The savior of the land of Yamanashi

Today, we visited a river. No, two rivers. Or was it three??
Well, basically we visited the place to learn about "信玄堤 Shingen-Dzutsumi" or "Shingen Riverbank". Why is it so important?

This is the river that we saw, by the way

Long ago, the river around the Shingen-Dzutsumi wasn't this shallow. It might be not shown, but this river is actually a combination of two rivers, combining into Kamanashi River. When the two rivers met, it caused a big bang and made the water flows to the land.

And thus the big flood would always happened in the area of Yamanashi, though not all.

That's why, the people of Yamanashi at the time made this device;

What is this...?

This device is called Hijiriushi. The main function of the so said device is to weaken the stream of the river, so it doesn't cause a bang. Because of the device, the land that wasn't possible to be resided in, became usable.

Ocha