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<br /> <br />flood events appears questionable. Bias is introduced through the pre- <br /> <br /> <br />ponderance of recorded snowmelt peaks at each station, which tends to <br /> <br /> <br />distort the higher variance associated with I'ainfall eventa in this region. <br /> <br /> <br />Irrigation diversions above the stations also change the flow characteristics. <br /> <br /> <br />In addition, the trend toward extensive urban development in the foothills <br /> <br /> <br />and plains portions of the basin in recent years haa changed the runoff <br /> <br /> <br />pattern of the lower basin and will continue to change as urbanization <br /> <br />progresses. <br /> <br /> <br />e. Discharge Probability Adjustment. According to Bulletin #17, "Floods <br /> <br /> <br />developed from precipitation can be used to adjust frequency curves including <br /> <br /> <br />extrapolation beyond experienced values." It appears likely that the more <br /> <br /> <br />infrequent flood events at the Golden and Derby geeing stations would be <br /> <br /> <br />caused fran rainfall runoff events since other streams located along the <br /> <br /> <br />front range and in the high pl.a.ins area have experienced this type of event. <br /> <br /> <br />In addition, it is believed that the urban development which has occurred <br /> <br /> <br />in the foothills and plains portion of the Clear Creek basin has changed <br /> <br />the runoff pattern in the lower basin. For these reasons a rainfall-runoff <br /> <br /> <br />approach was used to define the more infrequent flood probability values in <br /> <br />the Clear Creek basin. Two watershed runoff models (MITCAT and SWMM) were <br /> <br />used for the rainfall flood studies as discussed below. <br /> <br />. <br /> <br />5. MODELING STUDIES AT GAGE SITES. <br />a. General. Modeling studies of the Clear Creek basin were made in <br />two parts. The 4OO-square mile mountainous area lying upstream from Golden <br /> <br />4 <br /> <br />