Q/Qp Hydrographs
This method computes a hydrograph by using a dimensionless hydrograph template that has values for T/Tc versus Q/Qp. Time for any given ordinate can be computed by:
Any given ordinate flow can be computed by:
Q/Qp versus T/Tc
Example
Computing a Hydrograph Given Tc = 15 minutes Q = 60 cfs for the 100-year storm Compute A Q/Qp hydrograph Computing Hydrograph Solution
Hydrograph Time | Hydrograph Flow | ||
---|---|---|---|
T/Tc | T (min.) | Q/Qp | Q (cfs) |
0.00 | 0.00 | 0.00 | 0.00 |
1.00 | 15.00 | 0.15 | 9.00 |
2.00 | 30.00 | 0.20 | 12.00 |
3.00 | 45.00 | 0.28 | 17.00 |
4.00 | 60.00 | 0.44 | 26.00 |
5.00 | 75.00 | 1.00 | 60.00 |
6.00 | 90.00 | 0.34 | 20.00 |
7.00 | 105.00 | 0.27 | 16.00 |
8.00 | 120.00 | 0.19 | 11.00 |
9.00 | 135.00 | 0.12 | 7.00 |
10.00 | 150.00 | 0.00 | 0.00 |