Impervious Cover

land which cannot absorb rainwater, because something waterproof is on top of it.  E.g., streets, houses, etc.

For example, a concrete driveway is impervious cover, but a gravel driveway is not, because rainwater can pass through it and be absorbed by the earth underneath it.  Impervious cover usually results in less greenery, more gutters/sewers, and possibly more flash floods.