Flash floods are floods characterized by a very rapid rise of the water stage and they are known to be frequently generated in mountainous torrents. Many deaths are caused by the flash floods that occur almost every year. In Japan, a flash flood is called �gteppou�]mizu". The origin of this term is associated with silvicultural technologies for timber floating. For example, �gteppou�]zeki" is an artificial dam to flush timbers downstream even during mountainous torrents. �gTeppou�]mizu" is not a scientific term although it has been used as common term. After investigating the past usage of these terms in media such as newspapers and dictionaries, it turned out that �gteppou�]mizu" is generally recognized as a term referring to a phenomenon which generally differs from a debris flow or flood.

Key words�Fteppou�]mizu, debris flow, flash flood, dialect, common term