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<br />The Carl Smith Reservoir failed on the evening of May 2, 1998. Carl Smith Dam is <br />an 850 acre-foot, Class 1 off-channel reservoir in Leroux Creek Basin north of <br />Hotchkiss, Colorado. The failure was a result of a large slide on the downstream <br />slope that extended across the crest and into the upstream slope. The releasing <br />water swiftly eroded down through the top half of the remaining embankment and <br />quickly released about 500 acre-feet of storage. The peak discharge just below the <br />dam was determined to be around 3,300 cfs. Several residences were evacuated. <br />The only loss of life was livestock. The high water washed out numerous bridges, <br />and diversion structures were quickly rebuilt to restore water to irrigators. <br /> <br />C. Probability of Future Floods <br /> <br />Flooding will continue to occur in Colorado. As mentioned previously, between 20 and <br />30 large magnitude floods (in terms of peak discharge) occur somewhere in Colorado <br />every year. Furthermore, between 1965 and 1999, Colorado experienced nine major <br />flood disasters as indicated below: <br /> <br />. 1965: 33 Front Range communities <br />. 1969: 15 Front Range communities <br />. 1970: Southwestern Colorado <br />. 1973: 13 Front Range communities <br />. 1976: 2 Front Range communities <br />. 1982: Larimer County (dam failure) <br />. 1984: 15 Western Slope counties <br />. 1997: 13 Eastern Colorado counties <br />. 1999: 12 counties <br /> <br />In the 2004 update to the NHMP 2001 umbrella document, the probability of future <br />flooding was represented by Q3 Flood Data Product which is a digital representation of <br />certain features in the FEMA Flood Insurance Rate Map that can be used in spatial <br />evaluations. At that time, flood data were only available for nine counties: Adams, <br />Arapahoe, Boulder, Denver, EI Paso, Jefferson, Larimer, Morgan and Pueblo. The flood <br />hazard indicators were categorized using FEMA' s flood zone designations. Zones A and <br />AE represented areas that were in a 100-year floodplain or have a 1 % chance of flooding. <br />Zone X500 represented areas that were in a 500-year floodplain or have a 0.2% chance of <br /> <br />22 <br />