The government, which had established a river improvement plan in 1925, started improvement projects in 1930 on the Asahi River. Main purpose of the project was to improve the inland navigation system as well as flood control City planning law was applied to Okayama city in 1923.
Since the navigation system of the downstream of the Asahi River was very important for the urban development, it was asserted that the downstream of the Asahi River should be turned into a canal.
The Hyakken. River had been diverged from the main stream of the Asahi River in the 1600s.
The people of Okayama raised objections to the original plan, and besides, there was the intense struggle with the improvement plan between those who lived in the area near the main stream and those who lived in the area near the diverged channel.
Finally, the Hyakken River was officially designated as a diversion channel in the plan, and the main stream of the Asahi River was improved to serve the needs of navigation system as well as a flood flow channel.
