Friday, March 7, 2014

Severn Bore and Bacon Butties - Minsterworth 3-4 March

The Severn Bore approaches, Minsterworth, 3rd March
We’d booked our  trip to Gloucestershire in early March 2014 with a view to seeing the Severn Bore, in the upper reaches of the tidal Severn where the river is narrower, potentially making for a larger, more prominent wave; and in the daylight. This was something I hadn’t done for thirty years, my other half not at all. Previously (October 2006), we’d been to Newnham-on-Severn (with WOUGS), where the Severn begins to widen into an estuary. There, we saw the bore by night under a full moon, then in the daylight the next morning. The wave was very modest (no more than under a foot high). More impressive was the turbulence of the water during the tidal race which ensued behind it. Again with WOUGS, we tried again in September 2013 (see previous entries here) about 6 months ago. We were “a bit impressed” with the tantalising view we’d had from the Severn Bore Inn, in the dark on 20th September (to coin Jeremy’s description over dinner on the Saturday night), but still wanted a better view of it in daylight. For some reason, probably an astronomical one to do with the relative positions of the Moon and the Sun on the ecliptic, some years are better for bores than others. 2013 was relatively quiet, with a 4* bore in August, otherwise 3* or lower. 2014, by contrast looked set to be an auspicious year, with several 4* and 5* bores predicted in February and March, and again in August and September. 

What I hadn’t expected was for 2014 to get off to such a stormy, floody start - see notes for Upton-on-Severn for 1st March 2014 and flooding closer to home in my Water and Art blog.

As well as fluvial flooding, there was a lot of tidal trouble, too.  During the equivalent stages of the tidal cycle to this weekend – high spring tides just after new moon – the EA had issued severe flood warnings all along the Severn estuary as there was real risk of the tide overtopping floodbanks, which indeed it did at the Severn Bore Inn. There were road closures along the A48 and roads around Gloucester due to the double whammy of tidal flooding and the fluvial flooding.  The photo of surfers riding the crest of an impressive looking bore wave (probably further down the estuary at Newnham) on 2nd February made some of the frontpages. The Severn Bore Inn featured in news coverage, with reports of people standing far too close to the breaking waves and flooding in the car park during the rapid rise of the tide afterwards. I didn’t want to land my other half – or the still newish car, paid for out of his savings – right in any soggy repeat. Though where we were staying was well above flood level parts of the approach roads weren't, particularly at Longford where the road runs close to the river. These roads were flooded during the first half of February. The rain then eased off, nonetheless, I still knew we had to be careful where we parked. Floods or not, any large (4 or 5 star rated) bore over a weekend will attract large crowds of people, with parking everywhere along the bore’s route limited. After our walk on Sunday, we did a recce of the journey to Minsterworth. There was no flooding, but big potential for hold-ups on the Gloucester bypass. 

Our Severn Bore viewing spot on the Monday - looking upriver

We allowed plenty of time then to get to Minsterworth and park, leaving the B&B at half-seven on both mornings, even though the Tuesday one wasn’t due until nearly 10:00am.  Though we had a clear run on the Gloucester bypass and got there within 20 minutes, there were queues on both mornings eastbound along the A40 and northbound on the A48, the latter tailing back for about a mile. Sally at the B&B said it was like this most mornings because of the weight of traffic travelling towards Gloucester and the M5 from the Forest of Dean area and Welsh borders. On both days, we parked in the large layby at Denny Hill, on the west side of the A48 about ½ mile north of the Severn Bore Inn.

The bore appears, Minsterworth, Monday 3rd March

In the event, Monday’s bore was more or less on time, Tuesday’s about ten minutes late. Even in the rain shower on Monday morning, the wait for the bore after the early start was worthwhile – time to be at one with the river as were ensconced in our flasks of warm tea and packed breakfast of  bacon butties (thanks, Sally J). On the busier Monday, we were the envy of the other bore viewers. On Tuesday it was much quieter, the weather much drier and brighter. We had the river more or less to ourselves in the early morning sunshine, meeting mainly early dog walkers (and some chickens). Until the bore arrived, the river was still flowing outwards, the tide still ebbing. Monday’s bore was the more impressive of the two, with the wave breaking at its head and undulations formed by 4 or 5 smaller waves behind it. Tuesday’s was smaller and more subtle. We both found them difficult to photograph well with our handheld cameras, being fast moving and wide angled.  What impressed us just as much was what happened as the incoming flooded in behind the bore for about an hour afterwards. The water rose by several metres and, having been fairly slack during the first few minutes after the bore, the tidal current rapidly gathered speed.

Monday 3rd March


Saw Sally as we were leaving Brawn Farm. She said that there was still at least one big puddle along the road through Sandhurst after yesterday evening’s rain, but it was very shallow and OK if we took it slowly. This we did. It was a big puddle, though only a few cm deep.

We got to the layby just after 8:00am, about 1 ¼ hours before the bore was due at Minsterworth. Already the layby was getting very busy. Took the cars to be bore viewers, though there were also lorries in and out, some of them big thundering juggernauts. A van serving tea and hot snacks. We crossed the road and followed the pavement eastwards for about half a mile. The road ran very close to the river here, with views along it. We then took the public footpath over a stile on our right opposite Duni Farm (SO 763167). This took us across a narrow field onto the flood bank. The strandline from yesterday’s tides was worryingly close to the top it, but we hoped for the best. We positioned ourselves near the large trees halfway along the bank between the houses at either end. View across the river to Elmore with the Cotswold escarpment in the distance. Conveniently, someone had gathered chopped logs on the floodbank for us to sit on while we drank our tea.  Munros Man put on his over trousers when it started raining. I tried mine but gave up trying to put them on over my wellies on the muddy bank. The sky was very grey, though by about 9:00am it stopped raining. While we waiting other people arrived, most of them waited on the floodbank, though there was one guy with binoculars and a dog who got down onto the even muddier ground beneath the floodbank. 2 or 3 surfers entered the river in anticipation.

The bore breaks on the far bank
When it came, the bore was more or less on time, rounding the bend near Denny Hill with the leading wave breaking on the banks either side. My view looking downriver, though, was partially blocked by other people, particularly the guy standing at the water’s edge, beneath the floodbank. Because of the traffic noise from the A48 behind, I didn’t hear the bore rounding the bend before seeing it. It quickly swept towards and past us, the leading wave breaking and splashing near the top of the bank on the far side. I heard two waves break on the bank beneath us, though only saw the ripples bouncing back. No splashing of water over the bank. There were 4 or 5 waves behind the leading one, though most of them didn’t break. The surfers were disappointed, unable to mount the wave and ride it as it didn’t have the big breaking crests that their fellow boarders had further down the estuary enjoyed (see photos online at severnbore.co.uk).  We needn’t have worried about the wave overtopping the floodbank – it didn’t spill over at all. More of the danger was the rapid rise of the tide behind it. The bore heralds a step change in water levels, the incoming tide following on behind it. Most people drifted off once the waves had passed, us following them shortly. We saw most of the rise in water level, along with the swift current, walking back along the main road. As far as I know, the water didn’t spill over the road at high tide this time, but it was starting to flood into the fields on the far side of the river. From the road, we saw the berm beneath the trees where we’d been standing covered within half an hour of the bore passing. We passed two police vans parked on the road side, in case of trouble – Severn said to be helping police with their enquiries once again, then? No SFWs this time, but the EA still had four FWs along the Severn estuary – including here – and two on the lower Wye during this set of high spring tides.

The bore heads on upriver - 3rd March
The tide rises behind the bore


Looking back from the A48 to our bore viewing point as the tide rose on Monday - is the guy in hi-vis checking waterlevels?
Tuesday 4th March
A peaceful early morning on the Severn, Minsterworth, about 2 hours before the bore was due
Advice to bore riders near Minsterworth church

The orchard near where we viewed the bore on Tuesday, Minsterworth
Brickwork and rust, Minsterworth, near the orchard

This time, we arrived and parked with two hours to go before the bore. This and gave us time for a pleasant walk eastwards along the Severn at Minsterworth. We started off the same way as Monday, taking the footpath over the stile near Duni Farm. Having seen how the rapid rise of the tide yesterday, I took some before and after photos along the road here, the littered Yazoo milkshake my view marker.  As we walked along the floodbank, we also passed a wooden pole in the water close to the near bank and noted how far that was out of the water. From the stile, we followed the footpath along the floodbank, past the houses opposite Duni Farm, built very close to the river.  This brought us back to the road briefly, before returning to the river past Minsterworth Church. Reeds on the riverbank against the sun.  In front of the church, a lectern with bore timetables, the ink running with all the condensation on the glass. On the gate just ahead of us two notices: one for surfers, with cartoon diagrams of do’s and don’ts when riding the bore, the other was about viewing the snowdrops around Naight House – You may like to walk back along the berm between the floodbank and the river – if the bore tide has not covered it. You may think that the snowdrops are a different and new variety, but actually they are just silted brown from being recently underwater.   We found the snowdrops still flowering, along with a few daffodils, though the ones nearer the river now looked very brown and bedraggled. Going through the next gate, we past a shed behind the floodbank to our left, with earthy colours in the brickwork and rusting boards on the window, lit by the low morning sunshine. There were quite a few trees down in the orchard, the soil shallow and soft. People had gathered flotsam branches along the floodbank.  We breakfasted here on our bacon butties, bananas. Throughout our walk, the tide was ebbing, with a strong flow down river, though it seemed to lessen as we drew nearer the due time for the bore. Plenty of time to watch the water. The bore today was due at Minsterworth was 9:55am. It put in its appearance, rounding the gentle bend near the church at about 10:08, just as I was thinking Late today, but it will probably still get here before Southern [trains]. It was more subtle and more muted than Monday’s, not as high and the wave crests were much less pronounced. Again, the leading wave broke as it crashed into the soft banks on either side. I heard the wave break on the near side, but only saw the ripples bouncing back from the bank. I managed to zoom into the breaking wave on the far side as far upriver as far as the pylon. There were still several waves behind the leading one, but they weren’t as obvious.

The bore arrives on Tuesday - more muted and subtle than the day before

The bore breaks near the pylon as it moves upriver

There was nothing muted, about the incoming tide which followed behind the waves. Immediately behind the waves, the water was fairly calm, though we could see the water quickly rising up the bank on the far side. Before long, the current gathered pace, running most rapidly about half an hour after the bore. It was hard to say how fast it was going, but I was pretty sure it was faster than anything I’ve seen on any other tidal river in Britain, including the Arun, reputedly the second fastest after the Severn.  The volume of water and change in the height of the water were much greater, too.  “I think we need to get a move on”, my Munros Man said as we passed the wooden pole and saw that the river had risen more than a metre in half and hour. It was only that we’d been here the day before and therefore knew where to get off [the path along the floodbank] that I felt fairly confident about walking along here.  Today’s high tide wasn’t predicted to be as high, this month’s spring tidal cycle having peaked on Sunday and Monday. We did, nonetheless disturb the chickens near Duni Farm, their hatch positioned along the narrow floodbank between two gates. I thought they might make a bee-line for the gate at the far end when I opened it. Instead, they jumped off the bank and into the water spilling onto the berm. I hope no animals were harmed in this tide.

Some before and after the tide photos from Minsterworth on Tuesday - taken shortly after our arrival along the Severn, the tide ebbing, then during the rising tide 30 - 45 minutes after the bore.

Looking up the river from the A48 near Denny Hill




The pole



Bore Notes and News

Reference: Fred Rowbotham The Severn Bore, David and Charles, 3rd Edition (1983)
Wikipedia – Severn Bore - http://en.wikipedia.org/wiki/Severn_bore
The Severn Bore – Spectators and Surfers - http://www.thesevernbore.co.uk/home/4579550154
The Severn Bore at Minsterworth http://www.minsterworth.org/bore.htm


These were the predictions for March’s set of bores: (http://www.thesevernbore.co.uk/timetable/4579755614)



Monday’s bore was rated as a 5*, the highest in this set – 4 and 5 star bores are forecast when predicted high water at Sharpness is 10m aCD or higher. I don’t know whether it made its mark in the event. According to the EA (FW update for Minsterworth, Monday evening) high water was 5.68m aCD. This was in the range of their predictions (5.5 – 5.8m), but lower than in January and February (3rd  Jan 6.15m, 1st February – 6.08m). All high tides above 9m aCD at Sharpness should produce bores, but there are other factors affecting the timing, size and shape of the wave: weather; the course of shifting channels among the sand / mudbanks in the estuary; and how much freshwater is flowing down the Severn. Strong westerlies and southwesterlies in Atlantic off SW England and Ireland will increase the height of the bore and make it arrive early – as I believe was the case in January and February. Likewise low atmospheric pressure in the Atlantic. For our bores, the winds were fairly light, though they would have been stronger out at sea than inland. Too much freshwater in the river will decrease the height of the bore, particularly further up the river where we were. Though the fluvial floods along the Severn had abated, the river was probably still running well above its normal summer level. I suspect this diminished the bores we saw from what they might have been. The severnbore.co.uk site indicated the best surfing conditions would be further down the estuary around Newnham.

Though the first edition of Fred Rowbotham’s book is now 50 years old, mine over 30 (3rd Edition, 1983), it’s useful for its facts and figures, diagrams and well written account of how and why the bore forms. The bore wave forms as the incoming tide travelling from the open sea into the Bristol Channel is funneled along the progressively narrowing Severn estuary. Figure 3 shows a the cross-section of the estuary between Sharpness and Maisemore Weir, with the corresponding height of the water at different points along the Severn when the bore reaches Minsterworth. It shows that when the bore arrives, the water is still ebbing – as we saw. The bore wave heralds the incoming tide. In the upper parts of the tidal Severn it is a projected tide, detached from the tide in the estuary. By the time the bore reaches Minsterworth, the tide is ebbing at Sharpness. The figure also shows that high spring tides can travel beyond Maisemore Weir. The profile of the tide – plot of water height against time – changes moving up the estuary too (Figure 6). At Avonmouth, it’s a regular sine wave. Then, as the estuary narrows, the gradient of the graph as the tide rises steepens, meaning the tide rises over progressively shorter periods of time – at Avonmouth, it’s around 6 hours, at Minsterworth about an hour. The gradient on the ebb tide becomes shallower and predominates for most of the day at Minsterworth. The shape and form of the bore changes moving from the wide (250m+) estuary below Newnham with channels among sandbanks into the narrower tidal river around Minsterworth, 80 - 95m wide. In the narrower stretches, the bore is higher, though more likely to be affected by freshwater flowing downstream. My perception at least was that the bores we saw on this trip traveled faster than the ones we saw at Newnham and the Severn Bore Inn. More freshwater in the river would increase its depth, allowing the wave to move faster, though it might be slowed to some extent by the increased flow downstream. It might also be my memory and time appearing to going more quickly the older I get. The speeds given in the book (p98) for the bore wave are 10-13 miles per hour between Minsterworth and Gloucester (16 kmh-1 – 21 kmh-1, 8.6 – 11.3 kt, 4.4 – 5.8 ms-1), 5-8 miles per hour (8-13 kmh-1, 2.2 – 3.6 ms-1) in the sandy estuary. The figures given for the speed of the moving water at “maximum flood and ebb”, seem very modest after what we saw: 9.5 kmh-1 in the estuary, 8 kmh-1 Minsterworth and Gloucester: respectively 5.9 miles per hour / 2.6 ms-1, 5 miles per hour / 2.2 ms-1 respectively.

The Wikipedia article for the River Arun gives 4-6 knots, i.e, 7.4-11.1 km-1, 4.6-6.9 miles per hour, 2-3ms-1 for the tidal current in the lower reaches http://en.wikipedia.org/wiki/River_Arun, though it’s not clear whether these are maximum or average speeds. Elsewhere, I’ve seen 5 knots (average) – 8 knots (maximum) here, Littlehampton Museum, Southern Water Authority, 1987).

Severn Bore / Tidal surges / flooding  news and  video footage  
3rd January 2014
http://www.bbc.co.uk/news/uk-25585874 - Severn Bore Inn, with Chris Witts
http://www.bbc.co.uk/news/uk-25588798 - the Severn flooding from the air, Gloucester area, 3rd January

February 2014

http://www.bbc.co.uk/news/uk-26005363

http://www.bbc.co.uk/news/uk-england-gloucestershire-26007108

http://www.bbc.co.uk/news/uk-26005501

http://www.bbc.co.uk/news/uk-26005259

http://www.bbc.co.uk/news/uk-25996441


http://www.theguardian.com/theguardian/2014/feb/03/mainsection/uknews


A selection of Youtube videos posted by other bore viewers, January  - March 2014



Surfers riding the bore in the estuary on Sunday 2nd March - www.thesevernbore.co.uk - ends with gurling and splashing


The bore in the estuary - Monday 3rd March

https://www.youtube.com/watch?v=m0wPOwdYgRQ - 3rd March - Newnham and Minsterworth, probably the Severn Bore Inn. Here, some surfers were successful, but not everyone. The guy interviewed, with board, post bore said the power went out of the wave as it rounded the corner to where he was, whereas one other guy shooting along the near the bank, narrowly avoiding getting caught up in overhanging branches.


Tuesday's bore at Epney - estimated at 3* when it came


This is shakey footage from the big bore on Sunday 2nd February - as the commentary says, spoilt by the high volume of fluvial floodwater coming down the river. More of an eyeopener is the rapid rise in water afterwards. Water rose around the spectators on the bank, then overflowed onto the lane , the river breaking the bank to the left of the shot. This was at Elmore, on the opposite side of the river to Minsterworth.



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