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I I I I I I I I I I I I I I I Table 13 Precipitation Depths (inches) for I-Percent Chance Exceedcnce Ennt 2-Day General Rain Ennt on the Dolores River Areally Distribuled Precipitation SPECIFIC 1 ST CONe 2ND CONe 3RD CO;";C 4TH CO:-":C 5TH CO!'\C 6T11 CONe West Fork Dolores Dolores Dolores Dolores lost Canyon Time Umainstcm" Bear Creek near Stoner abo\'c Rico Upper Mid \lid Lo......er Creck I-hour 0.49 0.44 0.47 OA7 0.45 0.42 0.44 2-hour 0.83 0.73 0.78 0.79 0.76 0.69 0.72 J-hour 1.16 1.01 1.08 1.10 1.06 0.94 0.99 6-hour 1.91 1.65 1.76 1.81 1.69 1.51 1.60 12-hour 3.07 2.57 2.78 2.86 2.69 2.36 2.52 24-hour 3.81 3.23 3.38 3.57 3.33 2.96 3.13 48-hour 4.97 4.30 4.49 4.70 4.44 3.9] 4.14 I I I 7.511MS Basin Parameters for 1% Stoml. Based on the IIMS model calibrated for the September 1970 stonn event. the following parameters were used in the IIMS model tor the 1% general stonn. The loss ralcs used wcre: Initial Loss = 0.80 inch (the same as used for the 1970 stonn). and Constant Loss == 0.19 10 0.22 inch per hour. The constant loss rate of 0.19 inch per hour was used on the West Fork and on the East Fork upstream of Dolores Upper Mid/Bear Creek. A constant loss rate of 0.22 inch per hour was used for Dolores Mid, Dolores Lower, Dolores lower Out, Dolores at Dolores, Dolorcs Out, Lost Canyon Creck. and Lost Canyon Creek Out. The basellow paramctcrs used were: Inilial Basenow = 1.0 cfs per mi2 (based on a now of 500 cfs estimated for the Dolores gage at the start of the 5 October 1911 flood evenl). Recession Constant = 0.65 (ratio of present basellow to baseflow one day earlier). and Threshold Q = 0.2 (ratio of peak flow). The subbasin unit hydrograph parameters and upper Dolores Rivcr S-curve used in the HMS model for Ihe 1970 llood event were used for thc 1 % llood. The Muskingum rouling paramcters developed for the HMS model for Ihc 1970 llood event. listed in Tablc 9, were used for the 1% llood cvcnt. 27 I