FLOOD04828

• County: El Paso
• Community: Palmer Lake
• Stream Name: Arkansas River
• Basin: Arkansas
• Title: Palmer Lake Community File
• Date: 1/1/2001
• Prepared For: CWCB
• Prepared By: CWCB
• Floodplain - Doc Type: Community File

TO

OPTIONAL. FORM NO. 10
MAY IIlG EDITION
GS" FPMR (41 CFR) 10\-11.11

UNITED STATES GOVERNMENT

Memorandum

Code 4351 4016
SW Branch

'{'

Robert Jarrett. WRD

DATE: February 18, 1976

Through: District Chief, WRD, Lakewood' Colorado

FROM J. Davidian, Surface Water Branch
Mail Stop 415, Reston, Virgina

SUBJECT: WATER, SURFACE - Computations of Water-Surface Profiles in Open Channels

SOlO_l08

It was a pleasure to discuss with you, last Friday, the unusual control
situation you have in one of your step-backwater reaches. The approach
you suggested appears to be correct, and it shows considerable ingenuity.
congratulations. I suggest you discuss it with Merv Petersen before
proceeding. On my trip back to Reston, I thought of a way to simplify
it even more.

You have three different culverts situated far enough apart from each
other to consider them as separate entities. Break up the road abutment
between any two culvert openings on the basis of the adjacent gross-
opening areas. You will now have a separate channel for each culvert--
the pipe. the box, and the arch-type.

Rather than break up the road overflow into three parts, too, I suggest
you treat the entire roadway overflow in one section. Thus, you will
have only four distinct "channelsll rather than the six we discu~sed.
Compute the base rating for each "channel," and determine any submergence
effects as families of H4 curves for each.

For these four channels, you know that H4 must be the same for Ei!ach, and
that HI must be the same for each. You also know that:

Qpipe + Qbox + Qarch + Qroad

Qtotal

=

The proper subdivision of the total discharge, and the value of Hl will
all be simultaneously determined from the composite rating we discussed.

Insofar as calibrating the road-overflow section goes, I suggest you refer
for guidance to TWRI Book 3AS, pages 26-27, and to the attached material
by Matthai, "Computation of Discharge over Embankments--Highway and Railroad."

Merv Petersen can answer any questions that might arise. For sllbmerged-
road coefficients, you might refer to King's Handbook (page 4-18, fourth
edition, 1954).

I'll be in Denver again, March 1-5, and will be interested in how your
solution came out.

Attachment

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Copy to:

Regional Hydrologist, CR

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