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<br />depth of flow in the streets that will allow the street curbs to be overtopped. All of these <br />alternatives will be evaluated for the final master plan. <br /> <br />The City of Aspen has proposed to use the FLO-2D program to model the effects of debris flow <br />on existing and future development in the city, For review purposes, the results of the FLO-2D <br />model were compared to the CUHP/SWMM modeling results, where possible, The two models <br />were found to yield reasonably similar results atthose locations. Direct comparisons could not be <br />made for all of the basins. <br /> <br />The values of the soil parameters input into the FLO-2D model were meant to be representative <br />values for the basin, as a whole. Within the basin, there are areas with different types of soils that <br />have different infiltration and runoff characteristics. Due to the large number of grid nodes in the <br />FL0-2D model (6508 nodes), it was not possible, for the purposes of this study, to provide <br />individual soil parameter values for each node, Also, there is little soil information available up- <br />gradient from the City. <br /> <br />The accuracy ofFLO-2D and its correlation to the results of the CUHP/SWMlVI output could be <br />improved considerably by providing individual soil parameter values for each node, As a check, <br />the soil parameters input into FLO-2D were varied for two sub-basins (Sub-basin 13 and Sub- <br />basin 16), so that they reflected the values corresponding to the type of soil identified by the SCS <br />Soil Survey for those specific sub-basins, The outflow from these two basins using FLO-2D and <br />the more detailed soil parameters was very close to the outflow calculated by CUHP/SWMM, The <br />accuracy of the FLO-2D model could also be improved by increasing the number of nodes (or. <br />decreasing the node spacing) in the model. <br /> <br />The results from the CUHP/SWMM model were further compared using the HEC-I curve nwnber <br />method in Sub-basin 16. The output from the two models was also very similar, <br /> <br />In conclusion, the CUHP/SWMM model produced flow values similar to the results determined <br />by FLO-2D andHEC-I models at comparable locations, Based on these comparisons, we believe <br />that the CUHP/SWMM model produces accurate and valid results and is acceptable for <br />determining the runoff entering and flowing through the City of Aspen. <br /> <br />8 <br />