Click on a picture for a larger display or Slideshow button (right) for automatic display.November 2016. The Severn Bore is a natural phenomenon caused by a huge tidal range in the River Severn resulting in a tidal wave, or bore, which travels many miles up the river. The severn has the second largest tidal range in the world, as high as 15m, and the rising tide is funneled into the estuary mouth which causes a tidal wave which then travels up the river as far as Gloucester and beyond. The size of the wave depends on the state of the moon and the height of the river, but can occur more than 100 times per year. On big waves, surfers congregate and can travel large distances.
