The analysis of the designed storm pattern over Yichang

In this paper, fifty-eight year rainfall data of Yichang National Basic Meteorological Observing Station from 1956 to 2013 are used to investigate the designed storm pattern at Yichang by P C and Chicago methods, which is based on the time-intervals of 5 minutes to make an analysis of storm pattern over Yichang on 30, 60, 90, 120, 150, and 180 min of 2 years return period. The results show that nearly all the designed storm pattern of all rainfall durations in Yichang by P C method presents a single-peak pattern. The rainfall peak of the designed storm pattern on 30, 60 min is located at 1/3 over the whole rainfall period, while being1/4 on 120, 150, 180 min. The rainfall peak of the designed storm pattern by Chicago method on all rainfall durations over 2 years return period is located at 1/3 over the whole rainfall period. Although the rainfall intensity of rainfall peak presents a trend of decreasing-increasing-decreasing as the rainfall duration increases, the amplitude of variation is small. There are some common features of short duration storm patterns by P C and Chicago methods, such as"single-peak pattern, fast speed, high intensity, and long-lasting". So, the departments of the water conservancy bureau, the hydrology bureau,the residential construction and the flood control need to prepare for drainage early on, when the short duration storm happens.