FLOOD10395 (2) - Laserfiche WebLink

Home Browse Search

e e e! Table 13 Precipitation Depths (inches) for I-Percent Chance Exceedence Event 2-Day General Rain Event on the Dolores River Areally Distributed Precipitation SPECIFIC 1ST CONC 2ND CONC 3RD CONC 4TH CONC 5TH CONC 6TH CONC West Fork Dolores Dolores Dolores Dolores Lost Canyon Time "mainstem" Bear Creek near Stoner above Rico Upper Mid Mid Lower Creek I-hour 0.49 0.44 0.47 0.47 0.45 0.42 0.44 2-hour 0.83 0.73 0.78 0.79 0.76 0.69 0.72 3-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 l2-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 3.91 4.14 7.5 HMS Basin Parameters for 1 % Storm. Based on the HMS model calibrated for the September 1970 storm event, the following parameters were used in the HMS model for the 1 % general storm. The loss rates used were: Initial Loss = 0.80 inch (the same as used for the 1970 storm), and Constant Loss = 0.19 to 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, Dolores Out, Lost Canyon Creek, and Lost Canyon Creek Out. The baseflow parameters used were: Initial Baseflow = 1.0 cfs per me (based on a flow of 500 cfs estimated for the Dolores gage at the start of the 5 October 1911 flood event), Recession Constant = 0.65 (ratio of present baseflow to baseflow one day earlier), and Threshold Q = 0.2 (ratio of peak flow). The subbasin unit hydro graph parameters and upper Dolores River S-curve used in the HMS model for the 1970 flood event were used for the 1 % flood. The Muskingum routing parameters developed for the HMS model for the 1970 flood event, listed in Table 9, were used for the 1 % flood event. 27