Question

question 22
which of the following best describes a \100 - year flood\?
lasts for 100 years
occurs every 100 years
has a 1% chance of occurring in any given year
is twice as deep as a 50 - year flood

Explanation:

A 100 - year flood is a statistical term. The return period (T) of a flood event is related to its probability (p) of occurrence in a given year by the formula \(p=\frac{1}{T}\). For a 100 - year flood, \(T = 100\), so \(p=\frac{1}{100}=0.01 = 1\%\). It does not mean the flood lasts for 100 years (duration is not indicated by the term), nor does it mean it occurs exactly every 100 years (it is a probability - based concept, not a fixed - interval occurrence), and there is no direct relationship that it is twice as deep as a 50 - year flood (depth is not simply related in that linear way based on return period).

Answer:

Has a 1% chance of occurring in any given year.