Environmental Engineering Reference
In-Depth Information
Youlookouttosea,andevenonthecalmestdaysyoucandetectthesinisterpresenceoftheHelwick
Sands by a line of darker blue. Once the wind blows they break white with foam.
Wynford Vaughan-Thomas,
Portrait of Gower
I
T IS IMPOSSIBLE
to adequately describe the natural history of a peninsula without including the sur-
rounding sea. The underwater environment, however, is an unfamiliar one to many naturalists due to the
difficulties of access and the lack of research compared to terrestrial habitats. Marine ecosystems are also
much simpler than terrestrial ones, not because they are less intricate, but because of the physical proper-
ties of sea water. These properties control the environment in ways for which there is no comparison in
terrestrial communities. Waves, tides, currents, salinities, temperatures, pressures and light intensities for
the most part determine the plants and animals that occur and these, in turn, have a major influence on the
composition of sediments and the gases in solution.
The marine environment of Gower is greatly affected by the Severn Estuary. The Severn is one of our
largestestuariesandbecauseofitsclassicfunnelshape,whichisuniqueinBritain,ithasthesecondhighest
tidal range in the world. Near Chepstow there is up to 14 metres between high and low tides. The vertical
range around Gower is less, varying from about 4 metres on neap tides to over 9 metres on spring tides.
To the east of Swansea the Bristol Channel is truly estuarine, the water has a very high silt content, and
there is a limited range of plants and animals on the shore. Westwards though, around the peninsula, the
water is highly saline and the intertidal fauna and flora is much more varied. Even so the shores still lack
a proportion of the species that might be expected, partly because of occasional low surface salinities, but
to a large extent because of the persistent high turbidity created by the large rise and fall of the tides. Such
a high level of suspended sediment also reduces light penetration and the cloudy, silt-laden waters of the
Bristol Channel therefore have a major influence on the types of communities present on the seabed.
There are many more species present in the waters around Gower than most people realise. Sharks,
turtles, seals, porpoises, dolphins and even some of the larger whales have all been seen in the area and are
an important part of this rich resource.
THE ROCKY SHORE
ThefeaturesofCarboniferousLimestoneshoresarethattheyareveryporous,erodedandpitted.Theupper
shore in Gower therefore tends to be very irregular, ridged, and fissured, becoming smoother lower down;
extensive limestone platforms, once known as 'huvvers and scarras', are a characteristic of many sections
of the coast (Fig. 57). Vaughan-Thomas (1983) mentions that 'This shelf is surprisingly wide in places -
on Port-Eynon Point, for example, in Overton Mere and around Worms Head. I cannot think of any other
section of the Welsh coast with quite the same type of feature.' The Intertidal Survey Unit of the former
