About this metric

impervious runoff from hardtops

For impervious surfaces (e.g. asphalt, cement, and buildings) runoff is calculated as the difference between the surface water inputs and the sum of actual evaporation and the change in the soil water store.

Impervious runoff = surface inputs - evapotranspiration + change in impervious storage

Used to calculate: runoff into streams, stormwater drainage and floodwaters

Depends upon:

—Parameters: proportion of impervious water storage filled - initial conditions and proportion of wastewater piped

—Other metrics: ecosystem area, sewage from people, water used outside, rainfall and evapotranspiration

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