FLOOD09224

• County: Statewide
• Basin: Statewide
• Title: Steep Channel Water Surface Profiles
• Date: 7/1/1971
• Prepared By: CSU
• Floodplain - Doc Type: Educational/Technical/Reference Information

43

established, the assumption is made that flow at the section under

solution is governed by properties of that section. This allows

computations to proceed, based On an empirical equation,

Q=CAHm
s '

for flow through the section. Computations return to the Standard

Step Method when an energy relation between sections can be established.

Accuracy of solution is adequate for design and planning purposes.

In reaches where the Froude number ranges up to approximately 0.9

with an average depth of 7.5 feet, the mean deviation of the computed

from the measured profile is 0.65 feet. Stated another way, the

computed profile is accurate to I9%. Where the Froude number (calcu-

lated from measured flows) ranges from 0.9 to 1.5, the mean deviation

from an average depth of 12.5 feet is 1.36 feet. For this range of

Froude number, the computed profile is accurate to Ill%.

The three major accomplishments of the PR~FILE program are: (1)

the ability to compute a reasonable continuous water surface profile

for flows near critical; (2) ease of changing input data on cross-

sectional stationing, roughness and discharge; and (3) immediate

utility of output. Output is listed on a tabular form under headings

for water surface elevation, discharge, velocity head, friction head

loss, eddy head loss, mean velocity, elevation of energy grade line,

accuracy of solution, Froude number and roughness.

For utility in modeling various stream geometries, stations can

be freely added or subtracted in either the longitudinal stationing

sequence or any of the cross-sectional stationing sequences, up to the

limit of stations (100 stations along the thalweg). Roughness in a

reach may be altered by changing one roughness card for the reach.