Toyokawa

A river that runs through the eastern Mikawa region of Aichi Prefecture and empties into Mikawa Bay. It is a first-class river. It is 77 km long and has a drainage area of ​​724 square km. Its watershed with the Ochise River, which is part of the Tenryu River system, is Ikeba Pass. Its course runs along the Median Tectonic Line between the Yana-Yumihari Mountains and the Mikawa Mountains. It originates near Dandoyama on the Mino-Mikawa Plateau, joins with the Ure River (Miwa River) and other tributaries near Nagashino in Shinshiro City, and flows into Mikawa Bay in Toyohashi City. The upper reaches are also called the Kansa River. The upper reaches form beautiful river terraces, the lower reaches are alluvial lowlands, and the river mouth is a shallow coastline. The alluvial plain downstream frequently flooded, so the Kasumi Levee (Yoroi Levee) was built in the Sengoku Period to protect against flooding. The Toyokawa Floodway has now been built. In 1968 (Showa 43), the Toyokawa Irrigation Canal was excavated, resolving the water shortage on the terraces and on the Atsumi Peninsula.

[Gohei Ito]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

愛知県東三河地方を貫流し、三河湾に注ぐ川。一級河川。延長77キロメートル、流域面積724平方キロメートル。天竜川水系の大千瀬(おおちせ)川との分水嶺(ぶんすいれい)は池場(いけば)峠である。流路は八名(やな)・弓張(ゆみはり)山地と三河山地の間の中央構造線に沿っている。美濃(みの)三河高原の段戸山(だんどやま)付近に発し、宇連(うれ)川（三輪(みわ)川）その他の支流を新城(しんしろ)市の長篠(ながしの)付近であわせ、豊橋市で三河湾に流入する。上流を寒狭(かんさ)川ともよぶ。上流部はみごとな河岸段丘をつくり、下流部に沖積低地、河口付近は遠浅な海岸である。下流の沖積地はたびたび氾濫(はんらん)を起こし、洪水防御のため戦国時代霞(かすみ)堤（鎧(よろい)堤）がつくられた。現在は豊川放水路が設けられている。1968年（昭和43）豊川用水が開削され、段丘上と渥美(あつみ)半島の乏水性を解消させた。

［伊藤郷平］

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