Big Sioux River

The Big Sioux River collects the Rock River from the northeast in Sioux County, Iowa. Broken Kettle Creek has its confluence with the Big Sioux in Plymouth County, Iowa. Other creek tributaries include Peg Munky Run, North Deer, Sixmile, Skunk, Split Rock, Beaver, Brule, and Pipestone. ==Pollution==

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. ==Flood control==

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 of levees, a floodwall in downtown, and a diversion channel with a dam at one end and a spillway at the other. Additionally, a greenway covers much of the river's floodplain in southern and eastern Sioux Falls, further mitigating any property damage from high water. Flooding The Big Sioux River experienced record-breaking flooding during the 2019 Midwestern U.S. floods. 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. 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. ==See also==