Abstract
The high- and low-water design of river basins in Japan is mostly based on probabilistic precipitation and river discharge data. In this study, a number of hydrological and statistical analyses were executed using annual maximum one- and two-day precipitation data and annual maximum daily river discharge statistics for the Hii River basin for reference in high-water planning work. The results showed increases or decreases in many probabilistic hydrologic indexes between past and present, meaning that differences in design precipitation or design flood discharge may arise in the future even for the same return period. It was also concluded that the operations of flood control facilities may need to be improved.
