53:078 Principles of Hydrology (Spring 2004)
Problem #21
Unit Hydrograph Derivation by the Single Event Method
For an extreme rainstorm on a 23.9 mi2 catchment, hydrograph analysis
produced the following rainfall excess hyetograph and direct runoff hydrograph:
| Time (hours) |
0-3
|
3-6
|
6-9
|
9-12
|
| Pe (inches) |
0.00
|
0.29 |
0.36
|
0.00
|
| Time (hours) |
0
|
3
|
6 |
9 |
12 |
15 |
18 |
21 |
24 |
27 |
30 |
33 |
36 |
| DRH (cfs) |
0
|
0 |
340 |
970 |
700 |
492 |
347 |
229 |
130 |
73 |
42 |
19 |
0 |
Use this information to compute the following:
- Compute the unit hydrograph by the single event method.
- Determine the effective duration tr (hour) of the unit
hydrograph and justify your answer (one or two sentences).
- Check the result
by comparing (1) the actual rainfall excess pattern for the storm after
rescaling by rd, and (2) the true rainfall excess pattern for
a tr-UH (with tr as determined in part b.)
Last changed on
03/31/04
by aab.