For any given river, what is the probability that a 20-year flood will occur in 2018?

Study for the Introduction to Physical Geology Exam with flashcards and multiple-choice questions, complete with hints and explanations. Prepare for your geology exam now!

Multiple Choice

For any given river, what is the probability that a 20-year flood will occur in 2018?

Explanation:
In hydrology, a 20-year flood is defined by an annual exceedance probability of 1 in 20, or 5%. That means in any given year, the chance that the river exceeds this threshold is 5%, regardless of what happened in previous years. So for 2018, the probability of experiencing a flood of that magnitude is 5%. This doesn’t imply it won’t happen again soon or that it happens exactly once every 20 years; each year is an independent 5% chance.

In hydrology, a 20-year flood is defined by an annual exceedance probability of 1 in 20, or 5%. That means in any given year, the chance that the river exceeds this threshold is 5%, regardless of what happened in previous years. So for 2018, the probability of experiencing a flood of that magnitude is 5%. This doesn’t imply it won’t happen again soon or that it happens exactly once every 20 years; each year is an independent 5% chance.

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