Glossary of Terms

Aquifer: An underground layer of permeable rock containing groundwater in a quantity great enough to be extracted for human purposes.

Berm: A constructed barrier of compacted, raised earth used to prevent and slow the flow of runoff.

Bioretention Cell: A landscaped depression designed to remove pollutants from stormwater runoff through infiltration.

Buffer: The vegetated area between a water body and adjacent land uses; provides soil stability, slows the flow of runoff, and improves water quality by filtering out pollutants.

Catch Basin: The underground pit beneath a storm grate that collects rainwater from streets and serves as an entry point to the storm drain system.

Channel: The natural path of water and sediment flowing within stream banks.

Cistern: A storage tank located above or below ground that holds rainwater for beneficial reuse.

Clean Water Act (1972): The federal environmental law governing water pollution, establishing goals to ensure that surface waters will meet the chemical, physical and biological water quality standards for their intended uses.

Culvert: A tunnel, pipe or other structure that allows water to flow under a roadway, railroad or other obstruction.

Detention: Temporarily collecting and holding stormwater runoff while slowly draining to another location.

Discharge: 1. A flow of liquids from a source; can be made up of washwater, sewage, stormwater, wastes, tap water, spring water or other sources. 2. A measurement of the volumetric rate of water flow over a period of time, usually expressed as cubic feet per second.

Downspout: A typically vertical pipe that carries rainwater from a roof gutter to the ground level.

Drainage: The natural or artificial process of removing excess surface and sub-surface water.

Drainage Basin: All the land, surface water, and underlying groundwater that drains to a given point; also known as a watershed.

Dry Pond: A depression that temporarily holds stormwater and releases it at a slower rate until it enters a stream or collection system. Also known as a "detention pond."

Easement: A right to use and/or enter a specified area of land owned by somebody else; granted to utilities or municipal governments to maintain equipment or infrastructure, or to other private parties for a specified use.

EPA: United States Environmental Protection Agency, a federal agency with the directive to protect human health and the environment.

Ephemeral: Flowing only during or immediately after precipitation.

Erosion: The process of detaching and moving soil from one location to another; caused by the action of wind, water, or other forces working on the earth's surface. 

FEMA: Federal Emergency Management Agency, a federal agency designated to coordinate the response to disasters that overwhelm the resources of state and local authorities.

Flooding: The rising and overflowing of a body of water, submerging land that is usually dry.

Floodplain: An area of land adjacent to a stream or river channel that is susceptible to natural flooding during periods of high discharge.

Grading: The cutting, filling or other alteration of the land surface to a desired slope or elevation.

Green Roof: A roof partially or completely covered with vegetation, designed to absorb and filter rainwater and provide other environmental benefits. 

Groundwater: Water stored beneath the earth's surface in soil pore spaces and fractures of rock formations, accessible for human use when stored in aquifers, and recharged from surface infiltration.

Habitat: The natural environment in which a particular type of plant or animal lives and grows.

Hardscaping: Man-made features used in landscape architecture, such as paved areas, retaining walls, and stairs.

Headwaters: The source of a stream, or point farthest upstream from the mouth or downstream confluence.

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: The release of any material into the stormwater conveyance system which is not authorized by the regulating body and/or contains pollutants or pathogens.

Impaired Waterbody: A body of water that fails to meet one or more water quality standards, such as pollutant concentration or loading.

Impervious Surface: A hard surface that prevents or slows the entry of water into underlying soil, or causes water to run off the surface in greater quantities or rates of flow as compared to natural conditions prior to development.

Infiltration: The process of water soaking into the ground from the surface, commonly referred to as percolation.

Infrastructure: The set of fundamental facilities, systems, and equipment serving an area for public benefit, such as roads, pipes, and buildings.

Inlet: A point where stormwater enters a stormwater conveyance system, such as a catch basin.

Intermittent: Generally maintaining flow seasonally, rather than year-round (perennial) or only after rain events (ephemeral).

Large Woody Debris (LWD): Large accumulations of logs, branches, and other wood that falls into streams or rivers and can influence the flow or shape of the stream channel.

Level Spreader: An erosion control device, such as a concrete lip, designed to mitigate the impact of high-velocity stormwater runoff by evenly distributing flow.

MS4: Municipal Separate Storm Sewer Systems, a collection of structures designed to gather stormwater and convey it to local streams or rivers.

Native Plants: Plants that occurred naturally in a region or habitat without human introduction.

NCDEQ: North Carolina Department of Environmental Quality, a state agency whose purpose is to protect North Carolina's environment and natural resources.

NPDES: National Pollutant Discharge Elimination System, part of the Clean Water Act which requires permits for surface water pollution. In North Carolina, these permits are issued and enforced by NCDEQ.

Nuisance Flooding: Flooding which causes inconvenience, but little or no property damage.

Nutrient Load: The total input of nutrients into the ecosystem from human and non-human sources, which can become stressful to aquatic ecosystems in excess.

Outfall: A point where collected storm water runoff is discharged from an underground piped system or above ground conveyance into a receiving water body.

Peak Flow Rate: The maximum flow of water during a storm event, usually expressed in CFS (cubic feet per second).

Perennial: Streams, generally flowing year round, rather than seasonally or only after rain events.

Permeable: Having pores or openings that permit liquids to pass through, also known as "pervious".

Rain Barrel: A storage device that collects stormwater, usually from a roof surface, which can be reused for irrigation, washing vehicles, or other uses not involving human consumption. 

Rain Garden: A bowl-shaped area in the landscape planted with native shrubs and flowers, where rain water collects and is absorbed back into the soil.

Rainwater Harvesting: The collection and storage of rainwater in a container or planted area, preventing excess runoff and redirecting the water for beneficial use.

Receiving Water: Any water body that receives stormwater outflow, either from natural or man-made systems.

Restoration: Work conducted to repair creeks and creek-side areas damaged by erosion and/or sedimentation, to improve water quality, stabilize banks, and enhance habitat for aquatic life.

Retention Basin: An artificial pond where surface and stormwater runoff is collected and continuously stored. See "wet pond".

Retrofit: The modification of equipment or structures to add new technology; in stormwater, typically refers to the addition or modification of SCMs in older developments.

Riparian: Related to or adjacent to the banks of rivers and streams, and sometimes also wetlands, lakes, or tidewater.

Runoff: The flow of water across the ground surface when stormwater cannot infiltrate the soil rapidly enough.

Sedimentation: The process of depositing soil, clay, sand or other sediments that were moved by the flow of water.

Septic System: An underground, typically domestic, wastewater collection and treatment system.

Sewer System: The system of pipes and pump stations that collect and transport wastewater from homes and businesses to a wastewater treatment plant.

Stormwater: Water originating from rain, snow, ice melt, and other precipitation.

Stormwater Control Measure (SCM): Physical structures that are designed and constructed to remove pollutants from stormwater runoff, provide flood control, reduce downstream erosion, and/or promote groundwater recharge; common examples include bioretention cells, wet ponds, and stormwater wetlands.

Stormwater Conveyance: The network of above- and below-ground infrastructure that collects, conveys, stores or treats surface and stormwater runoff.

Stormwater Wetlands: Constructed systems that mimic the functions of natural wetlands and use physical, chemical, and biological processes to treat stormwater pollution.

Stream Buffer: The undeveloped, vegetated area parallel and adjacent to a stream that protects and enhances water quality.

Subwatershed: An area of land, surface waters and groundwater that drains to a particular point, designated as part of a larger watershed.

Surface Water: Water found on the surface of the earth such as a river, stream, lake, wetland, or ocean.

Swale: A broad, shallow, gently sloped, open channel that conveys stormwater runoff.

Toxic: Poisonous, carcinogenic, or otherwise directly harmful to life.

Tributary: A river, stream, or creek flowing into a larger river or lake.

Underground Detention Systems: Vaults constructed under parking lots, roads, or existing greenspaces to store (and sometimes treat) excess stormwater.

USACE: United States Army Corp of Engineers, an engineering part of the U.S. Army whose mission, among others, is to "deliver vital public and military engineering services" by planning, designing, and constructing civil works projects and administering several federal clean water programs.

USGS: United States Geological Survey, a science organization that provides impartial information on the health of ecosystems and the environment.

Water Quality Buffer: Buffers in which construction or development are specifically prohibited in order to maintain water quality of the stream or receiving water body.  More or less synonymous with "stream buffer".

Water Quality / Illicit Discharge Ordinance: The code prohibiting the discharge any contaminant into surface and storm water or ground water, through spills, illicit connections, contaminated stormwater runoff, etc.

Water Supply Watershed: A watershed whose receiving water body provides drinking/domestic water to the public, and therefore is subject to more stringent development and water quality standards.

Watershed: All the land, surface water, and underlying groundwater that drains to a given point; also known as a drainage basin.

Wet Pond: Drainage facilities for water quality treatment that contain a permanent pool of water, designed to optimize water quality by providing long retention times, allowing metals and other particles to settle out and biologic activity to occur that metabolizes nutrients and organic pollutants.

Wetland: A type of ecosystem that is flooded, permanently or seasonally, where oxygen-free processes occur; common examples are marshes, swamps, and bogs.