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1.
Mitigation
measures
are
implemented
to
reduce
the
impact
of
floods
and
help
prevent
floods
from
occurring.
Mitigation
strategies
Describe
the
strategy
Example
of
where
and
how
strategy
is
used
Describe
the
benefits
Describe
the
challenges
(A)
REGULATION
The
government
enforces
a
rule
or
a
law
which
states
where
and
how
developments
must
be
carried
out.
1)
Zoning
A
way
in
which
the
government
plans
the
physical
development
of
the
land
and
its
uses.
• Zoning
laws
specify
the
areas
where
residential,
industrial,
commercial
or
recreational
activities
may
take
place.
• Flood-­‐prone
areas
are
often
zoned
as
low-­‐
value
developments
such
as
parks
and
fields
for
recreational
activities
so
that
fewer
economic
losses
will
be
incurred
in
the
event
of
floods.
Eagan
City
in
Minnesota,
USA:
• Areas
near
the
flood-­‐prone
Minnesota
River
are
used
for
low-­‐
value
developments
such
as
the
Minnesota
Valley
National
Wildlife
Refuge
and
parks.
• Industrial
zones
and
residential
zones
are
located
further
away
from
the
river
so
that
factories
and
houses
may
be
safe
from
floods.
• Zoning
creates
spaces
of
green
areas,
such
as
parks
and
fields,
which
help
to
reduce
the
impact
of
flood
damage.
• Zoning
may
limit
the
development
of
available
land
because
only
certain
land
uses
are
permitted.
• Zoning
is
difficult
to
carry
out
because
of
competing
land
uses.
• People
may
also
not
abide
by
the
recommended
land
use.
2)
Elevated
properties
• Properties
are
elevated
or
raised
to
a
certain
height
to
prevent
floodwaters
from
entering
properties
during
a
flood
event.
Singapore:
• The
minimum
platform
level
(MPL)
is
imposed
on
new
and
existing
developments.
A
series
of
slopes
or
steps
are
built
to
meet
the
MPL
requirements.
• In
areas
with
no
flood
history,
the
MPL
is
300
mm
above
the
adjacent
road
or
ground
level.
• In
areas
with
a
flood
history,
the
MPL
is
600
mm
above
the
highest
recorded
flood
level.
• Properties
are
protected
against
floods
up
to
the
height
of
the
MPL.
• It
is
challenging
to
implement
MPL
because
of
the
increased
cost
of
development.
GQ4
How
should
cities
prepare
for
floods?

2. Mitigation
strategies
Describe
the
strategy
Example
of
where
and
how
strategy
is
used
Describe
the
benefits
Describe
the
challenges
(B)
INVESTMENT
IN
INFRASTRUCTURE
To
build
new
flood
barriers;
to
maintain
existing
flood
prevention
structures
to
ensure
they
are
in
working
condition.
3)
Levees
and
floodwalls
• Levees
are
raised
banks
which
can
be
natural
(made
of
mud)
or
man-­‐made
(made
of
concrete).
• Floodwalls
are
man-­‐made
structures
that
are
made
of
concrete.
• Both
levees
and
floodwalls
are
barriers
that
are
built
higher
than
floodplains
and
rivers
so
that
they
can
help
keep
out
floodwater
or
prevent
flooding.
Sacramento,
USA:
• In
the
1870s,
several
kilometres
of
levees
have
been
built
along
the
Sacramento
River
to
protect
the
surrounding
land
from
floods.
Hereford
in
Herefordshire,
UK:
• In
2008,
a
floodwall
was
built
along
River
Wye
to
protect
the
city
from
flooding
during
heavy
rains.
• It
is
cheaper
to
build
levees
and
floodwalls
as
compared
to
raising
the
height
of
the
land
surrounding
the
river.
• Regular
maintenance
is
required
to
ensure
that
the
levees
and
floodwalls
are
strong
enough
to
hold
back
floodwater.
• Levees
and
floodwalls
are
only
designed
to
hold
back
water
up
to
a
certain
level.
However,
they
are
unable
to
prevent
floods
beyond
that
level.
4)
Channel
improvement
• River
channels
and
canals
can
be
widened
and
deepened
to
increase
its
capacity
to
hold
water
and
carry
more
storm
water
away.
• They
can
also
be
straightened
so
that
water
can
be
carried
away
quickly.
• This
would
prevent
the
water
in
river
channels
or
canals
from
overflowing
and
flooding
the
surrounding
areas.
Singapore:
• A
section
of
the
Bukit
Timah
Canal
was
widened
and
deepened
to
increase
the
channel
capacity.
• Channel
improvement
makes
it
possible
for
moderate-­‐
value
and
high-­‐
value
developments
to
take
place
on
the
land
next
to
river
channels
or
canals.
• Is
difficult
to
carry
out
when
the
land
next
to
the
river
channels
and
canals
is
already
used
for
other
purposes.
• Channel
improvement
may
create
problems
for
areas
upstream
or
downstream
of
the
improved
area.

3. Mitigation
strategies
Describe
the
strategy
Example
of
where
and
how
strategy
is
used
Describe
the
benefits
Describe
the
challenges
(C)
DISASTER
PREPAREDNESS
5)
Forecasting
and
warning
system
To
warn
people
of
possible
floods.
• Water
levels
in
river
channels
and
canals,
tide
levels
in
seas
and
surrounding
weather
conditions
are
monitored
regularly
using
manual
monitoring
systems
and
technology
(eg.
remote
sensing
techniques
&
geographical
information
systems).
• The
information
collected
is
then
analysed
to
make
a
flood
forecast
on
the
areas
that
are
likely
to
be
flooded.
• Subsequently,
flood
warnings
are
issued
to
the
public
via
social
media,
television
and
radio
so
that
people
can
take
necessary
precautions
in
advance.
Singapore:
• Water
level
sensors
are
placed
in
canals
and
drains
to
gather
data
about
the
changing
water
levels
at
regular
intervals.
• Weather
instruments
are
used
to
monitor
the
tides
and
weather
conditions
on
a
daily
basis.
• A
forecasting
and
warning
system
provides
useful
information
so
that
there
is
time
for
people
to
take
action
to
minimise
flood
damage.
• Some
cities
may
not
have
the
expertise
and
technology
to
collect
accurate
data
and
make
accurate
flood
forecasts.
6)
Evacuation
drills
To
train
people
to
know
what
to
do
when
a
flood
occurs.
• A
form
of
preparedness
measure
where
people
practise
the
steps
to
leave
a
place
in
a
safe
and
orderly
manner
during
an
emergency.
• It
involves
people
moving
to
safe
locations
by
following
instructions
given
by
trained
personnel
and
practising
first
aid.
Singapore:
• PUB
has
provided
a
public
advisory
on
what
pedestrians,
motorists,
residents
and
business
owners
can
do
in
the
event
of
a
flash
flood.
• People
are
educated
on
what
to
do
when
a
flood
warning
is
issued
and
this
would
thus
reduce
panic
during
a
flood
event.
• Limited
participation
from
the
public
will
reduce
the
effectiveness
of
the
city’s
evacuation
plan.