New Wetlands in the Lower Tamar Valley

 

New Wetlands in the Lower Tamar

The Tamar, which forms most of the border between Devon and Cornwall, is a very ancient river. Physical geographers tell us the river was in place 70 million years ago, winding its way south, and as the land gradually rose in the area where Gunnislake is now, the river slowly eroded its way down through the rock, retaining its bends, known as ‘incised meanders’ which are typified by the steep rocky cliffs towering above the river banks in places.

The map of the lower Tamar from Gunnislake to the Tamar Estuary. Scale 1cm to I km.

Below Cotehele the valley widens out and the low-lying riverside meadows, known locally as ‘Hams’ are liable to flood. To safeguard property and retain the river meadows for grazing, a long levee was constructed in 1850, along the river bank on the Cornish side from Halton Quay to above Calstock, a length of getting on for three miles. The river is tidal all the way up to the weir just downstream of Gunnislake. At intervals ditches drain the meadows through culverts under the levee by means of tidal flaps. These allow water to run into the main river at low tide and closed as the tide came in so no water ran back into the meadows.

Some 15 years ago plans were being thought out to cut the levee in places to allow some of the low-lying meadows on the Cornish side to flood at high water and times of heavy rainfall, thus alleviating the risk of flooding Calstock and other low-lying properties in the lower reaches of the valley. At the same time this would enhance the habitat value by increasing the extent of wetland.

The scheme proceeded slowly. Vehement local opposition to the plan to flood Haye Marsh, an area downstream of Cotehele caused that project to be abandoned.

In October this year, a breach was made in the levee above the Cotehele car park and a long narrow meadow between the riverbank and a woodland on the rising valleyside, up as far as the river cliff downstream of Calstock was opened to inundation. This land belongs to the National Trust and the public footpath runs through the base of the adjacent woodland, so views can be had through the trees, of the newly-developing wetland.

There are several explanatory notices about the wetland project at the side of the woodland footpath at Cotehele.

Looking across newly flooding wetland upstream from the public footpath through the Cotehele woods above the car-park. So far, there aren't any places from which to get more than a glimpse.

You can see the cut in the riverbank towards the left of the picture.

A Little Egret quickly appeared and a Kingfisher was sitting at the side of the cut when we looked in October.

Over the past two years a project at Calstock has been the subject of considerable debate between the Environment Agency who own both the riverside meadows upstream of Calstock and the riverbank and levee, and a concerned local population. The path from Calstock along the levee to the fine set of restored limekilns at Okel Tor and either back the same way, or along a quiet lane running back to the village, is a popular walk. The prospect of this walk being curtailed by a breach in the levee was contentious to say the least.

The path along the top of the levee, walking south towards Calstock. The Tamar is on the left of the path.

                                                                                    

Common Darter dragonflies are abundant here, and frequently bask on the sun on the path on warm late summer days.

The matter was finally resolved when the Environment Agency agreed to construct a walkway spanning the breach in the levee, so at last, work went ahead.

Towards the end of 2020 extensive excavations were dug in the meadow to be flooded in order to build protective bunds at the lower end to protect the village playing and recreation fields, car park and low-lying part of the village; and at the upper end to protect the local sewage treatment works. These excavations would form shallow ‘scrapes’ or pools. The whole of this area was fenced off and declared a Nature Reserve with no public right of entry.

Driving piles many feet deep into black silt to make footings for the walkway when it crosses the cut to be made in the levee on the left of the picture.

Pools already forming in the scrapes at the southern, Calstock end of the area to be flooded. This was in October '21.

Looking  east across the flooding scrapes in October '21

Work proceeded in 2021 to construct the walkway before the cut was made in the levee. Until the early part of October, the levee path remained open to the public until the final stages of construction, and as I write, on November 12^th ’21 the breach is due to be made and hopefully the walking route will be resumed.

Meanwhile interested people, both local residents and those from further afield, are watching the development and future changes with interest. The shallow pools soon attracted water fowl. Green Sandpipers and Common Snipe could be seen regularly throughout the late summer/ early autumn period, together with numerous mallard and Teal. Black-headed Gulls, with the occasional similar Mediterranean Gull among them, appeared from time to time.

Drake Teal

Green Sandpiper, showing conspicuous square white rump when it flies.

Black-headed Gull. They almost invariably lose their black head in the winter and instead just show a black spot behind the eye. Black tips to the primary wing feathers show clearly.

Mediterranean Gull. Compare this with the Black-headed Gull above. In winter it also loses its black head and instead has a grey smudge behind the eye. Importantly, there are no black tips to the primary wing feathers.

This gull is being seen more often these days. It breeds on the north Brittany coast so hasn't got all that far to come

The extensive soil disturbance has initially given rise to a vast population of docks and thistles, but these will reduce in the course of the inundation and I understand there are plans to hasten the spread of the riverside fringe of reeds across the new wetland with more planting of this species. The gradual changes in the flora and fauna in this area will be monitored, and interesting to see, both at Calstock and Cotehele.

Latest news:

The cut in the levee was made on the 13th/14th November at low water, neap tides, to minimise the initial surge of silt flow. Only distant views were possible when we went to look at high water on 14^th, but the area will be watched closely as it develops.

There is a Facebook page about the project at Calstock : 

Calstock Wetlands Bird Watchers' Group.

The first morning after the breach in the levee. The first picture is looking inland towards the area which will be inundated at high tides. The lower picture is looking back towards the river. (Many thanks for photos by Peter Thompson.)

I follow this bog:

https://musingsfromhigherdowngateandelsewhere.blogspot.com

AUTUMN VISIT TO N.W.WALES

Autumn visit: NW Wales

Oct 16^th

Drove up from Cornwall on a quiet autumnal day with heavy mist as we skirted N. Dartmoor and then a pall of low cloud hung over us all the way up to Bristol before it lifted and  we could see shadows on the road. Most of the leaves haven’t yet coloured up, though the ash trees are going that clear yellow-green before they fall. As we drove through the hills in Central Wales the frequent roadside Rowans were still laden with a heavy crop of berries, not yet stripped by either local birds nor an influx of winter thrushes though they had dropped their leaves.

Lleyn Peninsula, N.W.Wales.

 

Upon arrival at Ty'n Gamdda  (Kim's home) and that first cup of tea and quick report on the drive up, our pre-dusk walk was to go and inspect the strange fungus Kim had uncovered a few days ago while clearing an overgrown flower bed in the garden.

 See where Kim's home (1) is on map before Oct 18th.

 

 

 

Devil's Fingers or Clathrus archeri, with five fat and writhing pink sections, a foul-smelling relative of the Stinkhorn.

This is an uncommon Australian native and it is a mystery how it has appeared twice now on Kim’s premises.

 

 

 

 

We then looked at Kim's yesterday evening’s moth catch saved from the clump of Ivy flowering down the track.

 

 

 

Among a sprinkling of moths feeding on the blossom was this handsome Red Swordgrass moth.

Status in Wales and nationally: Local, and immigrant at times.There are very few records of it on the Lleyn Peninsula.

 

Oct 17^th

Rain set in during the night; 5 mm and drizzle off and on all day with a mild breeze and heavy mist.

We girded up in waterproofs after lunch and inspected the new pond first.

 

Stone re-enforcing wall built outside the lower end and cobbles gradually being added round the margins with a few new plants being slowly introduced.

Kim's sheep, knee-deep in foggage, grazing in the field next to the new pond, keeping an eye on us. Most of the view was obliterated by mist.

Cosmos , a late-flowering clump attracted hoverflies when the sun shone. 

 

 

 

 

 

 

 

      Crab apples; being raided by a big flock of Jackdaws so we are picking them for jelly before they are really ripe. The flock has already raided the Borlotti beans.

 

 

 

Monday 18^th October

Wet and windy morning but it eased after lunch and we went up onto Bychestyn. Low cloud but a couple of choughs looped and swooped along the cliff, calling with clear, joyous calls  "Cheuff, Cheeuff" and a Kestrel hung motionless despite the keen wind, gazing down onto the vegetation below. Several Gannets flew low over the water, close in, looking bright white against the grey turbulent sea.It would have been a dirty crossing to the island today.(see where Bychestyn (2) is on map before note for Oct 19th. )

 We crawled under the fence and ventured across the wind-cropped turf to look down to the bouldery beach under the steep  cliff of the Parwyd . Kim had seen seal pups in there a while before. One was at the tide-line, dead, being pecked by gulls, and another, still in it’s white baby fur, hauled right up at the base of the cliff. It can’t have been more than a couple of weeks old.

As we walked along the lower cliff path  the cloud came down to the sea, blotting everything out and Bardsey was no more.

Large Parasol Mushrooms were conspicuous all along the cliff, standing up above the windswept gorse and grasses.

 

Tony has picked and feasted on them in the past but  this time he left them in favour of the small more delicate field mushrooms we’d be able to pick in the Cae Crin meadows further along.(see where Cae Crin (3) is on map before note for Oct.19th)

 

 

 

 

 

 Cae Crin . I have always fancied living here, looking out across the Sound to Bardsey. But as a gardener I might have regretted it. Cae Crin means land with poor thin soil which dries out quickly, leaving the plants frizzled.

 

 

 

 

 The overwintering bunch of cattle watched us pass They are very docile Stabilizers, a breed we’d never heard of. They are a cross between Red Angus, Hereford, Simmental and Gelbvieh (a Bavarian breed) and were bred to give good mothers, quiet temperament, fast maturers and good beef conformation. They come in various colours.

They have churned the cliff-side wet flushes into a quagmire of black slush, unfortunately wrecking the wet-loving plant assemblage there. Maybe it will recover when the cattle are taken off in the spring.

 

 

Key to map:

1. Ty'n Gamdda (Kim's property)

2.Bywchestyn (note for 18th)

3.Cae Crin (same note.)

4. Holy Well Ffynnon Saint near Aberdaron (note for Oct.19th)

5.Holy Well Ffynnon Aelrhiw near Llanengan (same note.)

6. Where we looked over Hell's Mouth (Porth Neigwl) (same note.)

7. Where we looked over coast at Aberdaron (same note.)

8.St. Mary's Well (Ffynnon Mair.) (note for Oct.20th)

9. Traeth Penllech (note for Oct 21st)

10.Pared Llech Ymenyn (see note for Oct 22nd)

11. Hen Borth  (same note)

12. Porthor or Whistling Sand. (see note for Oct.22nd)

Tuesday 19^th October

As I lay in bed this morning I could hear the wind on the roof, and more rain is sweeping in. A domestic morning I think.

This afternoon we girded up and defied the weather, first visiting Ffynnon Saint, just a mile down the road. Having been looking at a few of the Holy wells in East Cornwall over the last few weeks, I was interested to see a few round Kim’s.(see where Ffynnon Saint (4) is on map above.)

  Ffynnon Saint or the Saints’ Well is near the end of the Dark Ages and Medieval Pilgrim's Way leading to Bardsey. It’s situated in a small wet willow  wood with a low stone surround and nowadays is covered by an iron lid.

We drove on a mile or two in mist and driving rain and walked through a couple of small fields to Ffynnon Aelrhiw. This is a more elaborate affair (See where this well is (5) on map above.

 

  This well is fenced and cared for  and was claimed to cure certain skin disorders. The surrounding stone enclosure with a seat ledge on three sides was constructed in the 16 hundreds.

By this time, thoroughly wet, we decided to go a bit further to look across the fields at Llanengan, behind Hell’s Mouth. The meadows usually have flood pools lying on the grass in winter and following heavy rain, and can attract waders and other water birds. This time it still wasn't flooded but shining whiter than the grazing sheep were six Whooper Swans in the distance.

Starlings facing into the bad weather.

 

 

 

 

 

We drove back behind the long beach of Hell’s Mouth and walked across to the crumbling cliff edge which is subject to dramatic slumps and slippages of the thick ice-age clay deposits at the head of the beach.(site 6 on map above.)

Porth Neigwl or Hell’s Mouth is a notorious lee-shore and has been the scene of many shipwrecks in the days of small coasting craft. The sea was pounding in and the visibility was poor, with a mix of drizzle, mist and salt spray. Kim spotted a bunch of about a dozen Common Gulls, standing among the boulders on the beach below.

On summer visits we have run the moth trap on the cliff here.

 

 Looking east at Aberdaron and the beach.(site 7 on map above.)

At present it’s too wet, windy, foggy to go and look at the ivy flower at the bottom of the track, But it’s almost full moon and tonight there was a strong ring round the moon and it glimmered in the misty gap that opened momentarily between the shredded clouds.

 

Wednesday 19^th October

Rain and fog kept us in  apart from a quick scamper up to the north coast to watch a few gannets flying past. Then in the afternoon when we drove up to Mynedd Mawr, parked partway up and then walked over the close-bitten turf toward the coast. We headed towards the wide valley which runs down to a steep rocky cleft in which the famous pilgrims’ well of St Mary is in a small rock basin in the splash-zone level above high tide.(site 8 on map above.)

 

The Well of St Mary is in the gully below this grassy area. Bardsey is across the water.
 

The medieval ridge and furrow marks of old cultivation still show.

There were all sorts of fungi growing in the short turf.

 

 

 

 

 

In the bowl of sheltered grassland above the coast are the rectangular and lumpy remains, now completely obscured, of the chapel of St Mary, with several rectangular fields showing old ridge and furrow marks quite clearly.

 

 

 

 St Mary's Well is partway down the cliff on the right.

 

 

 

 

 

 

 

 

 

 The well is in the little horizontal slot in the middle of the picture. It is a tricky climb down to it, and it's sanctity is partly derived from the difficult access and because, even though it's in the splash zone, the water is always sweet and fresh.

 

 

 

Thursday 20^th October

Up to a dry day with broken cloud, sunshine and a frisky north wind. We hastened out before the weather changed its mind, and headed out to the north coast, to Penllech, a wide bay reached from a deserted car park and followed a stream through a couple of meadows. (site 9 on map above.)

The stream running down to Traeth Penllech.

 

 

 

 

 

 

 

 

 

It cuts its way through a gully and then  down a considerable waterfall as it plunges down though the glacial head to a fairly wide and long sandy beach. This is backed by a low cliff with rocky outcrops and small headlands of what is described as Gwna Melange, a Pre-Cambrian mix of igneous, heavily metamorphosed rocks in what was an ancient subduction zone where the crust is sinking below the earth’s mantle.

The sea was pounding in with a series of white-capped breakers crashing onto the sand where a large flock of mixed gulls alternately rose up in a white cloud and then settled on the sand.

Traeth Penllech looking east. A lot of seaweed has been washed up and partly buried under the sand.  A big flock of mixed gull species and Oystercatchers were feeding on the maggots in the rotting weed and now and then rising up in a white cloud.
 

 Egg cases of Bull Huss (Greater Spotted Dogfish) washed up on the beach.

 

 

 

 

 

 

 

 

In the afternoon we made a quick visit to the pool at Pwll Cyw to get a few roots of greater Water Plantain and Bog Bean which we potted up and plunged into the new pond. Tony walked home along the coast to look for seals and porpoises. We've been seeing porpoises this trip from along here.

 

Female Grey Seal hauled out at Pared Llech Ymenyn.
 (site 10 on map above.)

 

 

 

 

 

 

 

 

Female and very young seal pup, still in its white coat. Hen Borth.

 (site 11 on map above.)

 

 

 

 

 Friday 22^nd October 

(site 12 on map above.)

More rain this morning but after doing some geological read ups about the incredibly ancient, varied and mixed up rocks hereabouts, together with the thick layers of glacial drift overlying in places, we ventured out in the afternoon, this time to Porthor (Whistling Sands.) The name comes from the fact that at certain times and when the sand is dry, the shape of the sand particles makes them squeak as you walk.

 

 There was still a good rough sea pounding this north coast but we were surprised to see quite a few people around especially family parties and older kids. Is it half term?.

We saw this seaweed here and at Penllech. We don’t recognise it.This frond was about 40cms long.

We walked the length of the beach to the east end, and looked at the tortured rock. Now  we are familiar with the sight of the lava flowing from the recent Icelandic volcano shown in the U Tube videos, one can imagine that viscous material being stirred up like a black Christmas pudding and then left to harden. That’s what the rocks here look like. Pre-Cambrian in age, they were then at sometime cut off horizontally and then who knows what happened to this surface over the millions of years before a layer, tens of feet deep, of ice-age glacial deposits were laid down on top.

 

 

We walked back along the base of the cliff which showed signs of almost continuous slumping at different times and of varying size. The whole thing is acutely unstable, always on the slide, the clayey debris with unsorted stone from fine gravel to boulders, is lubricated by frequent runnels of water. Brookweed, Fleabane, Reed, Greater Horsetail, were growing on the cliff slopes.

We detoured on our way home to get some Purple Loosestrife and Water Mint roots for the new pond planting.

 

Saturday 23^rd October

Returned home today after a successful visit, as always , full of interest and we made the most of a ‘thank goodness for waterproofs’ week.