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<br />HYDRAULIC ENGINEERING '94
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<br />1980 1982 1984 1986 1988 1990
<br />YEAR
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<br />Figure l.--Relative frequency of occurrence of critical and
<br />supercritical flows, Toutle River system
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<br />1
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<br />IDI\eDllil
<br />Dobbie, C.B., aOG Volf, P.O., 1953, !he LJDIOlIth flood of 19S2, in. 'roeeeoiDgs: Institote of
<br />Chi! Eogiaeers, LOldol, t. 2, p. 522~S88.
<br />lerielratll, V.N., aDd Leatesley, G.B., 1981, Physical properties of ash frol MoUBt St. Beleas.
<br />relatioDship to raiD iofiltratiOl elperile1lts {abs.]: 19.[01101' Abstracts.. p. In. .
<br />JUda, ..J., Keyer, D.f., aDd CbildeIl, Dallas, 1984, SedileotatloD: aDd "eOlOlpblC cba~ges dunllt
<br />aDd following the 1980-1983 e[UpliODS of IIolOt St. Beleos, lIish1aqton {II: SblD-Sabor ,.
<br />31,1I0.2,p.10-36. . .. .
<br />Jarrett, R.D., 1984, Brdraulics of hiqh.gndieJIl streals. Journal Bydnllllc El1911eenog: bencal
<br />Society of Civil EI9ileers, ASCE, v. 110, uo. 11, p. 1519-1539.
<br />Job.D.SDB, I.G., aoo Beschta, R.I., 1981, Seasonal variitiOD of infiltratiou ca.pacities of soils in
<br />lIlesten Oregoa: O.S. Departlent of !gricnlture, Forest .Researcb Ser.Vlce Note. P~-J71.
<br />Lenesley, G.B., Lusby, G.C., aDd Lichty, R.W., 1989, lnfiltrahoo aDd erOSIon cba.ractenstics of
<br />selected tepbra deposits froltbe U80eruptiooof llouotSt. Beleos, Wasbllgtoo, USA:
<br />BydrologicalScieJlcesJounal,v.34,no.3,p.JJ9-J5J.
<br />Onig, C.E.. and Mathison, J.M., U82, Forecastiog coosiderationii iu Mount Saint Beleas affected
<br />rivers, in Proeeedhgs, Kouut 5t. lelels: Effects on Water Resources, Janhen Beacb,
<br />Oregon, p. 272~292. .
<br />SilOD, lodrew, 1992, Energy, tile, aDd cbauoel evoluti{)1I ill catastropbically disturbed fhuat
<br />systeu, il J.D. Phillips aDd W.B. Renwiet, eds., GeolOrphic 5yste.s: GeolorpbolOlJY, v.
<br />5,p,ll\'l12, ,
<br />5i101l, ladrev, aDd Thorne, C.R., iD press, bYluic adj\lstleut of aD unstable coars.e.gr.i1~ed
<br />river: Opposing trends of bouDdary and critical shear st!!SS and tbe apphcablhty of
<br />eJtrual hypotheses: Earth Surface Processes aDO Landforls. .
<br />SraosOD,'.J., Collios, B., OOllne,t., andWicherski,B., 1983. Eros ion of tepbra frolhll.lslope5
<br />near MOllnt St. Beleos and other ,0IcanDs. In Proceedillgs of the sYlposiul 00 erOSloa
<br />cootrol io ,01taoic areas, July 6.9,1982, Seattle and Vancouver, Wash.: h.cbnicalll....
<br />of Pllblic Works Research IIIstitllte 10. 1908, tsukuba, Jilpao, p. '183~222.
<br />Trieste. D.J., 19~2, EtaluatioD of supercriticalJsllbcritical flows il bigh.gradieot cballDe.I.
<br />JOllrnal of Hydraulic ElIljilleerilg: berican Society of Civil Engineers, v. n8, DO. 8, p.
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<br />Bed Load Roughness in Supercritical Flow
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<br />Scott E. Stonestreet' Member, Ronald R. Copeland2 Member,
<br />Daria C, McVan'
<br />
<br />Abstract
<br />
<br />A supercritical concrete channel has been proposed for Mission Creek
<br />located in Santa Barbara County, California. The proposed channel could
<br />transport gravels and cobbles as bed load during large flood events, Physical
<br />and numerical modeling have been conducted to determine the effect of the bed
<br />load transport on the hydraulic roughness of the proposed channel. The results
<br />of this study indicate a slight increase in hydraulic roughness with increased
<br />bed load concentration. Formation of bed forms did not occur for
<br />concentrations of less than 3000 ppm.
<br />
<br />Introduction
<br />
<br />The US Army Engineer District, Los Angeles, has proposed to improve
<br />the lower reach of Mission Creek (US Army Engineer District, Los Angeles,
<br />19861. located in Santa Barbara County, California. A rectangular concrete
<br />channel was designed to convey the 100-year peak flow of 224 m3/s at
<br />$upercritical flow. The right-of-way along the channel alignment is minimal
<br />which necessitated use of the supercritical rectangular channel.
<br />
<br />The Mission Creek watershed is capable of supplying large-si~ed material
<br />tor sediment transport. Since a debris basin is not included as pan of the
<br />project, there is a possibility that gravel. cobbles, and boulders may enter the
<br />chann~f. This Coarse material, moving as bed load along the channel bottom,
<br />could Increase the hydraUliC roughness to the point where the flow regime may
<br />change from supercritical to subcritical flow.
<br />
<br />lHvdraulic Engineer, US Army Corps of Engineers. Los Angeles District, PO
<br />Box 2711, Los Angeles, CA 90053
<br />
<br />IResearch Hydraulic Engineer. Hydraulics Laboratory, US Army Engineer
<br />Waterways Experiment Station, 3909 Halls Ferry Road. Vicksburg MS
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