The Big Sioux River is a tributary of the Missouri River in eastern South Dakota and northwestern Iowa in the United States . It flows generally southwardly for 419 mi (674 km), and its watershed is 9,006 sq mi (23,330 km). The United States Board on Geographic Names settled on "Big Sioux River" as the stream's name in 1931. The river was named after the Lakota people which was known by them as Tehankasandata, or Thick Wooded River.
15-638: The Big Sioux River rises in Roberts County, South Dakota 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
30-462: A 118-foot (36 m) spillway at the other. 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. 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). Additionally, a greenway covers much of
45-474: A dozen homes. Interstate 90 was shut down between Mitchell and Sioux Falls. The river once again flooded in 2024, resulting in at least one death and multiple destroyed homes, roads, and businesses. Most notably in the McCook Lake area. 42°29′27″N 96°26′47″W / 42.49083°N 96.44639°W / 42.49083; -96.44639 Roberts County, South Dakota Roberts County
60-407: Is a county in the U.S. state of South Dakota . As of the 2020 census , the population was 10,280. Its county seat is Sisseton . The county was named either for S. G. Roberts of Fargo, North Dakota , or for Solomon Robar, an early local French fur trader . It was created on March 8, 1883, and fully organized by August 6 of that year. Its boundary was altered once, in 1885. Roberts County
75-657: Is at South Dakota's northeastern corner. Its eastern boundary abuts Minnesota (across the Bois de Sioux River ), and its northern boundary abuts North Dakota . The Cottonwood Slough flows southward, draining the upper portion of the county into the River. The terrain consists of rolling hills, devoted to agriculture. The terrain slopes to the east; its highest point is on its upper western boundary line, at 2,047 ft (624 m) ASL. Roberts County has an area of 1,136 square miles (2,940 km ), of which 1,101 square miles (2,850 km )
90-463: Is banned. 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. 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
105-481: Is land and 35 square miles (91 km ) (3.1%) is water. The Traverse Gap is in eastern Roberts County along the Minnesota border. The Lake Traverse Indian Reservation covers most of the county. As of the 2020 census , there were 10,280 people, 3,844 households, and 2,568 families residing in the county. The population density was 9.3 inhabitants per square mile (3.6/km ). There were 4,788 housing units. As of
120-502: The 2010 census , there were 10,149 people, 3,823 households, and 2,655 families residing in the county. The population density was 9.2 inhabitants per square mile (3.6/km ). There were 4,905 housing units at an average density of 4.5 units per square mile (1.7 units/km ). The racial makeup of the county was 61.7% white, 34.5% American Indian, 0.2% Asian, 0.1% black or African American, 0.4% from other races, and 3.0% from two or more races. Those of Hispanic or Latino origin made up 1.2% of
135-517: The Big Sioux in Plymouth County, Iowa. Other creek tributaries include Peg Munky Run , North Deer, Sixmile , Skunk , Split Rock , Beaver , Brule , and Pipestone . 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
150-444: 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
165-817: The Missouri River from the north at Sioux City, Iowa . 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. The Big Sioux River collects the Rock River from the northeast in Sioux County, Iowa. A minor headwaters tributary of the Big Sioux in Grant County, South Dakota, is known as the Indian River . Broken Kettle Creek has its confluence with
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#1732844664900180-535: 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
195-420: The population. In terms of ancestry, 31.3% were German , 19.2% were Norwegian , 6.3% were Irish , and 3.8% were American . Of the 3,823 households, 34.4% had children under the age of 18 living with them, 49.1% were married couples living together, 13.4% had a female householder with no husband present, 30.6% were non-families, and 27.3% of all households were made up of individuals. The average household size
210-518: 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 . The Big Sioux River Flood Information System was used to model flooding during the March 2019 bomb cyclone event. The river overflowed its banks between September 12–15, 2019, flooding three blocks of Dell Rapids, South Dakota , and damaging up to
225-636: Was 2.58 and the average family size was 3.11. The median age was 39.5 years. The median income for a household in the county was $ 37,708 and the median income for a family was $ 46,146. Males had a median income of $ 34,080 versus $ 28,423 for females. The per capita income for the county was $ 19,825. About 14.3% of families and 20.0% of the population were below the poverty line , including 33.9% of those under age 18 and 11.0% of those age 65 or over. School districts include: 45°37′N 96°57′W / 45.62°N 96.95°W / 45.62; -96.95 Skunk Creek (South Dakota) Skunk Creek
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