The Qiantang River (also known as the Qian River) is a southeast Chinese river that originates in the borders of Anhui and Jiangxi provinces and passes through Hangzhou, the capital of Zhejiang province, before flowing into the East China Sea through Hangzhou Bay.
The river and bay are known for the world's largest tidal bore, which is up to 9 metres (30 ft) high, and travels at up to 40 km per hour (25 miles an hour). The tide rushing into the river from the bay causes a bore usually from 5 to 15 ft (1.5–4.6 m) high, which sweeps past Hangzhou and menaces shipping in the harbor. It is so dangerous that, until recently, no one attempting to surf it has managed to remain upright for more than 11 seconds.
On September 1, 2011, massive tidal waves exceeded 60 metres and damaged more than 100 metres of protective railings. Many people came to see this amazing natural phenomenon.