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step 5 - The discharge for the trapezoidal spillway based on critical depth is determined from the basic equation: v2 A where V = average velocity, A = area, T = top width 2g m ~ By a trial aDd error solution a depth of flow ("n") can be determined which will satisfy the above equation aDd provide an energy head which is equal. to "HE" from Step 3. This solution is accomplished as follows: First, a velocity head ("HV") of 30 percent of "HE" is assumed. Then the depth (HE minus HV), the top width, the area, the computed velocity head, aDd the computed energy head are determined. The act,ual aDd com- puted energy heads are then cc:mpared aDd if not within one tenth of a percent of the energy head the velocity head is assumed. again as half- way betYeen the assumed aDd computed velocity heads; if they are wi thin the allowable error the tailwater elevation ("APEL" + "n") aDd dis- charge (Q = AV) are computed. Step 6 - If variable "INDCON" = 0, proceed to Step 7. If equal to 10, the next step is to compute the discharge from the conduit or sluice. This is accomplished by first calculating the free flow discharge by Q - c..J1f where C = the coefficient of discharge (read in), H is the head causing discharge which for freeflow discharge is equal. to the current elevation ("ELEV(I)") minus the centerline of pressure ("CLIImP"- read in). The submergence is then calculated (by trial aDd error) by the same equation except the head is the difference between the "ELEV(I)" aDd the tailwater. The tailwater is calculated by table look using the conduit discharge only or both the spillway aDd conduit discharge (as determined by variable "ISPCTW" ). The total discharge is then calculated by adding the spillway and conduit discharges. Step 7 - The above procedure (Steps 3 - 6) is repeated for each elevation in the ELEV(I) table up to "ELTOP" (see Step No.2) unless a tailwater table look up of the spillway discharge limits the spillway discharge rating to an elevation below "ELTOP". , Step 8 - When the spillway rating has been completed, the computer starts the flood routing of the spillway design flood.. This routing is described starting with Step 9 :if variable "ITYSP" = 10. If the vari- able = 0, the flood. routing will be made as described in paragraph 3. Basical1;y, t):1e assumed. outflow will be determined according to the pool elevation assumed. Then the reservoir pool elevation will be computed using a trial aDd error method. by computing charge for the assumed. reservoir elevation, the reservoir capacity based on the assumed release, aDd the computed pool elevation. A new reservoir pool eleva- tion is assumed until the assumed and computed pool elevations are within .005 of a foot. This routing is made for each inflow until the last inflow is completed. With variable "ITYSP" = 0, the next step is No. 10. 9 '"