A probability plot of 19 yr of peak discharges for the West Branch of the Mahoning River n...

A probability plot of 19 yr of peak discharges for the West Branch of the Mahoning River near Newton Falls, Ohio, is shown in Figure. This is an example of Gumbel, or extreme-value I, probability paper. Simply use the straight, fitted line to obtain the answers.

(a) What is the 25-yr flow?

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(b) What is the 100-yr flow?

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(c) What is the return period of a flow of 4000 cfs?

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(d) What is the probability that the annual peak discharge will fall between 5000 and 7000 cfs?

Figure

Annual floods of the West Branch Mahoning River near Newton Falls, Ohio, 1927-1945, on Gumbel probability paper. Vertical lines on the plot correspond to the lower probability scale, F(x). (From National Bureau of Standards, 1953, Probability Tables for the Analysis of Extreme Value Data, Applied Mathematics Series 22, U.S. Government Printing Office, Washington, D.C.)