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Preliminary Design Report Addendum No.2 <br />3.7 HYDRAULICS <br />3.7.1 Channel Hydraulics <br />This section summarizes the results of a hydraulic analysis to evaluate the impact of the in- channel flow <br />diversion structure on the upstream water surface profile. Detailed channel hydraulic analyses results can <br />be found in Appendix A- 2. A hydraulic model was created for (1) the existing condition and (2) the <br />proposed condition, which includes the proposed 8 foot high in- channel flow diversion structure <br />(representing either the radial steel gate or air- inflated rubber dam). <br />The section of the Delhi Channel between Bristol Street and hvine Avenue is a concrete -lined rectangular <br />channel, with a width of 55 feet and a height of 16 feet. In the center of the channel is a 1 foot high <br />trapezoidal low -flow channel, with a base width of 6 feet and a top width of 14 feet. The dimensions of <br />the channel are based on the original model provided by the City of Santa Ana, and updated based on the <br />as -built drawings. <br />Figure A -2 -1 shows the model layout and cross - section stationing. The numbering for the stationing is <br />based on the as -built drawings. <br />Channel Discharge <br />Table 3- 3 shows the design discharge for the Delhi Channel. These values were provided in the model <br />from the City. Station 9400 represents the upstream station of the model at Bristol Street. At station 6541 <br />there is additional inflow from the Airport Channel. <br />Table 3- 4 Design Discharge for the Santa Ana Delhi Channel (eft) <br />Station <br />As -built flow <br />2 -year <br />5 -year <br />10 -year <br />25 -year <br />50 -year <br />100 -year <br />9400 <br />8,550 <br />3,033 <br />4,790 <br />5,990 <br />7,420 <br />8,200 <br />9,200 <br />6541 <br />8,770 <br />3,183 <br />1 4,940 <br />6,140 <br />7,570 <br />8,350 <br />9,350 <br />A relationship between discharge rate and return period was developed, in order to estimate discharge for <br />smaller return period increments (see Figure 3- 3 and Table 3- 4). <br />URS 11 <br />25F -143 <br />