b c d "Flood Control". City of Sioux Falls. Archived from the original on 2011-01-08. Retrieved 2010-04-19.
  13. ^ Jorgensen, Don. Sioux Falls diverts water to ease flooding [1] Archived 2011-09-27 at the Wayback Machine KELO-TV. March 15, 2010. (accessed April 19, 2010).
  14. ^ a b Nelson, Katie; Sneve, Joe; Ferguson, Danielle; Huber, Makenzie (September 12, 2019). "Big Sioux River surpasses March's record-breaking flood levels, I-90 closed from Plankinton to Sioux Falls". Argus Leader. Retrieved 2019-09-21.
  15. ^ "Big Sioux River Flood Information System Sees Heavy Use During Spring 2019". SDSU Extension. September 12, 2019. Archived from the original on September 21, 2019. Retrieved 2019-09-21.
  16. ^ Sneve, Joe (September 20, 2019). "Homes in Dell Rapids could be slated for demolition after floods". Argus Leader. Retrieved 2019-09-21.

Coordinates: 42°29′27″N 96°26′47″W / 42.49083°N 96.44639°W / 42.49083; -96.44639

Further reading[edit]