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18,000 <br />17,000 <br />16.000 <br />15,000 <br />14,000 <br />13,000 <br />12,000 <br />11,000 <br />10,00�'0 <br />U 9.000 / <br />8.000 <br />6.900 <br />5A00 <br />4,000 <br />3.000 <br />2,000 <br />1 ,000 <br />DAM BREACH ANALYSIS OUTFLOW HYDROGRAPHS <br />AT CALIBRATION CROSS - SECTIONS <br />12 <br />— West Fork of Little Thompson River, Upstream of Sunset Lake <br />Deer Creek. Upstream of Meadow Lake <br />West Fork of Little Thanispson River, Downstream From Me adovr Lake <br />Little Thompson River. Upstream of Confluence vrlth West Fork <br />— Little Thompson River, Near Pinewood Springs(NRCS Section) <br />Little Thompson River, Near X Bar 7 Ranch Subdivision <br />13 <br />14 <br />Sep2013 <br />Figure 23 — Breach model outflow hydrographs at each of the calibration sections including dam breaches. <br />Table 12— Model Peak OvertODDing Results Compared to Surveys <br />Table 12 above shows the model results for peak overtopping depth with respect to the surveyed <br />overtopping depth results. Also shown is a comparison of those values with the depths of <br />overtopping at the times the dams failed. These data were also used to provide confidence in the <br />model producing realistic results as the variation is within reasonable limits for this type of <br />analysis. <br />The failure of Willow Dam was difficult to model as eyewitness accounts and photo's show it <br />essentially failed twice. The first failure occurred on the native ground at the left abutment. <br />Water flowed through a low area on the left abutment and erosion resulted in partial reservoir <br />draining through that area in what was modeled as a second spillway. The sudden increase in <br />Report of the September 2013 Little Thompson River Flooding COLORADO <br />and Big Elk Meadows Dam Failures, June 2014 (Revised, Dec 2014) a Division of Water Resources <br />Page 33 of 48 b pirrment of r.a,urar $esourc , <br />DAM SAFETY BRANCH <br />Surveyed <br />Model Maximum <br />Model Overtopping <br />Reservoir Volume <br />Dam <br />Overtopping <br />Model Peak <br />Overtopping <br />Elevation/Depth at <br />at Time of <br />Res. El {Dam Crest El) <br />Depth (ft) <br />Depth (ft) <br />Dam Failure (ft) <br />Dam Failure (ac -ft) <br />Sunset <br />1.11 <br />7532.1 (7530.09) <br />2.01 <br />7531.2/1.11 <br />25.3 <br />Rainbow <br />2.65 <br />7521.4 (7518.9) <br />2.5 <br />7520.3/1.4 <br />65.1 <br />Willow <br />0.24 <br />7515.2 (7515.01) <br />0.19 <br />7512.7/ -2.31 <br />45.2 <br />Mirror <br />3.42 <br />7502.3 (7499.38) <br />2.92 <br />7500.6/1.22 <br />22.6 <br />Meadow <br />1.90 <br />7499.7 (7497.56) <br />2.14 <br />7497.56/0.04 <br />92.7 <br />Table 12 above shows the model results for peak overtopping depth with respect to the surveyed <br />overtopping depth results. Also shown is a comparison of those values with the depths of <br />overtopping at the times the dams failed. These data were also used to provide confidence in the <br />model producing realistic results as the variation is within reasonable limits for this type of <br />analysis. <br />The failure of Willow Dam was difficult to model as eyewitness accounts and photo's show it <br />essentially failed twice. The first failure occurred on the native ground at the left abutment. <br />Water flowed through a low area on the left abutment and erosion resulted in partial reservoir <br />draining through that area in what was modeled as a second spillway. The sudden increase in <br />Report of the September 2013 Little Thompson River Flooding COLORADO <br />and Big Elk Meadows Dam Failures, June 2014 (Revised, Dec 2014) a Division of Water Resources <br />Page 33 of 48 b pirrment of r.a,urar $esourc , <br />DAM SAFETY BRANCH <br />