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<br />~ <br />~ <br />~ <br />" <br />~ <br />~ <br />" <br />< <br />~ <br />.. <br />tf) Ct- <br />~ <br />W <br />" <br />Z <br />o <br />" <br />z <br />w <br />, <br />C I <br />I <br />0.011", <br />" <br /> <br />liJ2dj5 <br /> <br />......... l.EFTHMl:)C"lEEJ< <br />""IDOLf aO'..t..OElil C"lEEl< <br />-.-.-.- S.~E""ESCAE'E!( <br />:;)Af( CREEK <br />S::>I.:TI'1 FORK Co\C.-lE <br />LA "Ol.':IlE ~!VE~ <br /> <br /> <br />., <br />"<:-".. <br />'., <br /> <br />RE:..ATIVE PARTICLE ~i=lOTR'..JS;ON <br /> <br />Fig. 2. Comparuon of rC'f~rer.cr dll:]enSIOnle1S shear Sl:eS1. rOIl' <br />"trsus relael've p.1J'tlcle protrUSIon (d/d..;J deumnmed for fi'o'C' <br />gnyeJ.bee liyers. <br /> <br />;\{jc!.d.Ie Boulda Creek gage. This gage was seJe.:t~ for the <br />se::mll'o"ity anal)"SlS b!'.C3u.sc the tt.ost ex.l~nsi\'e :IU:<lS1.:rC'- <br />menu of bed.mau:rial trampon and the longest period of <br />rttord han betD collected th~. <br /> <br />4. EFFECTIVE BED.MATERIAL TRA-'iSPORTI:<G <br />DISCHARGES <br /> <br />The quanoI)' of bed-rn;uena! in each par.lcle size fracUon <br />transported by inCTements of discharge over the period of <br />record at ue.h gagmg Hanoe Ol.1y be dete:1D.ined eijjer by <br />calcu13lillg the qu.:mli[)" of baJ maten3.l tr:l.:lsponed eJcll <br />d;i}' during the penod of record or by the fio\!' durnLion - <br />sedimcDI transport method. Both approaches will gi"e the <br />same resu.J.l. 3:ld h.ave beo used in this smdy. Calculating <br />the qlJ.1D.tity of bed-matenal day-by-day p~rves valuable <br />lnfOrtIUtlo.c. cocceruiDg lemiX'raI va.-i.uility. 1:1 mlIl)' <br />lDSt.a.D.ceS. suc.h as t.l::e C"'alUllion of a proposed pro)e:cc, <br />however, a flow durauo::l. ~Iation will be more readily <br />available md reliable thi.:!. a :ime series of estim.a:ed daily <br />"a1ues. The obser....ed ~!at.ion between dimeoslowe:SS sheM <br />S[Tess iDd disc:.harge: at a gage ",,'as combined Wlt!:: tbe <br />bedload transport function for each panicle SIU bctioo <br />The du.r:allon of a gl"en discharge LOcremet.t c"er the: <br />penod of l'ttord ....6$ mul:lplied by the q:antlT)' of l'>ed <br />matenall.D i S\.z.e fractlon transpontd by the diSCharge per <br />unit tn:le. Results of these calt"Ula!lOtlS 1: si:J:. gi&IDK <br /> <br />lOO d <br /> <br />0991 S,~ 0_, 131 <br /> <br />A......DREWS .-\SD ~A:O-;KERYIS 1.57 <br /> <br />l <br /> <br />~IJUOnS UC: SUr:1IlJa.1zed l:l. FI,b\Ires 3~-f. Tr.e Sl:\ gr:sphs <br />....'ere :hoser. 10 illcma:e:.he ra."Ige of ~S".l!15_ The several <br />cur....es I:'. each graph r=-;:eser:t cur-'e C ~ Figure I (or :t:c <br />Idec.tiflee p:lr.lcle SIze fraCIIOll5. 1:.e 3.Il:.J bct""'eeo adjacer.r <br /><,;:l.I.rves is the Clean annual q"Janmy of bea ma:erial <br />~ar.sponed in the size.fraction The t::IeAD ~uaJ. qU;lJ'ltJ.ty <br />of bed N:enal UUlSpOlled lr. :l.l! size fracllons is the total <br />;uea t:..:lder the tOp lXrvC <br />In gc::!e:aJ. :.he :"'3r.ge of slgtUfica!lt bed-nu:enal <br />transpor:mg dischzrges is well--d.eflOed. Bed t::I.3.:erial begms <br />10 move on a'..erage at cischarges approximately 60 percc:nl <br />of the b:1:u:full cischarg: and 2-3 times the rnea.."l annual <br />discharge. >1any of ..ie dfectjve discbuge pl03 ate <br />ske.....ed to the l3:ge: d:scha:ges: however. discharges <br />greate: mar. r,,'ice the effe::tive value rrampon II telatively <br />sm.aJl fnctio::! of tl-.e ::Dean OWl"Jal load. For .II nver <br />reaches, the middle 80 perec::H of:te mean Utllwlload 15 <br />tIzcsponed, 00 a"cr::l.ge, by flo,*s between approximatel)' <br />0.8-1.6 times the bankf.tll discharge. For tl:.e 17 streams <br />srodied. the I:I.iddle 80 percent of the mea:l mnual bed. <br />m.aterialload is r:-..nspomd or. a...eraj;e during 15.6 days <br />per YeM by discbarges that repreSe.D.1 27 percent of the <br />r:t:.::4Jl :m:lual runoff and ra.,ge froc 17 to 40 perc~t of the <br />tDe.m ar.nu.a.\ CUIloff. On avenge:, discharges less than <br />bankfull tr:msl'or: 39 perc::.e:lt of :he mean :wlual b~. <br />matenalload. <br />The ullerval of discbarge chat transpons the largest <br />portiOll of the mean a!llIual bed-marerialload over ~ period <br />of years, i.e. che modal ..'a1ue. is termed the effective <br />diseh.rge (AMTt"WS. 1980]. It should be DOted that DO <br />special siguifleanee is .l""..a.cbed solely to 3. si:lgle dJsctLaree. <br />The effective discharge is a simple and stra.ig.l:tforward <br />represemauve for me ra.tlge of discharges ~'bic.h transpon <br />tht:: vast majority of the me.an annual bed-mau:nalload over <br />a period of yU""l. The effeai"e discharge computed for <br />e.u:b river reach is Iisled in Table 1. and compued i:1 <br />Figure 4 with che fi:ld-deterruined bankfull discharge. <br />Generally, there is a ~ood oc.e-tO-<llJC 3.greeClec.t beC"*eec <br />the field-determined bankfull discharge and the computed <br />effective: discharge:. The: meilD normalized differeoce <br />bet.....~ che effedive and barJdull discharges is 11 perte:lt. <br />This resuJt suppons the Wolman-Miller hyPOthens thaI <br />nv~r chanI:l.eI clu,neteristiC$, and specifically. the capadty <br />of the D.:I.mrally formed dUo.::lC:l. .....ill be detmnincd by the <br />ra.oge of cfucharges that tnJ1sport masl of Lte bed,.malenal <br />over a penod of years. The close agreemenl be1W~ tbe <br />effwive a::l.d bankfull discharge for the 17 river reach <br />sCUdy demoostrates that the range of effec.ive bed-muenal <br />rrmspollUlg disc.h.1tge.s are the flows which consrruCt md <br />maintain these cl:1.annels. <br />The effect of unee-r.ainry in :.be hydraclic CJantlensllcs <br /> <br />~ <br /> <br />1 <br />J <br />~ <br />. <br />j <br />1 <br /> <br />, <br />1 <br />1 <br /> <br />" <br /> <br />3J[~,3S lS3,OJ ;OSl <br /> <br />It:11 1Q1~1_6 .1- m <br />