RECONSTRUCTION OF WATER LEVEL DATA OF HISTORICAL FLOODS AT LAKE BIWA USING OLD DOCUMENTS

Abstract

There are some historical quantitative data on water level of Lake Biwa in Edo Era. Those are grouped into four types: 1) relative comparison of water level at peak between extreme floods, 2) observation records of water level using scaled posts, 3) inundation depth records of house, garden or rice field and 4) records on daily variation of flood level. In this paper, we picked up and collected historical records on water level of Lake Biwa from old documents, and attempted to represent daily water level data in Biwako Standard Level (B.S.L.) for three historical extreme floods at theend of Edo Era. Moreover, we reconstructed the water level at peak for other historical floods for about 150 years by estimating the standard level of Feudal Zeze Clan.