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

37

.

program, it appeared that the values of roughness generally had to be

modified upward in order to compensate for some energy losses in bends
and contractions. For example, a shift in the value of Manning's "n"
from 0.027 to 0.031 seemed adequate to compensate for form losses.
Due to the inability of this program to handle calculations for flows

with Froude numbers higher than about 0.7, it proved impractical to

attempt a computation series with it, even though it did yield a good

comparison, after roughness adjustment, to flow profiles at lower

Froude numbers (0.1 - 0.6).
The USBR program, since it contained a computation routine

for flow near critical, proved applicable for profile determination

in some sub-reaches. However, conditions such as steep chutes or

drops caused such larg~ energy losses that the program's computation

scheme was not adequate to continue calculations through the energy

change. Consequently, the only method of obtaining a profile along

the total reach length was to apply the program to sub-reaches of

tolerable energy change, then combine results of profiles for the

sub-reaches.

An attempt was also made to determine the suitability of the USCE

program to the mountain stream. The program had been originally

prepared for execution on a CDC 6600 computer with storage in excess

of 65,000 addresses, so several attempts were made to adapt it to the
available CDC 6400 computer. The lack of success of these attempts,

in addition to complexities in data preparation, resulted in no

evaluation of the USCE program.

The check run on program PR$FILE indicated that the program

provided a reasonable means for computation of water surface profiles

.

.

;

.