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<br />. <br /> <br />I <br /> <br />SOME FLOODS IN THE ROCKY MOUNTAIN REGION. 119 <br /> <br />proceeds downstream, but this one was augmented by floods from <br />all the tributaries. Undoubtedly one of the chief contributorS was <br />Crazy Woman Creek, which rises in the south end of the Big Horn <br />Mountains. Although no record of that stream is available, it is <br />known that pri~r to the time of the flood in Powder River a heavy <br />. fall of wet snow, beginning September 24, occurred in the mountains. <br />This was later followed by rain, which melted the snow and caused <br />all th~ streams that flow eastward from the mountains to reach <br />severe flood stages, <br /> <br />:&'LOOD AT A.ll.VADA. <br />In order to obtain all available flood data the gaging station on <br />Powder River at Arvada was visited on October 7 and 8. The gage <br />is at the highway bridge in the outskirts. of Arvada. Paint marks <br /> <br /> I - <br /> I <br /> r " <br /> / '\ <br /> f\ <br /> / \ <br /> I \ . . \ <br /> P weER RI ER <br /> /' 1923 \ ARK~~~ <br />: .- RIVfR,1921 <br /> . <br /> <br />- <br /> <br />,- <br /> <br />~ <br />";"eo.ooo <br />o <br />% <br />~ <br />~- <br />= <br />~ <br />~ --- <br />III <br />ii <br /> <br />zo,o'!O <br /> <br />C> <br />. Sept..27 za U 30. Oc:t.J 2. Jun. 3 + <br />FIo'OBJlll.-Hydrograpb3 of floods in 1923 on Powder Biver at Arvada.. Wyo., andJD 1921 onArtansas <br />Rivei' at Pueblo, Colo. <br /> <br />at each end of the bridge indicated the maximum stage; this was <br />determined by level to be 4.7 feet above the floor of the bridge, or <br />23,7 feet above the zero of the gage. . From statements of citizens <br />the height of the river at various times during its rise and fall was <br />determined. A fairly straight section of river beginning 200 yards <br />below the railroad bridge was selected to measure the high-water <br />slope and cross sections. The slope was well defined by fine drift <br />on one side of the river; on the other -the bank was formed by a <br />nearly vertical shale cliff. Two cross sections 515 feet apart were <br />measured to the water's edge, and the width. of the river at each <br />section Was determined by triangulation. From this the maximum <br />discharge was computed to be 95,000 second-feet, the value of "n" <br />being taken as 0.030. <br />An approximate hydrograph for the' period September 27 to <br />October 2 has been prepared (fig. 11) and shows that the river rose <br />