Big Muddy River Southern Illinois with "loess", fine grained, wind born deposits. At the edge of the floodplain, dunes, called "loess hills", formed. The Pine Hills are loess hills standing several hundred feet above the floodplain. Prior to the construction of Rend Lake, much of the ancient lake bed was swamp: a forested area that was covered by water through most of the winter, and during wet summers. When the Big Muddy flooded, the water covered the flat bottom of the ancient lake bed for miles either direction from the meandering channel. The upper reaches of the Big Muddy are near Dix, Illinois.
Muddy River (Nevada) National Wildlife Refuge Complex. In another effort to help protect and preserve the fragile habitats in the Muddy Springs area, the Southern Nevada Water Authority (SNWA) and various environmental associations have organized an effort to conserve these species. The area was part of the Native American Paiute peoples homeland for centuries, with the Mojave to the south. "Moapa" is a Southern Paiute language word meaning "muddy"; although "Moapa River" was formerly the official name, local usage tended to translate the name, and it was made official in 1960. The Old Spanish Trail originally followed the Virgin River all the way