The return period (T) of a flood is related to its annual exceedance probability (p) by:
Choose the correct answer
T = p
T = 1/p (return period is reciprocal of annual exceedance probability)
T = 1 − p
T = p/(1−p)
Correct Answer
B. T = 1/p (return period is reciprocal of annual exceedance probability)
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T = 1/p where p = annual probability of exceedance (probability that the event is equalled or exceeded in any one year). 100-year flood: T=100, p=1/100=1%. Probability of flood occurring AT LEAST ONCE in n years = 1 − (1−1/T)ⁿ. Design return periods: bridge 100 yr, highway culvert 25–50 yr, weir 100–500 yr.
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