Monobe River

A river that flows southwest through the central-eastern part of Kochi Prefecture and empties into Tosa Bay. It is a first-class river. It is 71 km long and has a drainage area of ​​508 square km. The upper reaches of the river are called the Makiyama River, and originate on the eastern slope of Mt. Shiraga in the Tsurugisan mountain range in the eastern Shikoku Mountains. It flows westward and merges with the Kaminiro River in Oodochi, Monobe-cho, Kami City to become the Monobe River. It flows south while developing river terraces, and downstream it forms the alluvial fan lowland and plateau of the Kacho Plain (the eastern half of the Kochi Plain), and enters Tosa Bay in the Yoshikawa-cho area of ​​Konan City. The tributary, the Kaminiro River, has the Nishikuma Valley and other sites, and the entire upper reaches are part of the Okumonobe Prefectural Natural Park. After World War II, the middle and upper reaches of the river saw the development of power sources, and the Nagase Dam was constructed. In the alluvial lowlands downstream, remains of rice paddies and jori-style structures from the Yayoi period can be seen. This was the core area of ​​Tosa agriculture, and rice was once cultivated twice a year, but nowadays greenhouse gardening is popular.

[Yasuhiko Owaki]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

高知県中東部を南西流して土佐湾に注ぐ川。一級河川。延長71キロメートル。流域面積508平方キロメートル。上流は槇山川(まきやまがわ)とよばれ、四国山地東部の剣山(つるぎさん)山系白髪(しらが)山東斜面に源を発し、西流して香美(かみ)市物部町(ものべちょう)大栃(おおどち)で上韮生(かみにろう)川と合流して物部川となり、河岸段丘を発達させながら南流し、下流に扇状地性低地・台地の香長(かちょう)平野（高知平野東半部）をつくり、香南(こうなん)市吉川町(よしかわちょう)地区で土佐湾に入る。支流上韮生川には西熊渓谷などがあり上流域一帯は奥物部県立自然公園域。第二次世界大戦後、中・上流は電源開発が進み、永瀬ダムなどがつくられた。下流の沖積低地には弥生(やよい)期の水田跡、条里遺構もみられる。土佐農業の中核地で、かつては稲の二期作が行われたが、現在は施設園芸が盛ん。

［大脇保彦］

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例