Quality of storm-water runoff from a residential area, Broward County, Florida

Rainfall, runoff, and water-quality information were collected in a 19.2-hectare single-family residential area in Broward County, Fla., between April 1974 and September 1975. During this period, 231 rainfall periods were recorded; 106 were large enough to produce runoff, and 30 were sampled for chemical analyses.

The fraction of rainfall that runs off is low, usually 5 to 10 percent. Several factors which combine to reduce runoff are the large area of pervious lawns (61 percent), the gentle slope of the area, and the use of grassy swales for routing storm water.

Bulk precipitation (rainfall plus dry fallout) quality is good by comparison to that of other metropolitan areas. As a consequence of the low runoff and the low concentrations of the bulk precipitation, loads for this residential area are small. Estimated annual load for chemical oxygen demand was 22.5 kilograms per hectare; total residue, 85.3 kg/ha; total nitrogen, 1.48 kg/ha; and total phosphorus, 0.21 kg/ha.