The Severn

The Severn bore-The River Severn is the longest river in Britain. From its rise at Plynlimon, in the mountains of Wales, elevation about 2000 feet above sea level, the river flows for 210miles, draining into the Bristol Channel. The Atlantic Ocean is the source for the second largest tide range in the world, which can exceed 15m in the estuary at Avonmouth. The combination of these two facts produces the phenomenen known as The Severn Bore. It is a large surge wave that can be seen in the estuary of the River Severn, where the river meets the Bristol Channel whose tidal range is the 2nd highest in the world, being as much as 50 feet (approx. 15.4m).

The shape of the Severn estuary is such that the water is funnelled into an increasingly narrow channel as the tide rises, thus forming the large wave. The river's course takes it past Avonmouth, near Bristol where it is approximately 4.5 miles wide, then past Chepstow and Lydney where it is approximately 1 mile wide, narrowing as it proceeds, soon reaching a width of a few hundred yards. By the time it reaches Minsterworth it is less than a hundred yards across, maintaining this width until it reaches Gloucester.

As well as the width of the river decreasing rapidly, so does the depth, thus forming a funnel shape. Therefore as the incoming tide travels up the estuary, it is routed into an ever decreasing channel. Consequently the surge wave or bore is formed. This occurs twice a day at high water, when the advancing wave meets the out-flowing river direction and reverses it. Enthusiastic surfers and canoeists love the buzz they get from trying to ride the wave as far as they can go up the winding river, and a calendar of the highest tides with a subsequent high bore, is eagerly scanned by the viewers and the daredevil wave riders alike. A following wind can increase its height and advance the time it arrives, so with the prevailing wind in the channel being from the southwest, when anything like a gale is blowing the bore can reach extreme heights and speeds. The bore is graded by a star system, two stars being a fairly low bore to five stars being an exceptionally high bore. The largest recorded bore was on 15 October 1966, when it reached a height of 2.8metres (9.2ft)

The moving tide may be visible in the estuary below Chepstow, on the Welsh border, but the bore head forms further upriver at Awre Point. The wave then travels, in irregular patterns, around the horseshoe bends for 10 miles before entering the river above Longney.

From here it adopts a more regular form, travelling the final 14 miles of its journey upriver passing the City of Gloucester on its way.

On September 20^th 2009 we joined dozens of other spectators at Minsterworth to see the bore. The calendar warned us that it would be only a two star performance, and the day being fine and dry with hardly any wind our expectations were not high. There were plenty of surfers and canoeists in the river, and as they were very expectant of a good ride on the bore, a party atmosphere soon began.

Shouts of 'Here she comes,' soon rang out and the surfers beyond the bend of the river were soon in sight. We could see the wave crashing into the sides of the river, sweeping muck and branches in its path, as the people in the water tried to get in a good position to ride on the crest of the wave. Some tumbled off their boards, one crashed into the far bank but many had a decent ride. We cheered them all on and the air was thick with laughter and shouting. As the fallen surfers clambered up the banks to jump in their vehicles and race up the road aiming for the next site where they could surf the severn bore, we clapped them for their excellent attempt and hoped that the next time we saw it, it would be a monster.

These Photographs by Mandie Heathfield