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<br />13 <br /> <br />Z and conveyance K as a power function of depth. All integration <br /> <br />. <br /> <br />methods use tables for the varied flow function. The flow profile is <br /> <br />. <br /> <br />computed by analyzing the channel slopes and cross-sectior~l shapes <br /> <br />and then dividing it into a number of reaches. Reach length is calculat- <br /> <br />ed from known or assumed depths at the ends of each reach, using a <br /> <br />table of varied flow functions. <br /> <br />. <br /> <br />The step method divides the channel length into short reaches and <br /> <br />carries step-wise energy computations from one end of each reach to the <br /> <br />other. The direct step method applies Bernoulli's equation to adjacent <br /> <br />sections in a stream. Computation is started at a section where the <br /> <br />energy level is known or can be computed from section properties. This <br /> <br />energy level is then equated to energy at the next adjacent section, with <br /> <br />adjustments for energy changes between the two sections. The formulation <br /> <br />. <br /> <br />as illustrated in Fig. 2-3, can be expressed as: <br /> <br />. <br /> <br />vf <br />So x + d1 + 2g = dz <br /> <br />v2 <br />2 <br />+ 2g + Sfllx <br /> <br />(2-6) <br /> <br />Solving for IIx, <br /> <br />IIx = <br /> <br />E2 - El <br />So - Sf <br /> <br />liE <br />So - Sf <br /> <br />(2-7) <br /> <br />where <br /> <br />v2 <br />E=d+- <br />2g <br /> <br />Successive application of Eq. (2-7) yields the profile. This method <br /> <br />. <br /> <br />is a simple method applicable only to prismatic channels; however, <br /> <br />other methods have been developed which have a great range of flexi- <br /> <br />. <br /> <br />bility, both as to channel shape and plan. <br /> <br />, <br />