Drainage Design Manual, Hydrology - Flood Control District of ...

Drainage Design Manual for Maricopa County
Hydrology: Unit Hydrograph Procedures
Table 5.1
RUNOFF HYDROGRAPH
Hydrograph
Translation, Instantaneous, Runoff,
Time (I) (O) (U)
Increment minutes cfs cfs cfs
(1) (2) (3) (4) (5)
1 5 9.7 2.8 1.4
2 10 82.3 25.9 14.3
3 15 234.7 86.4 56.1
4 20 393.3 175.4 131.9
5 25 416.2 245.2 210.3
6 30 304.9 262.6 253.9
7 35 123.4 222.2 242.4
8 40 32.7 167.2 194.7
9 45 0.0 118.7 143.0
10 50 0.0 84.3 101.5
11 55 0.0 59.9 72.1
12 60 0.0 42.5 51.2
13 65 0.0 30.2 36.3
14 70 0.0 21.4 25.8
Notes:
1. Δt = 5 minutes
2. R = 15 minutes
3. C = 2Δt/(2R + Δt) = 0.29
4. Assume O i-1 for increment 1 = 0.0
Notice that the Clark Unit Hydrograph itself was never developed per se, but the three principles
of the unit hydrograph were applied directly (mathematically) to the rainfall excess without performing
graphical superposition of ratios of a unit hydrograph. Computationally, this process can
be completed very quickly and conveniently with a computer program such as HEC-1.
August 15, 2013 5-9