The Red River or the Hong River (traditional Chinese: 紅河; simplified Chinese: 红河; pinyin: Hóng Hé; Vietnamese: Sông Hồng; Chữ Nôm: 瀧紅), also known as the Sông Cái (lit. "Main River"; Chữ Nôm: 瀧丐) in Vietnamese and the Yuan River (元江, Yuán Jiāng) in Chinese, is a 1,149-kilometer (714 mi)-long river that flows from Yunnan in Southwest China through northern Vietnam to the Gulf of Tonkin. According to C. Michael Hogan, the associated Red River Fault was instrumental in forming the entire South China Sea at least as early as 37 million years before present. The name red and southern position in China are associated in traditional cardinal directions. The river is relatively shallow, and carries a lot of reddish silt along its way, appearing red brown in colour.

Quelle: Wikipedia