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Protecting Northern Michigan's ​Water Resources

Stormwater Glossary

Stormwater Glossary

Stormwater runoff is the result of precipitation that does not infiltrate into the soil. Rather, it flows over land areas or through storm drains to streams, rivers, and lakes. This water collects pollutants as it moves over streets, parking lots, driveways, and other surfaces. 

Typically, stormwater runoff is untreated before being discharged to surface water. The quantity and quality of stormwater runoff is directly related to land use. According to the U.S. Environmental Protection Agency (EPA), highly urbanized areas generate over five times more runoff than naturally vegetated areas. There is a growing need for stormwater management at all levels – homeowners, local, state, and throughout the Great Lakes Basin. The following terms are commonly used to describe stormwater management practices.

Berm– A berm is a barrier constructed of compacted earth or other materials that is generally intended to restrict or direct the flow of water. In a rain garden, the berm is created to retain water within the garden.

Best Management Practice – A stormwater Best Management Practice (BMP) is a practice that is suitable for treating pollutants in stormwater runoff and/or reducing the volume of runoff. BMPs may include changing a cultural practice, such as reducing the amount of fertilizer (especially phosphorous) used; or a structural practice, such as a water harvesting system to collect, convey, and untilize water that would have otherwise run off the area. Stormwater BMPs are sometimes referred to as Stormwater Control Measures (SCMs).

Bioretention – Bioretention is the process of collecting stormwater in a treatment area consisting of soil and plant materials to facilitate infiltration and remove sediments and other contaminants through physical, chemical, and biological processes. 

Clean Water Act – The Clean Water Act (1972), adapted from the Federal Water Pollution Control Act (1948), is federal legislation that provides the legal basis for the National Pollution Discharge Elimination System. It established goals of eliminating releases of high amounts of toxic substances to water, eliminating additional water pollution, and ensuring that surface waters will meet the water quality standards for their intended uses.

Curb and Gutter – A curb and gutter system provides a defined drainage pathway along the edges of city streets or roadways for the flow of stormwater runoff.

Curb Cut – A curb cut is an area of curb that has been removed to allow an unobstructed pathway from the street level. Curb cuts are often used to redirect water from traditional drainage ways to a stormwater BMP.

Environmental Protection Agency – The Environmental Protection Agency (EPA) is a federal agency with the directive to protect human health and the environment. When Congress passes an environmental law, the EPA implements the law by writing and enforcing regulations. 

Erosion – Erosion is the process that moves material, especially soil, from one location to another. Erosion is caused by the action of wind, water, or other forces working on the earth’s surface. 

Green – The term “green” is used to describe a process, structure, or idea that integrates environmental considerations, i.e., green buildings, green cities, green roofs, etc. Energy efficiency and environmental sustainability are key characteristics of being “green.”

Green Roof – A green roof is partially or completely covered with vegetation. They commonly contain native or adaptive plants, soil, a root barrier, a drainage system, a waterproof membrane, and the roof support structure. Green roofs absorb and filter rainwater, provide building installation, enhance the roof lifespan, moderate roof deck temperatures, improve heating and cooling system efficiency, and amenity value for urban rooftop views and spaces. 

Groundwater – Groundwater is located beneath the ground surface in saturated soil and rock formations. 

Hardscape – Hardscape refers to the man-made features of a landscape constructed from concrete, masonry, wood, or other non-plant materials. This may include streets, sidewalks, patios, decks, etc. 

Impervious Surface – An impervious surface is any surface or ground cover that has very limited or no capacity to absorb and/or infiltrate water. Traditional asphalt and concrete, mortared brick, and highly compacted soils are examples. 

Low Impact Development – Low Impact Development (LID) is a land development approach that emphasizes site design and planning techniques that mimic the natural infiltration-based hydrology of the historic landscape. LID techniques generally manage stormwater by retaining and infiltrating runoff on-site.

Native Plants – Plants which occurred in an area before disturbance by humans are considered to be native. When properly sited, native plants are adapted to the climate, pests, soil, and other conditions. Native plants are often deep-rooted, which enhances the function of green infrastructure. 

Nonpoint Source Pollution – Nonpoint source pollution is pollution (sediments, nutrients, pesticides, bacteria, heavy metals, etc.) that cannot be easily traced to one source or one property. Rather, small amounts accumulate from many sources and many properties, eventually reaching concentrations that may impair water resources. Nonpoint source pollution is one of the leading causes of water quality impairment. 

Outfall – An outfall is the point where runoff water exits a drainage system and discharges into a receiving waterbody. 

Permeable Pavement – Permeable, pervious, or porous pavement includes several methods and materials that allow water and air to move through the pavement and into the underlying soil. Some examples of permeable pavement include specially designed and constructed concrete, asphalt, paving stones, or bricks. 

Point Source Pollution – Pollution that enters the environment from a single point such as a factory, an oil or chemical spill, a municipal wastewater treatment plant, or a stormwater discharge pipe. 

Rain Barrel – A rain barrel is a small storage device that collects stormwater, usually from a roof surface. Although use of the collected water for drinking and vegetable garden irrigation is not recommended, it can be used for washing your car, watering ornamental plants, and landscape irrigation. 

Rain Garden – A rain garden is a shallow landscape depression designed to capture and treat stormwater runoff. The plants and soil in the rain garden facilitate infiltration and pollution removal. 

Riparian – Riparian refers to the land immediately adjacent to a waterbody such as a river, stream, wetland, or lake. 

Runoff – Runoff is excess rainfall, snowmelt, or irrigation water that flows over the surface of the land. It will eventually infiltrate into the ground, evaporate, or flow into a storm drain system, stream, river, lake or other waterbody. 

Soil Amendments – Soil amendments include any material added to soil to improve its physical, chemical, biological, or structural properties or to provide enhanced plant growth. 

Stormwater – Stormwater is water from rainfall or snowmelt. Stormwater that does not immediately infiltrate into the soil becomes runoff. 

Watershed – The land area from which water drains to a particular waterbody such as a stream, river, or lake is a watershed. 

Wetlands – Wetlands are complex ecosystems that occur in the transition zone between land-based ecosystems and water-based ecosystems. A wetland has plants that are adapted to water, soils that have been formed under saturated conditions, and wetland hydrology.