7052

• UCREFRP Catalog Number: 7052
• Author: Andrews, E. D. and J. M. Nelson
• Title: Topographic Response of a Bar in the Green River, Utah to Variation in Discharge
• USFW Year: 1989
• USFW - Doc Type: American Geophysical Union
• Copyright Material: YES

r

Andrews and Nelson

473

MODEL INPUTS:
INITIAL CHANNEL PLANFORM
INITIAL CHANNEL TOPOGRAPHY
SEDIMENT SIZE
DISCHARGE OR ST AGEl
JISCHARGE AS A FUNCTION
OF TIME

flUID
DYNAMICAL
MODEL

ENGELUND.HANSEN
TOTAL LOAD
EauA TION

CAlCULATE

V.~, H-

NO

CHOOSE A I SUCH
THAT b.h<<h AND
CHANGE IN PLANFORM IS
SMALL. CALCULATE
NEW GEOMETRY.

III

Fig. 3. Iterative computation scheme.

in the Engelund-Hansen total load equation in order to obtain vector (Le.,
downstream and cross-stream) sediment fluxes over the bed. The divergence of
these fluxes yields the rates o( erosion and deposition on the bed. If the stage and
discharge are constant, the erosion and deposition on the bed are the only. temporal
changes. In this case, a time step is chosen such that the change in bed elevation is.
a small fraction of the flow depth at each point. This specified time step in
conjunction with the calculated erosion and deposition rates gives the predicted
channel topography after one time step has elapsed. The new topography is then
input to the flow model, and the entire procedure is repeated in an iterative manner.
If the stage and discharge also vary in time, the changes to the bed are
calculated from the erosion equation as above, and then the new channel
morphology is calculated using the "slicing" technique described above. In this
case, the time step chosen is such that both the change in bed elevation and the
change in planform due to stage variation are relatively small.