Urami River

...The water surface of the upper three lakes of Mikata, Suigetsu and Suga is continuous, and Suga Lake in particular is merely an inlet of Suigetsu Lake. Kugushi Lake and Hinata Lake were originally independent, but are now connected to Suigetsu Lake by the Urami River and the Saga Tunnel. In the great earthquake of 1662 (Kanbun 2), the upper three lakes, which had poor drainage, overflowed, and the fields around the lake shore were flooded, causing great damage.

*Some of the terminology that refers to "Uramigawa" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…三方，水月，菅の上三湖は水面が連続し，特に菅湖は水月湖の湾入にすぎない。久々子湖と日向湖はもと独立していたが，浦見川，嵯峨隧道（さがずいどう）によって，いまは水月湖とつながる。1662年(寛文2)の大地震で元来排水不良であった上三湖が溢水，湖岸周辺の田畑が冠水して大被害となった。…

※「浦見川」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報