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<br />4.4 COLORADO RIVER BASIN
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<br />4.4.1 COLORADO RIVER
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<br />Floods have occurred on the Colorado River in: 1884,1917,1920,1921,1935,
<br />1952,1957,1983, and 1984,
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<br />Flood of 1884, The first flood on the Colorado River of which definite knowledge
<br />is available occurred during June ,.nd July 1884 and was caused by the meiling of the very
<br />heavy snow cover, The Weather Bureau located the high-water mark left by the peak
<br />stage of 1884 at fruita, and in 1917 the Geological Survey by connecting this mark with
<br />the gage being maintained, found its el,wation to be 18,5 feet, as based on the gage
<br />datum, By running a line of levels across the area flooded in 1884 and extending the
<br />rating curve, the peak discharge was determined to be 125,000 cfs,
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<br />Flood of 1921, The largest snowmelt flood runoff of record on the Colorado River
<br />occurred in June 1921, Heavy rllin on June 14 and 15 augmented runoff to produce a
<br />peak flow of 81,100 cfs near Fruita,
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<br />Floods of 1983 and 1984. Peal. flows on the Colorado River at the State Line
<br />were approximately 61,000 cfs and 70,000 cfs in 1983 and 1984, respectively.
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<br />4.4.2 ROARING RIVER
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<br />Flood of Julv 1957, The flood resuiled from snowmeit and had an instantaneous
<br />peak of 19,000 cfs, No urban areas were affected by the flood, The principle items
<br />damaged by the 1957 flood were the agricuiturallands and roads adjacent to, or over, the
<br />river, A few farm buildings were flooded. The total known damages in all categories in
<br />this reach amounted to slightly more than $45,000. A common type of damage from the
<br />1957 flood was bank erosion, The slope of the stream ranges from 65 feet per mile above
<br />Basait to 40 feet per mile below Basait, Velocities probably in excess of 10 feet per
<br />second occurred during the 1957 flood, The banks are composed largely of sand, gravel,
<br />and cobbles overlain by a comparlltively thin mantle of soil, and are quite erosible, Spoil-
<br />type dikes, constructed by local interests with material bulldozed in the process of channel
<br />clearing, proved to be very erosible, More than one-hail of the known damages in the
<br />1957 flood were caused to roads and bridges in the area, with nearly $24,000 of damages
<br />being caused to three bridges and have since been restored, A third bridge, which was
<br />private, was completely destroyed and has not been replaced,
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<br />Colorado Flood
<br />Hydrology Manual
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<br />4,31
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<br />fRtJFT
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