Monitoring Of Coarse Sediment Inputs To The Colorado River In Grand Canyon

Coarse sediment (particles with an intermediate diameter greater than 64 mm) affects the primary components of the Colorado River ecosystem. The deposition of coarse sediment at tributary junctures builds large debris fans that constrict the river and form rapids. Debris fans, and the debris bars that develop below rapids, provide stable substrate for aquatic organisms, notably the alga Cladophora glomerata. The pool above and recirculating eddy below the debris fan effectively trap fine sediment for storage on the bed or in sand bars. Debris fans and debris bars form the fan-eddy complex that attracts humpback chub (Gila cypha), an endangered species. Monitoring the input of coarse sediment to the Colorado River ecosystem and its long-term redistribution by the river is critical to the understanding and management of these valued resources. This fact sheet presents an overview of methods for monitoring coarse sediment input and redistribution in Grand Canyon. These methods are discussed more thoroughly in Melis (1997), Melis and others (1994, 1997), and Webb and others (1999a, 1999b, 2000).