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11/14/01 draft report, Schmidt and Box The velocity of stream flow in each reach was estimated from statistical relationships between discharge and mean section velocity calculated from unpublished discharge measurements at the USGS gages (Table 3). These relationships are of the form v=aQb (1) where v is mean section velocity, Q is discharge, and a and b are coefficients. This relationship is one part of conventional hydraulic geometry relationships computed at gaging stations (Leopold and Maddock 1953). We assumed that the relationship for Deerlodge Park applied to the Yampa River reach, the Jensen relationship applied to the Green River upstream from Ouray, and a relationship calculated for the abandoned gage near Ouray (station number 09307000) applied further downstream. Although more sophisticated methods could be used to estimate velocity in each reach, we do not believe such methods are appropriate because of other large uncertainties in model parameters. Model comDonents: channel. eeomorpholoey The study area includes a 40 km-segment through the eastern Uinta Mountains and a 185- km segment across the Uinta Basin. The Uinta Mountains segment includes 2 reaches of narrow canyons with abundant debris fans and an intervening alluvial reach (Grams and Schmidt 1999). The Uinta Basin segment is composed of alluvial sand-bedded reaches. Channel geomorphology affects the proportion of the main flow lined by shear zones, and this factor, along with the exchange rate of water between main flow and backwaters, determine the proportion of the drifting population transported into backwaters. We assumed that the greater the proportion of the total length of main current flow bordered by shear zones, the greater the opportunity for movement of nursery fish into backwaters. Shoreline complexity is a function of discharge and the shape of the channel. We classified each reach as either meandering with a narrow alluvial valley (called fixed meanders by Ikeda 1989), meandering with a wider alluvial valley (called restricted meanders by Ikeda 1989), or canyons with abundant debris fans where fan-eddy complexes are numerous, as defined by Schmidt and Rubin (1995) (Fig. 2). We measured shoreline complexity in 35 percent of the study area, using aerial pootograp~s taken in late summer 1963 at base flows between 10 and 28 m3s-1, These photographs depict the Green River at the time of completion of Raming Gorge Dam. These photos are of about 1:2000 scale, except in the Uinta Mountains where the scale is somewhat smaller. The length , , of the shoreline of each bank was added and divided by the length of the channel centerline of each reach (Fig. 6). The minimum possible value of shoreline complexity is therefore 2. We estimated the complexity of unmapped areas by assuming that complexitywas the same as the average of mapped reaches with similar geomorphi<; characteristics, based on measurements of shoreline throughout the Green River (Table 4). 10 ....