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<br />5 <br /> <br />Limitations <br /> <br />The program developed may be applied to evaluations of flow <br /> <br />characteristics over a wide range of channel slopes. Since the method <br /> <br />is primarily a modeling tool for evaluation of changes in geometry, <br /> <br />more sophisticated techniques for evaluation of flows on overbanks, <br /> <br />around levees and under bridges are not included. Such techniques are <br /> <br />available in other programs. The primary feature of this program is a <br /> <br />calculation technique for flows near critical and for significant <br /> <br />changes in energy levels between adjacent stations. This program should <br /> <br />not, however, be applied to any stream without due regard for slope and <br /> <br />other channel characteristics. Flows in natural streams with rapidly <br /> <br />changing beds, such as braided streams under relatively high flows, can- <br /> <br />not be adequately described in program data entry. <br /> <br />Where flow is not near critical and the water surface elevations <br /> <br />are calculated by an energy balance, the conditions and assumptions made <br /> <br />for the analysis of gradually varied flow must be satisfied. These are <br /> <br />as follows: <br /> <br />A. Acceleration effects are small. <br /> <br />1. Flow is steady - the hydraulic characteristics of flow <br /> <br />remain constant at a section for the time interval under <br /> <br />consideration, while depth between sections varies <br /> <br />gradually. <br />2. The stream lines are practically parallel - hydrostatic <br /> <br />pressure distribution prevails over the channel section. <br /> <br />B. The head loss at a section is the same as it would be for a <br /> <br />uniform section, where velocity and hydraulic radius are the <br /> <br />same between the uniform and natural sections. <br />