APPLICATION OF HISTORICAL FLOOD INFORMATION TO PROBABILITY QUANTILE ESTIMATION FOR LAKE BIWA, JAPAN

摘要

A flood frequency analysis using historical flood information since the 18th century was carried out for Lake Biwa, central Japan. The probability distributions and the effects of incorporating historical flood data were examined by plotting positions on the Gumbel probability papers for the converted flood peak water level and the annual maximum rainfall total for 30 days reconstructed from historical documentary records. As results, when compared to the cases where only systematic gaged data are utilized, the inclusion of sample data plots for historical large floods revealed that the flood-frequency relationship for Laka Biwa is well described by the Gumbel distribution, and improved significantly the estimation precision of flood quantiles corresponding to return periods of several decades to a century, which is important for floodplain management or designs for flood control facilities in Japan.