One minute the spectators were standing by the banks of the Qiantang River, in east China’s Zhejiang province, there to witness Mother Nature’s annual spectacle. The next minute they were running for their lives as the huge wave burst through a dam and spilled over the riverbank, crashing towards them, engulfing the crowds while others looked on helplessly. While there were no fatalities, more than 20 people were injured after the wave swept through the throng, and some had to be carried to receive medical attention.
A tidal bore is a tidal phenomenon in which the leading edge of the incoming tide forms a wave (or waves) of water that travel up a river or narrow bay against the direction of the river or bay’s current. This is a true tidal wave and not a tsunami , which is a large ocean wave traveling primarily on the open ocean. The two key features of a tidal bore are the intense turbulence and turbulent mixing generated during the bore propagation, as well as its rumbling noise.
There are over 60 tidal bores located across the world. China’s Qiantang River boasts the largest tidal bore, which is up to 30 feet high and travels at speeds of up to 25mph.
In the U.S. Turnagain Arm part of Cook Inlet, Alaska has a tidal bore of 6.6 ft. which travels at a speed 15 mph.
In September 2008 a group of American surfers convinced the Chinese government to allow them to surf a section of the Qiantang river.