The USGS has maintained a stream gage on Big Creek at Hill City since 1964. The highest discharge recorded at this gage was 45,000 cfs in 1972. The base-10 logs of the annual peak discharges in cfs for WY 1965-2010 have a mean of 3.678 and a standard deviation of 0.456. Assume that the probability distribution of the annual peak discharges is log-normal (the logs of the annual peak discharges are normally distributed).
a. Find the 50-year discharge.
b. Find the return period of 1972 flood.
c. Find the discharge with an 80% risk of being equaled or exceeded at least once in the next 10 years. (Hint: first find the annual probability of exceedance for this discharge.)