Best Management Practices (BMPs): New and innovative environmental practices designed to reduce the quantities of pollutants, such as sediment, fertilizers, animal wastes, etc. that enter nearby streams, lakes, wetlands, and groundwater through stormwater runoff.

Landscape element designed to remove silt and pollution from surface water runoff. A bioswale consists of a graded drainage course with gently sloped sides and filled with vegetation, compost and/or riprap.

Catchment Basin (Drainage Basin): An area of land, including water features and terrain, that conveys water into a single large body of water.

Channelization: An engineering technique used to straighten, widen, deepen or otherwise modify a natural stream channel.

Combined Sewer: A sewer designed to carry sewage on dry days, and a mixture of sewage and stormwater runoff on rainy days.

Combined Sewer Overflow: Discharge of a mixture of stormwater and domestic waste, occurring when the flow capacity of a sewer system is exceeded during rainstorms.

Confluence: The location at which two bodies of water intersect and begin to flow as one body of water stream.

Container Garden: Plants grown exclusively in containers or pots instead of in the ground.

Culvert: A conduit used to enclose a previously above-ground body of water. Culverts may be used to allow water to pass underneath a road, railway, or embankment or historically to bury polluted streams for public safety.

Drainage Divide: The rim of a drainage basin.

Drinking Water Treatment Plant/Facility: A place where chemical, physical or biological processes are used to clean groundwater or river water in order to make it safe for human consumption.

Ecosystem: A natural unit consisting of all plants, animals and micro-organisms in an area functioning together with all of the physical factors of the environment.

Effluent: An out-flowing of material from a manmade structure, usually in reference to wastewater from industry or human activity.

Erosion: The physical wearing away of soil or rock on the Earth’s surface, caused by wind, water, ice or other natural processes.

Evaporation: The conversion of water from a liquid to a gas.

Evapotranspiration: The sum of water released into the atmosphere via evaporation and transpiration.

Floodplain: A flat area adjacent to a body of water that serves to retain and disperse flood waters.

Green Roof:
A roof of a building that is partially or completely covered with vegetation and soil planted over a waterproofing membrane.

Groundwater: Water stored underground in pores and cracks in soil and rock. The depth underground where all of the pores are saturated is referred to as the water table.

Habitat: The area where a particular plant and/or animal community normally lives.

Hydrologic cycle: The continuous circulation of water between the sea, land and atmosphere.

Hydrology: The study of water in order to understand the Earth’s complex water systems.

Impervious Surface (Impervious Cover): Surface (such as pavement) that does not allow, or greatly decreases, the amount of infiltration of liquid into the ground.

Infiltration: The process by which fluids move into a substance through pores or small openings.

Intercepting Sewer (Interceptor): A sewer that is constructed parallel to a stream that is designed to catch the flow from all of the transecting sanitary and combined sewers approaching the stream and divert the contents to a treatment plant to prevent pollution of the stream.

Invasive Plants: Plants that do not originate from the ecosystem they are in and are likely to grow quickly and aggressively, spreading and displacing native plants.

Native Plants: Plants that were growing in a particular area before humans introduced plants from different places. These plants coexist in the ecosystem providing benefit and benefiting from other local species.

Non point-source Pollution: Pollution discharged into the environment from many different sources, as opposed to one single source. Stormwater runoff is a good example of non point-source pollution because it picks up different contaminants from various places as it flows over the ground.

Pathogen: An agent of disease. Pathogens can thrive in untreated water supplies.

Peak Flow: The maximum instantaneous rate of flow during a storm or other period of time.

Point Source (Point-source) Pollution: Pollution that is discharged from a single location.

Porous Pavement: A permeable pavement surface that overlays a permeable reservoir, which is designed to allow Infiltration of water to reduce runoff. Water is collected in the reservoir and then slowly seeps into the surround rock or soil.

Precipitation: The discharge of water in a liquid or solid state from the atmosphere.

Rain Barrel: A large container used to collect and store rain water that falls on a roof, runs into gutters and flows down the rain spout to the holding container.

Rain Garden: A depression in the land planted with water-loving plants that holds back stormwater and filters out pollutants, thereby reducing the detrimental affects of stormwater runoff.

Riffle: Choppy water in a stream cause by a sandbar or shoal lying just below the surface of the water.

Riparian: riparian Pertaining to the banks of a stream.

Riparian Buffer: A zone of vegetation that runs parallel to the banks of a body of water. Important for protecting water resources from non-point source pollution and to provide bank stabilization and aquatic and wildlife habitat.

Rooftop Garden: Any garden on the roof of a building. [See also Container Garden and Green Roof.]

Runoff (Stormwater runoff): Rainwater that does not infiltrate into the ground and flows over the land.

Sewer: A man-made, underground conduit which conveys, by gravity, sewage, stormwater runoff, or a combination of the two (sewage and stormwater runoff) away from a populated area to a nearby stream, often via a sewage treatment plant.

Sanitary Sewer: A sewer designed to carry human waste from homes and businesses to treatment plants.

Storm Drain (Sewer Inlet): An outdoor drain that conveys Runoff to a storm sewer or to a combined sewer beneath the street.

Storm Sewer: A sewer designed to carry stormwater runoff collected by outdoor storm drains and roof gutters to a body of water.

Sediment: Any particulate matter that can be transported by fluid flow and which is eventually deposited. Particulate matter generally originates from weathering of earth surfaces.

Sewage Treatment Plant/Facility: A place where physical, chemical and biological processes are used to remove contaminants and large particulates from wastewater so that it can be safely released back into the environment.

Stormwater (Rain water): Water that originates from precipitation or melting events.

Stream Bank (Streambank): The lateral confines of a natural waterway.

Stream Bank Stabilization: A vegetative or mechanical method of preventing erosion or deterioration of the banks of waterways.

Stream Corridor: The stream, its floodplains, and the transitional zone between the floodplain and surrounding landscape.

Surface Water: Water on the surface of the earth.

Topography: Describes the relative relief and position of the natural and man-made features on the earth’s surface.

Transpiration: The transfer of water from vegetation to the atmosphere through evaporation.

Tributary: A stream feeding a larger body of water.

Wastewater: Any water that is adversely affected in quality due to human activity. Generally applied to sewage, water mixed with human or industrial waste.

Watershed: All of the land that drains into a specific body of water.

Wetlands: Areas where the water table is close to or at the surface of the land or the land is covered by water.

Sources: C. Drew Brown, Glossary of Drainage Terms, W. B. Langbein and Kathleen T. Iseri, Science in Your Watershed: General Introduction and Hydrologic Definitions, Monday Creek Restoration Project