In Japan, before river improvement works began from the age of civil strife wars in the 16th century, people had been allowing free floods on alluvial plains. It was construction of embankments in the river improvement projects that had gradually thrusted floods in river ways. In modern ages, embankments had become higher and stronger. Therefore, general people at present have naturally thought that rivers don't overflow their banks. Nowadays, if once we allow floods from rivers, it may cause heavy damages.
In Japan, it is said that the river improvement works by using high embankments to protect cultivated lands against overflow have begun since the Kyouhou period (1716-1736) in the Tokugawa era.
Nowadays, we can understand Water use and Control technologies at that time from literatures of the Tokugawa era. In order to know the change of river improvement methods of those days, we have tried to find out development of embankments in the Tokugawa era by using these existing literatures.
