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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />10 <br /> <br />I <br /> <br />The channel input includes lengr.h, slope, cross section, and <br /> <br /> <br />roughness coefficients. Direct flow elements do not route <br /> <br /> <br />upstream elements but instead add upstream hydrographs to give a <br /> <br />direct translation of incoming flows. <br /> <br /> <br />Existing channel/pipe elements are modeled as a low-flow <br /> <br /> <br />channel/pipe with an overflow section. Slopes and lengths were <br /> <br /> <br />measured from USGS maps. Typical cross sections for the low-flow <br /> <br /> <br />channel/pipe and overbanks were developed based on USGS maps, <br /> <br /> <br />City storm sewer maps, and fie 1 d inspection. Roughness <br /> <br />coefficients were estimated based on values given in the UDSWM2 <br /> <br /> <br />users manual. <br /> <br /> <br />The existing 6th Avenue detention basin was modeled using <br /> <br /> <br />storage versus outflow data obtained from the City. No future <br /> <br /> <br />channel or pipe improvements were considered in this study. <br /> <br /> <br />Figure 2.1 shows the flow network between subbasins. <br /> <br />I <br /> <br />4. Flood Flows and Design Hydroqraphs <br />Runoff hydrographs for the 100-year future condition at <br />selected locar,ions for the Granby and Sable Drainageways are <br />given ln Figures 3. Table 4 glves peak flows for each design <br />point for the future basin conditions for 10-, 50-, 100-, and <br />500-year frguencies. Figure 4 and 5 shows the discharge- <br />probability profile for Granby and sable Drainageways. <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />