Glossary of Common Watershed Protection and Stormwater Pollution Prevention Terms


Backfill – Earth refilling a trench or an excavation

Berm – An earthen mound used to direct flow of runoff around or through a structure.

Buffer strip or zone – Strip of erosion-resistant vegetation between a waterway and an area of more intensive land use.

Catch Basin – Curbside opening that collects rainwater from streets and serves as an entry point to the storm drain system.

Conduit – Any pipe for collecting and directing stormwater.

Conveyance system – Any channel or pipe for collecting directing stormwater.

Culvert – A covered channel or a large-diameter pipe that directs water flow below ground level.

Denuded – Land stripped of vegetation or land that has had its vegetation worn down due to the impacts from the elements or humans.

Discharge – The release of stormwater or other substance from a conveyance system or storage container

Erosion – The wearing down of land surface by wind or water. Erosion occurs naturally from weather or runoff but can be intensified by land-clearing practices related to farming, residential or industrial development, road building, or timber-cutting.

Excavation – The process of removing earth, stone, or other materials, usually by digging.

Filter fabric – Textile of relatively small mesh or pore size that is used to (a) allow water to pass through while keeping sediment out (permeable), or (b) prevent both runoff and sediment from passing through (impermeable).

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.

Grading – The cutting and/or filling of the land surface to a desired slope or elevation.

Gutter – The edge of a street (below the curb) designed to drain water runoff from the streets, driveways, parking lots, etc. into catch basins.
Hazardous substance – 1. Any material that poses a threat to human health and/or environment. Typical hazardous substances are toxic, corrosive, ignitable, explosive, or chemically reactive. 2. Any substance named by EPA to be reported is a designated quantity of the substance is spilled in the waters of the United States or if otherwise emitted into the environment.

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 activity or event which results in a release, leak, flow, escape or the placement of any material other than rain water (including liquids or solids) into the storm drain system.

Illicit connection – Any connection to the storm drain system that is not permitted: or any legitimate connection that is used for illegal discharge.

Illicit discharge – Any activity or event that results in a release, flow, spill, escape or disposal of any material other than rainwater (including liquids or solids) into the storm drain system.

Inlet – An entrance into a ditch, storm drain, or other waterway.

Material storage areas – On site locations where raw materials, products, final products, by-products, or waste materials are stored.

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.

Non-stormwater discharge – Any discharge to municipal separate storm sewer that is not composed entirely of storm water. Discharges containing process wastewater, non-contact cooling water, or sanitary wastewater are non-stormwater discharges.

Oil sheen – A thin, glistening layer of oil on water.

Organic pollutants – Substances containing carbon which may cause pollution problems in receiving waters.

Organic solvents – Liquid organic compounds capable of dissolving solids, gases, or liquids.

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.

Permeability – The quality of a soil that enables water or air to move through it. Usually expressed in inches/hour or inches/day.

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.

Pollutant – Generally, any substance introduced into the environment that adversely affects the usefulness of a resource.

Precipitation – Any form of rain or snow.

Retention – The storage of stormwater to prevent it from leaving the development site; may be temporary or permanent

Runon – Off-site flows which flows onto your site.

Runoff – Water originating from rainfall and other sources (e.g., sprinkler irrigation) that is found in drainage facilities, rivers, streams, springs, seeps, ponds, lakes, wetlands, and shallow groundwater.

Scour – The erosive and digging action in watercourse by flowing water.

Secondary containment – Structures, usually dikes or berms, surrounding tanks or other storage containers and designed to catch spilled material from the storage containers.

Sedimentation – The process of depositing soil particles, clays, sands, or other sediments that were picked up by runoff.

Sediments – Soil, sand, and minerals washed from land into water usually after rain, that pile up in reservoirs, rivers, and harbors, destroying fish-nesting areas and clouding the water so that needed sunlight might not reach aquatic plants. Careless farming, mining, and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

Significant materials – Include, but not limited to, raw materials; fuels; materials such as solvents, detergents, and plastic pellets; finished materials such as metallic products; raw materials used in food processing or production; hazardous substances designed under Section 101(4) of CERLCA; any chemical the facility is required to report pursuant to Section 313 of Title III or SARA; fertilizers; pesticides; and waste products such as ashes, slag and sludge that have the potential to be released with stormwater discharges.

Significant quantities – The volume, concentrations, or mass of a pollutant in stormwater discharge that can cause or threaten to cause pollution, contamination, or nuisance, that adversely impact human health or the environment, and cause or contribute to a violation of any applicable water quality standards for the receiving water.

Source control – Action to prevent pollution where it originates.

Source control BMPs – Everyday operational practices that prevent pollution by reducing potential pollutants at the source.

Spill guard – A device used to prevent spills of liquid materials from storage containers.

Storm drain system – A vast network of pipes and open channels designed for flood control, which discharges straight to the ocean.

Stormwater – Precipitation 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.

TMDLs – Total Maximum Daily Loads – A TMDL sets a limit for the total loading of a particular pollutant, such that the pollutant loads from all sources will not impair the beneficial uses designated for the water body.

Watershed – An area of land that drains water or runoff to a single point. For example, the watershed of the Ventura River would be the surrounding neighborhoods and natural terrain.


Glossary of Common Green Infrastructure Terms

Bioswale – a landscape element, often a vegetated shallow depression, designed to manage surface water runoff by removing silt, filtering pollutants, and increasing rainwater infiltration (A bioswale conveys water as opposed to an infiltration basin which retains it.)

Curb Cut – a cut in the street or parking lot curb used to redirect water from flowing in a gutter to instead enter a vegetated median, vegetated parkway, grassed areas, rain gardens or bioswales which allow infiltration.

Downspout Disconnection – is the process of disconnecting roof downspouts from the sewer system and/or the storm drain and redirecting roof runoff onto pervious surfaces, commonly a lawn, bioswale or rain barrel.

Green Roof (or Living Roof) – is the roof of a building that is partially or completely covered with vegetation and soil & planted over a waterproofing membrane. (Not considered a true water saving option in our area because they require irrigation during dry months.)

Green Street and/or Alley – are created by integrating green infrastructure elements such as bioswales, permeable pavement and planter boxes into the design.

Heat Island Effect – the effect of built-up urban areas being hotter than nearby rural areas. Urban greening and shade trees reduce Heat Island Effect.

Infiltration Basin – is a basin or shallow pond solely used to capture storm water runoff and infiltrate through permeable soil to replenish groundwater aquifers. (An infiltration basin which retains water as opposed to a bioswale which conveys water.)

Land Conservation – the act of protecting large natural open spaces to mitigate storm water runoff & flooding, and preserve the natural functions, beauty, and benefits to water, air and wildlife open space provides.

Land Conservation Easements – a voluntary legal agreement between a landowner and a land trust or government agency that permanently limits uses of the land or part of their land in order to protect its conservation values.

Permeable Pavement – is paving made with porous materials and allows stormwater to filter through it.

Rain Barrel – is a container or tank used to collect and store rainwater captured by diverting runoff from catchment areas (roofs) via rain gutters.

Rain Garden – is a planted depression that allows rainwater runoff from impervious area, like roofs, driveways, parking lots, and compacted lawn areas, to flow into the depression and gives the rainwater the opportunity to be absorbed. Rain gardens are often put in place by homeowners in place of a lawn or on a part of their property.

Rainwater Harvesting – is a technique used for collecting, storing and using rainwater for landscape irrigation and other non-potable uses. The rainwater is collected from various hard surfaces such as rooftops and/or other man-made above-ground hard surfaces.

Urban Tree Canopy – is the layer of leaves & branches of trees that cover/shade the ground when viewed from above.