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Sea defences
3.1.6 Concrete or wooden sea defence works are not represented along the Atlantic
coastline due to the lack of built-up areas. At Baile (NF9340 8150) on the
island of Bernerary, a short stretch of beach (c.25m) has been partially
consolidated by a dump of building rubble. Elsewhere within the study area,
attempts to consolidate sand dune deflation hollows using pallets appear
largely to be failing. This is mainly due to the massive loss of dune sand
caused by the storm event of 2005.
Sites of Special Scientific Interest (SSSI) and Geological Conservation Review
(GCR) Sites
3.1.7 There are five designated SSSI sites and two GCR sites within the study area.
The sites have been designated according to their biological and natural
historical importance. The northernmost SSSI includes the machair and dune
lands of Bernerary. Also included within this group is the machair land at
Robach and Newton, the island of Vallay, Balranald Bog and Loch nam
Feithean, the tidal and freshwater lochs at Clachan and the islands of
Baleshare and Eilean Chircebost. The north-west coast of Uist, has been
designated a GCR site and encompasses a strip of coast c. 10km long of more
or less unbroken and often three dimensional geological exposures. These
sites are important in demonstrating both the structural sequences affecting the
Lewisian rocks of North Uist and also as a classic locality in the history of
research into ductile shear zones of folded lithologies (SNH Site data)
including the coastline overlapping Balranald Bog.
3.2 Patterns and predictive rates of sea level rise in the Uists
3.2.1 The predictive rates of sea level rise and its effect on the intertidal areas within
the study area have recently been well-documented (Dawson et al 2001). A
critical factor in evaluating future sea level changes is the importance of
natural vertical land movements. These are the rates at which the coastline is
rising or falling as a result of isostatic adjustments. By combining the
proposed rates of uplift with the patterns associated with the Main Postglacial
Shoreline, maps illustrating the maximum and minimum rates of crustal
movement can be produced. Dawson et al (2001) considered the following
factors in their examination on the likely impact resulting from a future rise in
sea level:
• Areas experiencing relative sea level rise are becoming progressively
more susceptible to the effects of storm surge activity. However it is
noted that this will vary according to exposure.
• The impact of sea surface rise will be less noticeable in areas with a strong
sediment supply and where coastal progradation is taking place, for
example the Moray Firth coastline, parts of the north-east and east of
Scotland, parts of northern Scotland and parts of south-west Scotland. In
areas where sediment supply is scarce, the effect of a sea surface rise will
be more noticeable.
UISN/1051/0
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CFA