A massive tidal wave surges up the River Severn twice a day, every day.
In short: In England, the River Severn hosts a dramatic tidal bore—a shock wave that forces its way upstream against the current. This phenomenon, which can reach heights of nearly ten feet, has transformed from a historical navigation hazard for shipping into a unique playground for modern river surfers and canoeists.
The Severn bore is a tidal surge that occurs when the rising tide enters the funnel-shaped Bristol Channel and Severn Estuary. As the channel narrows, the incoming water is forced into a series of waves that travel upstream. While the estuary boasts one of the world's largest tidal ranges—reaching about 13 meters—the bore itself forms as the river narrows and the bed rises. It is not a solitary wave or soliton, but a shock wave generated because the tidal front moves faster than the water speed in the river ahead of it.
The bore occurs on approximately 130 days each year, typically following the new and full moon. Its intensity is influenced by several factors, including barometric pressure, wind direction, and the volume of fresh water flowing down the river. While the largest bores often occur around the equinoxes, the phenomenon is a regular occurrence, with waves traveling upstream at speeds between 13 and 21 kilometers per hour. The sound of the bore is largely produced by the churning of water and the popping of tiny bubbles within the wave front.
Historically, the bore posed significant challenges for vessels attempting to reach the port of Gloucester. This navigation difficulty was largely resolved in 1827 with the opening of the Gloucester and Sharpness Canal. Today, the bore is a destination for enthusiasts. The river was first surfed in 1955 by Jack Churchill, a military veteran who designed his own board. In 2006, Steve King set a world record by surfing the bore for 12 kilometers. Despite its popularity, the river remains hazardous, with potential dangers including floating debris, unstable banks, and strong currents that require caution from all who enter the water.
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Sources
- Summary by Intellect · source: Severn bore
- Also: Wikidata — Severn bore · CC0
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