Laserfiche WebLink
<br />Selection of Peak Flow Values <br />The peak flows obtained from the three different methods are <br />summarized in Table 1. The peak flow values from the Regional Curve <br />are substantially higher than those calculated by steps 1 and step 3. <br />The peak flows calculated from step 1 may be low because of the limited <br />data available. The step 3 method uses a regional curve (as represented <br />by a regression equation) which covers the entire mountain region <br />of Colorado. Values obtained from this regression equation may not <br />be particularly applicable to the Lake City area. Also, the regression <br />equation may emphasize snowmelt peaks and not storm runoff. <br />A major contributor to peak flows on the Lake Fork and Henson <br />Creek is high intensity rainstorms. Although these occur much less <br />frequently than the snow melt peak flows, their mangitude may be sub- <br />stantially greater. In preparing the regional curve, greater weight <br />was given to those stations which had included data from thunderstorm <br />runoff. Since the regional curve appeared to be more representative <br />of the Lake Fork and Henson Creek drainage basins, more credence was <br />given to this method and the selected value was obtained from this <br /> <br />146.8 <br />sq.mi. <br /> <br />Method <br />USGS OFR 84-137 <br />CWCS TM #1 ( 1) <br />Regional Curve <br />Selected Value <br /> <br />Floodflow by Recurrence Interval(cfs) <br />10 yr. 50 yr. 100 yr. 500 yr. <br />1270 1600 1730 2030 <br />1240 1610 1750 2080 <br />2000 3100 3620 5550 <br />2000 3100 3600 5600 <br /> <br /> <br />curve. <br /> <br />TABLE 1 <br />SUMMARY OF CALCULATIONS <br /> <br />Location <br />Lake Fork <br />above <br />confl uence <br /> <br />Drainage <br />Area <br /> <br />Henson USGS OFR 84-137 1260 1490 1580 1760 <br />Creek 91 Regional Curve 1360 2020 2340 3320 <br />sq.mi. <br /> Selected Value 1400 2000 2300 3300 <br />Lake Fork Regional Curve 2980 4800 5800 9500 <br />below 237.8 Summation 2530 3090 3310 3890 <br />confl uence sq.mi. CWCB TM#1 (2) 2094 3073 2892 3473 <br /> Selected Value 3DOO 4800 5800 9500 <br /> (1) Calculated from stream flow records <br /> (2) Calculated from regression equations <br />