At some sites in the UK, coastal defences installed by one local authority have contributed to erosion along frontages under the care of an adjacent authority. These difficulties can be avoided by recognising the natural divisions of a coastline, often called coastal "cells". Where the main concern in managing a shoreline is to defend against erosion or flooding, then the most useful definition of a cell is based on a consideration of the longshore drift of beach material, (sand and shingle). This is because most cases of severe coastal erosion are caused by interruptions to the natural longshore transport of sediment. An ideal cell would be entirely self-contained from a sediment transport view-point, i.e. there would be no nett import or export of beach material. In this case, although coastal defence works could affect the whole cell by interrupting the longshore drift, they would not affect beaches in other cells. Once established, these cells (and sub-cells) have proved to be a useful basis for wider planning purposes.
The report divides the coastline of the Western Isles into a number of cells (and sub-cells). "Management Units" are defined which concentrate in more detail on the pressures and responses of the coastal zone in each coastal cell. Each of these includes a description of the physical characteristics of the beach and coastal hinterland and the principal land uses of the coastal hinterland. The coastal response to both natural and other pressures acting on each unit is given, together with brief details of any management requirements.
The coastal response and management proposals for each sub-cell is summarised below.
Much of the east coast of Lewis and Harris within this cell is rocky with very few beach systems. Only three sub-cells on the north east coast of Lewis have been defined.
1. Gob na Creige to Gob Shilldinish (Braigh na h-Aoidh)
Coastal processes
The coastline is wave dominated with a general drift of material to the west. Wave erosion of the soft conglomerate cliffs provides an input of material to the beach. At present this rate is low and generally confined to times of storm conditions. Coastal flooding of the low lying land south of the airport occurs regularly. Groynes installed to control the longshore drift and the erosion at the eastern end of the isthmus are now in a relatively poor state of repair and appear to have little influence on beach longshore transport. Construction of the revetment and sea wall has shifted the erosion westward onto the mainland with further coastal protection works having been constructed. Directly to the west of the sea wall, a rock revetment protects the soft, low conglomerate face from wave action. Beyond this, the thin shingle ridge is breached regularly during winter storms flooding the marshy land behind and road to the Eye Peninsula. This ridge is regularly rebuilt by the Council, but it does not provide adequate protection. At Holm the shingle beach is low and shows signs of frequent overtopping.
Future management
Beach levels and the condition of all coast protection work is required to be monitored at regular intervals. Some protection work may be required to protect the cottage close to the coastal edge at Holm. The thin shingle ridge, south of the airport, does not provide adequate protection from coastal flooding. It is realised that any related coastal defence work, such as a sea wall would be too expensive given the value of the land at risk. The Council propose to raise elevation of the A866 at this location to prevent flooding. We agree that this is the most appropriate action. The rebuilding of the shingle ridge will increase the level of protection of the immediate hinterland from inundation under more commonly occurring wave and water level conditions. However, it has minimal value during the extreme conditions which affect the infrastructure in the hinterland. Once the road elevation has been raised to prevent flooding there is little point in continuing the rebuilding operation.
Much of the beach material found on the beaches around Broad Bay has been derived from erosion of these soft cliffs. Broad Bay can experience heavy swell following Atlantic Storms. Sediment transport and natural coastal erosion is wave dominated. On many of the beaches, sand is transported in both an offshore/onshore pattern due to storm and constructive swell waves respectively, with alongshore drift also evident. Nett transport within the inner part of Broad Bay is generally to the west.
To the north of Tong, the nett drift direction may tend to the north, but this is dependent on locally generated storm events from the south to south east within Broad Bay, which are relatively rare. The offshore reefs of Sgeir Leathann and Lada Sgeir at Gress beach will also provide protection to this beach.
Wind action is generally causing sand to be deposited on most of the dune faces found along the frontage. and has been attributed to the formation of the spit at Melbost Sands. Some localised areas of wind erosion do occur where other factors, such as pedestrian access through dunes, has caused such erosion to be initiated.
NB 558374
Coastal processes
To the east of the pier erosion is evident on the face of the till bank due to wave undercutting. Due to the protection afforded by the boulder beach, such erosion is limited to times of high water levels. Cut back is worst where the installation of sewage outfalls has disturbed the till material behind the beach.
It is unlikely that the low masonry walls in front of the sewage outfall locations will be able to withstand a significant storm event, but will provide adequate protection under less extreme wave conditions in the short term. Due to the low elevation the higher, more substantial wall protecting the road will most certainly be overtopped frequently at high tides under moderate wave conditions. The revetment shows little sign of having any effect on the thin shingle beach in front.
Future management
Some additional protection may be required to protect the road to the east of the pier. Due to the nature of the beach at this location, hard defences such as a rock revetment would be the most suitable option. Although overtopping of the upstand, and flooding of the road to the west of the pier will occur, even during relatively moderate conditions, given the low usage of the road this is not likely to be a significant problem. All present and future defences should be inspected periodically for any sign of deterioration.
3. Aiginis to Melbost Point (Branahuie)
NB 495328 to NB 469335
Coastal processes
The soft cliffs along the coastline to the east of St Columba's church are undergoing erosion due to wave action, the majority of erosion occurring during high tidal conditions. To the west of Aiginis, a constructed rock wall and till ridge protect the low-lying hinterland, but these have been overtopped with shingle deposited behind the crest. Large rock has been dumped down the cliff face at locations where erosion most seriously affects the road to the township. At the eastern end of the isthmus a concrete revetment, showing signs of wave damage, protects St Columba's church. At the time of the site visit, beach levels at the eastern end of the isthmus were low. This is attributed to two factors. Firstly the low input of beach material onto the frontage from eroding conglomerate cliffs on the Eye Peninsula, and the westerly drift along the frontage, results in a sediment deficit at the eastern end. Secondly, due to the lack of shingle on the upper beach, wave reflections from the highly reflective wall will result in beach material being transported seaward. Concrete groynes placed to control the drift and hold beach material at the eastern end are now in a badly deteriorated state and have little influence in controlling drift.
West of the cemetery, a track to the beach has caused localised erosion. Rabbits are responsible for small localised areas of erosion within the dunes.
Future management
Protection of the soft cliffs to the west of Aiginis is now needed to protect the road. Possible appropriate defence options include offshore rock breakwaters or rock sills. Such defences will increase protection of these till cliffs from wave attack and possibly promote an increase in the volume of beach material on the upper beach.
Monitoring of beach levels and of the hard defences particularly of the concrete apron protecting St Columba's Church, should be conducted at regular intervals. If beach levels at the eastern end continue to fall, toe protection may be required at the front of the seawall. A length of rock revetment would be sufficient. Shingle could be recycled from the western end and placed on the upper beach in front of the wall. Short rock groynes of offshore breakwaters or sills could also be used to maintain beach levels.
Access to the beach should be concentrated at either end of the isthmus and people dissuaded from gaining access to the beach though the dunes at the west of the cemetery to reduce erosion there.
4. Melbost Point to Aird Thunga
NB 469335 NB 468368
Coastal processes
The beach dune system at Melbost is fairly stable at present. At Aird Thunga the soft conglomerate cliffs are being actively eroded. Wave undercutting of the dune face above the shingle ridge is evident along much of the spit at Tong. The shingle beach provides adequate protection most of the time, but erosion occurs under extreme conditions. At present, the entire spit formation is in a relatively stable state.
Future management
At present anthropogenic influences are having little detrimental effect. Where erosion from natural causes has threatened infrastructure, such as at Tong, this has been adequately protected. Periodic monitoring of the entire frontage of this unit, and of the defences found within it, is required.
NB 468368 to NB 492392
Coastal processes
At present, the beach system is quite stable with the shingle ridge in front of the dune face almost completely covered in wind blown sand. Wave undercutting of the dune system during extreme conditions has occurred, but wind action is presently redepositing sand on the dune face. The conglomerate outcrop half way between the rivers is prone to erosion during high tides or storm conditions. Short stretches of a low wall protect one area of this cliff. Although wave action is reflected from the masonry wall, there is no evidence of beach erosion in the vicinity. A gabion wall protects the track at the northern end of the beach.
Erosion of the dune face at the location of the caravan park and car parks due to pedestrian access to the beach is serious with a number of small blowouts being formed and sand being blown inshore. Erosion of the machair area used for car parking is as yet not too serious.
Future management
Stabilised access to the beach is required at the location of the caravan park. At present erosion of the machair due to vehicular access is not too serious but cars should be prevented from parking close to the machair edge (say a 5m exclusion width). Caravans should be moved a similar distance inland. The car parking facilities should be continually monitored to check for any deterioration of the machair surface with appropriate restrictions applied if any such deterioration does occur. Monitoring of the beach levels, masonry wall and rock gabions should also be carried out.
6. Traigh Rebac and Traigh Ghriais
NB 492392 to NB 515420
Coastal processes
The shingle upper beach at Traigh Rebac provides some protection of the soft till cliffs behind from wave attack. Such erosion of this till material, under the most severe storm conditions, was evident all along the frontage. Shingle overtopping, due to storm events, was noted at the centre of the bay where the elevation of the cliffs is lowest. The headland at Gob Tais is being actively eroded by wave action when tidal levels submerge the abrasion platform.
South of the Gress river, wave erosion of the dune face during storm conditions is evident. There is no shingle ridge protecting the dune face at this location and it is suspected that shingle and part of the dune face have been extracted for building purposes. Wind is now causing some localised erosion with a vertical blowout developing and sand being blown over the top of the dune face. North of the Gress river the rock placed in a line parallel to the present river course will provide very little protection against coastal erosion. Shingle has been thrown up onto the dune face during storm conditions and there has been some undercutting and slumping of the dune face under such conditions. Coastal flooding of agricultural land adjoining Gress Saltings occurs during extreme tidal conditions.
At the northern end of Traigh Ghriais pedestrian access to the beach has destabilised the dune system, leading to a blowout and blown sand being transported inland. Wave erosion of the soft cliffs in front of Gress Lodge has lead to rock being placed to prevent such erosion.
Future management
Natural processes are responsible for the physical response of the coastal zone, particularly at Traigh Rebac with little infrastructure being affected. At Traigh Ghriais, any further sand or shingle extraction from the dune should not be permitted. Stabilised access to the beach is required through the dunes at the cemetery. Monitoring of the beach, dunes and gabions should be conducted periodically.
NB 543463 to NB 547467
Coastal processes
Giordale Sands is a small pocket beach situated at the base of high cliffs. The beach material has derived from the continual slow erosion of the cliffs at the back of the beach. Numerous cliff slips have occurred.
Future management
There are no processes other than natural developments occurring within this system with no infrastructure or other important features at risk. At present there is no requirement for management.
Only three sand beach units being found within this sub-cell owing to the steepness of the seabed slope. Their exposure to severe storm conditions will result in beach drawdown occurring at all three beaches, but sand will be moved back onshore under swell waves which are a common occurrence along this coastline
8. Traigh Mhor and Traigh Geiraha
Coastal processes
Both beaches are presently relatively stable with little natural erosion from waves and wind. The dune system at Traigh Mhor is still developing, with blown sand from the upper beach being deposited within the dunes. Some erosion of the dune face at the southern end does occur due to tracks caused by grazing sheep and the high rabbit population has eroded the machair To the north there are many tracks from the car park, through the dune system to the beach. At a number of locations there are eroded paths down the dune face. At present, this does not cause too much immediate alarm as sand is continually accreting on these dunes.
At Traigh Geiraha the machair surface has been severely eroded in the past mainly due to a combination of vehicular, pedestrian and animal grazing pressures. Stabilisation work was conducted in the mid 1980's consisting of revegetating the deflated area, fencing off the eroded machair area and restricting grazing to only one month per year. This has allowed the machair surface to improve considerably but the system is still extremely sensitive. The high pedestrian population and the large rabbit numbers are still causing a serious erosion threat to the machair.
Future management
Due to the large number of people using both beaches, boardwalk paths or equivalent should be constructed. At Traigh Mhor, this path should pass around the northern end of the dunes. At Traigh Geiraha, in addition to the boardwalking, the deflated area should be fenced off from both rabbits and pedestrians and in areas which will not recover naturally, a reseeding program initiated. The fencing should remain in place at least until a stable covering of vegetation has occurred. Some form of rabbit control should be considered.
NB 538637
Coastal processes
The narrow upper beach indicates that wave erosion of the soft cliffs backing the beach is occurring over a relatively high percentage of the time. The beach material has been derived principally from such erosion. Cliff erosion appears to be enhanced at the northern end due to reflection of wave energy from the harbour wall. Material transported from the south to the north is responsible for the siltation of the harbour.
Future management
SNH have already responded to local fears over the rate of cliff recession with a monitoring programme initiated. Erosion of the cliff is a natural process and it is only adjacent to the harbour breakwater that this process is being accelerated. Some toe protection for about a 20m length, or spur breakwater on the harbour arm may need to be considered.
The north western coastline of the Western Isles is dominated by wave action. Natural erosion of the coastal edge is dominated by wave action. This has probably been taking place since the end of the last Ice Age as sea levels rose. Erosion of the till cliffs has provided much of the shingle and sand beach material found along this coastline. It is probable that much of the sand sized material lost offshore under storm wave conditions, will be trapped by the rocky nature of the sea bed and not be moved back onshore during periods of constructive swell waves. The exception to this is around Eoropie, where the sand beach has been derived from the breakdown and onshore movement of shell material from offshore.
The principle direction of sediment transport has been to the south and is responsible for the shingle ridges damming up, and forming the brackish lochs found close to the coastal edge. The transport of the shingle material would only have occurred under severe storm conditions, with these shingle spit features taking many years to form. At present there is little evidence of any significant longshore drift taking place.
10. Traigh Sands to Dell Sands
NB 512648 to NB 487625
Coastal processes
The shingle and cobble upper beaches which front much of the till cliffs along this coastline will provide adequate protection to these cliffs under most tidal and wave conditions. Shingle on the upper beach will be drawn down under storm conditions will not be moved back onto the beach under more constructive swell conditions as the offshore rock platforms will dissipate much of the wave energy reducing most of the potential for such shingle movement.
The beach and dune face at Eoropie show no sign of storm wave attack, with the shingle ridge fronting the dune face completely covered by sand. The dune region backing the beach contains a large deflated area, with the frontal dunes extremely fragmented. At present the area is quite stable with little blown sand on the deflated area due to the proximity of the water table to the surface. Quarrying is still occurring within the dunes at the southern end of the system with much vehicle tracking occurring over the deflated area.
The machair areas behind Swainbost Sands show signs of erosion. It is likely that this was initiated by sheep tracking and grazing, and possible vehicle tracking. However wind action is intensifying erosion of these areas with some deflated areas beginning to occur.
Future management
At Eoropie, sand extraction does not cause any increase in natural erosional effects, with the visual aspect of such activity the main problem. As the deflated surface is naturally stable, the heavy tracking does not have a significant effect other than compacting the surface. Although this will limit any natural evolution of the tracked area, given the timescale that the deflated area has been in existence, such natural development is limited. It is recommended that quarrying activities be monitored however, with access directed away from the immediate coastal edge to allow this area to restabilise naturally. No quarrying should be permitted in the immediate beach or dune area.
Erosion of the till cliffs along this coastline is a natural process, with no external human or other influences directly affecting the coastal edge. Periodic monitoring, to determine retreat rates should be considered. Deflation of the machair is likely to continue occurring. Restricting access by sheep and vehicles will have some effect, but natural restabilisation is likely to take quite a long time.
NB 407574 to NB 372544
Coastal processes
Overwashing of the shingle ridge at both Borve and Shader occurs during severe wave conditions and at high tides. After the 'Braer' storm on 5 January 1993, shingle was found up to 50m behind the beach crest with 0.3-0.4m boulders also found inland at Shader. At the northern end of the beach, at Shader, erosion of the till cliffs is not directly affecting the archaeological site which is on higher ground.
Future management
Processes occurring along this coastline are entirely natural with no noticeable human influences. Some breaching and overwashing of the shingle ridge will occur during future storm events with flooding of the immediate hinterland occurring. Some restoration work may be subsequently required to repair any serious breaches of the shingle ridges. On neither beach is shingle found in abundance. Shingle extraction should not be permitted. Periodic monitoring of the entire frontage should be conducted, especially at the archaeological site at Shader. This is not directly affected by coastal erosion yet, but the severity of storms, particularly on high tides along this coastline, can cause substantial cliff retreat of these soft cliffs.
NB 346520 to NB 323508
Coastal processes
The wide shingle upper beach provides adequate protection to the dune and machair face over most of the hydraulic conditions experienced on the coastline at Barvas. Some overwashing is evident at the northern end, with boulders being deposited within the dunes which back the beach at the eastern end. Overwashing of the ridge at Loch Ereray is more severe with shingle deposited over much of the low lying hinterland.
Commercial sand extraction has destroyed most of the dune system, which is not restabilising naturally. Continuing wind erosion in the form of blowouts is currently a serious problem on the higher dunes with the cemetery being under threat from blown sand. Directly behind the coastal edge, quarrying has occurred down to the water table and consequently wind blown sand is less of a problem. Heavy rabbit and sheep grazing is also having a detrimental effect on the machair and dunes stability at the eastern end of the system. To the north of Lower Barvas, the sloping machair is severely deflated. This has been caused by a combination of cultivation practice and the high rabbit numbers. The extent of this deflation area is continuing to grow, with the rabbit population continuing to have a detrimental effect.
Future management
The quarry areas within the dune system at the northern end of the Barvas system will require major work to restabilise the damaged areas. The most suitable method is to reseed the deflated area and cover with a suitable mulch to prevent further wind erosion. Rabbits and livestock should be excluded from these areas until fully stabilised. Due to the size of the deflated area, the capital cost of conducting this work will be high and it may be necessary to conduct this work in stages. Similar stabilisation work will have to be conducted on the large deflated area landward of the Barvas machair. Again reseeding and covering with a mulch will involve a high capital cost. Soil conditioning treatment, which increases the moisture retention of the soil allowing the surface to stabilise and vegetation to establish, may provide a cheaper alternative.
It is recommended that the intensity of sheep grazing on the dunes at Barvas be reduced and that some form of rabbit control be conducted.
NB 306497 to NB 253484
Coastal processes
Breaching and overwashing of the shingle ridge occurs during high wave or tide conditions with shingle found deposited well behind the existing crest at all three beaches. At the outlet of Loch Ordais at Bragar, the end of the shingle spit feature has been completely flattened during a storm event. Rock has been placed to prevent breaching of the shingle ridge, and to protect the track at the east end of Shawbost.
Future management
Coastal erosion, as in most other parts of the north-west coast of Lewis, is naturally occurring due to the severity of the wave climate. Other than periodic monitoring of the coastline, the only location where some work may be required is at the cemetery at Bragar where protection of the till cliff may be required along the length of the access road. Given the nature of the wave conditions, a rock revetment would be most suitable.
NB 227459 and NB 215452
Coastal processes
Wave erosion of the machair is occurring at Dalbeg under high tidal or severe wave conditions. Under more moderate conditions the cobble storm beach provides adequate protection. Some erosion is noticeable down the edge of the machair to the east of the river due to pedestrian access. The machair backing the beach has been blocked off preventing vehicular access and although car tracking is still evident, this should stabilise in time.
At Dalmore, the edge of the machair has been protected by timber breastwork along most of the frontage. The machair between the beach and the western cemetery is used as a car park and is seriously eroded. Slight erosion is occurring at the western end due to pedestrian access. At the western end of the beach, where there are no coastal protection works, wave erosion of the machair edge has occurred. The steep machair behind this part of the beach is also severely eroded due to over-grazing by rabbits and sheep and associated tracking.
Future management
At Dalbeg, access down the machair edge should be discouraged and, if possible, concentrated just upstream of the river mouth. To gain access to the sand beach however, a wider expanse of boulders will have to be crossed at this point. Vehicular access should continue to be restricted at this site.
At Dalmore, car parking on the machair is preventing vegetation from becoming established. Despite this the machair surface is stable with wind erosion not presenting a problem. Given that car parking is a requirement at the site, the closeness to the coastal edge, and the present stability of the eroded area, it is suggested that the present arrangement is continued in the meantime, with frequent monitoring to ensure that this area does not deteriorate any further. Access to the beach should be encouraged at the river and not at the western end of the car park. At the western end of the beach the eroded machair surface is relatively fragile. If possible sheep should be excluded from the steep slopes at the western end of the beach and the area left to restabilise naturally.
This coastline experiences severe wave conditions resulting from the extremely long fetches of the Atlantic Ocean and deep water found close inshore. The few beaches that do occur along this coastline have formed generally where protection from wave attack is afforded by offshore islands or a milder offshore sea slope.
Despite the severity of the wave climate, wave erosion is only a significant factor at Traigh na Clibhe and Mangersta. Wave overwashing of the shingle storm beach has occurred regularly with shingle deposited behind the beach. At Valtos and Berie the offshore islands and reefs afford some protection to the beach. At Traigh na Clibhe the beach is more exposed to waves from the north-west with significant storm damage occurring. There is no indication of any nett sediment transport direction due to marine action at any of the three beach locations within this sub-cell.
The action of the wind is a relatively important process in shaping the physical character of the coastal zone within this cell. This is particularly evident at Traigh na Berie and Uig where wind action is mainly constructive, with the existing dune systems gaining sand, and embryo dunes forming, due to the abundance of sand on the upper beach.
15. Valtos and Traigh na Berie
NB 115360 to NB 096369
Coastal processes
The beach complex at Traigh na Berie is rotating in an anti-clockwise direction, with erosion of the machair edge occurring at the western end and accretion of sand within the dunes and beach to the east. Although erosion at the western end has been ongoing for some time, actual coastal edge retreat will only occur during storm conditions. Wind action is causing sand material to be deposited from the upper beach, into the dune system, with embryo dunes forming particularly around the central part of the beach frontage. The high volume of blown sand has also limited the effects of erosion caused by the number of streams which enter the sea through the beach. At the eastern end of the beach the dune condition is in a similar stable state with wind blown sand being deposited.
The effects of the caravan park and the high number of people using the beach are the principal cause of any instability within the system at Traigh na Berie. At the western end, access to the beach is contributing to the erosion of the low machair face although wind blown sand is presently deposited against this edge. The central section of the dune system is also being affected both by the presence of caravans within the dune system and by a high density of pedestrian tracks over the dunes. Vehicle tracking occurs over much of the machair at the caravan site. Along the eastern half of the beach, the effects of human activity are much less severe.
At Traigh Valtos storm wave erosion of the machair edge is occurring, however again sand is presently deposited against this edge. Access points to the beach will increase the risk of some flooding of the machair land behind. The short rock wall constructed to protect a house at Kneep at the eastern end of the beach has little effect on the beach and should provide adequate protection to the machair edge provided beach elevations remain at a similar level.
Future management
Due to the high intensity of caravanning occurring at Traigh na Berie it is now necessary to introduce a more formal management structure to such activity before severe instability of the system occurs. Vehicles and caravans should be excluded from the dune area to the east, and to the west of the toilets on the slopes of the headland separating Traigh na Berie and Kneep. Caravanning activities should be restricted to the flat machair area around the road and toilets. Due to erosion of the machair edge in this location no permanent structures or facilities should be constructed close to the machair edge with caravans and vehicles also being restricted to at least 5m behind the present machair edge. Coastal defence work should not be conducted as such work may cause a detrimental effect elsewhere along the frontage. Marine erosion should be allowed to continue with any decision on the siting of the caravan park taking this into consideration. It would be advisable to adopt a monitoring procedure along this part of the frontage to establish retreat rates. Car access may have to be restricted to parking caravans only to reduce the effect vehicles have on the machair surface. If such restrictions are to be enforced some formal car parking may have to be provided at the side of the road. Alternatively hard access to the caravan pitches will protect the machair surface from erosion. Such a measure should be limited to only the most severely eroded areas.
Access to the beach should be encouraged at the mouths of the streams where sand is accumulating, and trampling is likely to have less of an effect. Restricting caravanning should also decrease the pedestrian pressure on the dunes in this area.
At Valtos, sand is not abundant and sand extraction from the beach should be discouraged. Periodic monitoring of the rock wall and beach should be conducted.
NB 084365
Coastal processes
Wave undercutting during storm events or high tidal conditions is occurring on the machair edge with a 4m scarp face evident. Cut back is particularly bad at the mouth of the river. Wave action is most severe at the eastern end of the beach where a thin shingle ridge provides little protection to the machair edge. The car park will be vulnerable if further coastal edge retreat occurs. Wind deposits of sand are presently accumulated against the seaward face of the machair.
Pedestrian access to the beach from the car park is down the machair face and this is causing severe slumping. The steep machair land surrounding the beach is easily eroded due to the high numbers of rabbits and sheep causing a general thinning of plant cover.
Future management
Formal access to the beach is required to limit the damage to the face of the machair by pedestrians. The position of the car park makes direct access to the beach very difficult as the machair face along most of this frontage is high and steep. It is recommended that pedestrian access be channelled either via the eastern end of the beach, though again this is steep, or some way back at the river closer to the village of Cliff. This however means a long detour to reach the beach. Care must be taken to avoid enhancing erosion problems here.
Periodic monitoring of the beach and recession of the machair face should be conducted.
NB 051329 to NB 035318
Coastal processes
Wave erosion is limited due to the sheltered location, although wave undercutting of the dune face does occur directly behind the entrance to the bay. Embryo dunes are being formed at the southern end in front of the established dunes. Sand is still accreting within this dune system, being fed from the extremely wide upper beach in this area. To the north of the rock outcrop, the upper beach is much narrower and the dunes have experienced both wave and wind erosion, although at present there is wind blown sand deposition on the dune face.
The impact of the large number of visitors to the beach is noticeable at a number of locations. Well used pedestrian tracks run through the dunes from the machair, at the gate to the car park, to the beach. Many tracks were also found along the top of the frontal dunes. At the car park, the northern machair face which is only about a foot high is suffering erosion from pedestrian access to the beach. The machair itself is also beginning to show signs of becoming heavily tracked from the numbers of cars using it. Vehicle access can be gained to the beach and tyre tracks were found quite high up on a dune face.
Sheep and rabbits graze on the machair and dunes but do not have any significant effect on the system.
Future management
To restrict vehicular erosion of the machair a formal car park may need to be provided. Ideally this would be just inside the gate beside the toilets with vehicular access to the rest of the flat machair restricted. This would increase pedestrian numbers gaining access to the beach over the dunes from this point. Ideally pedestrian access should be concentrated at the northern end of the machair where the effects of erosion will be less severe on the low machair face. Visitors are unlikely to walk from any car park to the northern end to gain access to the beach and it is suggested that if a car park is to be constructed by the gate then boardwalks should also be provided to permit access to the beach through the dunes.
NB 007308
Coastal processes
The beach at Mangersta is exposed to the west and experiences very severe wave action due to the steep sloping offshore bathymetry resulting in deep water found close inshore. The cobble ridge shows signs of severe storm damage with cobbles deposited up to about 40m behind the ridge. The dunes at the back of the beach have been completely deflated down to the water table. The machair edge is quite sensitive and some erosion due to sheep grazing and tracking is evident on the face.
Future management
The area is relatively stable at present but will be sensitive to any change in the present regime. Periodic monitoring of the beach and machair system should be conducted to ensure sheep or rabbit numbers do not increase as this will have a detrimental effect on the system. Any future anthropogenic activity in this system should be discouraged.
The wave climate influencing this coastline is milder than that experienced in the previous two sub-cells due to the influence of the sea bed slope. The effect of wave action, under storm conditions is evident on virtually all the beaches, with the exception of the north facing coastline of Traigh Rosamol which is sheltered by the island of Taransay and North Harris.
Wind action is an important process on all of the dune systems along this frontage. Such action is most evident at Luskentyre where large dynamic blowout formations are found on the dune system of the Luskentyre banks. On virtually all of the beaches within this sub-cell, wind action is having both an erosive and a constructive effect.
NA 989120 to NA 997110
Coastal processes
The machair edge has been stabilised with top soil relatively recently and at present there is no sign of any wave undercutting. Sand, transported from the upper beach by wind action, was accreting against this edge. Undercutting of the machair edge is however likely under southerly storm conditions, and this could affect the road directly behind. The beach is used both by locals and by day tourists, and pedestrian access down the machair edge is causing some erosion on the face. To the north of the road parts of the machair have a very thin covering of vegetation which is due to the high rabbit population.
Future management
Periodic monitoring of the beach should be carried out particularly after southerly or south-westerly storms to assess whether wave undercutting of the machair face threatens the road. Access to the beach should be concentrated at the eastern end where a track is situated. This may be difficult to enforce unless a fence is constructed along the length of the road at the back of the beach. At present sand is not abundant on the beach and sand extraction should not be encouraged.
20. Traigh Rosamol to Traigh Nisabost
NB 068004 to NG 045976
Coastal processes
Storm wave undercutting is evident on all dune and machair faces not protected from direct wave attack by the island of Taransay. A cottage and partly constructed house are located right on the coastal edge at Luskentyre and, although protected from severe wave attack by the wide sand banks to the north-west of Traigh Seilebost, it is likely that these buildings will be affected by waves and possible coastal flooding during high tidal and storm wave events. Although wave erosion of the machair edge at Traigh Nisabost appears to be occurring, from comparison with a photograph in 1970, there appears to have been minimal coastal edge retreat. It is likely that the conditions necessary to erode the machair edge at Nisabost will occur relatively infrequently.
Wind action has both an erosional and accretional effect within this unit. The complex pattern of U-shaped blowouts found in the Luskentyre Banks have been dynamically active, and continually shifting in position for some time. Smaller, more recent blowouts occur on the frontal dune face of the south-west facing beach at Luskentyre and along Corran Seilebost. Nett aeolian transport of sand is to the north, from the beach of Traigh Seilebost and the sand flats south of Luskentyre. Severe sand blow can be experienced during winter months with fences being buried by up to 3m of sand during the 1980's. Embryo dunes are forming at the southern end of Traigh Rosamol, with this beach accreting sand, deposited by wind action.
The machair face of Traigh Nisabost is relatively stable. Severe tracking of the machair is occurring in a number of areas. These tracks appear to be relatively stable and are not being enhanced by wind erosion. Localised areas of wind erosion are occurring on the slopes of Aird Nisabost. These have generally been initiated by quarrying activities and sheep and rabbit grazing reducing plant cover.
Future management
The Luskentyre Banks are at present evolving naturally, but are extremely sensitive to any external influences. Although not a problem at present, livestock and access may need to be restricted from these features to allow them to continue to develop naturally. Access to the beach at the northern end of Traigh Rosamol should be encouraged as this has minimum impact on the system. Little can be done to limit the amount of blown sand which affects the township of Luskentyre during strong winds with such a large expanse of bare sand to the south west. This entire unit should be monitored periodically, particularly to check on the evolution of the blowout features at Luskentyre and to check the stability of the machair surface at Nisabost. Vehicle access may have to be restricted if erosion due to tracking increases.
NG 037972 to NG 019941
Coastal processes and response
Due to the exposed location, the dunes are experiencing wind erosion along the entire frontage of the bay with some large blowouts occurring in the frontal dunes and a large volume of sand being blown inland. At either end of the beach pedestrian access is causing localised erosion as the beach is heavily used for recreation and for access to McLeod's Stone. Sheep grazing occurs on the dunes and the machair behind but has little noticeable effect on the stability of the system.
At Borve, wave action on the dune face of the beach occurs only during high tides and is most severe at the southern end of the bay where the width of the upper beach is narrower. Evidence of erosion is found all along the beach but at present there is a large volume of blown sand on the dune face. With such a wide exposed area of sand, under strong onshore winds, sand blown inshore is likely to be a problem. Access to the beach is gained at the cemetery down the dune face. This is causing increased localised dune erosion, with a fence found slumped down the dune face. To the north of the cemetery the dune ridge is very narrow due to an old quarrying hole and although this has stabilised, there is a threat of a breach of this ridge due to the combination of pedestrian pressures and wind erosion at this point.
Future management
At the southern end of Traigh Iar, access to the beach should be provided down the machair face by the provision of steps to limit erosion of the machair face. At the northern end, although there is a well used track, the area is relatively stable. Monitoring however should be conducted to ensure conditions do not deteriorate.
At Borve, access to the beach is required to prevent further damage to the dune face. Alternative access to the beach, close to this point is not readily available. The most suitable position would be about 200m to the north, where the dune face is fronted by a rock outcrop or to the south where the stream enters the back of the beach. As the beach is principally used by local residents notices advising alternative access to the north may be sufficient to direct the majority away from the most eroded area. Monitoring of the present situation and of any future access areas should be conducted.
NG 009937 to NF 985927
Coastal processes
Wave action causes a transport of material to its southern end, with the dunes forming due to a nett wind blow drift to the north. Over much of its length the beach is extremely stable, with nett drift rates now relatively low. Some wave erosion of a sand cliff face during high tidal levels does occur at the northern end of the beach.
The dune system, on the other hand, is in a quasi-equilibrium state with a cyclic process of very large blowouts forming and then refilling with blown deposits of sand from the upper beach. Under certain conditions, the high volume of sand blown inland is a problem at the township of Scarastabeg. The process of these blowout formations is predominantly natural given the exposed location and nature of the beach. Although there is a moderate rabbit population inhabiting the dunes, and sheep tracks were found on the dune face, despite a fence restricting access, rabbits or sheep are not responsible for initiating such blowouts. On the machair, inland of the dunes, some slight localised rabbit erosion is found. Some quarrying is occurring but extraction rates are low.
Future management
The dune face is particularly sensitive and dynamic. Although pedestrian numbers are low, access to the beach should be encouraged only at the southern end behind the relic dune system where the beach/dune intersection is more stable. Fencing should be improved to exclude livestock from the dune face and from around any bare sand areas.
If sand blown inland becomes a serious threat to the cemetery and township, then it may be necessary to erect sand fencing.
23. Northton and Traigh na Cleavag
NF 985904 to NF 980912
Coastal processes
At Northton, the shingle ridge has developed from erosion of the till deposits behind the beach. At present the beach is in a healthy state with blown sand occurring on the upper beach and shingle ridge. A rock wall has been constructed at the back of the beach, to prevent wave erosion. The rock wall is having little effect on the beach, but the size of rock is such, that under severe storm condition extensive damage to the structure could occur.
At Traigh na Cleavag, the dune system has suffered from wind erosion with a number of blowouts occurring through the dune face. At present many of these blowouts have sand, blown from the upper beach accreting within them. Grazing mainly due to rabbits, but also sheep has caused localised deflation. The high number of rabbits are also destabilising many of the sand hillocks of the machair. A track leads through the machair and in some places is quite badly eroded. Some minor quarrying within the hummocky machair is also conducted.
Future management
The machair system behind Traigh na Cleavag is extremely sensitive. Sheep numbers should not be increased above present levels and the rabbit population should be controlled. Where possible, vehicles should try to pass the hummocky machair land by driving further to the north, by-passing these machair features. If possible, vehicular access should be minimised with no unauthorised vehicles allowed past the end of the village. At Northton the rock wall should be inspected periodically and after any severe storms.
Coastal processes
The beaches within this sub-cell, are affected by wave action. However the dissipative effects of a shallow sea bed slope and the occurrence of the many rock reefs, significantly reduce the levels of wave energy before such waves reach the shoreline. Despite these dissipative effects, storm wave damage to the dune faces of the more exposed beaches is a common occurrence with sign of recent erosion evident during the site visit. Wave action within the intertidal sand flat areas of Vallay and Vallaquie is much more limited, with small locally generated waves during high tides the only significant wave action within these areas.
Exposure of the beaches to the north and west does make them susceptible to the effects of wind. Such effects are evident on all of the dune systems on coastlines which face to the west or north-west within this cell. Wind erosion in the form of blowouts occurs along much of the coastline of the island of Berneray, with evidence of sand being blown inland indicated by a relatively modern fence being partially submerged. Similar effects are evident on the western coastline of the Machair Leathann. Despite the fact that large expanses of sand are exposed at low tide, blown sand from these areas is not a significant problem to the inhabitants or infrastructure bordering these areas.
NF 923838 to NF 887808
Coastal processes
The western coastline is extremely exposed with the dune system being affected by both storm waves and wind erosion. At present wind blown deposits from the beach are accreting on the lower dune face, but a number of relatively large blowouts occur all along this frontage. Coastal retreat of the dune crest is also occurring along the entire western facing coastline. Partially submerged livestock fencing indicates that large volumes of sand can be blown inland under strong onshore winds. Wind blown sand is accreting on the northern coastline. Storm wave erosion of the dune face is evident with the severity of such erosion decreasing to the east.
Grazing sheep can gain access to the dunes in the southern half of the island but are not responsible for any significant erosion.
Future management
All processes acting on this coastline are naturally occurring. As there is no infrastructure at risk, the entire system should be left to develop naturally. Sheep may have to be restricted from the immediate dune face in the south. Periodic monitoring should be encouraged to determine whether this would be necessary.
25. Newton Machair and Machair Robach
NF 888784 to NF 855761
Coastal processes
To the north of the island of Lingay, the dune face is stable with no erosion occurring. To the south of the island, storm wave erosion of the frontal dune system has occurred although blown sand was being deposited against the face at the time of the study. Blowout activity is occurring within the secondary dunes just to the north of the Goulaby Burn. Wave undercutting is very evident on the machair face on both sides of the river mouth. Similar processes are occurring to the south of the river with storm wave undercutting of the dune face and wind erosion causing large blowout formations in the secondary dune system. Cattle are fenced from the dune area, and although sheep were found on the dunes, little erosion can be attributed to them.
Storm wave erosion occurs over the entire length of the frontal dunes of Machair Robach. A number of small blowouts are actively developing at the northern end initiated by the high density of sheep tracking. Pedestrian access to this beach occurs at the northern end to the west of the cemetery. Serious trampling of the dune face at this location has resulted in this access route now passing under a fence which is found at the dune crest.
A large rabbit population inhabits most of the machair. The effects are most noticeable at the southern end in the sand hillocks. Some localised erosion is also occurring on the slopes of Suenish at the northern end. Quarrying for sand within the sand hills in the south of Machair Robach is having little detrimental effect with only a low volume being extracted.
Future management
The dominant processes causing erosion of the frontal dune system are all naturally occurring. Little can be done to prevent dune erosion at the northern end of Machair Robach, other than restricting pedestrian access to the beach. Rabbit control may be required if localised erosion within the sand hillocks increases. The frontal dunes and immediate machair should be inspected periodically to monitor the system.
NF 833792 to NF 796759
Future management
Rabbit control is required before more extensive deflation occurs within the machair. The sheep and cattle density also appears to be too great for this machair region. It is also recommended that fencing to prevent livestock access to the frontal dune face be erected at Traigh Udal, Udal and along the coastal edge to the north of the spit. Periodic monitoring to assess rates of dune retreat and machair erosion is required.
Wave action plays an extremely important part in the evolution of this coastline. Such wave action however is not as destructive as one would expect due to the protection afforded by the shallow sloping offshore bathymetry, limiting the severity of the waves reaching the coast. Despite the exposed location and the length of many of the beaches, there is little significant nett longshore drift in any of these areas. Sand is accreting, albeit at a very low rate, in the fords between the main islands. Severe wave conditions can occur from any direction effectively cancelling out any evidence of nett drift. Slight accretion is noticeable to the south of Ardivachar and in the Howmore estuary. The exposed beaches are heavily influenced by wind action. Most of the dune systems are presently undergoing wind erosion, with little evidence of any dune construction.
27. Griminish Point to Aird an Runair
NF 725766 to 697713
Coastal processes
Retreat is noticeable on all of the shingle beaches along this frontage. At Hoglan Bay, shingle overtopping during storm wave conditions has blocked the road to the house and has had to be cleared. Similarly shingle has previously blocked the road between Tigharry and Hougharry, with coastal flooding of this area also occurring during high tides. Rock walls have been built, to the north of Hougharry, to prevent shingle being deposited on the road.
Wave erosion is also evident on the dune face within the bay to the south of Hougharry. Wind erosion, due to the exposed location of this coastline is occurring in the dune systems at both Traigh Stir and Traigh nam Faoghailean. At Traigh Stir a number of large blowouts have occurred. Pedestrian access from the machair car park behind the dunes and livestock trampling is contributing to the formation of these blowouts. Some rubbish has been dumped within these dunes. The machair behind has a very large rabbit population which is affecting the stability of the machair surface with a number of localised deflation zones.
Similarly at Traigh nam Faoghailean large blowouts are developing within the dunes to the western side of the bay. Sand quarrying, livestock tracking and a large rabbit population is contributing to the instability of the dune system and of the machair on Aird an Runair. Much rubbish has been dumped in these blowout holes. Directly south of Hougharry, the bay is sheltered by offshore rock reefs and the dune face here is extremely stable.
Future management
Due to access to the beach from the machair car park, the dune system at Traigh Stir is likely to deteriorate. Pedestrian access should be encouraged to the north by the mouth of the river. Fencing, to prevent livestock, particularly cattle, gaining access to the dune and beach at Traigh Stir should also be considered. This will also have the advantage of preventing direct pedestrian access to the beach through the dunes. Car parking on the machair land is not causing any problems at present but the state of the machair surface should be inspected periodically. Dumping in the dune system should be actively discouraged.
Similarly at Traigh nam Faoghailean, livestock access should be prevented from the area of the dunes and machair experiencing erosion. Any quarrying of the frontal dune system or dumping in blowout holes should also be stopped.
Protection of the road to the north of Hougharry from shingle overtopping is generally adequate, although some shingle will probably still be deposited on the road under extreme conditions. Due to the low usage of the road to the house at Hoglan, clearing the road of shingle after any severe events will be the most cost effective method. Periodic monitoring of the coastline should be conducted.
28. Traigh Iar and Port Scolpaig
NF 691703 to NF 713682
Coastal processes
Any evidence of wave erosion is only visible on the dune face at Port Scolpaig, although some wave attack will occur on all of the frontal dune faces during southerly to westerly storm conditions. Wind erosion of the dunes is extremely severe, particularly at Traigh Iar where large blowouts dissect the frontal dunes. Cauldron blowouts also occur within the dune system. Quarrying for sand has taken place, with some large quarry holes evident, and this has obviously contributed to the detrimental state of the dunes. A high rabbit population is also contributing to dune, and localised machair, instability.
The dune system at Port Scolpaig is suffering from some of the worst livestock trampling evident during the survey. Serious slumping of the dune face is occurring due to the high cattle population, with wind erosion then intensifying this erosion. The machair behind the dune system is also seriously deflated due to the high rabbit and cattle population.
Future management
Some attempts have been made to stabilise the blowout holes at Traigh Iar by erecting sand fencing. This has proved effective as these structures are now almost completely buried. It is recommended however that sand quarrying within the dunes be stopped and livestock be prevented from gaining access to the dunes. This will allow the dune system to redevelop naturally. At Port Scolpaig, livestock access to the dune face should be stopped immediately. Fencing should be erected to keep cattle well back from the face and any blowout features. Within certain parts of the machair rabbit numbers should be controlled and livestock numbers reduced if possible. It will be necessary to fence parts of this machair off to allow severely deflated areas to restabilise.
29. Loch Paible to Kyles-paible
NF 712682 to NF 755671
Coastal processes
The wide upper sand beach that fronts much of Lagan Maskeir and the numerous offshore rock reefs protect the dune face from wave erosion. Lagan Arnal is more exposed to wave erosion with storm action evident on the dune face. At present wind blown sand is deposited against this face. Rubh Arnal is experiencing significant wave erosion during high tidal conditions due to the low level of the beach fronting the machair edge. To the east of Rubh Arnal, the shingle ridge affords some protection to the dune face although wave erosion will occur at high tidal levels.
Pedestrian access to the beach from the track leading from Knockintorran is through an old small blowout which has stabilised. Access to the beach at this point is not causing any significant erosion. A number of tracks allow access to the machair from the various townships. These are presently stable and are not causing any detrimental effects to the surrounding machair surface. To the east of Rubh Arnal, cattle and sheep can gain access to the dune face, but little erosion of these dunes can be attributed to livestock grazing and trampling.
Future management
Periodic monitoring of the entire frontage and dune system is advised.
30. Kirkibost Island and Baleshare
NF 752663 to NF 793579
Coastal processes
Storm wave effects are most noticeable on both the shingle storm ridges and the dune faces fronting these two islands. At Baleshare, shingle has been deposited up to about 40m behind the upper beach, onto the machair surface and into the dune system. Evidence of recent storm erosion, resulting in dune crest retreat, can be seen at Ceardach Ruadh where 4 to 5m of fencing has slumped down the machair face. To the south of Ceardach Ruadh some rock has been placed to protect the track. The shingle ridge further south of this exhibits the most distinct signs of uniform shingle beach retreat along the west facing coastline of the Western Isles. Wind erosion is evident on the dune face of Kirkibost and on the high dunes in the southern part of Baleshare with a number of large blowouts evident.
Future management
Erosion of this coastline is a purely natural process with no external influences causing any increase in this rate. The coastal system should be left to develop without any interference and only periodic monitoring is recommended.
NF 798575 to NF 758546
Coastal processes
The dune system at An Tom is fairly stable overall although wave erosion of the dune face occurs along the western coast at locations where the upper beach width is narrowest. The effects of wave erosion are most evident at the south western end where sewage outlets have been broken up, wave undercutting of the dune face has occurred and significant erosion is occurring of the till outcrop. The dunes on the northern side of An Tom are stable and have a good covering of dune vegetation. Wind blown deposits on the upper face and frontal dunes are, at present, plentiful.
At Balivanich, the constructed till ridge will provide little protection during a high tide, large wave combination. Such a storm event from the north-west, will result in overtopping and some coastal flooding of the immediate hinterland. Further west a rock revetment provides adequate protection to the road. At the school, shingle is overwashed during storm wave conditions. The shingle beaches and ridges of Aird, are only affected by large wave conditions, or during high tides, with some overwashing of the crest having previously occurred during such an event. Flooding of the marshy hinterland will also occur during winter storms.
Future management
The rock revetment should be extended eastwards at a similar elevation to the single house to the north of the road. The eroding soft cliff at An Ceothan also requires some form of protection and again a short section of rock revetment would provide the most suitable protection. Access to the beach at An Ceothanm is now very difficult due to the erosion and pedestrian access should be provided. The frontage should be monitored periodically.
NF 756544 to NF 756536
Coastal processes
Although the bay is relatively sheltered with a shallow offshore seabed slope, some storm wave erosion of the dune face occurs. The principal cause of erosion to the dune system is however due to pedestrian access and wind effects. A number of large blowouts occur along the length of the beach. Pedestrian trampling possibly initiated such features and is now certainly contributing to the destabilisation of these dunes.
Future management
Access to the beach should be restricted to the track onto the beach, from the car park, and via the track at the southern end. The dunes should be fenced off, particularly at the northern end, to prevent pedestrian access to the beach through them.
NF 757525 to NF 765497
Coastal processes
The shingle ridge protects the dune and machair face from all but the most severe wave conditions along this frontage. Some wave erosion during such conditions was evident on the machair face above the shingle ridge. At present, the dune system these areas have stabilised with a good covering of vegetation. Rubbish has been dumped in many of these blowout holes and is still visible at various locations. At present coastal retreat rates will be relatively low over much of the frontage, except during storm events severe enough to cause retreat of the shingle beach. As at Baleshare, the sand beach foreshore is extremely low exposing the shingle upper beach completely.
Future management
Periodic monitoring of this entire frontage is required.
NF 765497 to NF 742464
Coastal processes
Wave erosion is most noticeable on the machair face between Sidhean Bhuirgh and the track to the coast from the B892, where the thin shingle ridge provides little protection. Quite severe wave erosion of the dune face to the east of this is noticeable at some locations, particularly south of the hotel and leisure complex. Other parts of this dune system are stable and accreting sand. Pedestrian access to the beach from the leisure and hotel complex is noticeable through the dunes but is not causing significant concern at present. A small area of erosion, resulting from pedestrian access to the beach and further exacerbated by wind action, is occurring to the west of the highest dunes.
The orientation of Gualan island makes it more exposed to wave attack. The northern half is reasonably stable with a healthy shingle upper beach protecting the dune face. Where small blowouts have occurred, short stretches of sand fencing have been erected. The width of the shingle ridge dwindles to the south of the spit, where severe overwashing of the dune ridge has occurred during storm conditions.
On the north coast of South Uist, a rock revetment adequately protects the coastal edge along the township of Balgarva. To the west, around Hornish Point, substantial erosion of the coastal edge has occurred, but this is not yet giving any cause for alarm. During high tidal conditions flooding of low-lying land occurs along the coast to the east of Balgarva. Within North Bay, the coastal edge is stable with little erosion evident.
Future management
Monitoring of the entire frontage and periodic inspection of the coastal defences is required.
35. Ardivachar Point to Rubh Aird-mhicheil
NF 738456 to NF 729335
Coastal processes
Much of this frontage is well protected from significant wave undercutting of the dune and machair face by a wide healthy shingle ridge. Storm wave erosion is generally confined to localised stretches where the shingle ridge is not as large. This is most noticeable just to the south of Ardivachar, at a number of locations at the southern end of the RA Ranges, and at Howbeg. Wave erosion is also noticeable at Grogarry with a short stretch of fence slumped down the machair face. Given that the adjoining frontage is stable with a wide shingle ridge protecting the machair face, localised shingle extraction appears to be responsible for this area of erosion. The shingle ridge at Stoneybridge has been breached at least twice this century with flooding of the marsh land occurring. At the time of the visit evidence of previous shingle overwashing during storm events was noticeable. Outside these areas the coastline is stable, with the shingle ridge generally providing adequate protection.
Wind action is presently accreting material on much of the dune faces along this frontage. This is most noticeable at the northern side of the Howmore estuary and to the north of the RA ranges. Small blowouts occur on the frontal dunes to the south of the RA Ranges. Old blowout holes at the southern end of the RA Ranges are now relatively stable. Many of them have been completely filled in with building rubble, and other rubbish including old army vehicles.
Future management
The frontage is generally stable, with the dunes more so than in 1988. Periodic monitoring of the entire frontage is required to check on the stability of the area. The two most vulnerable areas are at Ardivachar where a fire station and cemetery are located close to the coastal edge and the area around the Howmore estuary where livestock tracking and pedestrian access may cause further detrimental effects. The shingle ridge at Stoneybridge will certainly be affected during storm conditions and it is suggested that the ridge be repaired after any such events. Given the land use of the hinterland no further work can be justified.
36. Rubh Aird-mhicheil to Rubha Ardvule
NF 729335 to NF 709299
Coastal processes
Wave attack and coastal retreat of the shingle ridge is occurring along this entire frontage, particularly to the north as the sheltering effect of Rubha Ardvule decreases. Shingle has been thrown up against, and over, the machair edge. The sand beach below the shingle ridge, as at all other similar areas of this coastline, is extremely low due to storm wave activity causing drawdown of the beach. This drawdown is likely to have occurred over a number of storm events during the last few years. Due to the severity of this drawdown, natural recovery will take a long time. The exception to this is at the southern end of the unit, where the sand beach levels are higher due to the sheltering effect of Rubha Ardvule. West of West Loch Ollay, blowouts are continuing to develop in the high machair face. Although much rubbish has been dumped in these blowout holes, this is neither increasing erosion nor stabilising these areas. The dune system to the west of Bornish is very badly eroded due to wind action. Large blowouts, some extending all the way through the dune system, occur along the entire length. It is difficult to identify any one factor for initiating these blowouts, but a combination of wave activity, vehicle tracks through the dunes and, possibly previous quarrying of the shingle storm beach, increasing the exposure of the dune face to wave attack may be responsible. At present there is little sign of any quarrying of shingle although sand is extracted in small amounts from the lower beach.
The machair at the Ormiclate is beginning to show signs of overgrazing, due to the high number of rabbits. Relatively high numbers of sheep are also grazed in this area. At Bornish the machair is stable at present, with the rabbit population lower than that to the north.
Future management
Complete stabilisation of the dune system at the southern end of the unit is a relatively large undertaking, with the dunes unlikely to stabilise naturally in the near future. Vehicle access to the beach through the blowout holes will contribute to the continuing erosion and this activity is unlikely to stop. Sand fencing or pallets, used in a similar manner as sand fencing, in the most severe blowout holes will help trap sand and reduce the amount blown inland. Quarrying for sand may be permitted in small quantities on the lower beach. However no sand should be extracted from any part of the dune system. Rabbit control is required on the machair land to the west of Ormiclate which has the potential for severe machair deflation.
37. Rubha Ardvule to Smerclate
NF 709299 to NF 737154
Coastal processes
Wave erosion of the dune and machair face along much of this coastline is variable. One contributing factor has been shingle extraction for building purposes. Where shingle has been removed, the level of protection afforded has been greatly reduced with wave cut back much more evident in these areas. The most obvious locations where such activities have been occurring are at Daliburgh and Askernish although some shingle appears to have been removed from the ridges between Rubha Ardvule and Kildonan and to the south of Milton where approximately 4m of fencing slumped down the machair face provides a good indication of recent machair edge retreat. At other locations, the machair face is extremely stable, with no evidence of wave erosion. These areas are generally close to the headlands of the bays or where offshore rock outcrops limit wave energy levels, in their lee, at the shoreline. To the south of Kildonan and between Daliburgh and Kilpheder, there is little sign of any erosion, with a healthy beach system and, unlike other parts of this coastline, the shingle storm beaches submerged by sand.
The road to Rubha Ardvule is protected by a rock apron and shingle lower beach, but storm wave activity will cause shingle to be deposited onto the road. Although relatively sheltered, Dun Vulan will be affected from wave run-up and shingle overwashing.
Wind erosion is generally occurring where vehicle tracks cut through the machair face resulting in a wind corridor. To the south of Ribha Ardvule a number of blowouts are developing through the edge of the machair with sand being blown inland at these points. Wind is also beginning to cause erosion to the edges of recent sand quarry holes in the dunes at A' Mheallach.
Future management
The shingle storm beaches found on this coastline are an integral part of this coastline's defences against wave attack. It can not be stressed too highly that extraction of this shingle should not be allowed and should cease at once. There is no natural supply of shingle to these beaches and once it has been removed, the affected parts of the coastline will suffer from significant cut back of the coastal edge.
At Rubha Ardvule, protection of the historic dwelling house, Dun Vulan, is required to protect this feature from wave attack. The cost of providing coastal defence work to provide adequate protection, given the location of the site and the wave climate experienced, would be high and it is doubtful whether the historic importance of the site could justify such expenditure given that there are many such sites to be found in these islands. As any defence work would be limited by the close proximity of the site to the coastal edge, any such defence would have to be constructed some way down the beach, increasing the size of the structure, and its impact on the area.
Sand quarrying within the dunes at A' Mheallach should be monitored as there appears to be a recent increase in the amount of material being extracted. Recent quarry holes will require further work to stabilise them or further wind erosion can be expected. Although some attempts to stabilise the edge of the quarry area with plastic bags and piles of stone have occurred, this is likely to have very little effect in the long term. Livestock access to these old quarry holes may have to be restricted to allow the area to revegetate. Vehicle tracking is also likely to deteriorate the machair surface further and if this intensity of vehicle tracking is to be maintained, then some armouring of the track surface would be advisable.
The dumping of scrap and waste in the blowout holes to the south of Rubha Ardvule only has a limited effect. This activity is more likely to be a convenient way of disposing of waste material than as a method of coast protection. The visual aspect of this activity is poor especially once wave action has distributed dumped material over the beach. A much more effective way of controlling wind erosion of these blowouts would be to construct sand fencing or to cover the exposed area with a suitable mulch such as seaweed.
Rabbit control may be required on the most heavily populated areas within the dunes at A' Mheallach where erosion of the sand dunes is already occurring. Other dune areas should be monitored to check on any detrimental effects of the rabbit population.
Livestock grazing is not having a significant effect on the machair surface or edge although, again, monitoring of the situation is suggested, particularly around Milton where cattle and sheep have access to the edge of the machair.
38. Smerclate to East Kilbride
NF 737154 to NF 777139
Coastal processes
Between Smerclate and Pollachar rock outcrops protect the beach from wave erosion. At the mid point of the bay between Smerclate and Pollachar, a line of rock has been placed in front of a low embankment. Along this part of the coastline there is little sign of any coastal retreat and only minimal indication of shingle being overwashed from the upper beach onto the immediate hinterland. To the north of Pollachar, the beach is slightly more exposed with shingle found washed onto the hinterland. Slight wave erosion of the bank face has also occurred in the past, however there is little sign of any recent activity, vegetation being present on the shingle storm beach. At the inn at Pollachar, wave erosion of the hinterland has threatened the road. This localised area has been protected adequately by a rock revetment.
Along the south facing coastline, shingle overtopping is evident. This is affecting parts of the road running along the back of the beach, with debris blocking the road a common occurrence after storm events. This has been addressed at a number of points with rock revetments and rock upstands providing some protection. There are still a number of positions along this frontage that will be affected under severe storm conditions. The most critical of these is between East and West Kilbride, to the south-west of Loch a' Choire, where a dip in the road makes it prone to flooding. Shingle overtopping also affects the road at the western end of the bay at East Kilbride. The third position is the bay in front of West Kilbride, and although some rock has been placed there, this may need to be extended.
Future management
Further work is required to protect the road at both East and West Kilbride at three main positions. The most critical positions are the first two mentioned above, with the road under serious threat between East and West Kilbride if a storm from a southerly direction were to occur. A similar rock revetment with upstand would provide an adequate level of protection and be the most suitable type of structure under the conditions likely to be experienced. As in all other parts of the western facing coastline of South Uist, monitoring of the coastal edge is required along with checks on the condition of the constructed defences.
NF 783125 to NF 786105
Coastal processes
Wave erosion of the machair face has lead to rock rip-rap being placed on the machair face along the entire frontage at Balla. The rock used is small and it is likely that damage will occur to these defences under storm conditions. Small eroded areas are evident on the machair behind the beach, possibly due to trampling by horses.
At Coilleag, storm wave erosion of the sand cliff has occurred. At present the upper beach is relatively wide with marine litter trapping wind blown sand. Although there are quite a large number of sheep grazing on the hinterland this is not causing any erosion.
Future management
At Balla monitoring of the rock rip-rap is required, particularly after any severe storm events, and maintenance work should be conducted if any such damage is observed. The state of the machair behind the beach should be monitored, with grazing access restricted on any areas which show signs of any increase in such erosion.
At Coilleag there are presently only natural influences acting on the system. Routine monitoring would be advised.
The west coast of Barra and Vatersay experience extremely severe wind and wave conditions. As along the South Uist coastline, the offshore seabed will dissipate some of the wave energy, by wave breaking and frictional effects, before these waves the coast.
The beaches on the west coastline are capable of withstanding the severe wave climate. Beach areas such as Traigh Eais and the west facing beach at Vatersay have a shingle storm beach which will protect the immediate dune face from wave attack during all but the most severe storm conditions. At Traigh Hamara and at Halaman there is no shingle storm beach but there is a sufficient width of sand on the upper beach to allow these beaches to respond to the incident wave conditions without significant erosion of the frontal dunes or immediate coastal edge. Some localised areas of wave erosion does occur. This is mainly limited to times of storm activity.
On the eastern facing coastline at Eoligarry and Vatersay the wave climate is much less severe due to a number of islands restricting fetch lengths and due to there being less wind activity from the easterly sector. The beach areas are sandy with a very low intertidal gradient reflecting the much milder wave climate. Slight machair and dune edge erosion does occur due to locally generated wind waves from an easterly direction during high tides.
Wind action has a significant direct effect on the evolution of the beach areas. These severe wind conditions are responsible for the large blowout features found at Traigh Eais and at other beach areas along the western coastline. Wind action is responsible for the input of beach material to Traigh Mhor from the beach and dunes at Traigh Eais.
NF 703095 to NF 714076
Coastal processes
Traigh Scurrival is a sheltered from severe wave action, and as a result there is very little evidence of wave erosion on the dune and hinterland edge, with beach levels also extremely stable. Similarly, wind action is not a significant problem, due to the orientation of the beach, apart from some small localised effects in the old quarry hole.
Heavy trampling of the dunes by both cattle and sheep to the north of Eoligarry is evident with eroded tracks occurring throughout the dunes. This is having the most significant effect in the quarry hole where it is slowing down, or even reversing, the natural stabilisation process.
Future management
Little management action is required within this unit other than periodic monitoring. Restricting livestock access to the old quarry hole and immediate dune face is recommended. Dumping of rubbish on the beach has no coastal engineering benefit and should be discouraged.
41. Traigh Cille-bharra and Traigh Mhor
NF 714076 to NF 711047
Coastal processes
Although the beach can be regarded as a relatively low energy system, there are a number of locations where wave undercutting of the machair and hinterland face is occurring. Erosion here has caused substantial cut back, forming a 3m high sand cliff for about a 400m length. Cars and other rubbish, including fishing nets placed along the eroded coastline have little effect.
Erosion of the machair face is also occurring at Traigh Mhor, to the north of the airport "runway". Cut back of the face due to locally generated wind waves during high tides has caused a fence running along the edge of the machair to be lost. The conditions required to cause such erosion in this area will only occur relatively infrequently, with any long term average rates of cutback likely to be fairly low. Outwith these two main areas of erosion, there is little wave activity affecting the system and the coastal edge is stable.
Future management
Monitoring of the entire frontage is required to ensure the rate of wave erosion does not increase. The dumping of cars and other rubbish should be discouraged. Although these cars may provide toe protection at the back of the beach, they may act as groynes trapping beach material and causing a detrimental effect elsewhere.
NF 696078 to NF 688058
Coastal processes
The beach is exposed to severe wind and wave action from the North Atlantic and the effects of these two influences are very evident on the beach/dune/machair system.
The effects of wind have had a dominating effect on the character of the system at Traigh Eais. The dunes backing the northern half of the beach are generally stable with only minor areas of wind induced erosion. To the south, the high dunes are extremely dynamic, with large blowout formations and a continually eroding and depositing system. Large volumes of sand can be transported by wind action across the machair and onto the beach at Traigh Mhor. Some attempts have been made by the Scottish Office Agriculture and Fisheries Department (SOAFD) to control such aeolian activity in the blowout holes by erecting sand fencing and by planting marram grasses. This has had some success in the areas where such work has been carried out, but SOAFD do not intend to continue with the scheme.
Quarrying of sand has occurred in a redeposited sand hillock within the machair. Given the nature of the wind climate, this feature is unstable, with large volumes of sand being blown onto the road and beach at Traigh Mhor during storm conditions. Some attempts have been made to stabilise the deflated areas using top soil quarried from the island of Orosay, however wind erosion is still causing a significant problem.
Future management
No influences, other than naturally occurring ones, should be allowed to affect the sensitive regime of the dune system. Particularly, livestock should be restricted from the dune system, and pedestrians dissuaded from using the blowout features as access paths to the beach. Aeolian sand transport will be a problem, and any significant control methods will have a detrimental effect on the naturally occurring geomorphological processes that are the predominant interest of the area.
43. Greian Head to Doirlinn Head
NF 646049 to NF 639006
Coastal processes
The erosive influence of waves and wind is evident all along this coastline. At Allasdale slight wave erosion is evident on the dune face, but much of this beach is protected from significant wave attack by the rock reefs in the intertidal zone. Numerous narrow blowouts occur through the sand hillock areas, with wind erosion especially evident where channels have been cut due to streams dissecting the beaches. The high numbers of cattle and sheep grazing in these dune areas are causing much trampling of the dune vegetation and slumping of the dune face. On the machair further inland, rabbit erosion is evident with such areas being further eroded by wind action.
At Traigh Tuath, rock rip-rap protects the road where wave erosion has threatened to undermine it at one location at the southern end. To the south at Traigh Hamara, the width of the upper beach protects the dune face from any wave erosion, although wind affects the channel cut through the dunes by the stream.
Similarly at Halaman Bay wind action is the dominant natural process. Such action, in conjunction with past quarrying practice, has resulted in large blowout features developing through the dune system at the southern end. Wind blown deposits from the upper beach are re-depositing sand back into the system, although due to the lack of dunes and vegetation cover, blown sand can affect the road and properties to the back of the system. A local resident has attempted to control blown sand within this region using old oil barrels and pallets. At the southern end, the old quarry system is being gradually infilled with dumped material with topsoil being placed to stabilise this area, but revegetation is slow due to the high number of sheep grazing on this machair. At the northern end of the bay, a rock revetment protects the machair land upon which the hotel is built from wave erosion. Erosion caused by a stream has created a sand cliff on the northern bank, and further action by the wind has resulted in the edge of the cliff now being very close to the road.
Future management
At both Allasdale and Halaman, livestock access to the immediate dune zone and area of low vegetation cover should be restricted to allow these areas to develop naturally. At Halaman, control of the erosion of the sand cliff at the northern end will be difficult. Traditional methods of controlling wind erosion, eg sand fencing, will not be suitable due to the steepness of the sand cliff. A possible solution is to stretch ropes from pegs at the top of the cliff down to the dunes on the other side of the stream. Old fish nets could then be draped over these ropes. This will have the effect of reducing wind velocities acting on the sand cliff and also promoting accretion of wind borne sand in this location.
Within the dunes at Halaman the pallets have a greater influence in controlling blown sand than the oil barrels. It is recommended that the pallets are placed so that the spars run vertically and that they are staggered, in order that one row does not stretch across the entire width of the blowout corridor. The oil barrels are not effective and should be removed. Dumping in the old quarry holes is not having an adverse effect on the beach system at present. However in the future dumping should not occur within the frontal dune ridge.
NL 632946 to NL 633954
Coastal processes
The western coastline is dominated by the severe wave and wind conditions experienced due to the exposed location, with large blowout holes occurring along the entire length. Sand blown from the western beach affects the whole of the isthmus and is the major source of sand to the eastern facing beach system. Wave erosion is evident on the dune face, however the shingle ridge protects it from all but the worst conditions.
Wave erosion of the dune face is evident on the eastern facing system although to a much lesser extent. Some wind erosion is also evident, with some small blowouts occurring, although these may have been initiated by other factors such as quarrying and vehicular access to the beach.
A number of other influences are causing a detrimental effect to the fragile stability of this system. Cattle and sheep grazing is permitted over the entire dune system and is contributing to the erosion of the dune system on the western side. Sand quarrying on the eastern side of the system is not causing any significant contribution to the overall erosion of the area although may contribute to the volume of blown sand inland. The dumping of cars and other rubbish is having little effect in stabilising the machair area.
Future management
The west facing system will continue to erode and redeposit sand within the isthmus. To allow this process to continue under purely natural influences it is recommended that cattle and sheep be excluded from the dune face and from any blowout areas and areas of low vegetation cover. Likewise dumping within the blowout holes on the western side should be discouraged. On the eastern face cars have been dumped indiscriminately within the machair. Although dumping should not be encouraged it is realised that there is a shortage of suitable dump sites. Any dumping should be concentrated in an old quarry hole at the south eastern end which is naturally stable, with any available top soil being used to cover the dumped material.
