Why is stormwater regulated?
• Stormwater runoff from lands modified by human activities can harm surface water and, in turn, cause or contribute to an exceedance of water quality standards by changing natural hydrologic patterns, accelerating natural stream flows, destroying aquatic habitat, and elevating pollutant concentrations and loadings. Such runoff may contain high levels of contaminants, such as sediment, suspended solids, nutrients (phosphorus and nitrogen), heavy metals, pathogens, toxins, oxygen-demanding substances (organic material), and floatables. Nationwide, polluted stormwater runoff has been identified as a leading cause of problems in nearly 40 percent of surveyed U.S. waters, which currently do not meet water quality standards. Over land or via storm sewer systems, polluted runoff is discharged, often untreated, directly in local waters. When left uncontrolled, this water pollution can lead to the destruction of fish, wildlife, and aquatic life habitats; a loss in aesthetic value; and threats
