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<br />Streamflow data <br /> <br />Streamflow data for the South Platte River basin that were analyzed by <br /> <br /> <br />Jarrett and Costa (1983) are shown in Table 1, Flood-frequency curves <br /> <br /> <br />exist for several streamflow-gaging stations near Estes Park. These curves <br /> <br /> <br />are shown for two sites in Figure 3a and 3b: The Big Thompson River at <br /> <br />Estes Park (site 18) and Little Beaver Creek near Idylwilde (site 25). The <br />separate snowmelt- and rainfall-flood-frequency curves for each site can be <br />combined to construct a composite curve, if the populations are indepen- <br />dent, by using the equation: <br /> <br />P(composite) = P(snowmelt) + P(rainfall) - P(snowmelt) x P(rainfall) (1) <br /> <br />where <br /> <br />P = the exceedance probability of occurrence (Crippen, 1978). <br /> <br />For both sites, the rainfall curve is much lower than the snowmelt and <br /> <br />composite curves, and in neither instance does rainfall contribute to flood <br /> <br />hazards. As elevation increases, the difference between the snowmelt and <br /> <br />rainfall flood-frequency curves increases, The floods of record at the <br /> <br />respective sites are 1,660 cubic feet per second (47.0 cubic meters per <br /> <br /> <br />second) and 28 cubic feet per second (0,79 cubic meters per second). Both <br /> <br /> <br />floods resulted from snowmelt runoff. The maximum rainfall floods at these <br /> <br /> <br />respective sites were 871 and 6.7 cubic feet per second (24.7 and 0.19 <br /> <br /> <br />cubic meters per second). <br /> <br />~o <br />