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6 D I I I I I I I I I I I I I l I I [ ~ B. The basic approach for the channelization between station 659+00 and station 696+00 (the sediment/debris pond) was to: I. Shift the main channel to the west (Reference 4) and recreate the main channel area to approximate the natural channel and allow for fish habitat improvements. 2. Fill the east floodplain area to provide more room for development and to provide greater distance between existing development and the river channel. The left overbank area was also assumed to be filled, however, the encroachment was limted to maintaining the present floodplain limits. Two channel configurations, Channel Type A (station 659+00 to 685+00) and B (station 685+00 to 712+30), were developed to better approximate the natural channel through the reach. Type A section is shown on Calculation sheet 5 and Type B on Calculation sheet 6. Proposed channel sections are plotted on existing HEC-2 model cross sections and presented in Appendix E. C. The fishing pond, (Station 675+00) was sized in a similar manner as the sediment/debris pond. The base flows would pass through the control section at a depth of 3.0 feet above the existing stream bed elevation and the 100-year flood would flow around the right bank area back to the natural channel. In addition, the entire fishing pond would be located off-channel. The pond would fill from seepage through the adjacent banks. To create a deeper pond for fishing, the area upstream of the embankment would be excavated. For HEC-2 modelling purposes, any excavation below the natural channel bed was not considered effective flow area. Therefor, proposed cross sections through the pond area are based on existing channel bed elevations The normal maximum water surface would be created by normal base flows through the channel and would be at approximately elevation 7615. Calculations for the fishing pond are presented in Calculation sheets 8 and 9, and a schematic of the pond is presented on Figure 2. 4.0 STUDY FINDINGS Model Development The results of the model development are presented in the following illustrations: A. Table 2 compares the 100-year WSE and the floodplain width for the Floodplain Information Report ("FPIR") to the baseline model ("BASE FLOOD"). The average WSE difference is 0.1 feet with the maximum difference of 0.2 feet. The average percent difference in the floodplain width is 3.1, with the maximum difference of 26 feet (section 667+ 10).