FLOOD05580

• County: Statewide
• Basin: Statewide
• Title: HEC-2 Water Surface Profiles - Users Manual
• Date: 11/1/1976
• Prepared For: US
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

WATER-SURFACE PROFILES

THE HYDROLOGIC ENGINEERING CENTER
COMPUTER PROGRAM 723-X6-L202A

1. ORIGIN OF PROGRAM

This program is a modification of program 723-G2-L2l4A, developed in The
Hydrologic Engineering Center, Corps of Engineers, 609 Second Street, Davis,
California by Bill S. Eichert (1964 version of 723-G2-L214A was from the
Tulsa District by same author). The input requirements have been modified
to allow the use of many additional options, to provide for future expansion
and to simplify input preparation. A supplementary program (723-Gl-L202B)
is available to convert data from the old program 723-G2-L2l4A to the new
program. Other changes have been made to increase the program's flexibility
to handle a wide variety of water surface profile problems, A data edit
program (723-Gl-L202C) which reads the data cards for program 723-X6-L202A
and checks the data for various input errors is also available.

2, PURPOSE OF PROGRAM

The program computes and plots (by printer) the water surface profile for
river channels of any cross section for either subcritical or supercritical
flow conditions. The effects of various hydraulic structures such as
bridges, culverts, weirs, embankments, and dams may be considered in the
computation, The principal use of the program is for determining profiles
for various frequency floods for both natural and modified conditions,
The latter may include channel improvements, levees and floodways. Input
may be in either English or Metric units,

3, DESCRIPTION OF EQUIPMENT

The program was written for use in the CDC 6600 computer but may be used
with minor modifications on other high-speed computers having four or more
magnetic tapes plus input and output units such as the I~~ 360, I~l 7094,
and GE 437, Various versions of the original program 723-G2-L214A can be
used on smaller computers such as the IBM 1620, GE 225, and IBM 1130,

4. DESCRIPTION OF PROGRAM

a, Basic Theory. The computational procedure is similar to !lethod I,
Backwater Curves in River Channels, Engineering Manual 1110-2-1409, U, S,
Army Corps of Engineers, 7 December 1959 (reference d). This method applies
Bernoulli's Theorem for the total energy at each cross section and Manning's
formula for the friction head loss between cross sections. In the
program, average friction slope for a reach between two cross sections
is determined in terms of the average of the conveyances at the two ends
of the reach (reference f). Other losses are computed using one of
several methods, The critical water surface elevation corresponding to
the minimum specific energy is computed using an iterative process.
Reference (a) describes this method in detail.