download - SCAPE

Sea defences3.1.6 Concrete or wooden sea defence works are not represented along the Atlanticcoastline due to the lack of built-up areas. At Baile (NF9340 8150) on theisland of Bernerary, a short stretch of beach (c.25m) has been partiallyconsolidated by a dump of building rubble. Elsewhere within the study area,attempts to consolidate sand dune deflation hollows using pallets appearlargely to be failing. This is mainly due to the massive loss of dune sandcaused by the storm event of 2005.Sites of Special Scientific Interest (SSSI) and Geological Conservation Review(GCR) Sites3.1.7 There are five designated SSSI sites and two GCR sites within the study area.The sites have been designated according to their biological and naturalhistorical importance. The northernmost SSSI includes the machair and dunelands of Bernerary. Also included within this group is the machair land atRobach and Newton, the island of Vallay, Balranald Bog and Loch namFeithean, the tidal and freshwater lochs at Clachan and the islands ofBaleshare and Eilean Chircebost. The north-west coast of Uist, has beendesignated a GCR site and encompasses a strip of coast c. 10km long of moreor less unbroken and often three dimensional geological exposures. Thesesites are important in demonstrating both the structural sequences affecting theLewisian rocks of North Uist and also as a classic locality in the history ofresearch 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 Uists3.2.1 The predictive rates of sea level rise and its effect on the intertidal areas withinthe study area have recently been well-documented (Dawson et al 2001). Acritical factor in evaluating future sea level changes is the importance ofnatural vertical land movements. These are the rates at which the coastline isrising or falling as a result of isostatic adjustments. By combining theproposed rates of uplift with the patterns associated with the Main PostglacialShoreline, maps illustrating the maximum and minimum rates of crustalmovement can be produced. Dawson et al (2001) considered the followingfactors in their examination on the likely impact resulting from a future rise insea level:• Areas experiencing relative sea level rise are becoming progressivelymore susceptible to the effects of storm surge activity. However it isnoted that this will vary according to exposure.• The impact of sea surface rise will be less noticeable in areas with a strongsediment supply and where coastal progradation is taking place, forexample the Moray Firth coastline, parts of the north-east and east ofScotland, parts of northern Scotland and parts of south-west Scotland. Inareas where sediment supply is scarce, the effect of a sea surface rise willbe more noticeable.UISN/1051/012CFA