Laserfiche WebLink
<br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />I <br />I <br />. <br />'. <br />I <br />. <br /> <br />profile and flooding limits corresponding to these flow rates. Also, <br />floodway limits were evaluated and backwater flood plain limits and <br />profiles were determined for tentative culvert-type road crossings. <br /> <br />II. DRAINAGE BASIN CHARACTERISTICS <br /> <br />A. <br /> <br />GENERAL <br /> <br />B. <br /> <br />COORDINATION <br /> <br />Appropriate methodologies for performing the necessary analyses were <br />established through consultations with the Urban Drainage and Flood Control <br />Di strict. <br /> <br />The Dad Clark Gulch drainage basin consists of approximately 7.6 square <br />miles of undeveloped area in the northwest corner of Douglas County, <br />Colorado. Currently, the gulch carries runoff following precipitation, but <br />it is normally dry. Further study is needed to determine if development <br />will cause more frequent runoff due to urbanization characteristics. <br /> <br />C. <br /> <br />METHODOLOGY <br /> <br />The basic mapping was made at 1 inch = 40 feet scale with one-foot con- <br />tours. These maps have been reduced to 1 inch = 200 feet scale for use in <br />this report. Land use data were obtained from the approved Development <br />Plan for Highlands Ranch. The Dad Clark Gulch drainage basin was divided <br />into 13 drainage subareas, and peak discharges at the downstream end of <br />each of these subareas were determined using the Colorado Urban Hydrograph <br />Procedure (CUHP). Water surface profiles and flood plain limits, as well <br />as floodway 1 imits due to encroachments, were determined using the HEC.2 <br />Water Surface Profiles computer program. The reader should refer to the <br />following sections for greater detail on the hydrologic and hydraulic <br />analyses used and to the tables, figures and drawings included in the <br />Appendix of this report for the results of these analyses. <br /> <br />The basin originates at Section 24, Township 6 South, Range 68 West, near <br />Daniels Park (see Vicinity Map, Basin Boundary Map and Sheet Index, <br />sheet 1 of 23 in Appendix), and extends approximately 6.5 miles in a <br />northwesterly direction to its eventual outfall point at the South Platte <br />River. The basin is presently an open undeveloped area, but will be devel- <br />oped over approximately a twenty to twenty-five year period. Development <br />in this basin will consist of single and multifamily residences, commer- <br />cial, light industrial, school sites and open space areas and is expected <br />to increase runoff rates over existing condition flows. <br /> <br />The entire drainage basin traverses various jurisdictions including Douglas <br />County, Arapahoe County, and the City of Littleton, and is crossed by <br />rights-of-way owned by various state and private entities. Dad Clark Gulch <br />basin is wholly contained within Urban Drainage and Flood Control District <br />jurisdiction. This report addresses only that portion of the drainage <br />basin which lies within Douglas County, i.e., southerly of County Line <br />Road. <br /> <br />B. <br /> <br />DAD CLARK GULCH <br /> <br />Dad Clark Gulch basin consists of SlX major waterways which are all tribu- <br />tary to the basin's outfall point. The extent and relationship of these <br />waterways can best be seen on the above referenced Basin Boundary Map in <br />the Appendix. The channels delineated on this map vary considerably along <br /> <br />2 <br />