Jncc coastal Directories Project Region 11 The Western Approaches

are present at Berrow and Merthyr Mawr, and to woodland
in the Fal/Ruan Estuary.  
Upper levels of grazed saltmarshes of the Severn
Estuary support an unusual and distinctive plant
community.  This is a type of Festuca saltmarsh and contains
the nationally scarce species bulbous foxtail Alopecurus
bulbosus, slender hare’s-ear Bupleurum tenuissimum and sea
barley Hordeum marinum.  Meadow barley Hordeum
secalinum is present in this vegetation in the inner Severn
(Rodwell in prep.).  The full extent of this vegetation type is
not known.  
The three British species of eelgrasses Zostera spp., all
nationally scarce, are present in intertidal and subtidal
zones in the region.  The Welsh shore of the inner Severn
Estuary contains an unusual eelgrass bed that is reputed to
contain all three Zostera species.  Other nationally scarce
plants found on saltmarshes in the region are: curved hard-
grass Parapholis incurva, marsh-mallow Althaea officinalis,
long-stalked orache Atriplex longipes and sea clover Trifolium
squamosum.  Such scarce species are mostly found at the
upper levels of the saltmarshes and in transitions to other
habitats.  Sea heath Frankenia laevis, a species of sand or
shingle margins of saltmarshes on the south and east coasts
of England, has been recorded at Merthyr Mawr saltmarsh
in the Ogmore Estuary.  This is one of only two records for
this species in Wales. 
Saltmarshes in the region provide roosting sites for
shorebirds and food for wildfowl.  The redshank Tringa
totanus breeding on saltmarshes on the north shore of the
Severn Estuary form a significant proportion of the Welsh
population.  The Severn also supports a significant breeding
population of shelduck Tadorna tadorna, which use the upper
levels of saltmarshes as nesting sites (Fox & Salmon 1988)
(see also 
section 5.11
).  
Saltmarshes in the Severn Estuary and Bridgwater Bay
are subject to erosion of the marsh edge, but many continue
to accrete vertically.  Elsewhere, the erosion or accretion
status of the marshes varies.  Some sites, such as the Hayle,
Camel, Taw-Torridge and Ogmore, have new saltmarsh
development (both lateral and vertical accretion) and others
such as the Fal and Gannel have erosion of the marsh edges
(lateral erosion and vertical accretion) (Pye & French 1993).
In many places the Severn saltmarshes are made up of a
series of terraced surfaces, separated by erosion cliffs.  These
represent periods of new saltmarsh formation, followed by
erosion.  Lateral erosion of the marshes, due to sea level rise,
has affected marshes of the outer and middle estuary since
at least mediaeval times.  More recently, since the 1970s,
erosion appears to have accelerated.  This is thought to have
been caused by an increase in the frequency of storm events.
Various methods have been used to try to slow the rate of
erosion of the marshes in the Severn, including the
construction of groynes and armouring of the seaward face. 
3.6.3  Human activities
Enclosure and drainage of saltmarsh in the Severn Estuary
since Roman times has created the extensive wet grasslands
of the coastal levels (see also 
section 3.5
).  Pye & French
(1993) estimate that 84,000 ha of saltmarsh has been
enclosed in the Severn Estuary.  Saltmarsh in the Taff/Ely
Estuary will be lost during construction of the Cardiff Bay
Barrage.
3.6  Saltmarsh
59
Table 3.6.2  
Saltmarsh sites surveyed
Name
Grid ref.
Area (ha)*
Cornwall
Fal Estuary complex
SW850405
93
Helford River
SW720258
4
Hayle Estuary
SW555375
19
The Gannel
SW809607
20
Camel Estuary
SW945739
50
Devon
Taw - Torridge
SS470310
240
Somerset
Bridgwater Bay/River Parrett
ST281485 &
487
ST294521
Avon & Gloucestershire
Severn Estuary
a
(England)
ST400800
583
Gwent
Severn Estuary
b
(Wales)
ST400800
349
South Glamorgan
East Aberthaw
ST042660
8
Mid Glamorgan
River Ogmore
SS870761
15
Source: National Saltmarsh Survey (Burd 1989a-d).  Note: for large
sites the grid reference given is a reasonably central point.  Key: 
a
20
separate sites; 
b
9 separate sites; *areas have been rounded to the
nearest whole hectare.
Table 3.6.3  
SSSIs containing saltmarsh in Region 11
Site name
Grid ref.
Other designations
Fal/Ruan Estuary
SW850410
pSAC
Hayle Estuary and
SW550370
-
Carrack Gladden
Taw-Torridge Estuary
SS470310
-
Porlock Marsh
SS880479
-
Bridgwater Bay
ST290480
NNR
Berrow Dunes
ST293520
LNR
Severn Estuary
ST480830
Ramsar, SPA, pSAC
Upper Severn Estuary
SO720060
Ramsar, SPA
Taff/Ely Estuary
ST185735
-
Cwm Cydfin, Leckwith
ST165739
-
East Aberthaw Coast
ST042658
-
Merthyr Mawr Warren
SS861768
-
Kenfig
SS790820
pSAC, NNR, LNR
Source: JNCC integrated coastal database.  Key: pSAC = possible
Special Area of Conservation; NNR = National Nature Reserve;
LNR = Local Nature Reserve; Ramsar = Ramsar site (wetland of
international importance); SPA = Special Protection Area for birds.
Spartina has gradually been replaced by sea club-rush,
common reed and bulrush Typha latifolia (Ranwell 1964a, b).
A similar pattern has been documented on the east side of
Bridgwater Bay at Berrow (Willis 1990), although in this case
a common saltmarsh-grass and glasswort Salicornia spp.
marsh pre-dated the establishment of Spartina.  The highest
saltmarsh around the driftline is usually dominated by sea
couch Elymus pycnanthus, with spear-leaved orache Atriplex
prostrata.  Saline pans on the upper marsh support a
vegetation of reflexed saltmarsh-grass Puccinellia distans and
lesser sea-spurrey Spergularia marina.  Because of substantial
land-claim of saltmarsh in the past, transitions to other
habitats are not widespread.  However, transitions to dune

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