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<br />herein reflect flooding potentials based on condi tions existing in the <br />community at the time of completion of this study. Maps and flood <br />elevations will be amended periodically to reflect future changes. <br /> <br />3.1 Hydrologic Analyses <br /> <br />Hydrologic analyses were carried out to establish the peak <br />discharge-frequency relationships for each flooding source studied <br />in detail affecting the community. <br /> <br />Hydrologic analyses for the detailed-study areas on the Roaring Fork <br />River below its confluence with the Fryingpan River, and on the <br />Fryingpan River, were carried out by the USACE, Sacramento District <br />(Reference 9), using the methodology detailed below. <br /> <br />The hydrologic techniques used are fully documented in a separate <br />report, Hydroloqy Report For City of Aspen and Pitkin County <br />(Unincorporated Areas) (Reference 7). <br /> <br />Data from a large number of stream gaging stations located within <br />the homogenous watershed area similar to Pitkin County area were <br />analyzed. These gages are located within Pitkin County and nearby <br />Summit, Eagle, Garfield, Mesa, Delta, and Gunnison Counties. The <br />streamflow data were separated into snowmelt and rainfall peaks and <br />analyzed separately. <br /> <br />Snowmelt peaks from a total of 40 gages, and rainfall peaks from <br />25 gages, were analyzed to obtain individual and regional <br />statistical parameters of mean, standard deviation, and skew for the <br />two flow peak types. In many instances, the rainfall peaks were of <br />very small magni tude. Several stream gages did not show any <br />significant peaks caused by rainfall. <br /> <br />Using log-Pearson Type III distribution as described in u.s. Water <br />Resources Council Bulletin 1 7A (Reference 10), the <br />discharge-frequency information was developed separately for the <br />snowmelt peaks and the rainfall peaks for the 10-, 50-, 100-, and <br />SOC-year recurrence intervals. These two distributions were <br />combined to obtain the overall peak discharge-frequency relationship <br />for each stream. <br /> <br />For ungaged streams, the values of regional statistical parameters <br />were used and the discharge-drainage area curves were developed for <br />the 10-,50-, 100-, and SOQ-year recurrence intervals. <br /> <br />9 <br />