Natur Cymru
Two centuries have passed since the Cob
was constructed by William Maddocks across the Glaslyn Estuary. The
influence of this development on the area's landscape, nature,
economy and society has been huge and far-reaching. Twm
Elias describes the substantial changes that were seen
back in the 19th Century and explains the change that is still
happening today as a result of dynamic river processes in a
confined estuary.
Potatoes instead of
cockles
Before constructing the Cob, 200 years ago, it
must have been an amazing sight to behold the sea at high tide
stretching all the way to Aberglaslyn, almost five miles inland,
and then the thousands of acres of mud and sand that came into view
when the waters receded. It was a very dangerous estuary which was
only safe to cross when the sea ebbed, and in the absence of a
flood in the river.
When William Maddocks, who gave his name to
Tremadog and Porthmadog, constructed his large sea wall, the Cob,
in 1811, the area changed for ever. Here is an English translation
of what Dafydd Siôn James said about it in 1813:
Potatoes instead of
cockles,
And ponies instead
of seals. (1)
Thousands of acres of farming land were gained
and a new road was created to connect the former counties of
Caernarfon and Meirionnydd. Before long, a tramroad was built from
the quarries of Blaenau Ffestiniog to carry slate to the ships
docked at the new harbour in Porthmadog to be transported across
the world. A shipbuilding industry soon developed here -
Porthmadog's famous small three-mast sailing boats – and that had a
major effect on the management of the area's native oak trees. The
commercial value and use of the trees increased substantially and
several new plantations were planted in the second half of the 19th
century, such as Coed y Borth near Borth y Gest. This site is now a
local nature reserve containing tall and upright oak trees which
are about 120 years old.
The habitats least affected by the
construction of the Cob were possibly the oak and birch trees on
the rocky ridges which are seen, here and there, above the flat
fields. These were islands at one time, as their names testify,
'ynys' being the Welsh word for island: Ynysfor, Ynys Ferlas, Hir
Ynys and so forth. They are of interest due to the variety of
lichen and bryophytes that grow along the tree branches.
Industrial development
It is difficult to believe today how much
economic development was seen in the Glaslyn Marsh area during the
19th century. Copper came from the Nant Gwynant area to be exported
through Porthmadog and substantial slate quarries, and their
connected railways, provided grey slate from Blaenau Ffestiniog and
Cwm Croesor on the Meirionnydd side of the Glaslyn River and from
the Stradllyn and Pennant Valleys on the Caernarfonshire side (2,
3).
The naturalist is reminded, unexpectedly so,
of the busy nature of the international slate trade. It is said
that, towards the middle of the 20th century, a number of exotic
plants would have established themselves on Ballast Island near the
mouth of the harbour. The evening-primrose, Oenothera
(agg.), seen on the Cob and in the Borth y Gest area, is
considered to have arrived here from America in the ballast of the
sailing ships, as also occurred with Welsh mudwort, Limosella
australis, from the north-east coast of the United States, and
seen in muddy pools on parts of the marsh (4). Unfortunately, the
island is now covered with thick scrub and there is no recent
evidence of the survival of other ballast incomers.
Another product of Ballast Island is building
stones – some from distant parts of the world. And because people
in the olden days begrudged wasting anything useful, some were
transported to construct the Britannia Bridge (the harbour bridge)
nearby, and were used as ornamental stones on some of the buildings
in High Street.
Land use
Agricultural land:
Alongside this industrial activity there was substantial
agricultural development, as the demand for food increased with the
rise in the country's urban and industrial population. Even before
the construction of the Cob, parts of the marsh had already been
reclaimed – including about 1,000 acres by William Maddocks himself
in the Tremadog area at the turn of the 19th century – and other
land in the Llanfrothen area and other places which were reclaimed
by a number of local landowners some half a century or more earlier
(1).
In order to create productive land from the
marsh after constructing the Cob, earth banks were built on either
side of the Glaslyn River, along with the streams running into it,
as well as a series of deep ditches and clay pipes in the fields to
drain the land. A great deal of good land was gained, although
large parts of it would tend to be wet for long periods over the
winter. As a result, the land of some nearby farms was
substantially augmented and one new large farm was established,
aptly named Tŷ Newydd Morfa (Marsh New House in English). The
ditches continue to be important connecting corridors for wildlife
today, although they have suffered from the spread of Himalayan
Balsam (Impatiens glandulifera), since the end of the
1990s.
The semi-intensive agricultural land on the
marsh, as seen, for example, between Llanfrothen and Pont Traeth
(near Prenteg) is of ornithological interest. Over the winter
between 40 and 80 whooper swans come to the flats, and during the
summer, at the top of the marsh, one of the few pairs of osprey
which nest in Wales has successfully bred here on an annual basis
since 2004.
Morfa Gwyllt : As
the Glaslyn River would often flood the land between the Cob and
the Cambrian railway (built in 1867), as well as land higher up the
marsh, there was no point managing the river nor treating the land
in the way it was done at the top of the marsh. Therefore, the only
agricultural control seen in these areas was some grazing by cattle
and sheep during the summer. From the outset, it was recognised
that this semi-unstable marshy land had another value besides
agriculture, namely shooting ducks in winter.
This part of the marsh is still extremely
important for ducks and other wetland birds. Over the winter, it
will be one of a number of sheltered spots through the Glaslyn and
Dwyryd Estuaries as far as Harlech marshes, where birds will roost
or shelter. From time to time during the winter, when there is a
combination of high tide and stormy weather, even scoters and other
birds more linked to the mouth of the estuary come here, including
divers and grebes, in order to shelter behind the Cob (5).
Today, wet areas of Morfa Gwyllt are a
valuable habitat for rare plants such as the Welsh mudwort (it is
only found in three other places in Europe); the dwarf spike-rush
(Eleocharis parvula) and the sharp rush (Juncus
acutis). On neutral grassland, at the south-eastern end of the
marsh, there are a number of other rare plants which are typical of
wet meadows. Of special interest here are the whorled caraway
(Carum verticillatum); Welsh broad-leaved marsh orchid
(Dactylorhiza majalis, ssp. cambrensis) and the
small-flowered evening-primrose (Oenothera cambrica)
(6).
Another important habitat here is the alder
marsh. One of Wales' largest wet alluvial woodlands is found on
Glaslyn Marsh and such habitats are of European importance. Mature
alder trees are most common here as well as some grey willows and
other trees in the drier parts (6). There is very little
disturbance here by man and beast and it is a very rich habitat
with regard to wetland plants and particularly its entomological
interest.
Changing the course of the
river
If the course of the River Glaslyn was
successfully managed and contained to a channel between substantial
earth banks in the upper reaches of the marsh, no effort was made
to do this for the wild parts of the marsh near the Cob. Therefore,
small occasional changes can still be seen today in the pattern of
the river channels near the Cob, and substantial new islands
appeared in the widest part at the end of the 1990s.
Before the Cob was constructed, the river
flow, in contrast to the sea's ebb and flow, would have been
responsible for constant (and unpredictable) changes in the pattern
of the river channels and the distribution of sand and mud beds. At
the time, the site which Porthmadog occupies today was only sand.
But having finished the construction and stabilising the spot where
the Glaslyn River flowed through large wooden gates near Ynys
Tywyn, the force of the river flow managed to open a deep new
channel with the side of the rock – creating a suitable spot for
ships. In 1821, William Maddocks obtained the right to build a new
harbour and town and it became known as Porthmadog (2).
For 200 years, therefore, the river's escape
from the Cob has been limited to one place, except between 1812 and
1814 when the sea wall was breached by storms. This had a major
effect on the dynamics of the rest of the estuary, including Traeth
Bach, the area through which the River Dwyryd flows to join the
Glaslyn. As the river could not wind its way freely between one
side of the estuary and the other, after the main channel was
limited to the western end of the Cob, the other sections of the
estuary were not affected by estuarine processes to the same
extent. As a result, the sand started to accumulate gradually in
sheltered spots, such as between the Cob and Trwyn y Penrhyn, and
on the south-eastern edges of Traeth Bach where the salt marsh on
the northern side of Harlech sand dunes is gradually filling up and
drying out. The mouth of the estuary, which is the most powerful
and dynamic part of it, is now gradually moving out to Tremadog
Bay.
TWM ELIAS is a lecturer
and course organiser at Plas Tan y Bwlch, Snowdonia National Park
Study Centre.
References
(1) Owen, Bob (1943). Diwidiannau
Coll
(2) Davies, Edward, (1913). Hanes
Porthmadog
(3) Gwyn, David (2006). Gwynedd:
Inheriting a Revolution
(4) Preston, C.D., Pearman, D.A. a Dines, T.D.
(2003). New Atlas of the British & Irish Flora (5)
Cambrian Ornithological Society Reports
(6) Site Description, SSSI, Glaslyn Marsh,
CCW
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