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taoo <br />16.06 <br />i[[1 A <br />12.00 <br />C <br />a <br />a 16.00 <br />CL <br />9 aw <br />a <br />E <br />604 <br />I'll's <br />2.0D <br />6.00 <br />917113 <br />Little Thompson River Total <br />Rainfall Accumulatioi <br />— I2OVYFLL GULCH 1 <br />LOWER WEST FORK 2a <br />— MLIGGINS GULCH 26 <br />LT BELOW PINS 2c <br />— SUNSET? RAI N BOWI W I LLOWI M IRROR 3a <br />— MEADOW 3b <br />NORTH FORK 4 <br />j <br />C <br />. —.�— <br />_ <br />9013 9013 9116113 9111 /13 9112113 9113+13 9114113 WV <br />Daterrime MDT (5- minutes) <br />Figure 19— Temporal distribution of the gage- adjusted radar rainfall for each subbasin in the study. The data forming <br />these curves were provided in 5- minute increments and displayed at the timescale shown for clarity. <br />10.7 Model Calibration <br />Results of the field investigations, datum analysis, basin delineation, and rainfall data analysis all <br />provide important parameters to be able to model the physical system of the basin as rain falls <br />and water runs off into the stream networks. Those previously discussed parameters are all fixed <br />once they are determined. The following parameters to be discussed are somewhat different. <br />Unit hydrographs, basin loss parameters, channel routing parameters, and dam breach parameters <br />are all more difficult to determine and some degree of subjectivity in parameter selection is typical <br />in all modeling efforts. This results in an iterative process being utilized to select the most <br />appropriate values of each of these parameters. This process is referred to as the "calibration <br />phase" of the modeling and is a standard practice when performing this type of study. <br />Accepted hydrologic literature typically assigns ranges of appropriate values for the parameters <br />listed above. In the modeling process, initial values for the parameters are assigned; the model is <br />run and output values are compared to those estimated through indirect methods at locations of <br />interest. The parameters determined to be sensitive, meaning a small change results in significant <br />changes in the model results, are modified, staying within the appropriate ranges, until the model <br />results compare favorably with the measured values at locations of interest, the calibration <br />sections. <br />Report of the September 2013 Little Thompson River Flooding COLORADO <br />and Big Elk Meadows Dam Failures, June 2014 (Revised, Dec 2014) * Division of Water Resources <br />Page 22 of 48 C+,partment or Itialurar s,,source. <br />DAM SAFETY BRANCH <br />