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<br />. <br /> <br />. <br /> <br />106 <br /> <br />HYDRAULIC ENGINEERING '94 <br /> <br />Rio Grande at the Vigil Ditch <br />Calibrated Manning's N = 0.028 <br /> <br />Elevation (m) <br />1,712 <br />1,710 <br />1,708 <br />1,706 <br />1,704 <br />1,702 <br />1,700 <br />o <br /> <br /> <br />Thalweg <br />--e- <br />Measured <br />-0- <br />Simulated <br />--lIE-- <br /> <br />1,000 1,600 2,000 2,600 <br />Di.tan<e downstnam (m) <br />Compuiaon ormeuund aDd eimuWed <br />water IUrlace .1eYaUoM for . diec:harp or <br />184 eu ... M., 1193 <br /> <br />3,000 <br /> <br />600 <br /> <br />Figure 3 _ Water surface profiles at Vigil Ditch for Manning's n calibrations. <br /> <br />Rio Grande at El Guique <br />Calibrated Manning's N = 0.049 <br /> <br />Elevation (m) <br /> <br />Th.,1weg <br />--e- <br />Measured <br />-0- <br />SImulated <br /> <br />1,733 <br />1,732.5 <br />1,732 <br />1,731.5 <br />1,731 <br /> <br />1,730.5 0 <br /> <br />" _.:-. 'C-...,...._+--_.__.~_._,. <br />~~.~,~- <br />. ..~.... <br /> <br /> <br />500 <br /> <br />600 <br /> <br />200 300 400 <br />Distance doWI18lre8m (m) <br />Comparison of aaIUftd and simulated <br />w.m- IUrfKe ekntIoU lor a clIIchup <br />of9ru rnIl..S!plea'hr1992. <br /> <br />100 <br /> <br />Figure 4 _ Water surface profiles at El Guique for Manning's n calibrations, <br /> <br />., <br /> <br />. <br /> <br />Floodflow Effects on Riparian Vegetation in Arizona <br /> <br />By <br />J.Y. Phillips' and H.W. Hjalmanon' <br /> <br />Ahstract <br /> <br />A relation for estimating changes in the condilion of riparian vegetation as a <br />function of stream power was developed for stream channels in centtal <br />Arizona. Flood and vegetation data were collected from 13 !lows at II <br />siles. Stream power was computed al cross seclions and plolled against the average <br />heighl of vegetation for each Row. The effecl of Ihe !low-no effecl, lillle effect, <br />laid over. or removed-on the riparian vegetation is related to stream power and <br />vegetation heighl. As vegetation height increases, Ihe magnitude of stream power <br />needed to affect the vegetation also increases. Scream power of about 72 <br />Newton-melers per second per meter squared is needed 10 layover t -meier-high <br />vegelation, and scream power of about 580 Newton-meters per second per meler <br />squared is needed 10 layover 5.5-meter-high vegetation. This relation can be used <br />to estimate vegetation conditions allhe lime of peak !loodflow. <br /> <br />Intnxluction <br /> <br />Riparian vegetation is comrtlOaly thought 10 significantly reduce the capacilY of <br />scream channels 10 convey the peak discharge of large Roods. During major <br />Rood!lows, vegetalion can be laid over or removed along many screams, a condition <br />thai causes a natural increase in channel conveyance. The U.S. Geological Survey <br />(USGS), in coopemtion with the Rood Control District of Maricopa County <br />(FCDMC), has been evaluating the effects of Rood!low on riparian <br />vegellition. This paper describes the developmenl of a relation to beller predict the <br />effects of changing riparian vegetation on channel conveyances of screams in central <br />Arizona. This relation is preliminary and will be refined as additional data are <br />obtained. <br /> <br />IU.s. GmIotical Survey.I54S Ullivel1ity BIYd, Tempe. AZ85281. <br />'PrivlUcatlWunl, HC7S Bca 3558, Camp VmIe. AZ86:J20. <br /> <br />1117 <br /> <br />--- <br />