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<br />AUG-29-2000 rUE 10:04 AM <br /> <br />FAX NO. <br /> <br />P. 07 <br /> <br />(see CWCB report dated 6/28/00). Although the 8/16/00 rainfall amounts were about 2 <br /> <br />inches in an hour (-4 to 40-year rain event, which is a fairly Infrequent, large rainstorm), <br /> <br />the rainstorm was extremely localized. Caution is needed not to assume the Bobcat burn area <br /> <br />may not have several additional floods this year (or the next few years), Buffalo Creek and <br /> <br />other recently burned areas experienced numerous hazardous flood conditions each year from <br /> <br />typical summer thunderstorms (say 0.5 to 1 inches of rain in an hour or less). If a <br /> <br />thunderstorm with lower rainfall amounts covers all of the Bobcat burned area, more severe <br /> <br />flooding than from the 8/16 storm is likely. Thus, residents need to stay alert for flood runoff <br /> <br />from a more widespread thunderstorm, even with less rainfall. For example, a more <br /> <br />generalized but still a "local" thunderstorm of one inch of rain In an hour (a recurrence <br /> <br />interval of about 2-3 years; figure 2) over the entire burned area would produce a smaller <br /> <br />flood Bobcat Gulch (still flood the road - a haZardo? situation~ut a much larger flood and <br />potentially serious hazards in the lower Cedar Cr~ {1~n~ lithe post-fire runoff relations for <br />^ <br />Buffalo Creek apply to the Bobcat area (as the 8/16/00 data suggest), the peak discharge at <br /> <br />Cedar Cove from a typical thunderstorm Is likely to range from 1,000 to 2,000 cfs. <br /> <br />Paleoflood data (flood deposit evidence In the channel), which was obtained several years ago, <br /> <br />suggests Cedar Creek basin is much more prone to flooding than most other basins In the <br /> <br />Colorado Front Range. Property owners at the mouth of Cedar Creek at Cedar Cove (at <br /> <br />confluence with Big Thompson River on US Highway 34) need to be alert for hazardous flood <br /> <br />condlions (because it may not even be raining at Cedar Cove). The Cedar Creak culvert crossing <br />to homes at the mouth of Cedar Creek poses a serious potential hazard to these homeowners. A <br /> <br />1999 flood in Cedar Creek al Cedar Cove was about 800 cfs and covered the road crossing with <br /> <br />several feet of fast moving flood runoff (data obtained during the B/19 visit). A moderate <br /> <br />rainstorm over the (unburned) basin In 1980 produced a flood of 1,580 cIs (USGS Water <br /> <br />6 <br />