# Rainfall-Runoff Modeling

## Presentation on theme: "Rainfall-Runoff Modeling"— Presentation transcript:

Rainfall-Runoff Modeling
Watershed Rainfall Runoff Rainfall-Runoff Model Rainfall Runoff 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) ] 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; 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. Rainfall-Runoff

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

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

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

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

Comparison of Time-of-Concentration Models
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 Rainfall-Runoff

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

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

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

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