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<br />Ii <br /> <br />storm producing the greatest peak discharge) and recommends that the SCS Type IIA <br />distribution be used to represent the 24-hourrainfall pallem. A rainfall distribmion for2-h.our <br />storms is also included in the Criteria MaflUIJI. Rainfall depths shown in lhc criteria manual are <br />based on Nation.al Oceanographic and Atmnspheric Administration (NOAA) AlIas 2. Rainfall <br />depths used in the modd are 4.40 inches and2.8R inch.es for the 24-hour and 2.hour, 1000year <br />storms respectively. It was determined through analysis that the 2-ho(lt" Slorm was the critical <br />storm. The rainfall depth for the 2-h.our, IO-year storm used in the analysis is 1.94 inches. The <br />use of the 2-hour stonn is consislCnt with the ongoing FEMA Restudy of Diny Woman and <br />Crystal Creeks. <br /> <br />Hvdrolo~icModelinl! <br />The hydrologic model consists of 95 sub.basins linked by drainageways or "reaches". <br />Presented on Exhibit 1 (in map pocket) is the Hydrologic Basin Map which shows the sub. basins <br />analyzed.. Hydrographs are accumulated at design points along the major drainages. A <br />hydrologic flow chart was developed and is presented in Figure 3-1. Both the existing and future <br />development condition hydrologic models are based on theCorrenl conflgunltion of both Dirty <br />Woman and Crystal Creeb and their tributary drainages. <br />The hydrologic model for the basin is based upon the I-inch to 200-foot topographic <br />mapping prepared by Landmark Mapping for this project. Basin areas, lengths, slopes, and flow <br />patterns were determined using these maps. <br /> <br />Results <br />The results of the hydrologic analysis have been presented in several formats. A basin <br />hydrologic map which contains the basin boundary, n:gional basins, channel routing scheme, <br />sub-basin locations, and design points is shown on Exhibit 1 which is contained in a map pocket <br />attached to this report. Rood discharge profiles for the various storm types analyzed a~ shown <br />on Figures 3-2 through 3-4, Summarizcd on Table 3-1 is the sub-basin peak discharge <br />information, Presented on Table 3-2 are the peak discharges for the key design poinls in the <br />basin. <br /> <br />The flows generated by the 2-hour stunn were greater than those generated by the 24- <br />bour stonn for this drainage basin. It was decided in the technical review meetings 10 use the 2- <br />hourslOrmforthisdraJnagebasinplanningsmdy, <br />The differences in the existing and future flow conditions were minimal. The rei1Ches in <br />the upper end of the basin show no difference betwcen the existing and future flow conditions. <br />The difference between flow rates is generated by thc potential future development along the <br />Intenltate 25 corridor and within the general area of the Town of Monument. The hydraulic <br />