Flood Control by Traditional River Technique in Japan

点击翻译按钮获取中文摘要

Flood Control by Traditional River Technique in JapanIn Kumamoto Prefecture, there were many flood protection works such as diversion structures, levees and groynes made of stones which were constructed by Kiyomasa Kato as a feudal lord in the early Edo era. However, most works have not been clarified with actual proof as to how they play a role in flood protection. In this paper, Kutsuwa Domo commonly employed by Kiyomasa, which entails the widening a river at the confluence or rushing points to weaken floods, was investigated from the viewpoint of historical river regulation methods by applying a hydraulic model to a kutsuwa domo located at Shimada district in the Hamado river. The model scale was 1/150. The results of this paper showed that Kutsuwa domo was originally created by Kiyomasa, different from Kasumi bank (open levee) and effective works for floods exceeding the design limit.The Hanaguri channel is known for mysterious-shaped structures, which was constructed in the Nakasu mountain to irrigate a paddy field lying in the middle reach of the Shira river basin by Kiyomasa Katou in 1608.In this study, a field investigation and a model experiment were carried out to grasp the actual status and hydraulic functions of the Hanaguri channel. The results showed that the Hanaguri channel had 26 walls with a semicircular hole which was dug in the lower part of the wall, and the flow between the walls exhibited the characteristics of wall jet and had enough tractive force to transport volcanic ashes erupted from the Mt Aso.