What is the difference in the historical adjustment procedure for high outliers and historical floods?
There is no difference in the computation; the historical adjustment computation does not distinguish between historical peaks and high outliers. The same threshold is used for adjusting for both types of floods. The number of peaks above the threshold is denoted as Z, and no distinction is made between high outliers and historic peaks in determining the value of Z. Historically adjusted moments are computed using a weight of 1.0 for the Z above-threshold peaks and a weight W = (H-Z)/(N+L) (H = total length of historical and systematic record; N+L = number of below-threshold systematic peaks, including low outliers and zeroes) for all systematic peaks below the threshold.
