The Severn Bore

Pre-dawn start - and no breakfast!
Pre-dawn start – and no breakfast!

Today’s adventure started even before the sun had risen. Though any change in the pattern of our life was not the reason. We had to be at the Severn Bore Inn before 8am. No not to eat or drink, before anyone has any ideas in that direction. I’ve been wanting to see the Severn Bore for years, and this week end the tide was right, the moon was right and the wind was right! Everything was right except for the time.

We arrived in plenty of time before the bore was due to reach this part of the river, and the pub was open for breakfast. The morning was good again! Having been refreshed with a hot cup of tea (very welcome) and a cooked breakfast (essential for me, but frowned upon by Aunty) we stood on the bank of the River Severn and waited with the growing crowd to watch the spectacle.

Crowd Control
Crowd Control

The police provided the crowd control, the Coast Guard provided intrigue and even the Environmental Agency made an appearance.

The entertainment was provided by the increasing number of surfers and canoeists plunging into the freezing cold waters ready to meet the wave. As it turned out only one of the them was able to surf the bore for any length of time. It did seem a lot of fuss to go to and then not do any surfing!

Hopefuls on their way to glory and the big wave.
Hopefuls on their way to glory and the big wave.

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 where it is approximately 5 miles wide, then past Beachley and Aust, then Lydney and Sharpness where it is approximately 1 mile wide, and soon the river is down to a width of a few hundred yards. By the time the river reaches Minsterworth it is less than a hundred yards across, maintaining this width all the way to Gloucester (1).

There are around 260 bores each year. i.e., 2 per day on about 130 days. But arge bores only occurs on about 25 days, in the morning and evening. Bores occur on all tides of 8 metres or over on the Sharpness gauge when river conditions are normal. But large bores occur with tides over 9.5 metres at Sharpness.

The Severn Bore approaching around the bend in the river
The Severn Bore approaching around the bend in the river

The height of the bore is affected by many factors such wind speed, amount of water in the river but can be up to 3 metres in mid-stream, but 1 metre is good. It’s height at banks is much greater than in mid-stream and further accentuated on outer banks of bends. In the sandy estuary width is unconfined and variable up to 250 metres. Minsterworth to Gloucester, bank to bank, 80 to 95 metres. The largest recorded bore was on 15 Oct 1966 downstream of Stonebench and attained a height of 9¼ ft (2.8 m). However, due to the depth of the river after all the recent rain the bore was not as high, but the speed remained impressive, Including the sight of it crashing along the back as it passed.

The speed of the bore is impressive to watch, and you can clearly see how fast it moves in the video that Aunty took. In the sandy estuary area down stream it travels between 8 to 13 kilometres per hour according to location. But as the river narrows upstream between Minsterworth and Gloucester it has been measured at between 16 to 21 kilometres per hour.

Still going!
Still going!

Bores occur all the year round with spring tides, but are biggest near an equinox. So the best time to see them is in Spring and Autumn; when the Vernal Equinox occurs around February-March-April, and the Autumnal Equinox, around the months of August-September-October. Maximum bores occur one to three days after new and full moons; smaller ones on days immediately preceding and following maxima.

Unfortunately is was over all to soon. The bore rushed past up on it’s way up towards Gloucester. Leaving only a slight sense of anticlimax. But this feeling must have been so much worse for the 20 or so surfers that missed the bore on this stretch of the river. they slowly swam back to the river bank and dripped their way back to their camper vans.

Making a splash
Making a splash

Will we go and see it again. Almost certainly. The Severn Bore Inn is a great place from which to watch the spectacle. Plus theres also the allure of a cooked breakfast as a bulwark against the early morning start. There are other places to watch from, Newham being one, where the river is wider and the surfers more numerous. But we’ll have to wait now until the Autumn as the tides will not be high enough to create as large a bore as occurred today. So until the next time.

1: http://www.severn-bore.co.uk/index.html

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