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<br />tit were reduced by 80%. The area available to store water and allow infiltration was also <br />reduced. <br /> <br />By accounting for the effect of the buildings in the hypothetical development, the model <br />shows that the maximum water depth increases by 4 feet at some locations. Figures 3 and <br />4 show the area south of Mill Street without the development constructed and with the <br />development in place, respectively. By comparing these two contour maps, the increase <br />in depth and area of increased depth is readily apparent. The depth of flow north of the <br />proposed development would increase from 1.5 feet to 5.5 feet. <br /> <br />DISCUSSION <br /> <br />Flow Comparison <br /> <br />tit <br /> <br />HEC-1 and CUHP/SWMM models were developed for two sub-basins above the City of <br />Aspen (Spar Gulch and Vallejo Gulch) and compared to the output from FLO-2D to <br />determine the validity of the FLO-2D output. The HEC-1 rainfall runoff model used several <br />types of infiltration methodologies. Table 1 presents the results of this analysis, and Table <br />2 provides the key input parameters that were used in the analysis. The data between <br />models was kept as consistent as possible, although it did vary slightly in some cases due <br />to model limitations. <br /> <br />In Vallejo Gulch, the CUHP/SWMM model produced a peak flow for the 1 DO-year, 2-hour <br />storm that was slightly less than the peak flow produced by FLO-2D and by HEC-1 using <br />the Green-Ampt and Holtan loss equations. <br /> <br />In Spar Gulch, the CUHP/SWMM 100-year, 2-hour peak flow is very similar to that <br />generated by HEC-1, but the flow generated by FLO-2D using the same infiltration <br />methodology is much less (532 cfs versus 340 cfs). This large difference in flow may be <br />due to FLO-2D's interpretation of the direction of flow off of the alluvial fan. FLO-2D may <br /> <br />e <br />