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<br />Precipitation data <br /> <br />Rainfall that produced the 1976 Big Thompson River flash flood in <br /> <br /> <br />Larimer County was reported to have occurred at an elevation of 8,300 feet <br /> <br /> <br />(2,530 meters) (Miller et al., 1984). This general statement, however, <br /> <br /> <br />needs clarification. The higher elevations where intense precipitation was <br /> <br /> <br />reported were associated with isolated mountain peaks above the general <br /> <br /> <br />topographic elevation of 7,500 feet (2,300 meters), The maximum flood <br /> <br /> <br />runoff occurred below 7,500 feet (2,300 meters) (McCain et al., 1979). <br /> <br /> <br />Miller et al. (1978) evaluated reconstructed flood peaks based on rainfall- <br /> <br /> <br />runoff analyses to estimate the storm precipitation in areas where <br /> <br /> <br />precipitation data were lacking. These investigators found it difficult or <br /> <br /> <br />impossible to reconcile slope-area indirect peak discharges with rainfall <br /> <br />measurements. Reconstructed peaks based on rainfall-runoff analyses <br /> <br />generally were 25 to 50 percent lower than slope-area measurements for the <br /> <br />higher-gradient streams, However, Miller et al. (1978) chose to accept that <br /> <br /> <br />the indirect peak discharges (McCain et al., 1979) were correct and to <br /> <br /> <br />increase the rainfall (intensities and volumes) accordingly for the storm. <br /> <br /> <br />This same practice was done for the 1964 Montana Storm (Boner and Stermitz, <br /> <br />1967). Jarrett (1986) has reported that peak discharges calculated using <br />the slope-area method for higher gradient streams (slopes greater than <br /> <br />0,01) consistently are overestimated, typically, by 75 to 100 percent, <br /> <br />/1 <br />