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<br />616
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<br />HYDRAULIC ENGINEERING ''14
<br />
<br />.' .. . .. 'd ilh the same pamOlclcrs (Rickcnmann. llJlJ I). A
<br />lranspnn cquallnns cXlucs.'iC w.. (' ) '~e rccnmmcm.lc:d range
<br />. . d d'.. ..' . . given 10 Ru:kcnmann In pfep. . III
<br />mure dClalle ISCusSUUlIS ". h n "'1 Ta""c ') They should only he
<br />. . l..'I' I'lh' prcscnlcdcquatlOnslSS uw ,.... '.
<br />01 apphcat'l ny u C 'd ,. 11 w rates noll'reater than abuul hank full discharge.
<br />used in natural streams an or u C'
<br />
<br /> S Qlm"/al I don Iml hid...
<br />E uatlon 0.3 . 2400 0.03 - 0.81 1-100
<br />2b . f5bl 0.0085 - 0.8 0.03 -140 0.05 -2.1 0.4-4
<br />2a .15a\ 0.8-63 0.03-2.1 0.4 -100
<br />/4 00085 . 20 0.14 - 2400
<br />
<br />TaMe 2: Rcctllnmcndcd range or app!il.:uliul1 for the equatiuns prcscnlCd ahove.
<br />
<br />Conclusions
<br />, ...' n now velocily in gravcl.bcd rivers nf lUounwin
<br />Il has been shuwn lhat the mea. . "Ih l'e parameters g Q S
<br />. .. ....d h power Inrm cxprcssmn W II . . .' '
<br />torrents can he cxprc~sc y~. n ',h licld data at least two separate cquauuns
<br />and d9{),. .UnwcY~r. In~ I~ ~st IJ ~I applied (0; lIifferenl slupe regions. The
<br />will~ dlllcrcnl ~x(l~).nc?~~.. .~. .... 'jenl clU\ also be cX(lrcsscd hy u.sing,lhe same
<br />cqUlvillcnl Manmngs rcSI:ilancc cnelll(': 'I 'l . (2h) may be used lur sln(lC~
<br />(laramclCrs. To estimate lhe mean l~oW ~~r'~~l~' .~I~icc(lCr than aboul O.K'~J.Thc
<br />below ah~lul O.H %, uhcn.d .':'Idu. u~i~~ u~ para:lC; rangc used in lhis analysis.
<br />rclalinnshl(ls shoulll nol use 0
<br />
<br />Reterences . .' ." . . J Hytlr.ling., ASCE. Vul. III,
<br />nalhurM. U:. (1IJKS): I'low rcsistlWCC eslunatlnll III mounlall1 ovcrs. .
<br />Nu. 4. pp. 62~-M3. '. J. Hytlr. Iliv., ASCI:, Vul UI1,
<br />(iriUilhs, <i.A. (lIJ81): Huw rcsisliUIf.'C III ('oarsc gravel bed nvu~
<br />IIY7, pfI. 81J1).'1I8, (' trph llogic der I'hulldl tlCli Slhllllung.switJcrslilIli.lc~ 111111
<br />lIudel. II. (1993): UlllcrsuchuUg, zur iet)lUt. l... ' lJ~) FlU Ziiricll
<br />des BicS!ivorgmlgcs ill.llcrll~~'hcn, I.)I~, h~II,.Nr,. ~'Ii 'Ir HI;', ASCE. Vnl. 110. Nu, II.
<br />lanclI, it.I>, (1984): Ilydrauh('s 01 lu&h-gradtcnt slreams. , YI. g,
<br />pp. 1519-IHIJ. . ,"1 Il,.w' ." >lccr sIU""'.li. MitlcilulI!t ,.II:I
<br />!tcdlt III Ir.uls('lllfl C'lpaclly u s ulTY .,. '..- -
<br />IUckclUnallU. I>. (IlJIJ()): ' ),l "'1' " .. '. FTII Ziilkh Nr !lll.24IJp
<br />V'r!oucb~lmit'lilrurWas.'\Crtlau,llydrulu'teUlld(I,I/.1H I~IC" " ," . 'I II!
<br />I. k c,'" I; ('I~JI)' lty",,'rUHlt:ClIlllllcd llnw llIW M:dilll~1I11ri1llS(M."t ill stcc~ sfnpc1'i, J. I Y
<br />tiC ClIll.'.It. .'.. . ..- 141~J.143'J.
<br />kllg., ASUI,.Vul, 117, Nt.': ~.I.' ':'.. . w' kcil ill WiWbiidlCII uud (icbill!.sllii1'i.<;Cll. l'ap;l
<br />RickclIlIlatlll. 1>. (U1 prcp,): I-IICSSgcS,"IlWlI Ig
<br />subnullcdlu'walioscr,cncrJl,ic,luU'. .' . . kcil in sellr nlllhcn ticrllllll'U
<br />It .. (' (lIJ88)' Nc~ Hrgchllb...c tiller dte l'llt:~..geschwmdl# .
<br />u. ;Willlrnk:I~'U).I~JC. llucll\lacvcnt, (.if;l/..l~d. 4. pp, 16;-.1?~ .', ,. Wiklhlll'll- 111111
<br />K" (i. (IljljU): Flicl'O...g.cschwilllhgkclI~n III .Ice Itucl/lSluhall..d/ltml
<br />II . . . 54 J II lIS pp.2ILJ.221. .
<br />t.OlWtllCIlVemilu.. . g.. " . " , Sl . SI .. Millcilllug der Vcrsrn:hs:ulst,dllut
<br />Sm:trt,li..Ju"i,M.(lIJM3):Scdnm:1I1 l~ilItS~Kt~I~. .L~p". uflcli'64 f'H
<br />W h lIydmtugicundGlanulut\1C bllll".um:b,Nr. , p. It: J
<br />. . iL"lil:S'.r "~'(" .p....U IJ I (I9~J): lIydrauhL"li ul" a lilf[!.!.: dmlllld f1iIvt:d wilh hnull '(S. .
<br />I1U"'llpSUII., ,1"1., .111 t..., ."
<br />Ilydr.ltcs., 17. nn. 4, pp. 341-354. .... '. lIyJr
<br />. I W (1IJ85)' Fslim'llmg fIIc"n vcltl('llY III U\nunt:U11 rIVC~,
<br />Thllfllc. C.lt., l".cvcllbergcll. ..' . ," .
<br />Hug.. ^SCl~. Vul. III. Nu.", pp..612-h24. . ,,' cI VUlI ^ Slnd..lcf
<br />., '11' J t1ljlH)' ller l{i1uhigkcil'ikllcUi/.icnl k-Slrki:.lcr III dcr Atlllus.<;lurm . .
<br />'.1; cr,.. . ., A 191)1
<br />M:lIIuskript mr 'W:lsscr, cllcrglc, lull. ug .
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<br />
<br />DESIGN OF M"NNING'S.ROUGHNESS-COEFFlCIENT STUDY
<br />IN NEW YORK STATE
<br />
<br />William F. Coonl
<br />
<br />ABSTRACT: Field-collected hydraulic data can be used to compute roughness cocffi-
<br />cicnls for channcl~ with differenl hydraulic charactcristics. Suggcslcd criteria for the de-
<br />sign of a roughness-cocflicient Sludy include: (1) location of the study reach close to an
<br />established streamDow-moniloring site with a slable high-now Slagc~lO-dischargc relation:
<br />(2) unifonn hydraulic conditions within, and upstream and downstream from, the sludy
<br />reach; (3) selection of atleasllhree cross seclions within the slud)' reach Ihal rcOectlhe
<br />average size and shape of the channel; (4) use of peak~stage recorders al eac.:h cross section
<br />to record the maximum cJevation of lhe waiCr surface for a given high now; (5) measure-
<br />mem of streambed panicle sizes and computation of characteristic diamelers, such as dso
<br />and dH4; (6) record of major Row-retarding factors (obstructions, vegetation. or frequent
<br />changes in channehize or shape) within the study reach thal could cause additional energy
<br />losses beyond lhose resulting from the bed and bank. materials alone; (7) documemation of
<br />channel condilions with photographs; (8) computation of the n value lhraugh a computer
<br />program dcveloped for this purpose; and (9) analysis oflhe data from each sile lodelcnnine
<br />Ircnd~ and changes ill the 11 value with now depth and to idemify discrepancies in lhe com-
<br />puted n values rcsulling from measurcf!lcm eITororviolalions oflhe assumplions on which
<br />Ihe compulatiunal method is based.
<br />
<br />INTRODUCTIClN
<br />Calculations of slream diSCharge and Boud-water elevations require evaluation of the
<br />lIow-resi~ting characlcriSlics of stream channels and their banks. Manning's roughness co-
<br />cl'ficienl (n) is commonly used 10 assign a quamitative value to represent lhe colleclive cr-
<br />!"eel of these characteristics. The procedure for cSlimating n values gcne....tlly is subjective,
<br />and the al'curacy is largely dependent on a hydrologist's or engincer'~ experience in esti-
<br />mating IlIese values over a wide range of hydraulic conditions. Computation of roughness
<br />cocllicicnls from hydraulic data collected from channels with diverse characterislics can
<br />incre~ our knowledge of roughness cocflicicms. and improve the accunacy of discharge
<br />and water-surface-elevation calculations Ihat arc dependent on reliable estimation of Ihis
<br />valuc. In 1983, Ihe U.S. Geological Survey (USGS), in coopcnllion witll thc New York
<br />Stale Dt:panmelll of Transponution, began as-year sludy to assess roughncss coefficients
<br />on New York channels. Thi~ paper describes .he design of this ~tudy, including sile sclcc.
<br />lion and mSlrumcntation. collection of dala, computation of roughness cocflicicl1ls. and
<br />analy~is orlhe data, It "Iso includcs suggeslions for improvemcnt of lhe study design and
<br />
<br />IlIydrologist, U.S. Geological Survey, 903 Hanshaw Road, Ithaca, New York, 14850
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<br />611
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