抄録
Upper bound for the total amount of precipitation is an important factor in determining the design discharge. The probable maximum precipitation can be examined by solving the governing equations of the hydrological processes, while the spacial distribution should be supported by evidence of the past records in the statistical sense. To estimate the upper bound will be a harder challenge than to do the return levels against finite return periods, because the degree of experience become to zero for the upper bound. This paper points out the difficulty which is caused by a trade-off with increasing sample size, and demonstrates how it appears by the numerical simulations.
