5. 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.
6. 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.
7. 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.
8. 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
9. 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.
10. • Plants
– 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.
Effects of a Flood on the – The nutrients carried by
Ecosystem the flood water can also
revive deprived plants
and aid in the
germination of seeds.
11. • Plants Continued
– Fl ood 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
Effects of a Flood on the herbaceous plants.
Ecosystem
12. 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.
13. Animals
• Flooding forces • Rats may be a
many wild animals problem during
from their natural and after a flood.
habitats. • The large amounts
of pooled water
• Domestic animals lead to an increase
are also left in mosquito
without homes populations.
after floods.
14. Effects of Floods on Water-
Based 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.
15. Effects of Floods on Water-
Based 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.
17. • An intense, rotating oceanic
weather system that What is a hurricane
possesses maximum
sustained winds exceeding
74 mph.
• It forms and intensifies over
tropical oceanic regions.
• Hurricanes are generally
smaller than storms in mid-
latitudes.
• 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.
19. 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.
20. 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.
21. 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.
22. 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
24. 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.
25. How Tornadoes
Form
• 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.
26. 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.
27. 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.
