Catastrophic Events
Impact on Ecosystems
Tornadoes
Hurricanes
Floods
Floods
• Flooding happens during heavy rains, when rivers
overflow, when ocean waves come onshore, when
snow melts too fast or when dams or levees break.
• Flooding may be only a few inches of water or it may
cover a house to the rooftop.
Floods
• Floods that happen very quickly are called
flashfloods.
• Flooding is the most common of all natural hazards.
• It can happen in every U.S. state and territory.
Environmental Impact of
Floods
• Floods are important
in maintaining
ecosystem habitats
and soil fertility.
• Human attempts at
managing flood prone
areas disrupt the
natural flood cycle.
Environmental Impact of
Floods
• Activities such as drainage of
wetlands and land clearance
for farming; upstream
development that replaces
natural vegetation with
paved asphalt; and
construction of channels,
levees, reservoirs change the
flood cycle and often result
in increases runoff,
destruction of riparian
habitat, and increased water
pollution
Effects of
Floods
• Floods destroy drainage systems causing raw sewage
to spill out into bodies of water.
• Buildings can be destroyed which can lead to many
toxic materials such as paint, pesticide and gasoline
being released into the rivers, lakes, bays, and ocean,
killing marine life.
• Floods cause significant amounts of erosion to coasts,
leading to more frequent flooding if not repaired.
• Floods positively impact the environment by
spreading sediment containing nutrients to topsoil.
• Plants
Effects of a Flood on the
Ecosystem
– On dry land, plant life can
benefit from the sudden
appearance of a large
quantity of flood water.
– Water stored
underground will be
replenished by the
floodwater, while soil
above ground will be able
to soak up the water.
– Plants will be able to
receive water as a result.
– The nutrients carried by
the flood water can also
revive deprived plants
and aid in the
germination of seeds.
• Plants Continued
Effects of a Flood on the
Ecosystem
– Food water may prove
a new lease on life for
an area.
– The soil is likely to be
more fertile, leading
to a suitable area in
which to grow crops.
– Flooding can kill
woody and
herbaceous plants.
How Flooding Affects Animal
Breeding
• The environment in
are areas where
floods have occurred
are more suitable for
the reproduction of
species of birds and
some other animals.
• Fish can breed and
give birth in the areas
where flood water
stays for an extended
duration.
Animals
• Flooding forces
many wild animals
from their natural
habitats.
• Domestic animals
are also left
without homes
after floods.
• Rats may be a
problem during
and after a flood.
• The large amounts
of pooled water
lead to an increase
in mosquito
populations.
Effects of Floods on WaterBased Ecosystems
• Coral reefs are particularly at
risk from the runoff from
floods.
• This runoff contains sediment
and products such as
pesticides and fertilizers, and
will carry these into the ocean
ecosystem.
• Habitats may be destroyed,
and animal and plant life are is
likely to suffer.
– Sediment may obscure the
sunlight which inhibits
photosynthesis of marine
plants.
Effects of Floods on WaterBased Ecosystems
• There are some benefits of
flooding on the ocean
ecosystems
– The sudden appearance of
an overflow of water can
wash away unneeded salt,
alongside man-made
products like chemical
waste.
– This helps the flora and
fauna thrive.
– The flood water can also
sweep away junk and debris
which may have
accumulated by the side of
rivers.
Hurricanes
• An intense, rotating oceanic
weather system that
possesses maximum
sustained winds exceeding
74 mph.
• It forms and intensifies over
tropical oceanic regions.
• Hurricanes are generally
smaller than storms in midlatitudes.
• At the ocean’s surface, the
air spirals inward in a
counterclockwise direction.
• This cyclonic circulation
becomes weaker with
height, eventually turning
into clockwise outflow near
the top of the storm.
What is a hurricane
How Hurricanes Affect
the Ecosystem
How Hurricanes Affect the Ecosystem
• Aquatic Ecosystems
– Sediment erosion and
deposition often affect
oyster beds and coral
reefs.
– Saltwater intrusion in
freshwater lakes and
streams causes massive
fish kills and affects the
lakeside habitat.
How Hurricanes Affect the Ecosystem
– The hurricane floodwater
often carries many toxic
substances (Heavy metals,
pesticides, ammonia,
phosphate, untreated
sewage)
• These substance can cause
degradation of water
quality, phytoplankton
blooms, a decrease in
dissolved oxygen and harm
to many organisms.
– Hurricanes have minimal
effect on oceanic
ecosystems since the
contaminants tend to be
flushed out by tidal flows.
How Hurricanes Affect the Ecosystem
• Terrestrial Ecosystems
– Hurricanes wreak havoc
on terrestrial ecosystems.
– Strong winds, storm
surge, flooding and
tornadoes all have an
impact.
– Coastal wetlands and
barrier islands take the
brunt of the storm surge.
– The storm surge causes
sediment to erode and
shift.
How Hurricanes Affect the Ecosystem
– Many barrier islands end
up shifted or eroded
below sea level.
– Mangrove forests are
devastated by wind. These
trees often become fuel
for wildfires.
• This forces birds to find
other places to rest.
– Saltwater intrusion from
storm surge also changes
the wetland ecosystems.
– Sea grass beds are often
destroyed.
• These are critical to feeding
and nesting for many
animals
Tornadoes
Tornadoes
• A tornado is a
violent rotating
column of air
extending from a
thunderstorm to
the ground.
• The most violent
tornadoes can have
winds up to 300
mph.
How Tornadoes
Form
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You need warm, moist air from the
Gulf of Mexico and cool, dry air
from Canada.
When the two air masses meet,
they create instability in the
atmosphere.
A change in wind direction and an
increase in wind speed with
increasing height creates an
invisible, horizontal spinning effect
in the lower atmosphere.
Rising air within the updraft tilts
the rotating air from the
horizontal to vertical.
An area of rotation, 2-6 miles
wide, now extends through much
of the storm.
Most strong and violent tornadoes
from within this area of strong
rotation.
Tornadoes Effect on
Ecosystems
• Vegetation is uprooted.
• Trees can be pulled out of
the ground and carried to
another location.
• Organisms that live in or
near these uprooted trees
need to relocate.
• This can cause a loss of
species of organisms
could also affect the
interaction between
plants and animals.
Tornadoes Effect on
Ecosystems
• The loss of plants caused by a tornado can allow
new species of plants to grow in the cleared area.
• Plants that survive can grow more abundantly then
other species.
• This loss of vegetation could also lead to soil
erosion.
Sources
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http://sciencepolicy.colorado.edu/socasp/weather1/myers.html
http://www.fema.gov/kids/floods.htm
http://sciencepolicy.colorado.edu/socasp/weather1/myers.html
http://www.ehow.com/list_7494478_effects-flood-ecosystem.html
http://www.uwex.edu/ces/ag/issues/effectsoffloodingonplants.htm
l
http://www.bt.cdc.gov/disasters/floods/pdf/animals.pdf
http://www.ehow.com/list_7494478_effects-flood-ecosystem.html
http://www.ehow.com/how-does_5170460_do-hurricanes-affectecosystem_.html
http://www.comet.ucar.edu/nsflab/web/hurricane/311.htm
http://www.weatherwizkids.com/weather-tornado.htm
http://www.wisteme.com/question.view?targetAction=viewQuestio
nTab&id=7397