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breaching the dams enable comparison of the effects of the flooding without dam failures to the <br />flooding effects caused by the dams failing as they did during the event. <br />11.1 No- Breach Model Results <br />Table 9 shows results of the model run with no dam breaches and includes a comparison of the <br />peak discharges calculated from the model to those calculated by indirect measurements by Dam <br />Safety Branch staff and calculated by others. Also shown is a calculation of percent difference <br />between those two sets of numbers. The percent differences are not excessive by hydrology <br />model standards and an average of over- calculations and under - calculations result in an average <br />percent difference of less than 10 %. This percent difference provides a moderate level of <br />confidence in the HEC -HMS model as configured. <br />Table 9 — Comparison of Indirect Flow Estimates and No- Breach Model Flow Estimates <br />Location of Indirect Measurement <br />Estimated <br />Modeled Peak <br />% <br />Modeled Time of <br />(Source) <br />Peak Flow(cfs) <br />Flow(cfs) <br />Difference <br />Peak Flow (MDT) <br />West Fork Little Thompson River, <br />3,657 <br />4,697 <br />22.1% <br />9/12/13, 4:20 AM <br />Upstream of Sunset Lake (WP60) <br />West Fork Little Thompson River, <br />4,056 <br />4,697 <br />13.7% <br />9/12/13, 4:20 AM <br />Upstream of Sunset Lake (WP27) <br />Deer Creek, Upstream of Meadow <br />1,764 <br />1,365 <br />-29.2% <br />9/12/13, 4:00 AM <br />Lake (WP 29) <br />West Fork Little Thompson River, <br />Downstream from Meadow Lake <br />4,201 <br />6,143 <br />31.7% <br />9/12/13, 4:10 AM <br />(WP20) <br />West Fork Little Thompson River, <br />Downstream from Meadow Lake <br />6,215 <br />6,143 <br />-1.1% <br />9/12/13, 4:10 AM <br />(WP21) <br />Little Thompson River, Upstream of <br />2,420 <br />3,312 <br />26.9% <br />9/12/13, 6:30 PM <br />confluence with West Fork (WP62) <br />Little Thompson River, Near <br />14,600 <br />10,190 <br />-43.3% <br />9/12/13, 4:45 AM <br />Pinewood Springs (NRCS, 2013) <br />Little Thompson River, Near X Bar 7 <br />15,731 <br />15,997 <br />-1.6% <br />9/12/13, 5:30 AM <br />Subdivision <br />Also shown in Table 9 is the time of peak discharge at each location as calculated by the model. <br />The variation in time of peaks is a function of the timing of the rainfall as it fell on each subbasin <br />and also the travel time along the stream courses to those calibration cross - section locations. The <br />model information shown in Table 9 is also shown graphically below in Figure 20. <br />Report of the September 2013 Little Thompson River Flooding COLORADO <br />and Big Elk Meadows Dam Failures, June 2014 (Revised, Dec 2014) A&V Division of Water Resources <br />Page 28 of 48 - - <br />■ 9go VM:1ovilH41:1 <br />