Boulder, Colo., USA: Steps and pools are among the most stable and functionally important features in the mountain river landscape. Their stability is important for dissipating stream energy, withstanding ordinary floods and resisting erosion, and regulating the flow and sediment dynamics feeding into lowland areas. Clasts comprising steps also offer habitats for sensitive and specialized organisms. The integrity of step-pool systems is therefore important in maintaining healthy ecosystems, as well as in keeping water and sediment hazards in check for human communities downstream.