Abstract
It is very important in the river-works design to estimate maximum hydrological quantities occurrence, such as the heavy rainfall and the flood. In this paper, assuming that the annual maximum values follow the log-normal distribution, we consider the distribution of the maximum values which occur within the lifetime of structure for river-works. And analyzing the data from four stations (Kanazawa, Toyama, Fukui and Nanao), we find that the hydrological variable in accordance with large return period is nearly equal to the value which is the mode of the annual maximum values distribution that can occur within the lifetime of the structure. Furthermore we suggest the statistical method to evaluate the occurrence times and magnitude when severe hydrological events occurred repeatedly in a fixed interval.
