Abstract
With design hyetographs, created by different ranking methods for the duration (24 h or 72 h) and a 100-year-return-period rainfall depth, a hydrological model simulated the peaks of discharge for extreme rainfalls in a southern Taiwan watershed under climate change. The discharge peak with the conventional ranking method can be overestimated by an enhanced effect of the temporal distribution's shapes of lower-intensity rainfalls. To reduce the overestimation, the peak-weighted and cumulative-rainfall-depth-weighted ranking (cumulative-depth ranking) methods determined by the shape characteristics of rainfalls are introduced into this study. For the peak-ranking method, the discharge peaks did not change those of the conventional method even in longer duration (72 h) of design hyetograph. The cumulative-depth ranking method resulted in at most 15% reduction of the peak from the conventional one. Under the effect of climate change, the cumulative-depth ranking method reduced the discharge peaks by approximately 4% for 24-h duration and approximately 15% for 72-h one, respectively.
