Laserfiche WebLink
10. <br />G 7, <br />m <br />M <br />u <br />n 6, <br />Preliminary Design Report Addendum No.2 <br />uuv <br />000 <br />—r <br />1.1-year <br />y= 1556.51n(x) +2199.6 <br />000 <br />... <br />R2 = 0.9927 <br />1.5- ear <br />9400 <br />2,200 <br />2,348 <br />000 <br />-- <br />000 <br />--- <br />6541 <br />2,350 <br />000 <br />— <br />2,758 <br />2,873 <br />000 <br />n00 <br />. <br />20 40 60 g0 100 120 <br />Return Period (years) <br />Figure 3- 3 Discharge Rate versus Return Period Relationship. <br />Table 3- 5 Design discharge for incremental return periods for the Santa Ana Delhi Channel (cfs) <br />Station <br />1 -year <br />1.1-year <br />1.2-year <br />1.3- ear <br />1.4-year <br />1.5- ear <br />9400 <br />2,200 <br />2,348 <br />2,483 <br />2,608 <br />2,723 <br />2,831 <br />6541 <br />2,350 <br />2,498 <br />2,633 <br />2,758 <br />2,873 <br />2,981 <br />Channel Hydraulic Analysis <br />A hydraulic model was developed using the USACE Hydrologic Engineering Center River Analysis <br />System (HEC -RAS) version 4.1 to determine the hydraulic impacts of the proposed in- channel flow <br />diversion structure. HEC -RAS was used to perform a one - dimensional, steady -state hydraulic analysis of <br />the Santa Ana Delhi Channel. The model was computed using the mixed flow regime to produce the full <br />range of water surface results. Normal depth was used as the boundary conditions. The upstream and <br />downstream normal depth slopes are 0.000738 and 0.000772, respectively; the slope changes <br />downstream of the confluence with the Airport Channel. A Manning's roughness coefficient of 0.013 was <br />used for the concrete -lined channel. <br />The Delhi Channel flows underneath Santa Ana Avenue, approximately 1,340 feet downstream of the <br />Bristol Street crossing. The channel flows through three parallel rectangular culverts, which were <br />included in the HEC-RAS model. <br />For the proposed conditions, the in- channel flow diversion structure was included in the model as an 8 <br />foot high and 4 foot wide broad - crested weir, with a weir coefficient of 2.6. It was located approximately <br />3,500 feet downstream of the Bristol Avenue crossing. <br />EW 12 <br />25F -144 <br />