Paving is common in urban areas and has a significant impact on infiltration and runoff.
When a Paved Area Fraction is specified, it is used as a linear scaling fraction for the Surface-Subsurface Leakage Coefficient. That is, the effective leakage coefficient is reduced by the Paved Area Fraction.
EffLeakCoef = (1-PAreaFrac) x SurfSubSurfLeakCoef
Note: Paving acts only as an extra reduction in leakage coefficient. It does not separate runoff from paved areas. Direct runoff from paved areas can be managed with the OL Drainage function.