I am designing a storm sewer system and currently have a structure with 3 upstream pipes (7-1 to 7-2, 7-10 to 7-2 and an existing pipe carrying 30 cfs to 7-2 which I input into the system as a link base flow discharge to my inlet node). When I run calculations and produce a report I'm left with these calcs shown below:
| DRAIN. | RUNOFF | CA | INLET | RAIN | RUNOFF | |||
| FROM POINT | TO POINT | AREA | COEFF. | INCRE- | ACCUM- | TIME | FALL | Q |
| REFERENCE | REFERENCE | "A" | "C" | MENT | ULATED | |||
| Ha | Minutes | mm/Hr | CMS | |||||
| 7-1 | 7-2 | 0.140 | 0.900 | 0.126 | 0.260 | 6.78 | 136.63 | 35.51 |
| 7-10 | 7-2 | 1.034 | 0.620 | 0.641 | 6.770 | 14.83 | 4.20 | 28.41 |
| 7-2 | 7-8 | 0.003 | 0.900 | 0.003 | 7.032 | 14.92 | 13.29 | 123.50 |
My questions on the calculations:
1) How is GEOPAK coming up with an intensity of 136.63 in/hr?
2) If you just add the runoff from the 3 pipes (35.51+28.41+30 cfs) you come up with 93.92 cfs or if you take the CA of the last link time the intensity of the last link (7.032*13.29=93.49 cfs). So how is GEOPAK computing the runoff to be 123.50?
When I looked at this closer and realized something was amiss, I removed the 30 cfs link base flow discharge and reanalyzed the network. Mind is now blow that it shows the flow at 93.50 cfs (but without the 30 cfs it should be closer to 63 cfs)??
Any help on this would be greatly appreciated.
Thanks,
Matt