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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />3.3 Streams <br /> <br />Streams (major drainageways) draining 130 acres or more of subwatershed area were <br />defmed as shown in Appendix G. To provide an orderly system of managing stream <br />information and hydrologic results, streams (above each confluence point) were design- <br />ated with an identification number. Streams were numbered consecutively from down- <br />stream to upstream. Coyote Run was designated as Stream 100. Thirty-eight tributaries <br />were identified in the Coyote Run watershed (Streams 101-138). Box Elder Creek within <br />the study area was designated as Stream 200. Fifty-one tributaries were identified in the <br />Box Elder Creek portion of the study area (Streams 201-251). In all, 91 separate streams <br />were identified within the study area. In addition, Box Elder Creek upstream of the <br />study area was given the designation Stream 400 and one tributary upstream of the study <br />area was identified with the designation Stream 401. <br /> <br />Each stream shown in Appendix G was divided into a series of adjoining conveyance <br />elements. The conveyance elements were designated with even numbers, increasing <br />consecutively in an upstream direction. Design points (direct routing elements) were <br />coded into the hydrologic models between each pair of conveyance elements. The design <br />points were designated with odd numbers that fall appropriately between each pair of <br />even conveyance element numbers. <br /> <br />Some of the streams shown in Appendix G appear, along with names and numbers, in the <br />Drainage Basin Description Maps, which were based on u.S. Geological Survey (USGS) <br />quadrangle maps, showing all watersheds within the UDFCD boundary (UDFCD, 1990). <br />A reference table is included in Appendix H to provide a cross reference between the <br />study stream numbers and the equivalent UDFCD numbers and names. Variations exist <br />between the stream delineations shown in the Drainage Basin Description Maps and the <br />streams shown in Appendix G. The streams shown in Appendix G represent major drain- <br />ageways (streams draining 130 acres or more), w!ri.ch include streams not shown on <br />USGS mapping and do not include USGS stream reaches that extend far upstream into <br />130 acre subwatersheds. Also, the streams shown in Appendix G are representative of <br />the flow routing that would generally take place during flood events, so in several <br />instances tributaries are shown taking a more direct path toward mainstem creeks than <br />indicated on USGS maps. The USGS maps may indicate two streams running close <br />together without joining, whereas Appendix G represents streams flowing at flood stagefwhen the streams, and their discharges, would be commingled. <br /> <br />3.4 Hydrologic Models <br /> <br />The UDFCD's Colorado Urban Hydrograph Procedure (CUHP) (UDFCD, 1985a) model <br />was used to develop runoff hydrographs for each subwatershed. The runoff hydrographs <br />were routed through the existing stream network using UDFCD's Storm Water <br />Management Model (UDSWM2) (UDFCD, 1985b). The UDSWM2 model does not have <br />a channel infiltration component; however, channel infiltration, even though it occurs, is <br />not expected to significantly affect peak discharges during extreme flood events. <br /> <br />DENlOOIS186.WPS <br /> <br />3-2 <br />