Rainfall Intensity And Their Formula - Civil Engineering

Monday, March 11, 2019

Rainfall Intensity And Their Formula

Rainfall Intensity

The rainfall intensity is the rate at which it is falling. It is expressed in cm / hr. It can be determined with the help of automatic rain gauges. 
Rainfall Intensity And Their Formula
Rainfall Intensity And Their Formula
The intensity of rainfall ig greater when shorter periods are considered while it is lower when large periods are considered.

Formula Of Rainfall Intensity

The intensity of rainfall (p) in mm/hr is given by the following general formula: 
p = 254a / (t+b) mm/hr
Where, t = Duration of storm in minutes, a and b are constants.

The following value of a and b are considered adequate
  • a = 30 and b = 10 when t is 5 to 20 minutes.
  • a = 40 and b = 20 when t is 20 to 100 minutes.

Duration of Rainfall

The duration of rainfall is the time for which rain falls with given intensity.

Frequency of Rainfall

The frequency of rainfall is the number of times it falls.
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