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

18

.

electronic computer. A brief review of the more salient points of some

of the computer oriented solutions currently in use for solution of

water surface profile problems follows. At least three United States

Governmental agencies have developed computer programs to fit their

particular needs. In addition, at least two other programs developed

by individuals are known to exist.

Governmental agencies which have developed computer methods for
water surface profile solution include the Geological Survey (USGS),
the Corps of Engineers (USCE) and the Bureau of Reclamation (USBR).
The USGS program incorporates the Standard Step Method. As in the
longhand calculation using this method, a step-wise s?lution becomes
impossible at critical flow. Since the method depends upon slope of
the water surface, and since this slope becomes theoretically infinite
as flow passes through critical, it becomes impossible to achieve an
energy balance between sections when flow is near critical. The USGS

Program is not equipped with any computational device to handle situa-

tions near the critical flow, so such situations cause the program to

stop. If the channel has any significant contractions or expansions,

the program may be prone to indicate a higher energy condition than

would actually prevail in the real case. In some cases, a condition near

critical may be indicated where it does not actually exist. This is due
to no provision having been made for contraction losses. However, if the

channel is fairly uniform and has tranquil flow at all discharges of

interest, the USGS program does a very good job. Data entry is fairly

easy--although it could be simplified--and output is concise and

readable. The strongest point of this program is its potential for

.

,

,

.

.

.