Figure 3.7: Flood frequency analysis for the Lake Te Anau three-day annual maxima for 1947-77 (lower line) and 1978-94 (upper line)

Text description of figure

This figures shows graphs of three-day annual maxima of flood peaks in cubic metres per second (y-axis) and annual exceedance probability (x-axis) at Lake Te Anau for 1947-1977 (lower line) and 1978-1994 (upper line). Although there nearly a constant offset between the lines, both show increasing flood magnitude as the annual exceedance probability reduces. For the 1947-1977 period the flood magnitude increases from about 900 cubic metres per second for an AEP of 0.99 to 3000 cubic metres per second for an AEP of 0.05. For the 1978-1994 period, the corresponding flood magnitudes, for the same AEP, are 1500 and nearly 4000 cubic metres per second respectively. Note: AEP is annual exceedance probability. The fitted lines are Gumbel, Extreme Value Type 1, distributions fitted using Probability Weighted Moments.