dThe Fukui River changed course to the Saza River
The high terrace is dotted with round basalt gravel. It is proof that Fukui River used to flow by the high terrace and run into Emukae River a long time ago. Later, the course changed to Saza River when Fukui River was dammed up at Tanomoto near Fukui River Bridge by a landslide. After the change of course to Saza River, the riverbed of Fukui River gradually lowered to the present level. As the riverbed lowered, the river ate at the mountain and formed the cavern terrain. The cavern terrain in the Fukui River basin is a result of the dynamic workings of nature.