Runoff

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