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duration which are highly dependent on Yampa River and Little Snake River flows (Nesler et al. 1988). The sediment load in the Green River downstream of Jensen maintains the active channel in the alluvial reaches. The quantity of sand in this system in the form of active sand bars enables more frequent inundation of the floodplain. Without a consistent supply of sand to the reach of the Green River from Jensen to Ouray, Utah, channel degradation would ensue, bars would become stabilized by vegetation and attach to the bank, active channel width would be reduced, and flooding of bottomland and backwater habitat would be diminished. During the period since 1963, the Green River sediment load at Jensen has decreased by approximately 50% (Andrews 1986). The Little Snake sediment load constitutes approximately 60% of the sediment load at Jensen since the closure of Flaming Gorge Dam. Once the sediment load from the Yampa River enters the Green River, the sediment is quickly transported downstream through Echo Park and Whirlpool Canyon. The next potential sand storage reach is Island Park/Rainbow Park just upstream of Split Mountain. At the upstream extent of this reach are several cobble and gravel riffles, the rest of the reach is a sand-bed channel whose sediment transport capacity determines the sediment load passing through Split Mountain and the Jensen gage. RCI (1991) referred to this reach as a sediment reservoir which may buffer the large sediment loads moving through the reach. Downstream of the Jensen gage, the Green River enters a wide valley of relatively mild slope. This reach has bottomland nursery habitat for endangered larval fish drifting downstream. High sediment loads help keep the channel active with pulses of sand moving through the system in large macroform bars. With loss of the sand being transported through the system, the channel geometry has 29