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i lowa	FACT SHEET

Iowa

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^ Kansas
Missouri

Number 1

Nebraska

Stream Channelization





Definition: Stream channelization describes anv activity that moves, straiahtens, shortens, cuts off, diverts, or
fills a stream channel, whether natural or previously altered. Such activities include the widening, narrowing,
straightening, or lining of a stream channel that alters the amount and speed of the water flowing through the
channel. Examples of channelization are: lining channels with concrete; pushing gravel from the stream bed and
placing it along the banks; and placing streams into culverts.







Social and Economic Implications of Channelizing Streams: straightening even small reaches of streams

can cause adverse stream impacts. Those impacts may require expensive private or public remedies. Channelization can:

fifl Pose threats to human safety. This can occur especially in concrete channels where banks lack measures for people and
animals to escape.

Efi Damage public or private roads and bridges due to undercutting, which can make them unsafe.

m Damage utilities and pipelines from uplifting and/or bank erosion, which can rupture lines and threaten human health
and aquatic life.

5$) Increase flooding either upstream or downstream due to the decreased capacity of the stream to carry flows.

Damage public or private property as a result of bank erosion or increased flooding, increasing maintenance costs for
landowners.

t£] Increase the amount and speed of water leaving impervious surfaces paved with concrete and asphalt, if the purpose
of channelization is to develop property.

5$) Reduce dollars spent on tourism, recreation and associated industries. Less stream habitat can result in fewer sport fish
t£] Increase costs for treatment of drinking water due to more nonpoint source pollution in runoff.
fiB Decrease property values in areas where flooding is more frequent.

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Permit Requirements: Channelization projects in streams may
require a permit from the Corps of Engineers under Section 404 of the
Clean Water Act. Please contact your local Corps District to find out if
your project requires a permit. You can find the nearest Corps office
via the Internet at: http://www.usace.army.miI/faq.html#Permits

"For if one link in nature's chain
might be lost, another might be lost,
until the whole of things will vanish
by piecemeal." - Thomas Jefferson



in

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Straightening a stream or
placing it into a pipe tends to
transfer problems from one
area to another.

¦4 Natural stream

Straightened stream that has
undercut its cement lining

Environmental Impacts: Generally, the adverse impacts created by channelization projects far outweigh the benefits they intend
to create. They tend to transfer problems from one area to another, either above, below or within a project area. For instance,
shortening the reach of a stream moves flooding from the channelized reach to a downstream reach.

Natural Stream Conditions

Channelized Streams

Natural streams are free-flowing
systems. They have meanders, swifter
flowing areas (riffies) and deeper, quiet
areas (pools).

(Sr! The length and spacing of
meanders and the size of the channel
match normal stream flows.

Trees and vegetation provide
natural protection against flood
damage and bank erosion, as well as
trap sediments. They also help
regulate the quality of the stream
ecosystem.

S Shorten and steepen streams. Channelization usually results in shorter and
steeper streams, which then cause faster stream flows and increased erosion (usually
eroding the bed downward and outward, and cutting banks).

S Reduce the ability of the stream to slow floods and absorb flood damage.

Meanders help slow flowing waters. Removing vegetation along banks reduces the
ability of the stream to buffer adjacent areas against floods and flood damage, also
reducing the quality of the stream ecosystem.

2 Change flood heights and frequency. A channelization project may target the
faster removal of water, but the removal of water in this manner can not only adversely
affect adjacent wetlands, but the stream itself. During drier periods of the year,
wetlands tend to discharge (slow release) water into streams, helping maintain flows.
(See picture below at right A )

ft Affect drinking water quantities.

When water moves away from an area
faster, the recharge of groundwater may
not occur (slow release of water into the
ground water table). Where groundwater
is important as a source of drinking water,
the supply of water to drinking water wells
may not be replenished at the same rate.

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Natural Stream Conditions

Channelized Streams

&& Provide habitat for
birds, fish, other wildlife,
and plants.

Intermittent streams or streams in the
upper portions of a watershed have the
ability to remove nitrogen more quickly,
reducing the amount that is transported
downstream in shorter distances.

# These streams also play an
important role in the primary production
of plant and animal food for downstream
areas,

/ They also provide spawning and
rearing habitat for fish species.

s Cause changes in the type and amount of habitat. When changes occur to the
material forming the stream bed (e.g., lining a stream with concrete or forcing flows
into a pipe, etc.), the plants and animals that depended on that specific habitat are
replaced by others that are able to survive the habitat changes. It is the cumulative
(additive) impact of many projects that can significantly affect species in terms of their
diversity and the numbers of individuals.

Cause changes in plant and animal communities (number of individuals in a
population and species that are present). This is a direct result of changes in habitat
and water flow patterns and duration. Plant species can be affected by changes in the
quantity and timing of flooding (either annually or seasonally) and changes in the
amount of sediment in flows, which can alter the overall plant community. Plant
community changes can adversely impact the quality of wetland and riparian areas
(areas that parallel stream banks). When plants are affected, changes can occur in
the animal species in the area that use plants for food, cover, and resting. Removing
plants in and along streams also reduces the amount of leaf litter (detritus) that serves
as food for animals at the bottom of food webs.

ft Cause declines in species. Water quality changes can
affect species. Increased sediments in a waterbody can
smother benthic (bottom-dwelling) organisms and limit light
penetration, which reduces microscopic plant production and
disrupts the aquatic food chain. Turbidity from bed and bank
erosion can impact species that are less tolerant to sediment in
stream flows.

Provide sources of drinking
water for most urban areas; water
for industrial use, including water
to cool energy plants; and water
for domestic uses, such as
cooking, bathing, dishwashing,
and cleaning.

@ Increased accumulations of nutrients in streams can create algal blooms
which can affect human and animal health (e.g., livestock).

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Natural Stream Conditions

Channelized Streams

Szj Provide water quality benefits

s Produce changes in water quality. Intermittent and ephemera! streams are
especially valuable in filtering out pollutants because more pollutants are filtered when a
larger portion of the water is in contact with such stream beds. When portions of these
streams are lost, especially the cumulative loss of many small segments of a stream,
adverse impacts to water quality can occur.

0



Rocks in streams help add oxygen to flows A

@ Cause changes in pollutants in streams. 0 When streams are channelized for
development, flooding problems can increase, and the water running off the land picks
up pollutants such as phosphorous, nitrogen, pesticides, sediment and heavy metals.
This degrades the stream water quality and can increase the cost of drinking water
treatment. 0 Removal of trees and vegetation along the stream bank can increase
the amount of pollutants in streams (such as nitrogen, phosphorous, E-coli bacteria,
pesticides, and sediment, etc.) and can result in increased water temperature and
decreased oxygen. Temperature is critical to many aquatic species, as it triggers fish
spawning 0 Added nutrients can result In algal blooms, which increase bacteria and
decrease the amount of available oxygen, often resulting in fish kills.

St, Provide economic benefits to
communities through tourist attractions
and associated services and industries.

The City of Great Bend, Kansas, has
capitalized on bird-watching in wetlands.

S Reduce ecotourism dollars through wetland loss (as a result of
flow changes) or the loss of sport fisheries (due to loss of free-
flowing habitat). Loss of wetlands can reduce tourism associated with
nature-related recreation, such as hunting, bird-watching, nature
photography, and associated service industries (food, gas, lodging, etc.).

Alternatives to channelizing a stream can be more environmentally friendly and less expensive!

8 Design projects to the lay of the land instead of cookie-cutter designs.

fi Use watershed best management practices, such as leaving a buffer width of trees along each side of the stream and retaining
wetlands. These are better solutions for reducing sediment and the effects of flooding,
i See our Fact Sheet on Urban Project Planning!

For additional information about streams or wetlands:

Contact the EPA WETLANDS HELPLINE at 1-800-832-7828 or
visit our Web site at http:\\www.epa.gov/owow
Fact Sheet Source: EPA Region 7, Section 404 of the Clean Water
Act/Wetlands Program, February 2005

For additional information about this Fact Sheet, other
educational materials about streams or wetlands, and
alternatives to stream channelization: Contact: Carl
Stevens, EPA Region 7. Phone: 913-551-7569;

E-mail: stevens.carl@epa.gov

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