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I I I I recommendations based on studies of mountain streams in Colorado (Jarrett, 1985). Channel velocities were determined using an HEC-2 subcritical analysis of surveyed cross sections or estimated using SCS velocity curves (SCS, 1986). I Curve Numbers were obtained following recommendations for Hydrologic Soil Group "D" soils (SCS, 1986). Using this information, the per cent of land use in each category in each catchment was determined using Figure 3, and average curve numbers were calculated for each catchment. An average ARC (AMC) ofII was assumed. Please refer to Table 1. Time of concentration calculations are shown in the Appendix_ Time of concentrations for each catchment are summarized in Table 2. I I I I I Table 1. P r . re IDllnarv urve Number a1culations, Catchments I-I., 1979 Land Land Use CN 1 2 3 4 5 6 8 9 10 Area (ac) 5962 3875 5208 490 1884 810 691 1552 1870 Area (so.mi.) 9.32 6.05 8.14 0_77 2.94 1.27 1.08 2.43 2.92 High Density Forest - D soil 79 65% 49% 64% 50% 65% 12% 48% 37% 69% High Density Forest -A soil (calibration) 36 0% 0% 0% 0% 0% 0% 0% 0% 0% Low Density Forest - D soil 83 19% 31% 21% 25% 15% 45% 21% 4% 0% Meadow 75 16% 20% 10% 21% 20% 40% 31% 50% 23% Low Density Residential 84 0% 0% 5% 0% 0% 0% 0% 0% 7% Med. Density Residential 90 0% 0% 0% 3% 0% 2% 0% 3% 0% Commercial 95 0% 0% 0% 1% 0% 1% 0% 6% 1% Avera!!e eN 79 79 80 80 79 80 79 78 79 C C o Use. I I I I I Note: See Figure 3 for land use and Figure 4 for Catchment locations_ Table 2. Summary of Time of Concentrations, Catchments 1-10. Catchment Tc Conunent (hr) I 0.85 NC6 2 L23 Silver Crk. + 45% NC5 to NC6 3 1.82 Missouri G. 4 1.01 NCC Catchment 4 + NC3-NC4 5 0.85 Chase VIS 6 L26 Chase DIS + 80% CI-C2 7 N/A 8 0_60 Gregory VIS 9 1.30 Gregory DIS (Prosser G_) + 65% GI-G2 10 1.24 Fourmile + 80% NCI-NC2 I I I I I I Note: See Figure 4 for Catchment identification and design point locations. -8-