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<br />inaccurate under certain conditions and could lead
<br />to errors in computations of peak-flow velocity and
<br />subsequent calculations of stream power.
<br />
<br />SUMMARY
<br />
<br />This report presents data and describes
<br />methods that are intended to aid water-resource
<br />managers and engineers in the process of assessing
<br />peak-flow resistance in vegetated channels. The
<br />semiempirical relation presented can be used to
<br />estimate the effects of flow on main-channel
<br />vegetation conditions and consequent effects on
<br />computations of channel-conveyance and water-
<br />surface elevations. The relation is presented for the
<br />purpose of mitigating possible gross errors in these
<br />conveyance computations.
<br />
<br />The data and relation presented in this report
<br />can be used for a wide range of hydraulic
<br />applications that require assessment of channel and
<br />vegetation conditions during peak flow. Potential
<br />applications include postflow-discharge deter-
<br />minations (indirect measurements), standard-step
<br />computations to delineate flood-plain boundaries,
<br />and capacity computations for hydraulic structures.
<br />Although transferable to sites with similar channel
<br />and vegetation conditions, the information
<br />presented in this report should only be applied on
<br />the basis of sound engineering judgment. The high
<br />degree of variability in channel and vegetation
<br />conditions may not be properly accounted for by
<br />the simple approach and methods set forth in this
<br />investigation. The most applicable and accurate
<br />transfer of results would be to vegetation growing
<br />in the main channel of trapezoidal, uniform reaches
<br />such as constructed channels in urban areas.
<br />Further research may result in development of a
<br />substantive relation that can reliably predict the
<br />shear stresses associated with vegetation removal.
<br />
<br />SELECTED REFERENCES
<br />
<br />Aldridge, B.N" and Eychaner, J.H" 1984, Floods of
<br />October 1977 in southern Arizona and March 1978
<br />in central Arizona: V,S. Geological Survey
<br />Water-Supply Paper 2223, 143 p,
<br />
<br />Aldridge, B.N" and Garrett, J.M" 1973, Roughness
<br />coefficients for stream channels in Arizona: U.S.
<br />Geological Survey unnumbered open-file report,
<br />87p,
<br />Arcement, GJ" and Schneider, V,R., 1989, Guide for
<br />selecting Manning's roughness coefficient for
<br />natural channels and flood plains: V.S, Geological
<br />Survey Water-Supply Paper 2339,38 p,
<br />Burkham, D,E" 1970, Precipitation, streamflow, and
<br />major floods at selected sites in the Gila River
<br />drainage basin above Coolidge Dam, Arizona: V,S,
<br />Geological Survey Professional Paper 655--{;,
<br />p. C I--{;I 3,
<br />1976, Hydraulic effects of changes in bottom
<br />land vegetation on three major floods, Gila River, in
<br />southeastern Arizona: V,S, Geological Survey
<br />Professional Paper 655-J, 14 p,
<br />Carson, M,A., and Griffiths, G.A" 1985, Tractive shear
<br />stress and the onset of bed particle movement in
<br />gravel stream channels--Different equations for
<br />different purposes: Amsterdam, The Netherlands,
<br />Journal of Hydrology, v, 79, no. 3/4, p. 375-388,
<br />Chow, V. T., 1959, Open-channel hydraulics: New York,
<br />McGraw-Hili, 680 p,
<br />Coon, W.F., 1995, Estimates of roughness coefficients
<br />for selected natural stream channels with vegetated
<br />banks in New York: V.S. Geological Survey
<br />Open-File Report 93-161, 127 p,
<br />Costa, J,E., 1987, A comparison of the largest
<br />rainfall-runoff floods in the United States with those
<br />of the People's Republic of China and the world:
<br />Amsterdam, The Netherlands, Journal of
<br />Hydrology, v, 96, p. 101-115,
<br />Cowan, W,L., 1956, Estimating hydraulic roughness
<br />coefficients: Agricultural Engineering, v. 37, no. 7,
<br />p.473-475,
<br />Dalrymple, Tate, and Benson, M.A., 1967, Measurement
<br />of peak discharge by the slope-area method: V.s.
<br />Geological Survey, Techniques of Water Resources
<br />Investigations, book 3, chap, A2, 12 p.
<br />Davidian, Jacob, and Cahal, D.I., 1963, Distribution of
<br />shear in rectangular channels: U.S, Geological
<br />Survey Professional Paper 475-C, p. C206-C208.
<br />Fathi-Maghadam, M" and Kouwen, N" 1997, Non-rigid,
<br />non-submerged, vegetative roughness on
<br />floodplains: American Society of Civil Engineers,
<br />Journal of Hydraulic Engineering, v, 123, no, I,
<br />p, 51-57.
<br />Garrett, J,M" and Gellenbeck, DJ., 1991, Basin
<br />characteristics and streamflow statistics in Arizona
<br />as of 1989: U,S, Geological Survey Water-
<br />Resources Investigations Report 91-4041, 612 p,
<br />Hirschboeck, K.K., 1985, Hydroclimatology of flow
<br />events in the Gila River basin, central and southern
<br />
<br />Summary 27
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