Question

The probability that a 100 year flood is equalled or exceeded, at least once in 100 years is

• A. 99%
• B. 64%
• C. 36%
• D. 1%

Answer 1

The correct option is B 64%

The probability corresponding to 100 years return period
$P=\frac{1}{100}=0.01$
The probability of the flood exceeding at least once in 100 years is
$R=1-(1-P{)}^{100}=1-{0.99}^{100}$
$=0.634=64\%$