Laserfiche WebLink
<br />. <br /> <br />TRIBUTARY INFLOW <br /> <br />The tributary inflow portion of the models was based on <br /> <br />both synthetic unit hydrographs and EPA's Surface Water Management <br /> <br /> <br />Model (SWMM). Synthetic unit hydro graphs were used for all of the <br /> <br />high plains tributaries downstream from Sand Creek. SWMM was used <br /> <br />for all tributaries between Chatfield Dam and Clear Creek plus the <br /> <br /> <br />high plains and foothills portion of the left-bank tributaries which <br /> <br /> <br />originate in the mountains. Pertinent information concerning the <br /> <br /> <br />tributary inflow development ia presented below. <br /> <br />. <br /> <br />Synthetic Unit Hydrographs. Synthetic unit graph development <br /> <br /> <br />was based on using Snyders unit graph equations derived from the <br /> <br />June 1965 inflow hydrograph to Cherry Creek reservoir. This <br /> <br /> <br />hydrograph is shown on plate 8 along with the derivation of a <br /> <br />I-hour Clarka unit graph from it. Snyders constants of C - 0.51 <br />t <br /> <br />and 640 C - 537 were computed from this Clarka unit graph. These <br />p <br /> <br />constants were also applied to smaller basins by assuming a 15- <br /> <br /> <br />minute unit graph duration. Synthetic unit graphs developed for <br /> <br />areas having or facing urban development were adjusted by reducing <br /> <br />peaking times 50 percent and increasing peak discharges 100 percent. <br /> <br />This adjustment was made in order to reflect the more severe runoff <br /> <br />characteristics that are associated with urbanized areas. <br /> <br />SWMM. The EPA Surface Water Management Model (SWMM) is based <br />on the collection and routing of rainfall runoff hydrographs from <br />small sub-area components of a tributary system. An overland flow <br />equation is used to compute runoff hydrographs from the sub-area <br />system and these hydro graphs are collected and routed through the <br />system to the point or points of interest. A detailed description <br />of the model is presented in an EPA publication entitled "Storm Water <br />Management Model, Volume I - Final Report, July 1971." Several <br /> <br />. <br /> <br />55 <br />