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<br /> <br />Figure 10,--The middle reach (river mile 2.1) of the Roaring <br />River showing the extensive areas of scour and fill along <br />the channe 1, <br /> <br />dam (fig, 9A) at the moment of failure of Cascade Lake dam was computed to be <br />4,500 ft3/s, This measurement was made from high-water marks upstream from <br />the dam that were set at the time of fa il ure, Note how the water 1 eve 1 <br />dropped 1 to 2 ft on the right (far) bank, in the series of photographs of <br />Cascade Lake dam failing (figs. 9A-D), because of failure of the dam, <br /> <br />A peak-discharge profile was constructed from Lawn Lake dam to Olympus <br />dam, Indirect peak-discharge measurements were considered more accurate than <br />dam-break model results; hence, the profile reflects indirect measurements <br />where both were available, The peak-discharge profile (fig, ll) reflects <br />adopted peak discharges and indicates the rapid attenuation of peak flows in <br />the downstream direction. Greatest attenuation probably occurred as the flood <br />traveled through Horseshoe Park, The peak di scharge more than doubled as a <br />result of the near-instantaneous failure of Cascade Lake dam. <br /> <br />Volume <br /> <br />Si nce the construction of Lawn Lake dam in 1903, there had been some <br />question as to its storage capacity, particularly the live capacity of the <br />lake. At the time of failure, several capacities were referenced. Minimal <br />information existed on the capacity of Cascade Lake, In District Court for <br />Larimer County, the reservoir was decreed to have a capacity of 759.6 acre-ft, <br />but a 1931 capacity survey indicated 817,2 acre-ft of storage at high water <br />(Office of the State Engineer, 1983). Minimal information existed on the <br /> <br />21 <br />