GATE 2018 CE (CE2) – Question 35
A culvert has design flood return period 100 years and useful life 20 years. Its design risk, to two decimals, is ______%.
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Correct answer: 17.50 to 18.50
Explanation
Annual exceedance probability is 0.01. Assuming independent years, probability of at least one exceedance in 20 years is $1-(1-0.01)^{20}=0.182093$, or 18.21%.