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

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Computation is done station by station. Initial energy conditions
may be specified by one of three ways: (1) critical depth (computed),
(2) known depth (specified) and (3) slope area method (estimated

initial energy slope). Computations may proceed in an upstream or

downstream direction, depending upon the wishes of the user. In

calculating sectional properties, main channel and overbank areas are

specified and the respective roughnesses for each of these channel

sections do not change until specified by a new roughness card. It

is possible to solve for these roughnesses by a knowledge of the water

surface elevation at each section and the relative magnitudes of the

roughnesses for the main channel and each overbank. During calcula-

tion, cross-sections may be altered by use of the previous cross

section, calculation of an intermediate cross-section or a vertical

encroachment on the channel. Flow in cross sections which traverse

levees may either be specified to be contained by the levees or to
pass on both sides of the levees. If flow goes past a bridge,

special provisions are made, depending on whether the flow is entirely

under the bridge, under the bridge and around the approaches or over

the bridge. Expansion and contraction losses are computed by

multiplying the difference in velocity heads by a constant. If

desired, graphical output of cross sections and profiles can be pro-

vided along the entire reach or any portion of it. The availability

of such a large number of options greatly increases the requirement

for control cards and program variables.

The USBR program (PSEUDO) is based upon USBR Method A for
computational procedure. As with the USCE program, eddy losses are

also calculated along with friction losses. Subroutines are included

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