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<br />, <br /> <br />.. <br /> <br />. <br /> <br />\ <br /> <br />IOQ\e 8oo1ies to t~p calculation of tile split flnw~. The sllort~r th.. sDlit flow <br />reaches an~ the ad~itional cross sections ~efining tltem, t~ more accurate will <br />be tile calculatl!!d outflows and water surface elevations. <br /> <br /> <br />The effect of subdividinq a split flow reaeh and a~~ition of cross sections <br /> <br /> <br />can be s~n in tile followinq example. Figure 2 shows a prOfile Dlot af a stream <br /> <br />an~ a split flow rpach which lias a total reaeh length of 1000 feet. The split <br /> <br /> <br />flnw reaeh was modeled in four ~ifferent ways. The first mod<ol represented the <br />split flnw reacll as a ~inqle lOOO foot long reaell. The s..con~ mon..l divided the <br />split flow reach into two 500 foot reac~es. Th~ third model divi~ed the sp~it <br />flow reach into four 250 foot reache" and the fourth ~l ~iyided it into ten <br />100 foot reaclles. Note that each reach has a cross section defining it upstream <br /> <br />and dOwnstream. Additional cross seetions must he us'" hecause the split flow <br /> <br /> <br />discharqes are calculate~ based on a lin~ar int..epolation of the upstream and <br /> <br /> <br />~~tr"am cross section water surface or en~rqy elevations. The effect of <br /> <br /> <br />~ivi~inq up the sDlit. flnw rl!ach into shorter an~ shorter segments, ls to <br /> <br />or~lIce answers which ar.e mor~ aecurate. The results from the~e four models are <br /> <br /> <br />presented on Floure 3, whieh shows plots of the flow in the main riv<'!!r -vs- <br /> <br /> <br />river ~istance. The results cl~arlv show tllat the 1000 foot reaeh shoul~ be <br /> <br /><'Ilyi<'led <br /> <br />into <br /> <br />shorter <br /> <br />reaches. <br /> <br />The <br /> <br />fourth <br /> <br />model produced the most accurate <br /> <br />results, that the secon~ an~ <br /> <br />results, but it is also clear from the plotted <br /> <br />thir<'l models gave acceptable results. <br /> <br /> <br />The examole also shows that the upstream portion of a uniform split flow <br /> <br /> <br />reacll should be diyi<'led into shorter seqments than thl!! ~~stream portion, <br /> <br /> <br />hecause a larger proportlon of the flow will he lost on the upper portion. <br /> <br />l3 <br />