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<br />It is of more significance that 0.85 in. (21. 6mm) of the July 24 rainfall <br /> <br />came ~n about a half hour at the weather station. <br /> <br />Rainfall intensities <br /> <br />and amounts in the basins are nDt known, but judging from the comments <br /> <br />of observers in the area, rainfall wE:S of a magnitude similar to that recorded <br /> <br />1n town. In view of the lack of dHta ]"u the basins it will be assumed <br /> <br />that rainfall intensity there waS 0,75 to 1.00 in. ()9 to 25 mm) during <br />the half hour period. <br /> <br />C. Rainfall and Debris-Flow l';robabil~ty_. <br />According to statistical analysis of NOAA rainfall data, the maximum <br /> <br />I-hour period rainfall to be expected in an.y lsiven 100-y,ear period at Glenwood <br /> <br />Springs is 1.58 in. (40.1 mru). Th" precipitation intensity observed during <br />the recent storm appears representative oE approximately a 100-year return <br /> <br />period. Therefore, the debl~is fJ.ows, in accordance with the discussion <br /> <br />of section A of this chapter, probably h,eve a return period of 100 years <br /> <br />or less. <br /> <br />Interviews with staff memberB of the Colorado Geological Survey and <br /> <br />local residents revealed that flo"s occurred here 3() to ".() years ago (the <br /> <br />exact date is in question). ThuB the flows apparently have recurred in <br /> <br />considerably less than a century. <br /> <br />Subsequently it will be assumed that <br /> <br />the flows have a return period ,of 50 years (annual probElbility of 2 percent). <br /> <br />- 31 -- <br />