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tit e e by volume, 45%, was assigned to the time that the peak flow occurred. Flows less than 10 cfs were assigned a sediment concentration of 20%. Sediment concentrations for flows between the peak flow and 10 cfs were varied to provide a smooth transition between the two values. These hydrographs with their associated sediment concentrations are then input through the nodes up-gradient of the City, and the flow of water and sediment is analyzed as it flows through the City to the Roaring Fork River. The peak sediment concentration was varied until the water and sediment flow just reached the river. This concentration would provide a conservative estimate of the effect of a mudflow or mud flood on the City or any future development. This value would optimize the area covered against the maximum depth of flow. Higher sediment concentrations would cause a greater depth of flow but would not cover as wide an area. Lower sediment concentrations would cause the flow to cover a greater area, but the depth of flow would be less. Input Data to FLO-2D For this study 6,508 nodes were established at a spacing of 100 feet. The amount of area over the entire basin that is available to store water and allow water infiltration is 80%. The study assumes that impervious objects (i.e. trees, rocks, buildings, etc.) occupy a significant portion of the basin (20%). The study also assumes that the maximum Froude Number for flow down steep slopes is 0.9. NOAA precipitation maps provided the depth of the 100-year, 1-hour rainfall event. The rainfall distribution developed for the Colorado Urban Hydrograph Procedure (CUHP) was used to convert this depth to a rainfall distribution for the 100-year, 2-hour event. This rainfall distribution was used in FLO-2D. Surface detention and abstraction was assumed to be 0.025 inches. For use in FLO-2D, the study assumed that the soil type was the same over the entire basin. The porosity was