Question

The probability that the annual maximum flood discharge will exceed $25000{\text{m}}^3/\text{s}$, at least once in the next 5 years is found to be 0.25. The return period of this flood event (in years, round off to 1 decimal place) is

• A. 17.9

Answer 1

The correct option is A 17.9
Probability to exceed maximum discharge at least once in next 5 years is given by
$=1-(1-p{)}^n$

$\Rightarrow 0.25=1-(1-p{)}^n[n=5\text{year}]$

$\Rightarrow p=0.0559$

$\Rightarrow \frac{1}{T}=0.0559$

$\Rightarrow T=17.9\text{year}$