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<br />up the reservoir while the positive wave is being produced downstream <br /> <br />from the dam. The geometry of Cranks Creek Reservoir caused a critical <br />depth control to form near river mile 4 which restricted this negative <br />wave from developing upstream from that point during Condition II. For- <br />tunately, the amount of storage capacity upstream frOlll mile 4 was small <br />and could be neglected because the computer program did not perform <br />satisfactorily for Bupercritical flow. Therefore, the upstream boundary <br />was shifted down to mile 4 in the routing model and the calculations <br />continued with no serious error resulting from this simplification. <br />Dry Channel at the Upstream Boundary <br />In Conditions! and III, there was sufficient initial depth so <br />the negative wave could pass upstream from mile 4 without developing <br />transitions between supercritical and subcritical flow. However, <br /> <br />as strong negative waves would approach the upstream boundary. the <br /> <br />water depth would temporarily go to zero which, again. caused the <br />computer program to malfunction. Attempts to eliminate this problem <br />by specifying a minimum stage at the upstream boundary caused other <br />instabilities even though I-second computation intervals were employed. <br />Therefore, routings were terminated. In all cases, the peak flow had <br />passed Martins Fork Dam before routings terminated. <br />Initial Depth in the Channel <br />In all three cases studied, there was a substantial depth of water <br /> <br />downstream from Cranks Creek Dam. Otherwise, a hydraulic bore would <br /> <br />IS <br />