Glossary of Stormwater Terms
Best Management Practices (BMPs): Good housekeeping solutions that include the proper handling, storage, and disposal of toxic materials to prevent stormwater pollution.
Catch basin: Curbside opening that collects rainwater from streets and serves as an entry point to the storm drain system.
First flush: The first big rain after an extended dry period (usually summer) which flushes out the accumulated pollutants in the storm drain system and carries them straight to the ocean.
Flood control channel: The open portion (often concrete-lined) of the storm drain system. Examples: Ballona Creek and the Los Angeles River.
Gutter: The edge of a street (below the curb) designed to drain water runoff from streets, driveways, parking lots, etc. into catch basins.
Household hazardous waste: Common everyday products that people use in and around their homes—including paint, paint thinner, herbicides, and pesticides—that, due to their chemical nature, can be hazardous if not properly disposed.
Illegal discharge: Any disposal into the storm drain system for which a person or business does not have a permit.
Illicit connection: Any connection to the storm drain system that is not permitted: or any legitimate connection that is used for illegal discharge.
Non-point source pollution: Pollution that does not come from a single, identifiable source. Includes materials that wash from roofs, streets, yards, driveways, sidewalks and other land areas. Collectively, this is the largest source of stormwater pollution.
Outfall: A flow of water from one drainage system into a larger system, or into a body of water like a lake, bay, or the ocean.
Point source pollution: Pollution from a single identifiable source such as a factory or a sewage-treatment plant. Most of this pollution is highly regulated at the state and local levels.
Source control: Action to prevent pollution where it originates.
Storm drain system: A vast network of underground pipes and open channels designed for flood control, which discharges straight to the ocean.
Stormwater: Rainwater that enters the storm drain system and empties into lakes, rivers, streams or the ocean.
Stormwater pollution: Water from rain, irrigation, garden hoses or other activities that picks up pollutants (cigarette butts, trash, automotive fluids, used oil, paint, fertilizers and pesticides, lawn and garden clippings and pet waste) from streets, parking lots, driveways and yards and carries them through the storm drain system and straight to the ocean.
Watershed: An area of land that drains water or runoff to a single point. For example, the watershed of the Los Angeles River would be the surrounding neighborhoods and natural terrain.
Back to Top
Program History | What is Stormwater Pollution? | Program Components |
Public Education | The Storm Drain System | FAQ’s | Pollution Abatement |
Federal Requirements | About the Staff | Newsletter | Hotline
Other City Environmental Links