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. 2 . .. channel may become narrower (Andrews, 1986). This can result in the abandonment of side channels except at the highest flows. Also, vegetation can become established in these areas due to the lack of disturbance (Graf, 1978). The river may develop new side channels adjusted to its new flow regime, but there is a change in the morphology of the river. Changes in peak flows on the Colorado River from dams and diversions are likely to result in habitat changes for the endangered fish, but prior to this study it was not known whether or not these changes were significant. Changes in the physical habitats of these fish may also have occurred due to bank stabilizing activities. Bank stabilization limits the river's ability to migrate and commonly causes a decrease in channel complexity (Li et al., 1987). Under natural conditions, the river would be free to change its course, form new channels and slowly abandon old ones. This would result in a dynamic network of islands and side channels which could provide a variety of habitats for the fish. Since the river is partially confined, it is possible that the overall complexity and habitat for the fish has decreased. . . . . .. . . . This report describes work in progress aimed at defining historic changes in river morphology, effects of the 1993 snowmelt flows on specific side channel/backwater habitats, and a preliminary evaluation of the threshold for transport of coarse bed material. A historic analysis of changes in channel morphology was completed by using historic and recent aerial photographs. These photographs were digitized and measurements of channel change were calculated using a Geographic Information System (GIS). In addition to this analysis, three backwater sites were monitored before, during, and after the 1993 spring runoff to determine the effects of these flows on the morphology of the sites. . . .