EPA Brochure - Protecting Water Quality from Urban Runoffand snowmelt remains above the
surface, where it runs off rapidly in
unnaturally large amounts.
Storm sewer systems concentrate
runoff into smooth, straight
conduits. This runoff gathers speed
and erosional power as it travels
underground. When this runoff
leaves the storm drains and empties
into a stream, its excessive volume
and power blast out streambanks,
damaging streamside vegetation and
wiping out aquatic habitat. These
increased storm flows carry sediment
loads from construction sites and
other denuded surfaces and eroded
streambanks. They often carry
higher water temperatures from
streets, roof tops, and parking lots,
which are harmful to the health and
reproduction of aquatic life.
from
Did you know that because of impervious surfaces like pave-
ment and rooftops, a typical city block generates more than
5 times more runoff than a woodland area of the same size?
The most recent National Water Quality Inventory reports that runoff
from urbanized areas is the leading source of water quality impairments
to surveyed estuaries and the third-largest source of impairments to
surveyed lakes.
In urban and suburban areas, much
of the land surface is covered
by buildings and pavement, which
do not allow rain and snowmelt
to soak into the ground. Instead,
most developed areas rely on storm
drains to carry large amounts of
runoff from roofs and paved areas to
nearby waterways. The stormwater
runoff carries pollutants such as oil,
dirt, chemicals, and lawn fertilizers
directly to streams and rivers, where
they seriously harm water quality.
To protect surface water quality and
groundwater resources, development
should be designed and built to
minimize increases in runoff.
How Urbanized Areas
Affect Water Quality
Increased Runoff
The porous and varied terrain of
natural landscapes like forests,
wetlands, and grasslands traps
rainwater and snowmelt and allows
them to filter slowly into the ground.
In contrast, impervious (nonporous)
surfaces like roads, parking lots, and
rooftops prevent rain and snowmelt
from infiltrating, or soaking, into
the ground. Most of the rainfall
The loss of infiltration from
urbanization may also cause profound
groundwater changes. Although
urbanization leads to great increases
in flooding during and immediately
after wet weather, in many instances
it results in lower stream flows
during dry weather. Many native fish
and other aquatic life cannot survive
when these conditions prevail.
Increased Pollutant Loads
Urbanization increases the variety
and amount of pollutants carried
into streams, rivers, and lakes. The
pollutants include:
• Sediment
• Oil, grease, and toxic chemicals
from motor vehicles
• Pesticides and nutrients from
lawns and gardens
• Viruses, bacteria, and nutrients
from pet waste and failing septic
systems
• Road salts
• Heavy metals from roof shingles,
motor vehicles, and other sources
• Thermal pollution from dark
impervious surfaces such as streets
and rooftops
These pollutants can harm fish and
wildlife populations, kill native
vegetation, foul drinking water
supplies, and make recreational areas
unsafe and unpleasant.
Clean Water Is Everybody’s Business
URBAN RUNOFFEPA 841-F-03-003
Relationship between impervious cover and surface runoff. Impervious cover in a watershed results in increased
surface ruunoff. As little as 10 percent impervious cover in a watershed can result in stream degradation.
Protecting Water Quality
Managing Urban Runoff
What Homeowners Can Do
To decrease polluted runoff from
paved surfaces, households can develop
alternatives to areas traditionally covered
by impervious surfaces. Porous pavement
materials are available for driveways and
sidewalks, and native vegetation and mulch
can replace high maintenance grass lawns.
Homeowners can use fertilizers sparingly
and sweep driveways, sidewalks, and roads
instead of using a hose. Instead of disposing
of yard waste, they can use the materials to
start a compost pile. And homeowners can
learn to use Integrated Pest Management
(IPM) to reduce dependence on harmful
pesticides.
In addition, households can prevent
polluted runoff by picking up after pets and
using, storing, and disposing of chemicals
properly. Drivers should check their cars
for leaks and recycle their motor oil and
antifreeze when these fluids are changed.
Drivers can also avoid impacts from car
wash runoff (e.g., detergents, grime, etc.) by
using car wash facilities that do not generate
runoff. Households served by septic systems
should have them professionally inspected
For More Information
U.S. Environmental Protection Agency
Nonpoint Source Control Branch (4503T)
1200 Pennsylvania Avenue, NW
Washington, DC 20460
www.epa.gov/nps
and pumped every 3 to 5 years. They should
also practice water conservation measures to
extend the life of their septic systems.
Controlling Impacts from New
Development
Developers and city planners should
attempt to control the volume of runoff
from new development by using low
impact development, structural controls,
and pollution prevention strategies. Low
impact development includes measures that
conserve natural areas (particularly sensitive
hydrologic areas like riparian buffers and
infiltrable soils); reduce development
impacts; and reduce site runoff rates by
maximizing surface roughness, infiltration
opportunities, and flow paths.
Controlling Impacts from
Existing Development
Controlling runoff from existing urban
areas is often more costly than controlling
runoff from new developments. Economic
efficiencies are often realized through
approaches that target “hot spots” of
runoff pollution or have multiple benefits,
such as high-efficiency street sweeping
(which addresses aesthetics, road safety,
and water quality). Urban planners and
others responsible for managing urban
and suburban areas can first identify and
implement pollution prevention strategies
and examine source control opportunities.
They should seek out priority pollutant
reduction opportunities, then protect
natural areas that help control runoff, and
finally begin ecological restoration and
retrofit activities to clean up degraded water
bodies. Local governments are encouraged
to take lead roles in public education
efforts through public signage, storm drain
marking, pollution prevention outreach
campaigns, and partnerships with citizen
groups and businesses. Citizens can help
prioritize the clean-up strategies, volunteer
to become involved in restoration efforts,
and mark storm drains with approved “don’t
dump” messages.
Turn Your Home into a Stormwater Pollution Solution!
www.epa.gov/nps
This web site links to an EPA homeowner’s guide to healthy
habits for clean water that provides tips for better vehicle and
garage care, lawn and garden techniques, home improvement, pet
care, and more.
National Management Measures to Control Nonpoint Source
Pollution from Urban Areas
www.epa.gov/owow/nps/urbanmm
This technical guidance and reference document is useful to local,
state, and tribal managers in implementing management programs
for polluted runoff. Contains information on the best available,
economically achievable means of reducing pollution of surface
waters and groundwater from urban areas.
Onsite Wastewater Treatment System Resources
www.epa.gov/owm/onsite
This web site contains the latest brochures and other resources
from EPA for managing onsite wastewater treatment systems
(OWTS) such as conventional septic systems and alternative
decentralized systems. These resources provide basic information
to help individual homeowners, as well as detailed, up-to-date
technical guidance of interest to local and state health
departments.
Low Impact Development Center
www.lowimpactdevelopment.org
This center provides information on protecting the environment
and water resources through integrated site design techniques that
are intended to replicate preexisting hydrologic site conditions.
Stormwater Manager’s Resource Center (SMRC)
www.stormwatercenter.net
Created and maintained by the Center for Watershed Protection,
this resource center is designed specifically for stormwater
practitioners, local government officials, and others that need
technical assistance on stormwater management issues.
Strategies: Community Responses to Runoff Pollution
www.nrdc.org/water/pollution/storm/stoinx.asp
The Natural Resources Defense Council developed this inter-
active web document to explore some of the most effective
strategies that communities are using around the nation to
control urban runoff pollution. The document is also available in
print form and as an interactive CD-ROM.
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