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<br />August 1999
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<br />COLORADO WATER
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<br />7
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<br />In 1986, the
<br />process of merging
<br />the capabilities of
<br />the two models into
<br />a unified multi-
<br />purpose modeling
<br />system began, and
<br />thus was born the
<br />new RAMS code.
<br />To introduce a high
<br />degree of flexibility
<br />and versatility in
<br />RAMS and to take
<br />advantage of the
<br />ever-increasing
<br />capabilities in
<br />computer hardware
<br />and software, RAMS was built on an entirely new framework, with numerical schemes and parameterizations from the earlier
<br />models adapted to the new model structure. After two years of concened effon, the first version of the new RAMS code was in
<br />use as a research tool. A major program of development has continued to the present day, resulting
<br />in many improvements and new capabilities
<br />
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<br />Current research using RAMS includes atmospheric scales ranging from large eddy simulations of
<br />boundary layer clouds, to simulations of large convective systems, to regional climate studies.
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<br />
<br />THE u.s. ARMY CORPS OF ENGINEERS' CHERRY CREEK DAM STUDY
<br />
<br />
<br />'"1 Jhen the National Weather Service, in the late 1980s, revised its maximum possible
<br />VV rainfall standards, the revision resulted in Cherry Creek Dam being listed as deficient.
<br />The revised standards increased the maximum possible rainfall by more than 50 percent.
<br />Many have challenged the amount, saying it is several times higher than any flood the area
<br />has ever seen. The NWS's "extreme meteorological event" of 25 inches of rain in 72 hours
<br />is double the amount that fell in the Cherry Creek area during the 100-year flood of 1935,
<br />which led to the construction of Cherry Creek Dam. However, if water ever did top the dam,
<br />it could result in a crumbling dam that would send water toward Denver at 1.7 million cubic
<br />feet per second, potentially killing as many as 10,000 people and causing $15 billion in
<br />damage, according to the Corps' project manager.
<br />
<br />The Corps points out that it uses four different standards to determine a spillway design flood (SDF). Standard 1 applies to the
<br />design of dams capable of placing human life at risk or causing a catastrophe, should they fail. Cherry Creek Dam falls into this
<br />category. For Standard 1 dams, the SDF is based on the Probable Maximum Precipitation (pMP) occurring over the watershed
<br />above the dam site. This standard is applied to all dams designed today by the Corps, and was used on Chatfield dam, Westerly
<br />Creek dam, and Bear Creek dam spillway designs. The original rainfall eveni and PMP studies for Cherry Creek dam spillway
<br />design flood and subsequent dam safety analyses are listed below followed by Table I, which lists peninent data for each event.
<br />The critical amount of runoff needed to fail Cherry Creek dam is also displayed.
<br />
<br />. . 1935 Event - May 30-31, 1935 event over the South Republican River basin transposed over Cherry Creek.
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