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<br />, <br />1 <br /> <br />24 <br /> <br />The USGS program is intended for application to channels of mild <br /> <br />slope with considerable variation of roughness. No provision is made <br /> <br />for bend losses, as distance is specified by thalweg stationing only. <br /> <br />. <br /> <br />As mentioned previously, there is wide latitude for variation of <br /> <br />roughness across the channel; this feature would seem to make the <br /> <br />program particularly adaptable for use on braided channels, so long <br /> <br />. <br /> <br />as flow remains tranquil. Since this program uses total cross- <br /> <br />sectional flow area in calculations, it may not adapt well to areas <br /> <br />with relatively large portions of overbank flow. The requirements for <br /> <br />specification of number of stations in a cross-section and sequential <br /> <br />numbering of all data cards effectively limit this particular program <br /> <br />to analysis of one stream configuration only. <br /> <br />Of the programs reviewed, the USBR program is the most versatile <br /> <br />for its size. It contains approximately four times as many statements <br /> <br />as the USGS program, but it offers a considerable range of options. <br /> <br />. <br /> <br />The availability of a subroutine for flows near critical does not <br /> <br />restrict the program to channels of mild slope, although restrictions <br /> <br />of energy balance tolerances within the program prevent calculations <br /> <br />from proceeding if a solution Within the prescribed tolerance cannot <br /> <br />be attained (this is often the case for flow near critical). Stationing <br /> <br />is by thalweg stationing only, as in the USGS program. Roughness <br /> <br />is expressed for the main channel and each overbank, with a provision <br /> <br />for variation of roughness along the entire reach by use of a factoc. <br /> <br />Roughness can also be calculated if a profile for a given discharge is <br /> <br />available. The option for evaluation of sedimentation effects can be <br /> <br />used by specifying the elevation, at a cross-sectional station, to <br /> <br />which aggradation is anticipated. Flow under bridges is calculated by <br />