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# 2.1.3.2 Runoff Coefficient

The runoff coefficient is the ratio of the inflow rate, $$i\*Area$$, to the peak discharge rate, $$q\_{peak}$$. The coefficient will vary from storm to storm and is calculated with the equation:

$$C=\frac{Q\_{surf}}{R\_{day}}$$                                                                                                                                                              2:1.3.15

where $$Q\_{surf}$$ is the surface runoff (mm H$$*2$$O) and $$R*{day}$$ is the rainfall for the day (mm H$$\_2$$O).