"Rivers are the great shapers of . Rivers transport supplied for hillslope and , in some cases controlling the gradient of the hillslopes (Burbank et al., 1996). As they incise or aggrade to maintain a consistent relationship with their base level, rivers create s that in turn influence local climate; provide travel corridors for animals and humans; and support aquatic and riparian ecosystems that contain some of the Earth's highest levels of biodiversity. ... Although the study of rivers is well-established, the great majority of investigators have worked on the lowland rivers where most people live. Mountain rivers began to receive increasing attention as a subset of rivers only during the last two decades of the twentieth century."