The various concern related rainfall runoff have been included

1. Rainfall-Runoff
Rainfall-Runoff Modeling
Watershed
Rainfall Runoff
Rainfall-Runoff
Model
Rainfall Runoff

2. Rainfall-Runoff
Modeling Considerations
• Development of a rainfall-runoff model depends on
(1) Time scale
(2) Basin scale
For larger time scale (month, year, or longer)
Runoff = f(Rainfall); VQ = g(VRain)
For shorter time scale (eg. Storm events)
Runoff Hydrograph = f( Rainfall Hyetograph)
Q(t) = f [ I(1), I(2), …, I(t) ]

3. Rainfall-Runoff
Rational Formula
• First proposed by Kuichling in 1889
• Qp = k C i A
where k = unit conversion factor,
1.008 for English unit; 0.278 for metric unit
Qp = peak discharge (ft3/s or m3/s);
i = rainfall intensity (in/hr or mm/hr)
A = drainage area (acres or km2)
• Note: i = average intensity of rainfall corresponding to the
duration of time-to-concentration.

4. Rainfall-Runoff
Time-of-Concentration
• Definition:
• It is an elusive hydrologic variable and it is very difficult to
measure.

5. Rainfall-Runoff
Time-of-Concentration Methods (1)

6. Rainfall-Runoff
Time-of-Concentration Methods (2)

7. Rainfall-Runoff
Time-of-Concentration Methods (3)

8. Rainfall-Runoff
Comparison of
Time-of-
Concentration
Models

9. Rainfall-Runoff
Time-Area Method
• Can be considered as an extension of the rational method
in which rainfall intensity in not uniform over the storm
duration

10. Rainfall-Runoff
Time-Area Method (Eg. 1)

11. Rainfall-Runoff
Time-Area Method (Eg. 2)

12. Rainfall-Runoff
Time-Area Method (Eg. 3)

13. Rainfall-Runoff
Time-Area Method (Eg. 4)