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I I I I I I I I I I I I I I I I I I I 14 In general, there was a decrease in water area and side channel/backwater area for both areas, but an increase in island area in the Ruby-Horsethief Canyon reach. Since the Grand Valley reach is alluvial, it would be expected that channel changes in this reach would be more significant than in the Ruby-Horsethief Canyon where general channel morphology is strongly controlled by bedrock. The increase in island area in Ruby-Horsethief Canyon is probably due to the accretion of sediment to pre- existing islands. In the Grand Valley it is likely that this same process has occurred, but the islands have accreted to the floodplain. Although there was an overall decrease in side channel/backwater area through time, some reaches show an increase in area. Some of these reaches include areas which were changed in 1983 and 1984 when high flows breached dikes and flooded abandoned gravel pits. The current affect of these flows on the 1993 photographs is unclear, but it is likely that loss of side channel/backwater area would be greater if these flows had not occurred. The 1954-1968 analysis is perhaps a better measure of general channel change since there were no extreme flow events during the period. During this period, the mean annual flow was exceeded at the Cameo gauge only 5 times, which suggests that when peak flows are below average for several years in succession, the channel becomes narrower and there is a systematic loss of side channel/backwater habitat (Pitlick and Van Steeter, 1994). COMPARISON OF 1993 AND 1994 FLOWS The flows of 1993 and 1994 provide a good example of the year to year variability in runoff of the Colorado River. The two gauges used for this summary are: 1) the Colorado River below the Grand Valley diversion near Palisade, at the most upstream end of the study area; and 2) the Colorado