Laserfiche WebLink
<br />b. A tail.water curve must be read into the computer. This tail.- <br />water rating curve will be used to compute the submergence (caused by <br />the conduit and spillway discharge) of the conduit or Bl.uice if vari- <br />abl.e "ISPC'l'W" is equal. to zero. If ISPCTW = l.0, the conduit discharge <br />only will be considered in computing submergence. The tail.water for <br />the spillway can be the tail.water curve read in or, if the tail.water <br />is not dependent upon downstream conditions but on the spillway apron <br />el.evation (such as a high l.evel. s8ddl.e spillway), the tail.water can be <br />computed by the specific energy equation assuming a l.0 percent l.oss o:f <br />energy going over the weir. With variabl.e "ISPITW" = 0, the spillway <br />taUwater is the tabl.e that was read in, but if the variabl.e = l.0 the <br />tail.water is based on the specific energy equation. <br /> <br />, <br /> <br />! <br /> <br />c. The abutment contraction coefficients (for various val.ue of <br />HE/lID) are read into the computer al.ong with other values which are <br />stored in tabl.e form. The coefficients normally used are for adjacent <br />earthen embankment sections as shown in the Waterways Experiment Charts <br />lll.-3/2; however, adjacent concrete section coefficients using ZKA = <br />0.1 at HE/lID = 1.0 based on WES l.ll-3/l. can be used by setting IABCOA <br />equal. to ten. <br /> <br />d. This progrllDl will also compute a spillway rating curve for a <br />trapezoidal. (or rectangular) spillway based on critical. depth control. <br />at the weir. This rating woul.d be appllcabl.e to a spil.lway with a <br />minimum control. section where the approach depth was less than 10 per- <br />cent of the design head, where the spillway apron el.evation was only <br />a foot or two below the spillway crest el.evation and where the exit <br />channel. was sloped at a grade greater than the critical. slope. The <br />critical depth rating at the weir can be adjusted due to approach losses <br />by the same routine as the ogee rating. (See paragraph 4, step 3). <br /> <br />e. The flood routing portion ct: this program uses either a storage <br />indication routing for uncontrolled spillways or for projects with no <br />induced surcharge, or it uses a routing based on gate schedule curves. <br /> <br />f. The storage indication routing procedure for uncontrol.led <br />spillways only makes releases equal. to the freeflow discharge when <br />the elevation is greater than the top of the induced surcharge pool <br />"ELTSUR", (ICASE=l). When the pool elevation is below the spillway <br />crest a release equal to "QMINl" is made (ICASE-14) and when the <br />pool is above the crest elevation but below the elevation of "EISURO" <br />a release of QMIN2 is made (ICASE=15). When the pool is between <br />"EISURO and ELTSUR" (ICASE=13) a release is made which includes the <br />freeflow discharge of the spillway if any, plus a conduit release <br />which is interpolated between the freeflow discharge at elevation <br />"ELTSUR" and the desired conduit release at "EISURO". These cases <br />are sUllllllllrlzEd in Tabl.e 2, and are shown graphically on Exhibit 3. <br /> <br />2 <br /> <br />...... <br />