Construction of semi-permeable fences along the seaward face of dunes will encourage the deposition of wind blown sand, reduce trampling and protect existing or transplanted vegetation. A variety of fencing materials can be used successfully to enhance natural recovery. Fencing can also be used in conjunction with other management schemes to encourage dune stabilisation and reduce environmental impacts.
Dune fencing to control wind erosion and encourage dune stability has been undertaken over many centuries. Success depends on the void to solid ratio of the fence, the availability of blown sand, the frequency of wave attack at the fence and the amount of vegetation available to stabilise the accumulated sand. Success will be enhanced by other management schemes, like dune grass transplanting,or beach recycling/regrading to establish new foredunes. Post project monitoring should be undertaken at least bi-annually to assess the beach-dune evolution and the success of the scheme relative to the objectives.
Sand fences cannot prevent erosion where wave attack is both frequent and damaging, but they will encourage foredune growth and resist some erosion. Fences reduce wind speed across the sand surface and encourage foredune deposition. They also act as a modest barrier to wave attack, reducing the erosion potential of waves near the limit of uprush. Success depends on the void to solid ratio of the fence, the availability of blown sand, the frequency of wave attack at the fence and the amount of vegetation available to stabilise the accumulated sand.
Fencing materials can include chestnut palings, brushwood, wooden slats or synthetic fabrics. To be effective a void: solid ratio of 30% to 50% is required. Choice of materials will depend on required life, length of frontage commitment to maintenance and potential for vandalism.
Vegetation transplanting will encourage dune growth and enhance the shoreline environment. Fencing without transplanting will have a short term impact only as any accumulated sand will remain unstable.
Political & social feasibility
Sand fences limit public access to the dunes and beach, and can be visually intrusive. Fencing may accumulate blown litter or strand line debris, while damaged fences may interfere with the amenity use of the beach.
Access routes to popular public beaches should be defined by the fencing at regular intervals (say 100m) along the dune face. Poorly planned access routes will encourage the public to damage fences in order to create their own paths. Educational displays at backshore car parking areas or along footpaths should be used to explain management schemes and encourage public interest and support for the management objectives.
Before installing the fences, local interest groups, such as landowners, nature trusts, fishing associations and recreational users, should be consulted early to ensure that a broad view of the shoreline and nearshore zone.
Cost of implementation & maintenance
Fencing costs vary according to labour, type of material used, quality, length and spacing of posts, frequency of spurs, frequency of public access points, need for management and the cost of ancillary works. Regular maintenance should be undertaken to repair fencing and remove rotting or unsightly debris that may be caught along the fencing. In general, the costs of this measure are considered to be rather low, but require on-going maintenance and the life-span of the measure may vary.
Fencing along the dune toe allows public access to be controlled and reduces trampling of vegetation along the seaward edge of the dunes. Fencing and associated vegetation transplanting can help to stabilise the foredunes and will extend the dune habitat.
Non-degradable synthetic materials should be avoided in areas likely to be heavily affected by storms, as any material carried away by waves may become a hazard to swimmers, navigation and sealife.