Abstract
The Asahi river is the big river in Okayama prefecture. The Hyakkenn river is the flood control channel which was constructed in Edo-era for preventing the castle town of Okayama from flood disasters. Mr. Banzan Kumazawa and Nagatada Tsuda were river engineers and they planned river improvement works. In this paper the river improvement works are investigated by using a hydraulic model of which scales are 1/500 in horizontal and 1/200 in vertical. The works were a river channel work and a diversion work with fuseplug levee. From the results it is concluded that these works are effective for preventing the castle town from floods.
