FLOOD05475

• County: Statewide
• Community: Nationwide
• Basin: Statewide
• Title: An Evaluation of Flood-Level Prediction using Alluvial-River Models
• Date: 1/1/1983
• Prepared By: National Research Council
• Floodplain - Doc Type: Educational/Technical/Reference Information

9

where
V = mean flow velocity
y = flow depth
a, b, and c = coefficients determined by means of regression analysis

The regression coefficients are determined either from field data or by
generating data using the Meyer-Peter and M'~ller formula and Einstein's bed-
load function for bed-load and suspended-load discharges, respectively. The
model does not take into account changes in bed-material composition.

5. Numerical Scheme:

KUWASER first solves (2-7) and (2-9) for a spatially-varied, steady flow
by means of the first order Newton-Raphson method. Equations (2-7) and (2-9)
are combined to yield the following expression for the sole unknown, flow
depth at section 2, O2:

2
Q2 a2
aC2g" O2

2
411X Q2
+ O2 -
2 a4 a6
K1 + 2K1a302 + a502
2
alVl
+ a6~ + z2 - HI = 0

.... (2-11)

where
Q2 = water discharge at section 2
Kl = conveyance at section 1
z2 = bed elevation at section 2
aI, a2' a3' a4' a5' and a6 = regression coefficients determined from field
data

Note that effect i ve depth and wi dth, cross-sect i on area, conveyance, and
velocity-head correction factor are all expressed in terms of power functions
of the thalweg flow depth, O. Once the backwater calculation is co""leted,
sediment-transport rates at all cross sections are co""uted from (2-10). The