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<br />" <br /> <br />August 1999 <br /> <br />COLORADO WATER <br /> <br />7 <br /> <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 concerted effort, 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 /> <br />U~~I7lC fJlr;ecasfrnoileloycr [;;olorailo since 1991. . .... .. <br />Mhlllam 60ttOB' . <br /> <br />t( fj'l\ <br /> <br />p..:....:....:...:::.-.::.";,,,,<;;.""-Z ~ <br />:.::~:~:~~:~::'J-~: \~~D.)\ <br /> <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. <br /> <br /> <br />THE U.S. ARMY CORPS OF ENGINEERS' CHERRY CREEK DAM STUDY <br /> <br /> <br />'l"l Jhen the National Weather Service, in the late 1980s, revised its maximum possible <br />V V 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 event 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 pertinent 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. <br /> <br />~~~~ <br />