Agricultural soil erosion concerns many people in the United States. The depletion of topsoil and formation of gullies reduce the productivity of farmland, and farm family income, foreign trade income, and food production potential are threatened. Much of the soil eroded from farmland is carried by runoff water into the streams and reservoirs where it contributes to undesirable and even harmful environmental problems. These include reduced capacity of streams and reservoirs to supply water as well as increased flood danger, navigation obstacles, and water pollution with its many consequences.