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<br />Flood proulems in this area have been primarily the result of snO~l-
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<br />melt "ith rainfall added on in the more extreme floods. The Id[';hest run-
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<br />off of record on the Yampa River occurred on June 14, 1921 and was 'the
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<br />result 'of a heavy rain (2.57") ,fallinr, on a melting SnOH pack with about a
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<br />once in 20 year snm,'!::e1t flow in the Yampa River. Another high flow bccurred
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<br />in April 1974 "hen il record 10" elevation snow pack melted out rapidly and
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<br />was augnented by .47 inches of rain. Gaging data for 'the Yampa River is
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<br />extensive uut very limited on the various creeks above Steamboat Springs.
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<br />C3~inb E'.t<-~ti_ons t;'lithin t~\e basin are. listed on table II~ Frequency curves
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<br />for t",o of these g,,[;es llre shmm on charts 5 and 6.
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<br />The unit hydro[';rnph for the Yampa River was derived by the L.A. S-graph
<br />
<br />mcthod ,.lith the use of the Farminf~ton S-graph. This S-[';rnph is the same one
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<br />used in the Durango FPI study to produce a unit hydrograph for the Animas
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<br />River and tributaries. The S-graph used to produce the unit hydrographs for
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<br />the other stre","" above Steamboat Sprin[';s was the genernl mountain S-graph
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<br />for Arizona, Colorado, Utah and Hyominr, from L,A. District. The "n" values
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<br />used "ere '.OS for the smaller streams and .07 for the Yampa River. A higher
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<br />"n" value- was used above. StcaJ:1boat Springs becnuse of a much higher density
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<br />of vegetation there thau on the Ym'pa River.
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<br />Stonns of the genel:a1 rain type that produce major flood problems in
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<br />Western Co1orCldo almost a1\,;,ys occur during the months of September,
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<br />Onohcr allt! nOVl'ln],,,,. (cl1:1rt [J). A ,!u,!],HyInr, ,;lorm 18 one wIth gr"Clter than
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<br />. 5 inches of prc'cLpJ tad on for a ?l, hour period. The mos t severe storms
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<br />are nur,I:lcnted by ':Ioisturc from tropical storms as indicat.ed by chart 7.
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