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within this range have occurro only in 1969 and 1985 (the 1993145m3/s peak exceeded 140 m3/s for only 2 hours and is not included in this general discharge range; annual peaks in 1970,1983, and 1984 attained and eventually exceeded this range). Streamflows in this range and higher now result from a combination of Crystal Reservoir releases through the outflow structures and over the spillway. These streamflows are infrequent downstream from the reservoirs because the BOR tends to avoid spillway use except in emergency situations. Snowmelt conditions that could create very high streamflows in the Gunnison Gorge also produce high runoff in the North Fork (Figure 1). An effort is made by BOR to prevent flooding below the confluence with the North Fork by keeping Crystal Reservoir releases relatively low. The water-surface elevation associated with these and greater discharges was estimated with a step-backwater simulation (Shearman,1991). Several terraces, much of the riparian zone, many river-side trails, and some campsites are inundated when flows are in this range. Fishing activities diminish. Bed shear stresses are adequate to entrain particle sizes larger than d50, suggesting bed-material mobility and the possibility of reworking in many riffle/ pool reaches. This streamflow range could include the lower limit of discharge necessary for channel maintenance in these reaches, although additional bed mobility analyses are necessary to establish this. BLM activities are directed to addressing inquiries about accessibility and whitewater navigation and toward safety and rescue preparedness. Whitewater conditions become very technical in this flow range and it is common for the county sheriff's office to close the Gunnison River to recreational use. Flood peaks greater than 250 m3/s have been rare since upstream reservoir construction and occurred only in 1970,1983, and 1984. Streamflow filling the river channel to the average elevation of the lowest Utah juniper trees (310 m3/s), approximately 1.5 to 2 rn above the current bankfull stage, was a common event before 1966 (3.2-year recurrence interval). Since then, this discharge has a recurrence interval of approximately 40 years. The post-regulation absence of flood magnitudes in this range probably has had the greatest effect on fluvial geomorphology, bed armoring, bar and terrace stabilization, and riparian vegetation composition and density. Geomorphic and vegetation changes resulting from the 1983 and 1984 floods were not well documented, but field observation revealed a few recent sandy deposits one or two meters above the current bankfull stage. Box elder trees along the mainstem near Big Cove and Long Gulch showed undercutting, scarring, and regrowth that dates to 1983 or 1984. Bed shear stresses are sufficient to entrain particle sizes larger than d50, indicating bed-material mobility in most riffle/pool reaches. The high stage associated with this discharge range inundates a large area of many tributary debris fans and creates the possibility for entrainment -of sediment farther up the fan surface and widening of debris-constricted river reaches. Flow depths and velocities may be sufficient to scour_some bank and terrace deposits; however, the effect of these discharges on riparian vegetation is unknown and requires additional study. Large standing waves, high velocities, and few eddies for landings make whitewater conditions in the narrower Gunnison Gorge reaches hazardous. DISCUSSION AND SUMMARY The fluvial and riparian environments in the Gunnison Gorge are undergoing long- term adjustments to mainstem streamflow regulation and flood-peak attenuation that began