HR: 0830h
AN: NG51A-0839    [PDF]
TI: Froude-number based spatio-temporal scaling of braided stream channels
AU: Grant, G e
EM: grantg@fsl.orst.edu
AF: Forest Service Laboratory, Oregon State University, Corvallis, OR 97331-5506 United States
AU: Gupta, V K
EM: gupta@cires.colorado.edu
AF: CIRES, University of Colorado, Boulder, Boulder, CO 80309 United States
AB: The lifetimes, t, of individual channels in braided streams are known to be proportional to the square root of their lengths. Since the acceleration due to gravity, g, is constant, this combination L/t*t is clearly the same as obtained from the physically-based constraint that the Froude number, Fr, be a constant. Both observation and theory imply that bed mobility tends to limit supercritical flow, i.e., to reduce Fr to 1. This is associated with a tendency to optimize dissipation. A new result for the downstream particle flux as a function of particle size appears to give a concrete way to relate the length and time scales of Fr to channel lengths and lifetimes. Thus the basis for the channel scaling appears to be the tendency to optimize dissipation, and therefore sediment transport, in steep gradient channels with mobile beds.
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1860 Runoff and streamflow
SC: Nonlinear Geophysics [NG]
MN: 2003 Fall Meeting