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<br />22 <br /> <br /> <br />- <br /> <br />""'...;- <br /> <br />, <br />f <br />! <br /> <br />I <br />I <br />I <br />163w'",," <br /> <br />'~:~~---~ <br />. ---- ~ --, <br />~~ --~--~ <br /> <br />I <br /> <br />'''''''. <br /> <br />"- <br /> <br />lllUre 12. A hyPothetical example of runoff resulting <br />trOll.. .lns1e statlll event. Data were collected at all <br />established C.S. Geological Survey ~.llaglng stat Lon. This <br />plot of the data 1s called a stream hydrQgraph. <br /> <br />(i.e., 8, 16, 24, 32) show the percentage of annual runoff that normally <br />occurs in each month of the year. Note that the least variation i:n flow <br />occurs in some rivers of the southeast. Gre,atest vari'ltion tends to occur <br />in mountainous regions. High flows last fe.,er months 1:han low flO'u. Flow <br />is generally greater than the mean annual flow (repres4lnted by the 8 <br />percent line) in spring and summer. <br /> <br />table 6. Avual. dany natuul .trea.flow for the North Forlt of the Phtte <br />liver at Grand Gaule (I cubic foot per second. 60 aCrl! teet per <br />.-onth). <br /> <br />Honth <br /> <br />Average C.t.l. <br />Dally <br /> <br />Average Acre Ireet <br />MOnthly <br /> <br />January <br />February <br />Han::h <br />April <br />ltay <br />June <br />July <br />Augu.t <br />Septe.ber <br />October <br />Nove.bet <br />Dec..bet <br /> <br />18 <br />16 <br />18 <br />l2 <br />129 <br />24' <br />141 <br />84 <br />49 <br />36 <br />" <br />22 <br /> <br />1,080 <br />960 <br />1,080 <br />1,920 <br />7,740 <br />14,640 <br />t1,460 <br />5,040 <br />2,940 <br />2,160 <br />1,740 <br />1,320 <br /> <br />Veloci ty <br /> <br />The velocity (or speed) is the distance a mass of water moves per unit <br />of time. Measurements are generally expressed in centimeters, feet, or <br />meters per second. Stream velocities show a wide range from near 2:ero to <br />high rates of nine meters (30 ft) or more per second. Velocity i. strongly <br />influenced 111 volume of water, the gradient IInd the load of suspended <br />secl1aentl.'tlood plain streams of low gradient flow much more slo..ly than <br />steep gradient mountain streams. As stream gradient in,crease., anCl volliDle <br />increa..., ,vater velocity i. increased. Th. rouJhn.sa ot'. .tr.a.l~d ' <br />cnatej~ldi:d&n~iDd tend. to c1ecrease v.locity.' Therdon, velodt1e. may <br />vary considerably acrose the channel, from top to bottclm and atresia waters' <br />ar. alw.y. turbulent. Velocity varies invenely with t.he suspended <br />sediment load. <br />