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<br />28 <br /> <br />length of channel where the flow can be more accurately described as <br /> <br />. <br /> <br />a series of reaches with tranquil flow, interspersed with a series of <br /> <br />rapid flow control sections. <br /> <br />. <br /> <br />The computational scheme which seems the most versatile and has <br /> <br />the greatest flexibility for the conditions encountered in steep, rough <br /> <br />mountain streams is the Standard Step Method, with proper account <br /> <br />. <br /> <br />taken of eddy losses, as well as friction losses. The Standard Step <br /> <br /># <br /> <br />Method is coupled with a method to carry computations through control <br /> <br />sections with rapid flow. A flow chart for such computations is shown <br /> <br />in Appendix A. The first requirement for the program solution, that of <br /> <br />the Ml and M2 curve types, is accomplished by a program which is <br /> <br />essentially the same as the USGS program. The computation is initiated <br /> <br />by determining depth as the difference between starting water surface <br /> <br />. <br /> <br />elevation, which is reaq in, and elevation of the channel invert. <br /> <br />Knowing depth, area is calculated and velocity determined by dividing <br /> <br />. <br /> <br />the given discharge by area. The channel elevation, depth and velocity <br /> <br />establish the initial energy conditions. The energy at the initial <br /> <br />section is compared to the energy at the next upstream cross-section, <br /> <br />subtracting out friction and other energy losses. Friction energy is <br /> <br /> <br />calculated from Manning's equation, in the form of S~/2 = ~ ' where <br /> <br />2/3 <br />Q is discharge and K is conveyance equal to 1.485/nAR Total <br /> <br />Sf + Sf <br /> <br />friction loss is calculated as h = L ( 1 2, h h is <br />f 2 J, were f <br /> <br /> <br />total head loss in the reach due to friction, L is reach length, <br /> <br />Sfl is friction slope at the downstream section and Sf2 is friction <br />slope at the upstream section. <br /> <br />. <br /> <br />Eddy losses are based upon a comparison of velocities at each <br /> <br />station. When calculations are proceeding in an upstream direction, <br />