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Project #4 conditions indicated rates of deposition of 3.2, 9.7 and 31. 5 ft/day for the 50-year, 100-year and standard project flood respectively: roughly twice the values for project #3. Although actual depths of scour or deposition for single flood events cannot be predicted with certainty, the above analysis indicates that the project #4 levee configuration has greater potential for deposition. A reach of scour (near river mile 1198.9) was also analyzed. The hand computations showed the following scour rates for existing conditions: 0.1, Q.l, and 0.3 ft/day corresponding to 50-year, 100-year and standard project flood. Project #3 conditions indicated scour rates of 1.9, 3.4 and 14.1 ft/day. Project #4 conditions indicated rates of scour of 4.9, 9 ~l and 31.3 ft/day. From this analysis it can be seen that the project #4 levee configuration has greater potential for scour than the project #3 levees. The analysis also showed that significantly more local scour and deposition may occur under project conditions as compared to existing conditions. The rates of scour and deposition calculated above are based on the conditions at peak flow, which exist for only a few hours. As the bed adjusts and hydraulic conditions change, scour and deposition will occur at different rates. To estimate a depth of deposit/scour, the rate is multiplied by the duration of the peak flow. This approach will give an upper bound for the actual expected depths of deposit/scour. 5.6 Intet'Pretation of simulation Results and Conclusions The channel response due to a single flood event is affected by many factors. Some of these factors (such as sediment inflow from local drainage and changes in watershed conditions) were not incorporated in the above analysis. For this reason, the simulated results should be interpreted as showing general trends of aggradation and degradation in the main river channel. The actual magnitudes of bed changes in the results should be considered as approximate values for the general scour or depositional trends the river may have for these kinds of single events. Appendix F presents plotted results of channel deposition vs. time at each cross section for existing, project #3 and project #4 conditions. Examination of these results shows that at many locations within the project reach, both project #3 and project #4 conditions caused channel scouring to occur where little or no scour had occurred under present natural conditions. In addition to increased scouring within the project reach, greater depths of deposit occur just downstream from the project for both project #3 and #4 conditions, compared to existing conditions. Conclusions reached from analyzing the simulation results are highlighted below: . The river bed appeared to be fairly stable for existing conditions. , Both project conditions (project #3 and project #4) indicated significant scour in the project reach between cross sections ll96.9 and 1198.9. The levee configuration for project #4 resulted in more scour upstream from the project. The maximum water depth for the SPF was about three feet greater for project #4 conditions than for project #3 conditions. This is because the levees are closer together for proj ect #4. 61