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<br />6 : feet. 4: inches p'-igh constl'llcted ,in, a ,trench' in"the, natural ground
<br />entirlllY:ibelow,the artificial embankment.,'This, tunnel is' provided
<br />with:two 3Q,inch pipe inlets equipped "with: gate valves.,' A spillway
<br />for, the, reservoir, WllS provided. over i a rock, cliff. some distance from
<br />t~e dam. ,'/ :.;'-' . :-. ;!',,'" j,'.. J ",:!!;r ,,'~!>~;'~\;':.:l Ii
<br />.. This reservoir successfully, withstood, t.he flood; storing all the run-
<br />off above it until..the high ,water had passed.:' ,.;:,
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<br />METHOD OF DETERMINATION.
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<br />,"'. .As ~o gaging stati~~~! l~~r~,~~i~t~i~e;l'~~' 't~~;~t~~ams within t.he
<br />.."." areas.of intense ra~nfall, it wasnecel!Sary to, determine the maximum
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<br />discharge by the slope method afte!; theJIood had passed. The work
<br />was done with ,a plane-table equipped with a Johnson quick-leveling
<br />head, a reconnaissancealidade ,having a 3-inch ,striding level, It'
<br />t'.. . 14-foot st3;dia, 1'04 graduated to half-tenths, and a IOO-foot steel tape.
<br />All distances :yvere J,I1easur~dwith th~ tape and checked by stadia.
<br />,.,',~.;,EachtI'ibutary,stream,w8,s:meas~r\ld,:as. near, the mouth as the
<br />condition pf th~ channel ,permitted.: ,A careful inspection wns mnde
<br />~o locatl) ,a ~gment, of.. channel ,which -,va~, reasonably straight and
<br />free, from brush" or other obstruction, and,,in: which the discharge
<br />had been confined totheregu,lar,chanriel with little or no overflow,
<br />III the portio-ll o( the stre!tmo measUJ;ed cross sections, were measured
<br />at the upper.en4,middle, and .Iower end., Plate'.IV,A, shows a typi-
<br />c,al segment~" ,At: each, of ,the three, sectilons: stakes. were set. at ,the
<br />high-water line ,on' eac):l side. of, theichannel. J~eginning 'at the 'UP"
<br />stream encl a)ev:elline,was run ar9und th~,sj.x, stakes, closing on the
<br />initial point, with an allowable ,err,oJ: ,of 0.05 foot. ,The distance on
<br />each side bet~een ,stakeS ; wasmeasu~d ! alollg, the high-water line.
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<br />.. . The cross ,section between eac;:h, pair of sta.kes pn opposite'sides of the
<br />&;i:~; cp.annel i was c;:arefupy: measured., .The, general location of ' each
<br />:;,::{i"3 measuring point, .was <;letermined by refer!mce ,to section corners.' Ow-
<br />irig to the effect .!>f:~nds.,in,t~e, ,channeUhatcouldnot be entirely
<br />':i"~;t~ avoided, the differlln<.:e in; elevatioll between ,adjacent cross sections
<br />_" was not the sanIe on both, llidesof the ~tream" nor ,was the distance as
<br />,<,>, , measured along the, high~..water..line,t4e ,same' on, both ,sides. ' Both'
<br />"',; 'distances and differences in, elevation ;~ere averaged to determine the
<br />meanslope between !ldjacent section!,!, ",'" ".. . '
<br />, , Each cross section was plotted on a)arge ,scale, and the area was
<br />, "::; determined by planimeter. By, means of tables based on, Kutter's
<br />';\e.. formula for flow ,in open ch~,npels the.diischarge between; ,the upper
<br />'::,> and middle cross sections und that' between the middle and lower sec-
<br />'>~: Hons were determined, the areas of the two cross sections being aver-
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