Severn Estuary - Beachley Point and Sedbury Cliff

Second Severn Crossing from Beachley Point

This excursion was part of a Geological field trip, organised by the Wessex Branch of the Open University Geological Society WOUGS, led by Alan Holiday on Saturday 21^st September. After doing the Upper Soudley Geological Trail on the eastern side of the Forest of Dean during the morning (see separate entry), we headed south along the A48 to the Severn estuary near Chepstow and the First Severn Bridge.

To get to Beachley Point, we turned off the main road just before the Chepstow bypass bridge over the Wye. This took us through Beachley, past the army barracks and college. We parked at the end of the road, underneath the bridge. The bridge towers were now painted off-white. Near here was the quay for the ferry which plied the Severn between here and Aust, before the bridge was completed in 1966. There was also a slipway for the SARA, the Severn Area Rescue Association who go out in high speed motor boats to assist people in trouble in the treacherous estuary. Indeed turbulent water swept round the slipway, the bridge spanning narrows in the channel. Beachley Point has the highest tidal range in the UK and one of the highest globally, after the Bay of Fundy in eastern Canada. Spring tides can exceed 14m (46 feet). Hence the massive support pillars at the base of the bridge towers.

Geologists at the rock face

Thankfully, the tide was now well out, enabling us to turn left off the track and on to the shore to the rock outcrops. These were set back from the water and the banks of deep, soft Severn Mud, behind salt marsh grasses. Judging from the flotsam on the grasses, it still looked as if high spring tides could reach the foot of the rocks. Perhaps they’d done so this morning and last night.

We started with the exposure beneath one a tall electricity pylons. On our left, facing the rockface, was cream coloured Carboniferous limestone. On our right were rusty red Triassic beds – mudstones, sandstones and conglomerates. These were brought together by a fault, which was most obvious when stood back from the cliff. This was also an unconformity in which strata spanning much of the upper Palaeozoic era were missing. A bit further along, near the fine grained, slippery low cliff of limestone we clambered over, there was some conglomerate – fine grained rusty red Triassic material containing rounded pebbles of limestone from the Carboniferous, and a fault breccia with more angular pebbles. This and the limestone were coloured with yellow lichen above the high tide mark Some of the limestone was stained red from the Triassic material being washed over it.

Carboniferous outcrop at Beachley Point

From here, there were good views of both Severn bridges, as well as Austcliff on the far side of the other side of the first bridge. The first bridge, now known as the Severn Road Bridge, is a Suspension Bridge, like the Forth Road Bridge which was completed two year earlier and is now afflicted by corrosion problems in the cabling. The same problem is highly here, then. Being a suspension bridge, it is vulnerable to the wind and, used to be at least, closed during high winds. The estuary here is about three quarters of a mile wide. At the Second Crossing it is about three miles wide, where the Severn estuary opens out into the Bristol Channel. This is a sturdier bridge – only the middle bit is suspension. Of the two, I reckon it’s the better looking one. The first one looks a bit old tired by comparison (like many other structures built during the 1960s-1970s do now), even if the view is more restricted when crossing.

Views of the bridges

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Both bridges have become increasingly expensive to cross – the tolls are now £6.20 for cars, payable going west only. In my dim and distant past (mid-1970s) they started at 12p. For some time, they’ve been steep enough to put people off crossing too often, though I dare say that if they lowered them the traffic and development would become even crazier.

Pedestrians enjoying a traffic-free Severn Road Bridge

It took me a while to register it, but there were no cars or lorries crossing on the bridge as we went under it walking to and from the rockfaces, only a few vans which were probably people working on the bridge. It was closed at least throughout this weekend for maintenance – it’s always needed lots of that. I now saw why the M48 was so quiet when we came into Chepstow yesterday. Come to think of it, I don’t think I registered much road noise. Invariably it’s so ubiquitous that it blends into the background. There were, though, quite a few pedestrians. Locals, perhaps, enjoying a rare, quiet traffic-free view. There is a foot-cycle way on the north side. The Second Crossing is motorway only. As with any normally busy road devoid of traffic, it seemed a bit creepy. It would just have needed thick Severn fog to complete the picture.

Further to the lecture given by engineers from Cardiff University at this year’s WOUGS AGM my Water & Art piece shortly afterwards (30/01/13 – Renewed Interest in Severn Barrage, ref 5), nothing’s happened and it looks unlikely that anything will for the foreseeable future (ref 6,7)

Sedbury Cliff

Leaving Beachley, we continued north of the bridge, onto Sedbury Cliff parking on the road out from Beachley (Loop Road), just opposite the public footpath sign for the southerly end of Offa’s Dyke . We crossed the road and followed dyke part of the way, before turning right and going through the wood down to the shore. As at Beachley, a wide strip of saltmarsh grass separated the cliff here from water and mud of the estuary. The First Severn Bridge was now to the south.

Ammonite

The geology in the cliff is the same as Austcliff across the estuary: rusty red Triassic mudstones overlain with younger Blue Lias beds of Jurassic age, though actually, these were pale creamy colour limestones and shales. One of the upper layers in the Triassic sequence is known as the Westbury Bone Bed as it contains the bones of fish and marine reptiles living in lagoons in a hot dry desert. A small landslip near the northern end of the cliff had brought down chunks of the creamy material containing fossils. One chunk was full of oyster fossils. A couple of other pieces contained small ammonites, up to 10cm across. Otherwise rockwise, there was less to see here than we’d hoped. This is because the cliff was tree-clad and overgrown. According to Alan, it had become all the more so since his recce in July. The last bit we looked at was muddy underfoot, too.

Austcliff

Though Austcliff is much better exposed, it doesn’t seem as easily accessible as Sedbury (conveniently accessible via Offa’s Dyke), though it is listed as an SSSI and described in a Geology Guide to South Gloucestershire (ref 4). I went down there on a field trip led by my secondary school Geography Teacher during the mid-1980s, later that same February Saturday he took us to the see the Severn Bore (see separate entry). From about that time, too, I have a photo of my father sketching the First, then only, Severn Bridge, above the cliff. This would have at Aust Services, on the way to Pembrokeshire, or the camping in the Forest of Dean. Back then, it was the highlight of the journey, though very regrettably now, that’s all gone. There’s still Severn View Services near the bridge, but that’s set back about 600m from the bridge, the area where we’d picnicked for free having been privatised with the building of motel and conference centre. From Sedbury we could see a silvery sheened executive building just north of the bridge. As we saw on the way to Pembrokeshire last week, there are no services near the Second Crossing. I won’t bang on about much more here, but when they tell motorists and their car loads to take a break from the motorway, please give us a proper break, with seating outside, away from the car park for some air.

Views of the Severn estuary from Sedbury

Naturally, I was reluctant to head back to the cars from the Severn, seemingly so soon, just as the weather was brightening, with the sun on the river, bringing out the rivulets in now silvery looking mud (mentally filtering out d Oldbury Power Station, of course). Continuing on from the series of paintings and printmaking I’ve done on this theme during the past year, I’d looked forward to revisiting the Severn estuary this year for more reference material and inspiration. I took lots of photos, but was unable to do any sketching, due to time constraints. I’d liked a bit more time at Beachley, particularly, to walk along the track above the rocks to get a better view of the confluence of the Wye., though I did go down that way in 2003.

  

References and Links

1.Alan Holiday, The Severn Bore, Soudley, Beachley Point and Sedbury Cliff, Open University Geological Society Wessex Branch field trip handout (2013).

2. Wikipedia – Severn Bridge, accessed 24/09/13

http://en.wikipedia.org/wiki/Severn_Bridge

3. Wikipedia Aust Cliff

http://en.wikipedia.org/wiki/Aust_Cliff

4. The story of landscape and geology in South Gloucestershire, Avon RIGS pdf

http://www.brerc.eclipse.co.uk/files/rigs_boards/geo_landscape_sglos.pdf

5. Joan Lee, Renewed Interest in Severn Barrage, Water & Art, 30/01/13

http://artywater.blogspot.co.uk/2013/01/renewed-interest-in-severn-barrage.html

6. Wikipedia – Severn Barrage -

http://en.wikipedia.org/wiki/Severn_Barrage

7. MPs say case for Barrage Unproven, June 2013

http://www.parliament.uk/business/committees/committees-a-z/commons-select/energy-and-climate-change-committee/news/severn-barrage-publication/