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<br />II <br /> <br />II] <br /> <br />II <br /> <br />III, HYDROLOGIC ANALYSIS <br /> <br />II <br /> <br />A, General <br /> <br />Drainageway A (1020 acres) drains the northern core area of the City of <br /> <br /> <br />Louisville. The basin extends from the ridge west of Eisenhower Boulevard to <br /> <br /> <br />Coal Creek, between the ridge north of South Boulder Road and Spruce Street. The <br /> <br /> <br />watercourse consists of a steep well defined channel upstream of Via Appia and <br /> <br /> <br />through the Parkwood Area, a broad swale between Jefferson Avenue and Main Street, <br /> <br /> <br />a stOrm sewer and street flow along Lafayette Street, South Street and Spruce <br /> <br />Street, and a broad swale from Highway 42 to Coal Creek. The major features of <br /> <br />the basin are the Hillsborough West Subdivision, the southern area of Mesa Point <br /> <br /> <br />Subdivision, Parkwood No.2, Louisville Middle School, and the Louisville sewage <br /> <br /> <br />treatment plant. <br /> <br />II <br /> <br />II <br /> <br />The purpose of the hydrologic analysis was to define the storm runoff peak <br /> <br />flows and volumes at selected design points along the drainageways, The peak flows <br /> <br /> <br />and volumes are used to evaluate existing drainage facilities, assess flood prone <br /> <br /> <br />areas, and suggest possible drainage improvements. The current Urban Drainage and <br /> <br />Flood Control District (UD&FCD) procedures (Reference-2) were used in developing <br /> <br /> <br />storm runoff peak flows and volumes. The specific details used to define the <br /> <br /> <br />required hydrologic data are presented in this chapter, The results of the analysis <br /> <br />are shown in the Design Peak Flow Diagrams (Drawings-5 and -6) and the Design <br /> <br /> <br />Flood Hydrographs (Drawing-7). <br /> <br />Drainageway B (211 acres) is the smallest basin in the planning area, The <br /> <br />watercourse drains a portion of the southern residential area of the City of Louis- <br /> <br /> <br />ville. The watercourse consists of a storm sewer and street flow along Pine Street <br /> <br /> <br />and Elm Street, and a broad swale downstream of State Highway 42. The major feature <br /> <br /> <br />of the basin 1S the Louisville Elementary School, <br /> <br />1\ <br /> <br />II <br /> <br />II <br /> <br />II <br /> <br />B. Major Drainageway <br /> <br />Drainageway C (824 acres) drains the southwest area of the City of Louisville <br /> <br /> <br />from the Davidson Mesa to the Colorado and Southern Railroad. The watercourse con- <br /> <br /> <br />sists of a well defined channel at Eisenhower Boulevard, a broad swale below the <br /> <br /> <br />Goodhue Ditch, and a storm sewer along Rex Street and South 96th Street. Recent <br /> <br /> <br />construction north of Daly Road and west of the Bella Vista Subdivision has altered <br /> <br /> <br />the drainage flow patterns by providing detention ponds, grass channels, and storm <br /> <br />sewers to carry the flow along Daly Road to Coal Creek. The major features of the <br /> <br /> <br />basin are Harper Lake, Centennial Valley Filing No. I, and a part of Louisville <br /> <br /> <br />Elementary School, <br /> <br />II <br /> <br />The first step 1n determining the runoff peaks and volumes was to define the <br /> <br /> <br />basin and sub-basin boundaries and major drainageways. For the purpose of this <br /> <br />study, a major drainageway was defined as an outfall system, which drains an area <br /> <br /> <br />130 acres in size or more. The basin and sub-basin boundaries were defined through <br /> <br />a detailed investigation of the flow patterns in the area, using the Louisville <br /> <br /> <br />and Lafayette Quadrangle Maps, mapping provided by UD&FCD at a scale of I" = 200' <br /> <br /> <br />with a contour interval of 4-feet, aerial orthophotos provided by UD&FCD, and <br /> <br /> <br />several field inspections to locate and measure all hydraulic structures which <br /> <br />effect the basin definitions. Where marked changes in existing land use and <br /> <br /> <br />impervious areas were encountered, additional sub-basins were defined to avoid <br /> <br /> <br />the reduction 10 peak flows due to the effects of averaging over a large basin. <br /> <br />Also, where a drainage basin narrowed into a Itbottleoeck" shape for an extended <br /> <br /> <br />distance, the basins were split into separate suh-basin. Using this procedure, <br /> <br />the planning area was divided into 10 separate outfall drainage basins and 51 <br /> <br /> <br />sub-basins (see Drawing-2). A discussion of each outfall drainageway is presented <br /> <br />below. <br /> <br />Drainageway D (598 acres) drains the area directly north of Delaney Road from <br /> <br />the Davidson Mesa to Coal Creek. The watercourse throughout the basin consists of <br /> <br />a broad swale. The major feature of the basin is the proposed Heritage Subdivision, <br /> <br />II <br /> <br />1\ <br /> <br />II <br /> <br />II <br /> <br />II <br /> <br />II <br /> <br />Drainageway E (442 acres) drains the area north of the Denver Boulder Turnpike <br /> <br /> <br />(State Highway 36) from the Davidson Mesa to Coal Creek. The watercourse throughout <br /> <br /> <br />the basin consists of a broad swale. The major feature of the basin is the Denver <br /> <br /> <br />Boulder Turnpike and Eisenhower Boulevard. <br /> <br />1\ <br /> <br />-8- <br /> <br />II <br /> <br />-7- <br />