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<br />e <br /> <br />., <br />I <br /> <br />. <br /> <br />Monitoring and Modeling the Transport of Coarse Single Particles <br />in Mountain Rivers <br /> <br />Peter Ergenzinger & Carmen de long' <br /> <br />Abstract <br /> <br />The dynamics of single cobbles was studied in the alpine river Lainbach <br />using the Magnetic Tracer Technique (MA Tr) and radiotransmitters (PETS\' <br />= PEbble Transmitter SYstem). Our measurements were based on the <br />approacb of H.A. Einstein (1937) determining total travel length of single <br />particles during a Dood and different step lengths and rest periods of radio <br />tacked cobbles. Special studies were undertaken to continuously measure lih <br />and shear forces at tbe beginning of erosion of a coarse sphere using the <br />CObble Satellite SYstem (COSSY). <br /> <br />The main results of the COSSY investigations support the theories "I <br />H.A. Einstein suggesting that shear forces are dominant for erosion only when <br />the particle is situated on the river bed. When the particle is level with its <br />neighbouring particles, the dominant force is lift and erosion occurs only in <br />cases when lift is about twice as great as shear. <br /> <br />Step lengths of the PETSY cobbles was studied both in the laborat"", <br />and in tbe field. In contrast to the proposals of H.A. Einstein, the be" <br />approach to describe step lengtbs distribution is by a Gamma function. The <br />rest periods in between tbe movements are best described by an e-function <br />The model of single particle transport was developed on tbe basis of these <br />results. What must be known in addition are tbe geomorphic properties of <br />the related mountain rivers. In a step pool system tbe probabilities or <br />accretion are e.g. far higher in the pool. The results of the model were tested <br />againsttbe results of tbe obselVed transport lengths of tbe MATT trace red <br />material. <br /> <br />'Berlin Eaviroomenlal Research Group (D.E.R.O.). Institute or Geographical Scieucc:s, Frele <br />Univcniuel, Grunewaldmade 3.5. 1000 Berlin 41 Germ.DY. <br /> <br />6.14 <br /> <br />. <br /> <br />Problem!i with Indirect Determinations of Peak <br />Streamftows in Sleep. Desert Stream Channels <br /> <br />By Patrick A. Glancy, Member, ASCE, and Rhea P. Williams I <br /> <br />Abstract <br /> <br />Muny peak streamnow values used in Rood analyses for desert areas are derived <br />using the Manning equation. Data used in thc equation are collected aftcr the now has <br />suhsided, and peak nuw is thereby determined indirectly. Mosl measurement pmhlems <br />nnel associated errors in peak-Row determinations result (rom (I) channef erosion or <br />dcpmition that cannot be discerned or properly evaluated ancr the fact. (2) unsteady <br />and non-unifornl now that rupidly changes; in magnitude, and (3) appreciable sediment <br />Iransport that has unknown effects on energy dissipation. High calculated velocities <br />and Froude numhers are unacceptable to some inve.'itigators. Mea'turement results <br />could be improved by recording flows with a video camera, installing a recording <br />slrcam gage and recording rain gages, measuring channel scour with buried chains, <br />analyzing mea'iured data by muhiple techniques, and supplementing indirect <br />measurements with direct measurements of stream velocities in similar ephemeral <br />slreams. <br /> <br />Inlroduction <br /> <br />The arid regions of the western United States have few perennial rivers and <br />streams, but severe floods are common in their ephemeral drainages. These drainages <br />range in size from less than I kmZ to several thousands of square kilometers. She-am <br />gages for longMlerm, peak-discharge data are scarce in ephemeral drainages. Rapid <br />population growth near many ephemeral channels has increased the potential for <br />damage by flooding and 3S.'tocialed debris tnmsport. Because of the paucity of stream <br />gagc.'O. important data for prediction of ~Ireamnow magnitudes and recurrence <br />frequencies. which are needed for flood zoning and hazard assessments in ephemeral <br />Slrc.ml environments, are attainable mainly through indirect mea'turemenls of peak <br />nows (Benson and Dalrymple, 1967). A variety of measurement problems can cause <br />uncertainty during the application of indirect-determination methods. These <br />uncertainties reduce confidence in the accuracy or the quantitative resuhs. The purpose <br />of this article is to discuss uncertainties in indirect flow determinations in arid-zone <br />ephemeral channels and to present some strategies for improvement of these ' <br />determinations. <br /> <br />'lIydrolugi5ts. U.S. Geological Survey. Water Rl!sourct:s Division, JJJ W. Nyc t.ane:, Carson Cily. <br />NV 89706 <br /> <br />flJ5 <br /> <br />- <br />