Oigawa Plain

…It originates on the southern slope of Ainodake (3,189m) in the northeastern Akaishi Mountains on the border between Shizuoka and Yamanashi prefectures, flows south from Ikawa in Shizuoka city, forming the border between Suruga and Totomi, and empties into Suruga Bay at the southwestern end of the Oigawa Plain. It is the largest river that ends within Shizuoka prefecture, and its main river length of 160 km is one of the largest in Japan. However, its total drainage area of ​​1,280 km2 is extremely narrow compared to its length, and it is one of the fastest rivers in Japan. …

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

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…静岡･山梨県境の赤石山脈北東部，間（あい）ノ岳(3189m)の南斜面に源を発し，静岡市井川の下流からは駿河･遠江の国境をなしつつ南流し，大井川平野の南西端で駿河湾に注ぐ川。静岡県内に終始する河川としては最も規模が大きく，特に幹川流路延長160kmは日本の河川の中でも上位だが，反面，全流域面積1280km2は長さに比べて著しく狭く，日本でも屈指の急流である。…

※「大井川平野」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