Written by Jerry Ratzlaff on . Posted in Geotechnical Engineering

Runoff, abbreviated as Q, is the water flow that occures on the ground surface when the soil is at full capacity from excess water from rainfall.


Runoff formula

\(\large{ Q =  \frac { \left( p \;-\; I_a \right)^2  } { P \;-\; a_i \;+\; S  } }\)   


 Units English Metric
\(\large{ Q }\) = runoff \(\large{ft^3}\) \(\large{m^3}\)
\(\large{ I_a }\) = initial abstraction, the amount of water before runoff \(\large{ft^3}\) \(\large{m^3}\)
\(\large{ S }\) = maximum soil moisture retention after runoff begins \(\large{dimensionlessa}\)
\(\large{ P }\) = rainfall \(\large{in}\) \(\large{mm}\)


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Tags: Equations for Soil Equations for Geotechnical