Severn Bore: What is it and why does it happen?

It's called the Severn Bore but it's certainly not boring.

Surfers and kayakers look forward to this world-famous natural phenomenon where they can take to the waves on the Severn Estuary.

There's only expected to be one "five-star" bore this year and people have been making the most of it.

But what is the Severn Bore and why does it happen? Keep reading to find out all about it.

The Severn Bore is a world-famous tidal surge in the Severn Estuary which is where the River Severn meets the Bristol Channel.

A tidal bore is a strong tide that pushes up a river against a current which can sometimes cause impressive waves.

A bore can travel at a speed of between 10 and 13mph and the largest bores can reach up to two metres high.

Tidal bores happen where a river empties into the sea and are caused when the tide rises.

Usually water flows from the river into the sea, but it's the other way around during a tidal bore.

The Severn Bore creates waves thanks to the shape of the Severn Estuary which gets narrower and more shallow.

This squeezes the water level upwards and forwards, creating waves.

The tidal range here - which is the difference in height between low tide and high tide - is the second highest in the world.

This is why the waves can be so good, but they only happen when the tide goes over a certain height so the conditions have to be perfect for the best waves to surf.

There are between 250 and 260 tidal bores in the Severn Estuary a year.

Tides are the regular rise and fall of sea levels and they're caused by the gravitational pull of the Moon and Sun.

Therefore, tidal bores are associated with the phases of the Moon.

Tides are at their highest in the Spring and Autumn around the vernal equinoxes. That's when the Sun is exactly above the equator and day and night are equal lengths.

Bores are rated by a five-star system, with the most spectacular gaining the five-star rating. There's only expected to be one five-star Severn bore in 2024.

Many surfers see the Severn Bore as one of the best river waves to surf in the world.

That's why people flock to the area in the Spring and Autumn to have a go at riding the waves - although it can be a bit dangerous.

The first surfer to ride the Severn Bore was Colonel 'Mad Jack' Churchill in July 1955.

In 2006, Steve King set the World Record for the longest surfing ride on the Severn Bore racking up a distance of 7.6 miles.

It took him an hour and 17 minutes.

Tidal bores happen on rivers and estuaries around the world, but many people say none are quite as spectacular as the Severn Bore.

It's not the highest tidal bore in the world though, that award goes to the Qiantang River in Hangzhou, China and it's nicknamed the Silver Dragon.

Tidal bores also happen on the largest river in the world - the Amazon River - where it empties into the Atlantic Ocean.