Stormwater, also spelled storm water, is water that originates during
precipitation events and snow/ice melt.
Stormwater can soak into the
soil (infiltrate), be held on the surface and evaporate, or runoff and
end up in nearby streams, rivers, or other water bodies (surface
In natural landscapes such as forests, the soil absorbs much of the
stormwater and plants help hold stormwater close to where it falls. In
developed environments, unmanaged stormwater can create two major
issues: one related to the volume and timing of runoff water
(flooding) and the other related to potential contaminants that the
water is carrying (water pollution).
Stormwater is also a resource and important as the world's human
population demand exceeds the availability of readily available water.
Techniques of stormwater harvesting with point source water management
and purification can potentially make urban environments
self-sustaining in terms of water.
Stormwater runoff as a source of pollution
3 Urban flooding
5 Integrated water management
6.1 United States
6.1.1 Federal requirements
6.1.2 State and local requirements
Nonpoint source pollution
Nonpoint source pollution management
7 Public education campaigns
9 See also
11 External links
Relationship between impervious surfaces and surface runoff
Because impervious surfaces (parking lots, roads, buildings, compacted
soil) do not allow rain to infiltrate into the ground, more runoff is
generated than in the undeveloped condition. This additional runoff
can erode watercourses (streams and rivers) as well as cause flooding
after the stormwater collection system is overwhelmed by the
additional flow. Because the water is flushed out of the watershed
during the storm event, little infiltrates the soil, replenishes
groundwater, or supplies stream baseflow in dry weather.
A first flush 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 result in high levels of pollutants discharged from storm
sewers to surface waters.:216
Pollutants entering surface waters during precipitation events is
termed polluted runoff. Daily human activities result in deposition of
pollutants on roads, lawns, roofs, farm fields, etc. When it rains or
there is irrigation, water runs off and ultimately makes its way to a
river, lake, or the ocean. While there is some attenuation of these
pollutants before entering the receiving waters, the quantity of human
activity results in large enough quantities of pollutants to impair
these receiving waters.
Further information: Urban runoff
Stormwater runoff as a source of pollution
Urban runoff being discharged to coastal waters
In addition to the pollutants carried in stormwater runoff, 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
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, encourage weed
invasion, and alter natural flow regimes. Native species often rely on
such flow regimes for spawning, juvenile development, and migration.
In some areas, especially along the U.S. coast, polluted runoff from
roads and highways may be the largest source of water pollution. For
example, about 75 percent of the toxic chemicals getting to Seattle,
Puget Sound are carried by stormwater that runs off paved
roads and driveways, rooftops, yards, and other developed land.
Stormwater is a major cause of urban flooding. 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 or snow melt, 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, 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, utilities
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.
Urban flooding has significant economic implications. In the U.S.,
industry experts estimate that wet basements can lower property values
by 10 to 25 percent and are cited among the top reasons for not
purchasing a home. According to the Federal Emergency Management
Agency almost 40 percent of small businesses never reopen their doors
following a flooding disaster. In the UK, urban flooding is
estimated to cost £270 million a year (as of 2007) in
Wales; 80,000 homes are at risk.
A study of Cook County, Illinois, identified 177,000 property damage
insurance claims made across 96 percent of the county’s ZIP codes
over a five-year period from 2007 to 2011. This is the equivalent of
one in six properties in the County making a claim. Average payouts
per claim were $3,733 across all types of claims, with total claims
amounting to $660 million over the five years examined.
An example of Urban flooding control project is the Brays Bayou
Greenway Framework. The Brays Bayou Greenway Framework is
federally funded improvement project. Brays Bayou starts from the
Bayou's mouth at Buffalo Bayou and the Ship Channel in the east to the
Barker Reservoir and George Bush Park in the west. In aim to identify
a broad set of potential recreation and open space opportunities along
the 35 miles of Brays Bayou, Brays Bayou and its tributaries provide
drainage to a watershed of approximately 88,000 acres south of
downtown Houston, Texas. Project Brays responses to the present
flooding problems in
Houston and creates a short-term solution by
improving the bayou's drainage capacity, also considered a long-term
solution for flooding preventing.
Stormwater filtration system for urban runoff
Managing the quantity and quality of stormwater is termed, "Stormwater
Management." 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 ponds) 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, including:
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 so contaminants are
removed before they pollute surface waters or groundwater resources;
acquisition and protection of natural waterways or rehabilitation;
building "soft" structures such as ponds, swales, wetlands or green
infrastructure solutions to work with existing or "hard" drainage
structures, such as pipes and concrete channels;
development of funding approaches to stormwater programs potentially
including stormwater user fees and the creation of a stormwater
development of long-term asset management programs to repair and
replace aging infrastructure;
revision of current stormwater regulations to address comprehensive
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,
and about what it can do to improve water quality; and
planning carefully to create solutions before problems become too
Integrated water management
Rain garden designed to treat stormwater from adjacent parking lot
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 when considered in the design
process. Professionals in their respective fields, such as Urban
planners, architects, landscape architects, interior designers, and
engineers, often consider integrated water management as a foundation
of the design process.
Also known as low impact development (LID) in the United States,
Water Sensitive Urban Design (WSUD) in Australia, IWM has the
potential to improve runoff quality, reduce the risk and impact of
flooding and deliver an additional water resource to augment potable
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 (to restore the natural recharge of groundwater),
biofiltration or bioretention (e.g., rain gardens) 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, bioswales, infiltration trenches,
sustainable pavements (such as permeable paving), 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, biofilters, 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 our environment and precious water resources.
United States regulation of point source water pollution
Retention basin for management of stormwater
In the United States, the Environmental Protection Agency (EPA) is
charged with regulating stormwater pursuant to the Clean
(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 (sewage)
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.
To address the nationwide problem of stormwater pollution, Congress
broadened the CWA definition of "point source" in 1987 to include
industrial stormwater discharges and municipal separate storm sewer
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
A silt fence, a type of sediment control, installed on a construction
EPA has authorized 46 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
Maryland requires erosion and sediment controls on
construction sites of 5,000 sq ft (460 m2) 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
Nonpoint source pollution management
Agricultural wastewater treatment
Agricultural wastewater treatment and Erosion
Agricultural runoff (except for concentrated animal feeding
operations, or "CAFO") is classified as nonpoint source pollution
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) in the U.S. Department
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, Michigan to reach the
Grand River.) Its outreach activities include a rain barrel
distribution program and materials for homeowners on installing rain
Other public education campaigns highlight the importance of green
infrastructure in slowing down and treating stormwater runoff. DuPage
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.
Since humans began living in concentrated village or urban settings,
stormwater runoff has been an issue. During the Bronze Age, housing
took a more concentrated form, and impervious surfaces emerged as a
factor in the design of early human settlements. Some of the early
incorporation of stormwater engineering is evidenced in Ancient
A specific example of an early stormwater runoff system design is
found in the archaeological recovery at Minoan
Phaistos on Crete.
Nationwide Urban Runoff Program
Nationwide Urban Runoff Program (U.S. research program)
Sanitary sewer overflow
^ Schueler, Thomas R. "The Importance of Imperviousness." Archived
2014-03-27 at the Wayback Machine. Reprinted in The Practice of
Watershed Protection. 2000. Center for Watershed Protection, Ellicott
^ Metcalf, Leonard; Eddy, Harrison P. (1916). American Sewerage
Practice: Disposal of Sewage. III. New York: McGraw-Hill.
^ Alex Maestre and Robert Pitt; Center for Watershed Protection
Stormwater Quality Database, Version 1.1: A
Compilation and Analysis of
Stormwater Monitoring Information."
Report prepared for U.S. Environmental Protection Agency (EPA),
Washington, DC. September 4, 2005.
^ Washington State Department of Ecology. "Control of Toxic Chemicals
in Puget Sound, Phase 2: Development of Simple Numerical Models"
Archived 2017-03-02 at the Wayback Machine., 2008
^ Indoor Air Quality (IAQ) Scientific Findings
(IAQ-SFRB), "Health Risks or Dampness or Mold in Houses" "Archived
copy". Archived from the original on 2013-10-04. Retrieved
^ The Prevalence and Cost of Urban Flooding. Chicago: Center for
Neighborhood Technology, 2013.
^ "Protecting Your Businesses". Washington, D.C.: U.S. Federal
Emergency Management Agency. 2015-04-22.
^ Parliamentary Office of Science and Technology, London, UK. "Urban
Flooding." Postnote 289, July 2007
^ The Prevalence and Cost of Urban Flooding. Rep. Chicago: Center for
Neighborhood Technology, 2013
^ Brays Bayou Greenway Framework - ASLA 2009 Professional Awards
^ a b Washington State Department of Ecology (2005). Olympia, WA.
Stormwater Management Manual for Western Washington." Archived
2012-04-02 at the Wayback Machine. Publication No. 05-10-029.
^ "Reading: Urban
Stormwater Management in the
United States The
National Academies Press". www.nap.edu. Retrieved 2015-09-19.
^ Debo, Tom; Reese, Andrew (2003). "Chapter 2.
Stormwater Management. Boca Raton, FL: CRC Press.
^ Prince George's County, Maryland. Department of Environmental
Resources (January 2000). Low-Impact Development Design Strategies, An
Integrated Design Approach (Report). EPA. EPA 841-B-00-003.
Water Sensitive Urban Design - Melbourne Water".
Wsud.melbournewater.com.au. Retrieved 2011-12-05.
^ United States. Federal
Water Pollution Control Amendments of 1972
Water Act"). Pub.L. 92–500, October 18, 1972.
^ United States.
Water Quality Act of 1987, Pub.L. 100–4, February
4, 1987. Added CWA section 402(p), 33 U.S.C. § 1342(p).
Stormwater Discharges from Municipal Sources.
NPDES State Program Information". National Pollutant Discharge
Elimination System. EPA. 2016.
Stormwater Design Manual (Report). Baltimore, MD: Maryland
Department of the Environment. 2009. Archived from the original on
^ State of Maryland. Code of
Maryland Regulations (COMAR). Activities
for Which Approved
Erosion and Sediment Control Plans are Required.
Water Act sec. 319, 33 U.S.C. § 1329.
^ "Developing an MS4 Program". NPDES/
Stormwater Discharges from
Municipal Sources. EPA. 2016.
^ West Michigan Environmental Action Council (WMEAC), Grand Rapids,
MI. "Stop Hydrofilth." Accessed 2013-08-26.
^ WMEAC. "15 to the River" Accessed 2013-08-26.
^ WMEAC. "
Rain Gardens... beautiful solutions for water pollution."
^ DuPage County
Stormwater Management. "Education and Outreach."
^ Trimble, Stanley W. (2007). Encyclopedia of
Water Science. Boca
Raton, FL: CRC Press. ISBN 0-8493-9627-1.
^ C. Michael Hogan, "
Phaistos Fieldnotes." The Modern Antiquarian
Stormwater at Curlie (based on DMOZ)
Stormwater Permit Program
Stormwater Model USGS Stochastic Empirical Loading and Dilution Model
Stormwater Model USEPA Storm
Water Management Model (SWMM)
Stormwater Best Management Practices (BMP) Database
Stormwater management structures
Treatment / Containment
Stormwater detention vault
Continuous Monitoring and Adaptive Control
Flood control channel
Flow control structure
Environmental impact of shipping
Fish diseases and parasites
Marine garbage patches:
Mercury in fish
Nonpoint source pollution
Plastic particle water pollution
Point source pollution
Shutdown of thermohaline circulation
Pollution / quality
Ambient standards (USA)
Clean Air Act (USA)
Fossil fuels (peak oil)
Non-timber forest products
Types / location
storage and recovery
Earth Overshoot Day
Renewable / Non-renewable
Agriculture and agronomy
Decentralized wastewater system
Asbestos cement pipe
Cast iron pipe
Vitrified clay pipe
Combined sewer overflow
Sewer dosing unit
Sewer gas destructor lamp
Stormwater detention vault
Biogenic sulfide corrosion
Sanitary sewer overflow