Stormwater Glossary and Acronyms

Berm: A mound of earth formed to control the flow of surface water.

Best Management Practice (BMP), nonstructural: Strategies implemented to control stormwater runoff that focus on pollution prevention such as alternative site design, zoning and ordinances, education, and good housekeeping measures.

Best Management Practice (BMP), structural:Engineered devices implemented to control, treat, or prevent stormwater runoff pollution. Bioengineering Restoration and stabilization techniques that use plants, often native species, to mimic natural functions and benefits.

Biofiltration: The use of vegetation (usually grasses or wetland plants) to filter and treat stormwater runoff as it is conveyed through an open channel or swale.

Biological Diversity: The concept of multiple species of organisms living together in balance with their environment and each other.

Bioretention: The use of vegetation in retention areas designed to allow infiltration of runoff into the ground. The plants provide additional pollutant removal and filtering functions while infiltration allows the temperature of the runoff to be cooled.

Brownfields: Abandoned or underutilized properties where development is complicated by real or perceived contamination.

Buffer Zone: A designated transitional area around a stream, lake, or wetland left in a natural, usually vegetated state so as to protect the waterbody from runoff pollution. Development is often restricted or prohibited in a buffer zone.

Catchbasin: An inlet to a storm or combined sewer equipped with a sediment sump, and sometimes a hood, on its outlet pipe to the sewer. Catchbasins can collect some of the sediment and debris washed off the streets, and help to provide a water seal against the venting of sewer gases. Catchbasins should be cleaned out regularly to function properly.

Channel Erosion: The widening, deepening (called channel scour), and upstream cutting of a stream channel caused by moderate and extreme flow events. Channel erosion is one way that a stream reacts to changes in flow patterns.

Conservation Design: Site design that incorporates conservation measures such as on-site tree preservation, concentrating homes on a limited percentage of the site, preserving natural areas and open space, and reducing the amount of impervious cover.

Constructed Stormwater Wetland: A water quality BMP design to have similar characteristics and functions to a natural wetland, with the specific purpose of treating stormwater runoff through uptake, retention, and settling.

Detention: The storage and slow release of stormwater following a precipitation event by means of an excavated pond, enclosed depression, or tank. Detention is used for both pollutant removal, stormwater storage, and peak flow reduction. Both wet and dry detention methods can be applied.

EPA:  United States Environmental Protection Agency

ESC:  Erosion and Sediment Control

FEMA:  Federal Emergency Management Agency

Filter Strip: Grassed strips situated along roads or parking areas that remove pollutants from runoff as it passes through, allowing some infiltration, and reductions of velocity.

First Flush: Describes the washing action that stormwater has on accumulated pollutants. The first runoff, especially off streets and parking lots, washes them clean and carries pollutants with it. The first one inch of runoff carries 90 percent of the pollution.

Floodplain: Can be either a natural feature or statistically derived area adjacent to a stream or river where water from the stream or river overflows its banks at some frequency during extreme storm events.

Geographic Information System (GIS): A database of digital information and data on land-use, land cover, ecology, and other geographic attributes that can be overlaid, statistically analyzed, mathematically manipulated, and graphically displayed using maps, charts, and graphs

Groundwater: Water that flows below the ground surface through saturated soil, glacial deposits, or rock.

Hydrology: The science addressing the properties, distribution, and circulation of water across the landscape, through the ground, and in the atmosphere

IECA:International Erosion Control Association

Illicit Connection: Illicit connections are defined as illegal and/or improper connections to storm drainage systems and receiving waters.

Illicit Discharge: The discharge of anything other than stormwater to the municipal separate storm sewer system. No debris or waste should be dumped into the MS4 since these materials are quickly carried to nearby waters. 

Impervious Surface: A surface that cannot be penetrated by water such as pavement, rock, or a rooftop and thereby prevents infiltration and generates runoff. 

Infiltration: The process or rate at which water percolates from the land surface into the ground. Infiltration is also a general category of BMP designed to collect runoff and allow it to flow through the ground for treatment. 

LID:  Low Impact Development 

MARC:  Mid-America Regional Council 

MS4:  Municipal Separate Storm Sewer System 

National Pollutant Discharge Elimination System (NPDES):A provision of the EPA Clean Water Act that prohibits discharge of pollutants into waters of the United States unless a special permit is issued by the EPA to a state, or (where delegated) a tribal government or and Indian reservation. 

Natural Buffer: A variable width area maintained with natural vegetation between a pollutant source and a waterbody that provides natural filtration and other forms of protection. 

Nonpoint-Source Pollutants: Pollutants from many diffuse sources. Nonpoint-source pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters, and even underground sources of drinking water. 

Outfall:The point of discharge from a river, pipe, drain, etc. to a receiving body of water. 

Peak Discharge: The greatest volume of stream flow occurring during a storm event. 

Performance Standard: An established amount or limit of a specified pollutant that can be discharged from a land-use activity or BMP. 

Pervious: Surfaces which allow the penetration of water into the ground. 

Point-Source Pollutants:Pollutants from a single, identifiable source such as a factory or refinery; also called single-point-source pollution. 

Polluted Runoff:Rainwater or snowmelt that picks up pollutants and sediments as it runs off roads, highways, parking lots, lawns, agricultural lands, and other land-use activities that can generate pollutants. 

Runoff: Water from rainfall, snowmelt, or otherwise discharged that flows across the ground surface instead of infiltrating the ground. 

Sanitary Sewer System:Underground pipes that carry only domestic or industrial wastewater to a sewage treatment plant or receiving water. 

Sediment: Material carried with stormwater runoff; sediment fills drainage ditches, rivers and lakes, degrading water quality. 

SMAC:  Stormwater Management Advisory Council 

Storm Sewer System: A system of pipes and channels that carry stormwater runoff from the surfaces of building, paved surfaces, and the land to discharge areas. 

Stormwater: Water derived from a storm event or conveyed through a storm sewer system. 

Stormwater Utility: A utility established to generate a dedicated source of funding for stormwater pollution prevention activities where users pay a fee based on land-use and contribution of runoff to the stormwater system.

SWMP:  Stormwater management plan (or program) 

SWPPP:  A plan to describe a process though which a facility thoroughly evaluates potential pollutant sources at a site and selects and implements appropriate measures designed to prevent or control the discharge of pollutants in stormwater runoff. 

Surface Water: Water that flows across the land surface, in channels, or is contained in depressions on the land surface (e.g. runoff, ponds, lakes, rivers, and streams). 

Swale: A natural or human-made open depression or wide, shallow ditch that intermittently contains or conveys runoff. Can be used as a BMP to detain and filter runoff. 

TMDL:  Total Maximum Daily Load. The maximum allowable loading of a pollutant that a designated water body can assimilate and still meet numeric and narrative water quality standards. 

Urban (Metropolitan) Runoff:Runoff derived from urban or suburban land-uses that is distinguished from agricultural or industrial runoff sources. 

Watershed: The land area that contributes water to a specific waterbody. All the rain or snow that falls within this area flows to the waterbodies as surface runoff, in tributary streams, or as groundwater. 

Wet Detention Ponds: A BMP consisting of a permanent pool of water designed to treat runoff by detaining water long enough for settling, filtering, and biological uptake. Wet ponds are also often designed to have an aesthetic or recreational value. 

Xeriscaping TM: An alternative landscaping technique that focuses on water conservation through plant selection and site design.