Stormwater, also spelled storm water, is
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
that originates from
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
(
storm
A storm is any disturbed state of the natural environment or the atmosphere
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmos ...
), including heavy
rain
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...
and
meltwater
Meltwater is water released by the melting of snow or ice, including glacial ice, tabular icebergs and ice shelves over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing. Meltwater can be ...
from
hail
Hail is a form of solid precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets generally fal ...
and
snow
Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes.
It consists of frozen crystalline water throughout ...
. Stormwater can soak into the soil (
infiltrate) and become
groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
, be stored on depressed land surface in
pond
A pond is an area filled with water, either natural or artificial, that is smaller than a lake. Defining them to be less than in area, less than deep, and with less than 30% emergent vegetation helps in distinguishing their ecology from th ...
s and
puddle
A puddle is a small accumulation of liquid, usually water, on a surface. It can form either by pooling in a depression on the surface, or by surface tension upon a flat surface.
A puddle is generally shallow enough to walk through, and too sma ...
s, evaporate back into the atmosphere, or contribute to
surface runoff
Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when th ...
. Most runoff is conveyed directly as
surface water
Surface water is water located on top of land forming terrestrial (inland) waterbodies, and may also be referred to as ''blue water'', opposed to the seawater and waterbodies like the ocean.
The vast majority of surface water is produced by prec ...
to nearby
stream
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...
s,
river
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...
s or other large
water bodies
A body of water or waterbody (often spelled water body) is any significant accumulation of water on the surface of Earth or another planet. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as p ...
(
wetland
A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...
s,
lake
A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...
s and
ocean
The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...
s) without treatment.
In natural landscapes, such as forests, soil absorbs much of the stormwater. Plants also reduce stormwater by improving infiltration, intercepting precipitation as it falls, and by taking up water through their roots. In developed environments, such as
cities
A city is a human settlement of notable size.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routledge. It can be def ...
, unmanaged stormwater can create two major issues: one related to the volume and timing of runoff (
flooding
A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrolog ...
) and the other related to potential contaminants the water is carrying (
water pollution
Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water ...
). In addition to the pollutants carried in stormwater runoff,
urban runoff
Urban runoff is surface runoff of rainwater, landscape irrigation, and car washing created by urbanization. Impervious surfaces (roads, parking lots and sidewalks) are constructed during land development. During rain , storms and other precipit ...
is being recognized as a cause of pollution in its own right
Stormwater is also an important resource as human population and demand for water grow, particularly in arid and drought-prone climates.
Stormwater harvesting Stormwater harvesting or Stormwater reuse is the collection, accumulation, treatment or purification, and storage of stormwater for its eventual reuse. While rainwater harvesting collects precipitation primarily from rooftops, stormwater harvesting ...
techniques and
purification could potentially make some urban environments self-sustaining in terms of water.
Impacts of stormwater
Stormwater pollution
![Stormwater Pollution Diagram](https://upload.wikimedia.org/wikipedia/commons/e/e8/Stormwater_Pollution_Diagram.svg)
With less vegetation and more
impervious surfaces
Impervious surfaces are mainly artificial structures—such as pavements (roads, sidewalks, driveways and parking lots, as well as industrial areas such as airports, ports and logistics and distribution centres, all of which use considerable pav ...
(
parking lot
A parking lot (American English) or car park (British English), also known as a car lot, is a cleared area intended for parking vehicles. The term usually refers to an area dedicated only for parking, with a durable or semi-durable surface ...
s,
road
A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation.
There are many types of ...
s,
building
A building, or edifice, is an enclosed structure with a roof and walls standing more or less permanently in one place, such as a house or factory (although there's also portable buildings). Buildings come in a variety of sizes, shapes, and fun ...
s,
compacted soil
In geotechnical engineering, soil compaction is the process in which stress applied to a soil causes densification as air is displaced from the pores between the soil grains. When stress is applied that causes densification due to water (or othe ...
), developed areas allow less rain to
infiltrate into the ground, and more runoff is generated than in the undeveloped condition. Additionally, conveyances such as ditches and storm sewers quickly transport runoff away from commercial and residential areas into nearby water bodies. This greatly increases the volume of water in waterways and the
discharge of those waterways, leading to erosion and flooding. Because the water is flushed out of the
watershed during the storm event, little infiltrates the soil, replenishes
groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
, or supplies stream
baseflow
Baseflow (also called drought flow, groundwater recession flow, low flow, low-water flow, low-water discharge and sustained or fair-weather runoff) is the portion of the streamflow that is sustained between precipitation events, fed to streams by d ...
in dry weather.
A
first flush
First flush is the initial surface runoff of a rainstorm. During this phase, water pollution entering storm drains in areas with high proportions of impervious surfaces is typically more concentrated compared to the remainder of the storm. Conse ...
is the initial runoff of a rainstorm. During this phase, polluted water entering storm drains in areas with high proportions of impervious surfaces is typically more
concentrated compared to the remainder of the storm. Consequently, these high concentrations of
urban runoff
Urban runoff is surface runoff of rainwater, landscape irrigation, and car washing created by urbanization. Impervious surfaces (roads, parking lots and sidewalks) are constructed during land development. During rain , storms and other precipit ...
result in high levels of pollutants discharged from storm sewers to
surface water
Surface water is water located on top of land forming terrestrial (inland) waterbodies, and may also be referred to as ''blue water'', opposed to the seawater and waterbodies like the ocean.
The vast majority of surface water is produced by prec ...
s.
[Alex Maestre and Robert Pitt; Center for Watershed Protection (2005]
"The National Stormwater Quality Database, Version 1.1: A Compilation and Analysis of NPDES Stormwater Monitoring Information."
Report prepared for U.S. Environmental Protection Agency (EPA), Washington, DC. September 4, 2005.
Daily human activities result in deposition of pollutants on
road
A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation.
There are many types of ...
s,
lawn
A lawn is an area of soil-covered land planted with grasses and other durable plants such as clover which are maintained at a short height with a lawnmower (or sometimes grazing animals) and used for aesthetic and recreational purposes. L ...
s,
roof
A roof ( : roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of temper ...
s,
farm
A farm (also called an agricultural holding) is an area of land that is devoted primarily to agricultural processes with the primary objective of producing food and other crops; it is the basic facility in food production. The name is used fo ...
fields, and other land surfaces. Such pollutants include trash, sediment, nutrients, bacteria, pesticides, metals, and petroleum byproducts. When it
rain
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...
s or there is
irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
,
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
runs off and ultimately makes its way to a
river
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...
,
lake
A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...
, or the
ocean
The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...
. While there is some
attenuation
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable att ...
of these pollutants before entering receiving waters, polluted runoff results in large enough quantities of pollutants to impair receiving waters.
Stormwater runoff as a source of pollution
![View of urban runoff discharging to coastal waters](https://upload.wikimedia.org/wikipedia/commons/2/2b/View_of_urban_runoff_discharging_to_coastal_waters.jpg)
In addition to the pollutants carried in
stormwater runoff
Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the s ...
, urban runoff is being recognized as a cause of pollution in its own right.
In natural catchments (
watersheds) surface runoff entering waterways is a relatively rare event, occurring only a few times each year and generally after larger storm events. Before development occurred most rainfall soaked into the ground and contributed to groundwater recharge or was recycled into the atmosphere by vegetation through
evapotranspiration
Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the atmosphere. It covers both water evaporation (movement of water to the air directly from soil, canopies, and water bodies) and transpi ...
.
Modern drainage systems, which collect runoff from impervious surfaces (e.g., roofs and roads), ensure that water is efficiently conveyed to waterways through pipe networks, meaning that even small storm events result in increased waterway flows.
In addition to delivering higher pollutants from the urban catchment, increased stormwater flow can lead to stream
erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...
, encourage weed invasion, and alter natural flow regimes. Native species often rely on such flow regimes for spawning, juvenile development, and migration.
Stormwater runoff from roadways has been observed to contain many metals including zinc (Zn), cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), chromium (Cr), manganese (Mn), iron (Fe), vanadium (V), cobalt (Co), and aluminum (Al) (Sansalone and Buchberger, 1997; Westerlund and Viklander, 2006) and other constituents
In some areas, especially along the U.S. coast, polluted runoff from roads and highways may be the largest source of
water pollution
Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water ...
. For example, about 75 percent of the toxic chemicals getting to
Seattle
Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest regio ...
, Washington's
Puget Sound
Puget Sound ( ) is a sound of the Pacific Northwest, an inlet of the Pacific Ocean, and part of the Salish Sea. It is located along the northwestern coast of the U.S. state of Washington. It is a complex estuarine system of interconnected ma ...
are carried by stormwater that runs off paved roads and driveways, rooftops, yards, and other developed land.
Urban flooding
![Trounce Pond](https://upload.wikimedia.org/wikipedia/commons/5/52/Trounce_Pond.jpg)
Stormwater is a major cause of
urban flooding
Urban flooding is the inundation of land or property in a built environment, particularly in more densely populated areas, caused by rainfall overwhelming the capacity of drainage systems, such as storm sewers. Although sometimes triggered by even ...
. Urban flooding is the inundation of land or property in a built-up environment caused by stormwater overwhelming the capacity of
drainage systems, such as
storm sewers. Although triggered by single events such as
flash flooding
A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice or snow flowing o ...
or
snow melt
In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many part ...
, urban flooding is a condition, characterized by its repetitive, costly and systemic impacts on communities. In areas susceptible to urban flooding, backwater valves and other infrastructure may be installed to mitigate losses.
Where properties are built with
basements
A basement or cellar is one or more floors of a building that are completely or partly below the ground floor. It generally is used as a utility space for a building, where such items as the furnace, water heater, breaker panel or fuse box, ...
, urban flooding is the primary cause of basement and sewer backups. Although the number of casualties from urban flooding is usually limited, the economic, social and environmental consequences can be considerable: in addition to direct damage to property and infrastructure (
highways
A highway is any public or private road or other public way on land. It is used for major roads, but also includes other public roads and public tracks. In some areas of the United States, it is used as an equivalent term to controlled-access ...
,
utilities
A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and r ...
and services), chronically wet houses are linked to an increase in respiratory problems and other illnesses. Sewer backups are often from the sanitary sewer system, which takes on some storm water as a result of
Infiltration/Inflow
Infiltration/Inflow (I/I) causes dilution in sanitary sewers. Dilution of sewage decreases the efficiency of treatment, and may cause sewage volumes to exceed design capacity. Although inflow is technically different from infiltration, it may be d ...
.
Stormwater creation of sinkhole collapses
An example of urban stormwater creating a sinkhole collapse is the February 25, 2002 Dishman Lane collapse in
Bowling Green, Kentucky
Bowling Green is a home rule-class city and the county seat of Warren County, Kentucky, United States. Founded by pioneers in 1798, Bowling Green was the provisional capital of Confederate Kentucky during the American Civil War. As of the 2 ...
where a sinkhole suddenly dropped the road under four traveling vehicles. The nine-month repair of the Dishman Lane collapse cost a million dollars but there remains the potential for future problems.
In undisturbed areas with natural subsurface (
karst
Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...
) drainage, soil and rock fragments choke karst openings thereby being a self-limitation to the growth of openings.
[Palmer, Arthur ]
"Groundwater processes in karst terranes."
Ground water geomorphology (1990): 177-209. The undisturbed karst drainage system becomes balanced with the climate so it can drain the water produced by most storms. However, problems occur when the landscape is altered by urban development.
[Veni, George]
Living with Karst
American Geological Institute, 2001. In urban areas with natural subsurface (
karst
Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...
) drainage there are no surface streams for the increased stormwater from impervious surfaces such as roofs, parking lots, and streets to runoff into. Instead, the stormwater enters the subsurface drainage system by moving down through the ground. When the subsurface water flow becomes great enough to transport soil and rock fragments, the karst openings grow rapidly.
Where karst openings are roofed by supportive (
competent) limestone, there frequently is no surface warning that an opening has grown so large it will suddenly collapse catastrophically.
Therefore, land use planning for new development needs to avoid karst areas.
Ultimately taxpayers end up paying the costs for poor land use decisions.
Stormwater management
![Red rain barrel](https://upload.wikimedia.org/wikipedia/commons/6/69/Red_rain_barrel.jpg)
Managing the quantity and quality of stormwater is termed, "Stormwater Management."
[Washington State Department of Ecology (2005). Olympia, WA]
"Stormwater Management Manual for Western Washington."
Publication No. 05-10-029. The term ''
Best Management Practice'' (BMP) or stormwater control measure (SCM) is often used to refer to both structural or engineered control devices and systems (e.g.
retention pond
A retention basin, sometimes called a wet pond, wet detention basin, or stormwater management pond (SWMP), is an artificial pond with vegetation around the perimeter and a permanent pool of water in its design. It is used to manage stormwater r ...
s) to treat or store polluted stormwater, as well as operational or procedural practices (e.g. street sweeping). Stormwater management includes both technical and institutional aspects.
[
]
Technical aspects
* control of flooding and erosion;
* control of hazardous materials to prevent release of pollutants into the environment (source control);
* planning and construction of stormwater systems like
retention basin
A retention basin, sometimes called a wet pond, wet detention basin, or stormwater management pond (SWMP), is an artificial pond with vegetation around the perimeter and a permanent pool of water in its design. It is used to manage stormwater r ...
s, buried
vaults with various kinds of
media filter
A media filter is a type of filter that uses a bed of sand, peat, shredded tires, foam, crushed glass, geo-textile fabric, anthracite, crushed granite or other material to filter water for drinking, swimming pools, aquaculture, irrigation, storm ...
s, and
vortex separators to remove coarse solids before they pollute surface waters or groundwater resources;
* acquisition and protection of natural waterways or rehabilitation;
* building
nature-based solutions
The term Nature-based solutions (NBS) refers to the sustainable management and use of natural features and processes to tackle socio-environmental challenges. These challenges include issues such as climate change ( mitigation and adaptation), ...
such as ponds,
swales,
constructed wetlands
A constructed wetland is an artificial wetland to treat sewage, greywater, stormwater runoff or industrial wastewater. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land developmen ...
or
green infrastructure
Green infrastructure or blue-green infrastructure refers to a network that provides the “ingredients” for solving urban and climatic challenges by building with nature.Hiltrud Pötz & Pierre Bleuze (2011). Urban green-blue grids for sustainab ...
solutions to work with existing or "hard" drainage structures, such as pipes and concrete channels (constructed wetlands built for stormwater treatment can also serve as habitat for plants, amphibians and fish)
Institutional and policy aspects
* development of funding approaches to stormwater programs potentially including
stormwater user fees and the creation of a stormwater utility;
* development of long-term asset management programs to repair and replace aging infrastructure;
* revision of current stormwater regulations to address comprehensive stormwater needs;
* enhancement and enforcement of existing ordinances to make sure property owners consider the effects of stormwater before, during and after development of their land;
* education of a community about how its actions affect
water quality
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...
, and about what it can do to improve water quality.
Integrated water management
Integrated water management (IWM) of stormwater has the potential to address many of the issues affecting the health of waterways and water supply challenges facing the modern urban city. IWM is often associated with
green infrastructure
Green infrastructure or blue-green infrastructure refers to a network that provides the “ingredients” for solving urban and climatic challenges by building with nature.Hiltrud Pötz & Pierre Bleuze (2011). Urban green-blue grids for sustainab ...
when considered in the design process. Professionals in their respective fields, such as
urban planner
An urban planner (also known as town planner) is a professional who practices in the field of town planning, urban planning or city planning.
An urban planner may focus on a specific area of practice and have a title such as city planner, town ...
s,
architects
An architect is a person who plans, designs and oversees the construction of buildings. To practice architecture means to provide services in connection with the design of buildings and the space within the site surrounding the buildings that h ...
,
landscape architects
A landscape architect is a person who is educated in the field of landscape architecture. The practice of landscape architecture includes: site analysis, site inventory, site planning, land planning, planting design, grading, storm water manage ...
,
interior designers
Interior design is the art and science of enhancing the interior of a building to achieve a healthier and more aesthetically pleasing environment for the people using the space. An interior designer is someone who plans, researches, coordina ...
, and
engineers
Engineers, as practitioners of engineering, are professionals who invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considering the limit ...
, often consider integrated water management as a foundation of the design process.
Also known as
low impact development (LID) in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, or
Water Sensitive Urban Design (WSUD) in
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
, IWM has the potential to improve runoff quality, reduce the risk and impact of flooding and deliver an additional water resource to augment potable supply.
The development of the modern city often results in increased demands for water supply due to population growth, while at the same time altered runoff predicted by climate change has the potential to increase the volume of stormwater that can contribute to drainage and flooding problems. IWM offers several techniques, including stormwater harvest (to reduce the amount of water that can cause flooding),
infiltration
Infiltration may refer to:
Science, medicine, and engineering
*Infiltration (hydrology), downward movement of water into soil
*Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings
*Infiltration (me ...
(to restore the natural recharge of groundwater), biofiltration or
bioretention
Bioretention is the process in which contaminants and sedimentation are removed from stormwater runoff. The main objective of the bioretention cell is to attenuate peak runoff as well as to remove stormwater runoff pollutants.
Construction of ...
(e.g.,
rain gardens
Rain gardens, also called bioretention facilities, are one of a variety of practices designed to increase rain runoff reabsorption by the soil. They can also be used to treat polluted stormwater runoff. Rain gardens are designed landscape sites t ...
), to store and treat runoff and release it at a controlled rate to reduce impact on streams and wetland treatments (to store and control runoff rates and provide habitat in urban areas).
There are many ways of achieving LID. The most popular is to incorporate land-based solutions to reduce stormwater runoff through the use of retention ponds,
bioswale
Bioswales are channels designed to concentrate and convey stormwater runoff while removing debris and pollution. Bioswales can also be beneficial in recharging groundwater.
Bioswales are typically vegetated, mulched, or xeriscaped. They co ...
s, infiltration trenches, sustainable pavements (such as
permeable paving
Permeable paving surfaces are made of either a porous material that enables stormwater to flow through it or nonporous blocks spaced so that water can flow between the gaps. Permeable paving can also include a variety of surfacing techniques ...
), and others noted above. LID can also be achieved by utilizing engineered, manufactured products to achieve similar, or potentially better, results as land-based systems (underground storage tanks, stormwater treatment systems,
biofilter
Biofiltration is a pollution control technique using a bioreactor containing living material to capture and biologically degrade pollutants. Common uses include processing waste water, capturing harmful chemicals or silt from surface runoff, and ...
s, etc.). The proper LID solution is one that balances the desired results (controlling runoff and pollution) with the associated costs (loss of usable land for land-based systems versus capital cost of manufactured solution). Green (vegetated) roofs are also another low cost solution.
IWM as a movement can be regarded as being in its infancy and brings together elements of drainage science, ecology and a realization that traditional drainage solutions transfer problems further downstream to the detriment of the environment and water resources.
Regulations
United States
Federal requirements
![National Map of Regulated MS4s 2009](https://upload.wikimedia.org/wikipedia/commons/e/ee/National_Map_of_Regulated_MS4s_2009.png)
In the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, the
Environmental Protection Agency
A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
(EPA) is charged with
regulating stormwater pursuant to the
Clean Water Act
The Clean Water Act (CWA) is the primary federal law in the United States governing water pollution. Its objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters; recognizing the responsibiliti ...
(CWA). The goal of the CWA is to restore all "Waters of the United States" to their "fishable" and "swimmable" conditions. Point source discharges, which originate mostly from municipal
wastewater
Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industr ...
(
sewage
Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residenc ...
) and industrial wastewater discharges, have been regulated since enactment of the CWA in 1972. Pollutant loadings from these sources are tightly controlled through the issuance of National Pollution Discharge Elimination System (
NPDES) permits. However, despite these controls, thousands of water bodies in the U.S. remain classified as "impaired," meaning that they contain pollutants at levels higher than is considered safe by EPA for the intended beneficial uses of the water. Much of this impairment is due to polluted runoff, generally in urbanized watersheds (in other US watersheds,
agricultural pollution
Agricultural pollution refers to biotic and abiotic byproducts of farming practices that result in contamination or degradation of the environment and surrounding ecosystems, and/or cause injury to humans and their economic interests. The pol ...
is a major source).
To address the nationwide problem of stormwater pollution,
Congress
A congress is a formal meeting of the representatives of different countries, constituent states, organizations, trade unions, political parties, or other groups. The term originated in Late Middle English to denote an encounter (meeting of a ...
broadened the CWA definition of "point source" in 1987 to include industrial stormwater discharges and Municipal Separate
Storm Sewer
A storm drain, storm sewer (United Kingdom, U.S. and Canada), surface water drain/sewer (United Kingdom), or stormwater drain ( Australia and New Zealand) is infrastructure designed to drain excess rain and ground water from impervious surface ...
Systems ("MS4"). These facilities are required to obtain NPDES permits. In 2017, about 855 large municipal systems (serving populations of 100,000 or more), and 6,695 small systems are regulated by the permit system.
State and local requirements
![Silt fence EPA](https://upload.wikimedia.org/wikipedia/commons/9/9a/Silt_fence_EPA.jpg)
EPA has authorized 47 states to issue NPDES permits. In addition to implementing the NPDES requirements, many states and local governments have enacted their own stormwater management laws and ordinances, and some have published stormwater treatment design manuals.
Some of these state and local requirements have expanded coverage beyond the federal requirements. For example, the State of
Maryland
Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...
requires erosion and sediment controls on construction sites of 5,000 sq ft (460 m
2) or more. It is not uncommon for state agencies to revise their requirements and impose them upon counties and cities; daily fines ranging as high as $25,000 can be imposed for failure to modify their local stormwater permitting for construction sites, for instance.
Nonpoint source pollution management
Agricultural runoff (except for concentrated animal feeding operations, or "
CAFO
In animal husbandry, a concentrated animal feeding operation (CAFO), as defined by the United States Department of Agriculture (USDA), is an intensive animal feeding operation (AFO) in which over 1,000 animal units are confined for over 45 day ...
") is classified as
nonpoint source pollution
Nonpoint source (NPS) pollution refers to diffuse contamination (or pollution) of water or air that does not originate from a single discrete source. This type of pollution is often the cumulative effect of small amounts of contaminants gathered ...
under the CWA. It is not included in the CWA definition of "point source" and therefore not subject to NPDES permit requirements. The 1987 CWA amendments established a non-regulatory program at EPA for nonpoint source pollution management consisting of research and demonstration projects. Related programs are conducted by the
Natural Resources Conservation Service
Natural Resources Conservation Service (NRCS), formerly known as the Soil Conservation Service (SCS), is an agency of the United States Department of Agriculture (USDA) that provides technical assistance to farmers and other private landowners an ...
(NRCS) in the U.S.
Department of Agriculture.
Public education campaigns
Education is a key component of stormwater management. A number of agencies and organizations have launched campaigns to teach the public about stormwater pollution, and how they can contribute to solving it. Thousands of local governments in the U.S. have developed education programs as required by their NPDES stormwater permits.
One example of a local educational program is that of the West Michigan Environmental Action Council (WMEAC), which has coined the term ''Hydrofilth'' to describe stormwater pollution, as part of its "15 to the River" campaign. (During a rain storm, it may take only 15 minutes for contaminated runoff in
Grand Rapids, Michigan
Grand Rapids is a city and county seat of Kent County, Michigan, Kent County in the U.S. state of Michigan. At the 2020 United States census, 2020 census, the city had a population of 198,917 which ranks it as the List of municipalities in Mi ...
to reach the
Grand River.) Its outreach activities include a
rain barrel
A rainwater tank (sometimes called a rain barrel in North America in reference to smaller tanks, or a water butt in the UK) is a water tank used to collect and store rain water runoff, typically from rooftops via pipes. Rainwater tanks are device ...
distribution program and materials for homeowners on installing
rain garden
Rain gardens, also called bioretention facilities, are one of a variety of practices designed to increase rain runoff reabsorption by the soil. They can also be used to treat polluted stormwater runoff. Rain gardens are designed landscape sites t ...
s.
Other public education campaigns highlight the importance of
green infrastructure
Green infrastructure or blue-green infrastructure refers to a network that provides the “ingredients” for solving urban and climatic challenges by building with nature.Hiltrud Pötz & Pierre Bleuze (2011). Urban green-blue grids for sustainab ...
in slowing down and treating stormwater runoff.
DuPage County
DuPage County ( ) is a county in the U.S. state of Illinois, and one of the collar counties of the Chicago metropolitan area. As of the 2020 census, the population was 932,877, making it Illinois' second-most populous county. Its county seat is ...
Stormwater Management launched the "Love Blue. Live Green." outreach campaign on social media sites to educate the public on green infrastructure and other
best management practices for stormwater runoff. Articles, websites, pictures, videos and other media are disseminated to the public through this campaign.
History
Since humans began living in concentrated village or urban settings, stormwater runoff has been an issue. During the
Bronze Age
The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second pri ...
, housing took a more concentrated form, and
impervious surface
Impervious surfaces are mainly artificial structures—such as pavements (roads, sidewalks, driveways and parking lots, as well as industrial areas such as airports, ports and logistics and distribution centres, all of which use considerable p ...
s emerged as a factor in the design of early
human settlement
In geography, statistics and archaeology, a settlement, locality or populated place is a community in which people live. The complexity of a settlement can range from a minuscule number of dwellings grouped together to the largest of ci ...
s. Some of the early incorporation of stormwater engineering is evidenced in
Ancient Greece
Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity ( AD 600), that comprised a loose collection of cult ...
.
A specific example of an early stormwater runoff system design is found in the
archaeological
Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, biofacts or ecofacts, sites, and cultural landscap ...
recovery at
Minoan
The Minoan civilization was a Bronze Age Aegean civilization on the island of Crete and other Aegean Islands, whose earliest beginnings were from 3500BC, with the complex urban civilization beginning around 2000BC, and then declining from 1450B ...
Phaistos
Phaistos ( el, Φαιστός, ; Ancient Greek: , , Minoan: PA-I-TO?http://grbs.library.duke.edu/article/download/11991/4031&ved=2ahUKEwjor62y3bHoAhUEqYsKHZaZArAQFjASegQIAhAB&usg=AOvVaw1MwIv3ekgX-SxkJrbORipd ), also transliterated as Phaestos, ...
on
Crete
Crete ( el, Κρήτη, translit=, Modern: , Ancient: ) is the largest and most populous of the Greek islands, the 88th largest island in the world and the fifth largest island in the Mediterranean Sea, after Sicily, Sardinia, Cyprus, and ...
.
[C. Michael Hogan]
"Phaistos Fieldnotes."
''The Modern Antiquarian'' (2007).
See also
*
Nationwide Urban Runoff Program (U.S. research program)
*
Sanitary sewer overflow
Sanitary sewer overflow (SSO) is a condition in which untreated sewage is discharged from a sanitary sewer into the environment prior to reaching sewage treatment facilities. When caused by rainfall it is also known as wet weather overflow. Cause ...
*
Stochastic Empirical Loading and Dilution Model
References
External links
*
EPA Stormwater Permit ProgramStormwater ModelUSGS
Stochastic Empirical Loading and Dilution Model (SELDM)
*
Stormwater Model USEPA Storm Water Management Model (SWMM)
International Stormwater Best Management Practices (BMP) DatabaseStormwater YouTube Page
{{Natural resources
Environmental soil science
Stormwater management
Drainage