The December 1982 floods in southeast Missouri were the largest on record for many rivers. Overbank sand and gravel were deposited on many flood-plain sites, and scouring of flood-plain surfaces was common. The flood plain of the Gasconade River near Mt. Sterling, Missouri, underwent significantly greater erosional and depositional alteration than any other locality in the region. Here, sand and gravel derived from the Gasconade channel were deposited on the flood-plain surface as a lobate ridge 30–100 m wide, 1–2 m high, and about 1 km long. A large scour hole occupying an area of 5 ha was vertically eroded into the flood plain to a maximum depth of more than 7 m. These processes destroyed prime farmland and threatened bridge safety. Normal flood effects were exaggerated at Mt. Sterling by changes made on the flood-plain surface prior to 1982 during construction of a new bridge.