Related to
agricultural runoff and
urban runoff,
suburban runoff is what you get when everyone in a
middle-class neighborhood decides to coat his or her
lawn in
fertilizers and
toxins. When it
rains, these
chemicals wash
downstream into the neighborhood's pretty
duck pond or the nearby
lake -- wherein
all biochemical heck breaks loose.
Fertilizer is good at making plants grow -- not only your grass, but also algae and miscellaneous even less tasty flora. Some of these are poisonous. Meanwhile, weed killer and insecticide will happily kill not only your crabgrass and Japanese beetles, but all manner of other plants and critters. That's why there are no ducks in the neighborhood duck pond.
Many of your neighbors, however, won't care that they have made the lake too toxic to swim in -- because there's a new health club in town with a big, sparkling blue, chlorinated swimming pool.