“Scour holes” or “blew holes “provide unique habitats on the Missouri River floodplain. They form during flood events as floodwaters encounter an obstacle, usually a levee, a road or other man-made structure. If a portion of the structure gives way, the flood water pours through a constricted opening and blows out or scours the substrate away, forming a plunge pool. When the flood water recedes, a semi -permanent water body (1-40 acres) is left behind. Scour holes provide habitat for fish, amphibians, turtles, birds and mammals.