A Study on the Phased Construction Executed on the Flood Control Improvement for the Kiso, Nagara and Ibi River during the Houreki Period in the Edo Era

Abstract

The Kiso, Nagara and Ibi River, which were flowing on the Central Japan, are known generally as “Kiso Sansen” . To control floods occurring on these rivers, the large-scale river improvement was executed from the year 1754 to 1755 for the Houreki period during the Edo era . The officials of the Tokugawa Shogunate made the plan for this improvement . And the feudal domain of Satsuma paid the expenditure and oversaw the construction work at sites.In those days, the river improvement works were organized by using the natural materials such as woods and stones. And the planner could not measure using such as modern mathematical theory . Therefore, some plans or constructions were phased checking the change of river flow and bed .Nowadays, such phased construction is named “Mitameshi” in Japan. And the Japanese traditional river improvement techniques have been used some rivers. The purpose to apply these old techniques is to make the natural circumstances on the river channel. For the circumstances, it is important that engineers check the changing of river flow and bed. However, the phased construction is not used now .To execute these traditional river improvements and make natural circumstance on Japanese rivers, this study traces the large-scale river improvement of the “Kiso Sansen” during the Houreki period and makes clear the process of the phased construction.