Bore, also eagre, in physical geography, wave front generally more than 1 m (3.3 ft) high, advancing swiftly up a funnel-shaped estuary or bay. When a large volume of water, usually from rising tides, accumulates in the mouth of the funnel more rapidly than it can flow upstream, a crested wave, or bore, gradually forms and rushes up the estuary with great violence. The highest known bore in the world is at the mouth of the Qiantang (Tsientang) River, on Hangzhou (Hangchou) Bay, in China; it may reach a height of 4.5 m (15 ft). Large bores also occur in the River Severn; the Bay of Fundy, Nova Scotia, Canada; the Amazon, Brazil; and the Brahmaputra, India.