Soil Conservation

Terracing is the construction of earthen embankments that look like long stair-steps running across the slope of rolling land. A terrace consists of a channel with a ridge at its outer edge. The channel intercepts and diverts downhill runoff. Terraces help to prevent soil erosion by increasing the length of the slope, thereby reducing the speed of overland water flow to allow for greater infiltration. The channels redirect excess runoff to a controlled outlet. Terraces help prevent the formation of gullies and retain runoff water to allow sediment to settle.

Extensive systems of irrigated terraces have long been used in numerous countries, including Yemen, the central Andes, the southwestern United States, Ethiopia, Zimbabwe, and northern Cameroon. Soil terraces occur widely in Southeast and South Asia, New Guinea, East Africa, and Nigeria.

The construction of reservoirs, usually ponds, is another barrier method for intercepting the surface runoff of water and sediment. Reservoirs increase soil moisture, thereby improving the resistance of soil to erosion. Water stored in reservoirs is also available for use in irrigation.

Contouring is plowing, planting, cultivating, or harvesting across the slope of the land, instead of up and down the hillside. Contouring reduces the velocity of surface runoff by impounding water in small depressions.