Inlet and Estuary - Gower - page 180

FIG 100. Aerial view of the Burry Inlet and Loughor Estuary. (Royal Commission on the Ancient and Historical
Monuments of Wales)
THE GREAT MARSH
In the more sheltered areas, where plants have been able to colonise the intertidal mud flats, the fourth
largest area of salt marsh in Britain has developed. It currently covers 2,121 hectares (Fig. 101). When
the salt marsh first began to grow is not known, but the now wooded limestone cliffs along the Gower
shore were active sea cliffs 5,000 years ago so any marsh must have originated later. The marsh on the
southern side has accumulated in the shelter of Whiteford Point, a shingle ridge, which seems to have
originated as a glacial moraine later covered by sand dunes. Sediments forming the marsh derive mainly
from the redistribution of glacial deposits, together with sand and shell fragments from the seabed. The
area is of national significance due to the variety of features, which include erosion cliffs, creeks and
saltpans. The current marsh has grown from east to west along the southern shore and this sequence has
providedimportantinsightsintosaltmarshdynamics,sedimenttransportandsea-levelchangesaroundthe
British coast. At the eastern end the mature marshes at Berthlwyd have well-developed terraces and there
is an eroding marsh cliff, while to the west at Landimore the marsh is cut by numerous creeks and pans
(Fig. 102). Research has shown that the upper parts of the marsh are very stable, with the creek patterns
changingverylittleoverhundredsofyears,whilethelowerreachesvaryconsiderablyduetothechannels
being blocked by fresh sediment and new courses developing.
The sediments of the marsh are unconsolidated and easily eroded, so at any point in time the marsh
representsadelicatebalancebetweensedimentationanderosion.Althoughapparentlylevelithasagradi-
ent of 1:240 towards the sea, interrupted by the presence of small breaks of slope, which indicate that it
has built up and subsequently eroded, the secondary marsh developing at a lower level. The development
of these terraces or 'micro-cliffs' is caused by scour associated with the main estuary channel.
On the Gower shore there has been very little land claim in comparison to sites elsewhere in Britain,
where saltmarsh succession is often truncated by embankments and other coastal defences. On the north
shore, in contrast, the urban development of Llanelli has led to a significant loss of habitat except near