Friday, 18 May 2012

An example of coastal squeeze described by Ivor Rees

On a recent walk with Geoff along the section of the Cardigan Bay coast north of Barmouth, I was struck by the visible evidence for past changes in this low-lying coast. Whenever forecasts of sea-level rise come up for discussion, “Coastal Squeeze” of natural habitats gets mentioned. Though usually applied to salt-marshes in front of sea walls, it may also be used in other situations where intertidal habitats cannot roll-back as they come up against artificial structures or steeper land. Cardigan Bay is famous for evidence of change in coastal alignments. The place where these interactions were obvious was along 2km of coast north of Llanaber halt, on the Cambrian Coast railway line.
For about 1km north of Llanaber rock armour protects the railway, but more natural conditions prevail beyond this, with a shingle storm beach defining the coast line. On the landward side of this beach there is an elongated triangle of Phragmites marsh and willow scrub. Below the storm beach we saw one of the most extensive exposures of peat to be seen on any sandy shore in Wales. Continuity over time between the peat on the shore and the marsh as the shingle ridge has migrated landward is obvious. Unlike some of the other submerged forest peat beds on Welsh beaches, this one has few tree stumps. Peat tends to persist where it has been covered for much of the time by sand. Perhaps there are old photographs of this shore before the rock armouring was installed?
Ivor Rees

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