Glossary

100-year flood – Describes a flood that has a 100-year recurrence interval. The probability of a flood of that magnitude happening is one percent in any given year.

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 state to protect the waterbody from runoff pollution. Development is often restricted or prohibited in a buffer zone.

Catchbasin – An inlet to the storm 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 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 pollutant removal, stormwater storage and peak flow reduction. Both wet and dry detention methods can be applied.

Filter strip – Grassed strips situated along roads or parking areas that remove pollutants from runoff as it passes through, allowing some infiltration and reducing 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 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 the banks during extreme storm events.

Groundwater – Water that flows below the ground, 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.

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

Illicit discharge/illegal dumping – 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 and rooftops, which prevent infiltration and generate 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.

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, or drain 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 land use or BMP.

Pervious – Surfaces that allow the penetration of water into the ground.

Point source pollutants – Pollutants from a single, identifiable source, such as a factory or refinery.

Polluted runoff – Rainwater or snowmelt that picks up pollutants and sediments as it runs off roads, highways, parking lots, lawns, agricultural lands and other areas 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.

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 – Excess water from a storm event, conveyed through the storm sewer system.

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

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 depression or wide, shallow ditch that intermittently contains or conveys runoff. Can be used as a BMP to detain and filter runoff.

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. Many wet ponds are also often designed to have an aesthetic or recreational value.

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

Acronyms

BMP – Best Management Practice

EPA – United States Environmental Protection Agency

ESC – Erosion and Sediment Control

FEMA – Federal Emergency Management Agency

GIS – Geographic Information System

IECA – International Erosion Control Association

LID – Low Impact Development

MARC – Mid-America Regional Council

MS4 – Municipal Separate Storm Sewer System

NPDES – National Pollutant Discharge Elimination System, the two-phased surface water quality program authorized by Congress as part of the 1987 Clean Water Act.

SMAC – Stormwater Management Advisory Council

SWMP – Stormwater management plan

SWPPP – Stormwater Pollution Prevention Plan. A plan to describe the process of evaluating potential pollutant sources at a site, selecting and implementing appropriate measures prevent or control pollutants in stormwater runoff.

TMDL – Total Maximum Daily Load: the maximum allowable loading of a pollutant that a designated water body can contain and still meet water quality standards.