An estimated half-million miles of these channels have been constructed in the United States and elsewhere. Most, designed over the past 50 years, use engineering criteria developed and tested at Stillwater. Eroding streambeds and banks destroy land and move excess sediment downstream. Stream-stabilizing structures are often required to control bed erosion and let trees, grasses, and other vegetation anchor the banks. These measures, properly applied, allow people to productively share the floodplain with the rest of the ecosystem.
Floods can cause extreme destruction to cropland and river environments.
In many areas, especially the central United States, seasonal thunderstorms can dump very large volumes of water on small watersheds. The purpose of these reservoirs is to temporarily contain floodwater and release it at a rate the downstream channel can hold. Besides reducing flooding and sedimentation, the reservoirs provide recreational fisheries, wildlife habitat, and wetlands above the containment. Each upland flood-control reservoir consists of multiple components. Each component is a hydraulic structure that must operate properly if floodwaters are to be controlled.