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Mathematics Connect 4

Flooding is a common natural disaster
in the United States. The name
'100-year flood' can be confusing
because it makes us think that a river
will flood only once every hundred fliisstrsfimS
years. This is not necessarily the
case. The 100-year flood describes
the estimated probability of a 1%
chance that this flood will happen in
any given year. Even if the flood just
happened last year, it might happen
again the next year. The chance of
l.'tOl _ li)'Ung
an occurrence of the next flood is
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independent of the previous flood. In
ISWU _ -I0.3nti
fact, there is a 63% probability that 1
or more such flood could occur within
a period of 100 years.
_
Similarly, a 10-year flood will have a
Sfdi-tBarta
10% chance of occurring in any given aioso-iu;
IS99__I.13fW
year or a 500-year flood will have a
0.2% chance of occurring in any given
year.
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In the 1960s, the United States 2002 13. jiuii
government decided to use the 1 %
figure as an indicator for the size of
the flood where the citizens can be
protected via insurance against the
n)2o_ _ S Sflrt
perils of flood damage. For some
people who are staying in an area
where there is a high risk of flooding,
it may be compulsory for them to buy
such an insurance. The 100-year flood
will then be a useful indicator to the
authorities to decide if a coastal area
is 'high risk' or not.
Find out more on this link.

The Passau flood scale
^3i> UNIT 18
probability