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Living with Dams: Know Your Risk | April 2012
What Dams Provide
Dams are often hidden assets but they
can also be hidden liabilities.
Dams provide vital benefits including
flood protection, water supply,
hydropower, irrigation and recreation.
Imagine the impact of losing a major
reservoir or flood control dam:
Would there be catastrophic
flooding? How many homes and
businesses might be flooded? How
many people displaced?
Would there be adequate water for
domestic use? Irrigating crops? Caring
for livestock? Fighting fires?
Are local utilities dependent on
hydropower? How many lives and
jobs could be affected by temporary
shutdown or closure of an industry
dependent on hydropower?
How would transportation
systems—roads, railroads, navigable
waterways—be affected?
How would economies, jobs and
areas dependent on recreation be
affected should the reservoir be lost?
Dams can pose risks to those living
downstream if they are not maintained
and operated correctly.
Some dams
increase safety risks to an often unaware
public when they age, deteriorate or
malfunction, releasing sudden, dangerous
flood flows.
There are over 85,000 dams in the
U.S. Most every state has at least several
hundred dams.
More than half of these dams are older
than 50 years and many are in need of
extensive rehabilitation.
Many communities in the United States
are impacted by at least one dam. In
many cases large populations, vital
elements of our infrastructure, jobs, and
businesses are located downstream of
dams.
When dams fail or malfunction, they can
adversely affect people, their livelihood
and property.
Dam failure floods are almost always
more sudden and violent than normal
stream, river or coastal floods. They often
produce damage that looks like tornado
damage.
Dams are owned and operated by many
different types of owners. Sometimes
they only serve the interest of the
owner—for instance in the case of a
neighborhood association that wants
its homes built around a lake—and
sometimes they serve the interest of
communities—for instance in the case of
a water supply utility.
Downstream development affects a dam’s
risk. Dams that used to be out in the
rural areas, affecting nothing but open
fields, are now affecting neighborhoods
and industrial areas. Due to increased
development, dam failure consequences
have become much higher. The number
of dams that pose a risk to human life is
steadily increasing. In the last decade, the
number has increased by over 1,000 to a
total of about almost 14,000. The cause
of this increase is a combination of new
dam construction and/or downstream
development.
The point is twofold: any dam has
the potential to adversely affect
downstream areas and lives; Many
dams, should they fail, can also affect
the delivery of essential utilities or flood
control.
Although dam failures are
infrequent, the impacts can
be catastrophic, often far
exceeding typical stream/river
flood events.