Restoration of Historical Flood Data at Lake Biwa and Its Qualitative Estimation

Abstract

There are some historical information on water level of Lake Biwa in Edo Era. In this paper we restore annual maximum values of water level and areal thirty days precipitation of Lake Biwa in order to introduce those historical and paleoflood information in flood frequency analyses. In addition to change of reference level at gage station, effects such as dregging of outlet river at Lake Biwa and expansion of flow capacity at outlet weir are considered in the estimation of water level of Lake Biwa. The hydrological data on flood peak from the year 1718 to 1911 reproduced with those historical data and the systematic observed data since the year 1912 are compared qualitatively with the paleolimnological data of Lake Biwa.