DOWNSTREAM RESPONSE OF GRAVEL-BED STREAMS TO DAMS; AN OVERVIEW.

Experience with sand-bed streams suggests that the downstream response of a river to a dam that cuts off the majority of the sediment supply is degradation, eventually limited by the formation of an armor. Degradation can occur downstream of dams, but depending on circumstances aggradation is also common. Even when degradation occurs, this may or may not be accompanied by a coarsening of the existing pavement, which is a response to mobile-bed conditions, into a static armor. This paper outlines the conditions governing these responses, and several of their environmental implications. A sample prediction of the initial response of the Rogue River, Oregon, to Lost Creek Dam is presented.