This document provides information about floods from a geography textbook. It defines floods as large amounts of water overflowing land that is usually dry. It describes three main types of floods - coastal floods caused by storms, river floods caused when rivers overflow their banks, and flash floods which happen suddenly. The document also lists and explains several common causes of floods like heavy rainfall, snowmelt, and storm surges. It discusses factors that make some cities more prone to flooding, such as their height above sea level and proximity to water bodies. Finally, the summary outlines some social, economic, and environmental impacts of floods in cities.

1. EDGEFIELD
SECONDARY
SCHOOL
SECONDARY
TWO
GEOGRAPHY
CHAPTER
FIVE:
FLOODS
Name:
_______________________________
(
)
Class:
2
_______________
Date:
______________
Definition
of
floods
Floods
are
large
amounts
of
water
that
overflows
onto
land
that
is
usually
dry.
Types
of
floods
(1)
Coastal
floods
• Occur
in
areas
along
the
coast
(especially
low-­‐lying
coastal
land,
such
as
river
mouths).
• Are
caused
by
intense
storms
(eg.
as
tropical
storms,
typhoons
or
hurricanes)
or
tsunamis.
• During
storms,
strong
winds
cause
large
waves
known
as
storm
surges.
These
storm
surges
bring
about
higher
water
levels
that
lead
to
coastal
floods.
(2)
River
floods
• Occur
when
water
in
the
river
rises
and
overflows
its
banks.
• Occur
on
the
floodplain,
which
consists
of
the
river
and
the
low-­‐lying
land
on
either
side
of
it.
• May
be
caused
by
dam
failure,
snowmelt
or
heavy
rainfalls.
(3)
Flash
floods
• Takes
place
suddenly
and
lasts
for
a
short
period
of
time.
• It
is
recognised
by
its
quick
rise
in
water
level.
• May
be
caused
by
heavy
rainfall,
coastal
floods
or
river
floods.
Causes
of
floods
(A)
Heavy
rainfall
• Characteristics
of
rainfall
include:
o Rainfall
duration
(hours)
refers
to
how
long
the
rain
event
lasts
for.
o Rainfall
intensity
(mm/h)
refers
to
the
rate
at
which
rain
falls
to
the
ground.
Tropical
storms
usually
have
a
high
rainfall
intensity.
o Rainfall
frequency
refers
to
the
probability
that
a
certain
amount
of
rain
falling
within
a
certain
period
of
time
will
occur
(eg.
England
experienced
a
1-­‐in-­‐50-­‐year
storm
in
June
2012).
GQ1
What
are
floods?

2. • In
densely
built
up
areas,
rainwater
may
not
be
able
to
infiltrate
the
ground
or
be
drained
off
fast
enough
during
a
heavy
rain
or
prolonged
rainfall
event.
The
accumulation
of
rainwater
on
the
ground
surface
thus
leads
to
flooding.
(B)
Snowmelt
• When
ice
and
snow
on
the
ground
or
mountain
melt,
snowmelt
flows
over
the
land
into
rivers,
increasing
the
amount
of
water
in
the
river.
This
causes
the
river
to
overflow
its
banks
and
flood
the
surrounding
areas.
(C)
Storm
surge
• During
a
storm,
strong
winds
push
water
towards
the
coast.
This
creates
huge
waves
which
are
piled
up
against
the
coastline,
causing
the
areas
near
the
coast
to
become
flooded.
(4)
Failure
of
man-­‐made
structures
• Examples
of
man-­‐made
structures:
o Dams
(a
barrier
built
across
a
river)
o Levees
(raised
banks
that
act
as
flood
barriers)
o Floodwalls
(flood
barriers
that
are
made
of
concrete)
• When
these
structures
crack
or
collapse,
large
amounts
of
water
previously
stored
behind
these
structures
will
gush
through
and
flood
the
surrounding
areas.
Which
cities
are
prone
to
floods?
Floods
can
occur
almost
anywhere.
Factors
that
cause
cities
to
be
more
prone
to
floods
(I)
Height
of
land
above
sea
level
• Cities
that
are
located
on
low-­‐lying
lands
are
more
prone
to
floods
because
even
a
little
rise
in
sea
level
will
cause
these
cities
to
experience
flooding.
(II)
Proximity
to
water
bodies
• Cities
located
near
water
bodies
are
more
prone
to
floods
because
these
cities
would
experience
flooding
whenever
water
overflow
the
banks
of
these
water
bodies.
(III)
Permeability
of
surface
cover
• Permeability
refers
to
how
easy
water
can
infiltrate
into
the
ground.
• As
concrete
surfaces
are
almost
impermeable,
water
cannot
infiltrate
the
ground.
This
leads
to
a
higher
surface
runoff
and
eventually
a
higher
likelihood
of
floods.
• As
vegetated
surfaces
are
more
permeable,
water
can
infiltrate
the
ground
easily.
This
leads
to
less
surface
runoff,
thereby
lowering
the
likelihood
of
floods.
GQ2
Why
are
some
cities
more
prone
to
floods
than
others?

3. (IV)
Channel
capacity
• Floods
may
occur
when
the
amount
of
rain
exceed
the
capacity
of
the
channel.
• In
cities
with
a
high
proportion
of
built-­‐up
areas
and
concrete
surfaces,
it
is
likely
to
experience
large
amounts
of
surface
runoff
during
a
rain
event.
Canals
may
not
have
the
capacity
to
carry
this
runoff
away
fast
enough,
thereby
leading
to
floods.
Flooding
in
cities
tends
to
affect
many
people
due
to
the
high
population
densities
in
cities.
Impact
of
floods
(A)
SOCIAL
IMPACTS
1)
Injuries
and
loss
of
lives
• Fast
moving
floods
waters
can
cause
buildings
to
collapse.
• Objects
and
debris
are
also
washed
along
by
fast-­‐moving
water.
• As
a
result,
people
and
livestock
are
swept
away
and
it
can
cause
injuries
and
deaths.
2)
Affects
physical
health
• As
people
may
get
caught
in
the
flood
for
too
long,
it
can
cause
people
to
suffer
from
hypothermia
(symptoms
of
constant
shivering,
confusion
&
loss
of
coordination).
3)
Affects
emotional
and
mental
health
• Loss
of
homes
or
livestock
due
to
floods
can
cause
mental
stress
to
people.
• Loss
of
loved
ones
or
family
members
during
a
flood
can
cause
emotional
distress
to
flood
victims.
4)
Spread
of
diseases
• During
a
flood,
water
supplies
may
be
contaminated
by
chemical
spills.
This
cause
people
to
be
exposed
to
contaminated
drinking
water
which
results
in
the
spread
of
cholera
and
dysentery.
• Stagnant
pools
of
floodwater
encourage
mosquitoes
to
breed
and
this
leads
to
more
cases
of
malaria
and
dengue
fever.
5)
Homelessness
• Floodwaters
can
damage
property
and
sweep
houses
away.
This
cause
people
to
lose
a
roof
over
their
head
and
people
may
have
to
evacuate
to
emergency
shelters.
6)
Disruption
to
clean
water
supply
• Floodwaters
can
damage
water
pipes
and
this
causes
disruption
to
water
supply.
• Water
supply
may
also
be
contaminated
due
to
burst
sewage
pipes.
GQ3
How
do
floods
affect
people
living
in
cities?

4. Impact
of
floods
(continued)
(B)
ECONOMIC
IMPACTS
1)
Damage
to
machinery
and
equipment
• Machinery
and
equipment
may
be
submerged
or
damaged
by
floodwaters.
• As
a
result,
factories
are
unable
to
operate
and
this
causes
them
to
suffer
economic
losses.
• Companies
may
lose
profits
and
have
to
spend
money
buying
new
equipment.
2)
Damage
to
transport
infrastructure
• Transport
infrastructure
may
be
submerged
or
damaged
by
floodwaters.
• As
a
result,
people
are
unable
to
travel
to
work
and
tourists
may
not
want
to
visit
this
area.
• This
causes
an
overall
reduction
in
productivity,
employment
and
profits.
3)
Disruption
to
energy
supply
• During
a
flood,
power
lines
may
be
damaged.
This
causes
power
outages
to
occur
and
leads
to
the
lack
of
electricity.
• As
a
result,
companies
and
factories
are
unable
to
operate.
This
leads
to
the
loss
of
employment
and
income
for
individuals
and
companies.