![]() ![]() The Lupar Benak bore in Sarawak, Malaysia, nearly drowned the British author Somerset Maugham during a 1949 visit. Each year, the U.K.’s Severn River sees some 250 bores move upriver. ![]() Some tidal bores have global reputations for their beauty and destructive power. Eventually, the wave breaks-and a bore is born. As it encounters shallow water, the crest of the wave moves faster than its trough, sharpening its peak. Bore-bearing rivers also need to experience large swings in water level between high tide and low tide in their estuaries, where the river and sea meet and mix.Īs high tide rolls into one of these bore-prone estuaries, the influx of water becomes more confined as it moves upriver. "Two principal factors affect the size and strength of bores … the magnitude of the tidal range and the shape of the river at its estuary,” said Victor Miguel Ponce, a professor in the civil and environmental engineering department at California's San Diego State University, in a 2005 interview with National Geographic.īarring extreme weather conditions, bores form only when a river’s mouth is shallow, uniform, and resembles a funnel. More than 80 rivers around the world have tidal bores, according to one widely-cited 1988 catalog. While this phenomenon may look like a tsunami, it’s actually a tidal bore, a wave that flows upstream in some rivers as high tide approaches. On October 6, more than a hundred thousand tourists gathered on the banks of China’s Qiantang river to witness an extraordinary sight: a wall of water several feet tall racing its way upriver. ![]()
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