Rainfall-Runoff Rainfall-Runoff Modeling Watershed RainfallRunoff Rainfall-Runoff Model...
-
Upload
stanley-houston -
Category
Documents
-
view
269 -
download
9
Transcript of Rainfall-Runoff Rainfall-Runoff Modeling Watershed RainfallRunoff Rainfall-Runoff Model...
Rainfall-Runoff Modeling
WatershedRainfall Runoff
Rainfall-RunoffModel
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) ]
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.
Time-of-Concentration• Definition:
• It is an elusive hydrologic variable and it is very difficult to measure.
Time-of-Concentration Methods (1)
Time-of-Concentration Methods (2)
Time-of-Concentration Methods (3)
Comparison of Time-of-Concentration Models
Time-Area Method• Can be considered as an extension of the rational method
in which rainfall intensity in not uniform over the storm duration
Time-Area Method (Eg. 1)
Time-Area Method (Eg. 2)
Time-Area Method (Eg. 3)
Time-Area Method (Eg. 4)