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<br />20 <br /> <br />. <br /> <br />computational process indicates a water level near critical, the <br /> <br />critical elevation can be computed by a separate iterative process. <br /> <br />In the event of flow passing through critical, it is recommended that <br /> <br />the entire profile be computed twice, alternately assuming sub critical <br /> <br />and supercritical flow, then applying judgment by the field engineer <br /> <br />to the results to arrive at the most likely case for the water surface <br /> <br />profile. Options include that flow may be altered by a factor or by <br /> <br />substitution; roughness may be indicated or solved for, if a given <br /> <br />water surface profile is known; cross-sections and profiles may be <br /> <br />plotted. Due to the great number of options available in the program, <br />it is extremely lengthy--so much so that routine use for repetitive <br /> <br />calculations for variable crosS-sections proved to be impractical be- <br /> <br />cause of complex data entry. Conditions of roughness, sinuosity, <br /> <br />critical flow possibility, levees, interpolated sections, presence of <br /> <br />bridges and desired output plots must be specified for each section. <br /> <br />One very nice feature of the program, however, is the ease of entry for <br /> <br />roughness data. Entries are only required for initial roughness and <br /> <br />thereafter only for changes in roughness. Roughness is entered as <br /> <br />channel roughness, right overbank roughness and left overbank rough- <br /> <br />ness. The only provision available for variation of roughness with <br />stage is a multiplying factor, other than the variation due to overbank <br /> <br />flow at higher stages. Two distinct features of the USCE program relate <br /> <br />to handling of flood flows. For appropriate entries on conditions at <br /> <br />bridges and levees, the program will calculate flow conditions around <br /> <br />these obstructions; again, this tends to complicate data entry. Output <br /> <br />readability is, as complex as input; a reasonably good familiarization <br /> <br />with the program variables is required for interpreting output. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br />