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At the head of the riffle (XS 12.1), which is indicative of conditions associated with formation of the tertiary bar along the left bank at this location, the material is in motion at all discharges greater than about 1,000 cfs (Figure 3.10). Backwater from the bend clearly creates conditions that form the primary bar and reduce the shear stress at high flow at the base of the riffle. Because of the height of the riffle, however, the backwater is insufficient to affect the hydraulics at the head of the bar (Figure 3.6). Based on the results of the above analysis, it can be concluded that: 1. Discharges greater than about 25,000 cfs are required to transport gravel and cobble sized material through the upstream pool (XS 13 and XS 14) and into the reach containing the primary bar (Figures 3.9, 3.10). 2. Based on the cross sectionally averaged dimensionless shear stress, any coarse grained material carried through the upstream pool will deposit on the bar under the full range of flows modeled (up to 32,300 cfs) (Figure 3.9). 3. Based on the maximum shear stresses in the channel, material delivered across the riffle at the head of the primary bar can be transported through the reach along the bar at discharges greater than about 5,000 cfs, but appear to be stopped in the bend at discharges less than about 22,000 cfs (Figure 3.10). 4. The bank-attached bar between XS 5 and XS 6 is related to local flow separation which causes deposition of coarse material transported through XS 6 at discharges greater than about 5,000 cfs. At lower flows, this bar is probably inactive. 5. At the base of the riffle near the head of the bar (XS 10), coarse materials can be mobDized at flows greater than about 630 cfs. However, due to the backwater created by the downstream bend, the dimensionless critical shear stress stays very close to critical conditions over the full range of flows modeled, actually decreasing slightly above about 2,000 cfs (Figure 3.13). 6. The analyses indicate that, if near critical conditions (incipient motion) are necessary for the creation of suitable spawning habitat, these conditions are met over a broad range of flows above about 630 cfs near the base of the riffle. In contrast, the bank-attached bar between XS 5 and XS 6 and the bar at the head of the riffle near XS 12.1 are near critical conditions over a very narrow range of flows (near 5,000 cfs and 1000 cfs, respectively). At both of these locations, higher flows increase the shear stress significantly above the incipient motion condition, which results in high rates of sediment transport that would make the locations unsuitable for spawning. 3.2. Cleopatras Couch (RM 16.5) In order to address the question of the required frequency of bar building events at the known squawfish spawning sites it is necessary to develop a data base consisting of topographic changes and sedimentologic changes through time. Bar building occurs as a result of both vertical accretion of the bar as well in-filling of the eroded chute channels. The maximum bar elevation is controlled by the local hydraulic conditions and it is reasonable to assume that the highest portions of the bar at present 3.27 Resource Consultants & Engineers. Inc.