We analyzed annual peak flow series from 127 naturally flowing or naturalized streamflow gauges
across western Canada to examine the impact of the Pacific Decadal Oscillation (PDO) on annual flood risk,
which has been previously unexamined in detail. Using Spearman’s rank correlation q and permutation tests on
quantile-quantile plots, we show that higher magnitude floods are more likely during the negative phase of the
PDO than during the positive phase (shown at 38% of the stations by Spearman’s rank correlations and at 51%
of the stations according to the permutation tests).
