Abstract
In Lake Biwa area, there are some quantitative hydrological data in historical years, such as monthly water level data recorded by Feudal Zeze Clan in Edo Era. This paper proposes the estimation procedure of areal duration precipitation at historical flood of Lake Biwa, using the water level records at the beginning and the end of the flood, and the hyetograph reconstructed from weather records of old diaries. Furthermore, this procedure is applied to the recent floods and the reliability of reconstructed flood is evaluated. As results, this procedure is effective especially for large floods, and the precision of the water level data at peak is important for reliability of the estimated value.
