Home Database Adaptation options Dune construction and strengthening
Website experience degraded
We are currently facing a technical issue with the website which affects the display of data. The full functionality will be restored as soon as possible. We appreciate your understanding. If you have any questions or issues, please contact EEA Helpdesk (helpdesk@eea.europa.eu).
Adaptation option

Dune construction and strengthening

Coastal dunes and their associated natural grassland communities act as a barrier to storm surges by reducing flooding and coastal erosion. Erosion is a natural phenomenon caused by wind and coastal waves; yet it is exacerbated by human activities such as coastal urbanisation and unsustainable tourism. Climate change is amplifying the erosion of dunes by means of increased storms, severe weather, floods and sea level rise. Dune construction, strengthening and rehabilitation measures intend to restore the sand barrier functions of dunes to gain coastal protection benefits. 

Dune construction and strengthening can involve the following processes: 

  • Dune grass planting: plant dune grasses to reduce wind speed across the surface and thereby trapping and holding sand. Planting vegetation helps to stabilise dunes, encourages dune recovery and may be used after storm damage. Alternatively, vegetation may be planted when new embryonic dunes become high enough. In this way a buffer is created at the seaward front of existing dunes contrasting erosion during storm surges. In general, the number of plant varieties that can be planted on dunes is relatively small. Selected species must be resistant to silting, wind and salinity. When the grass cover is established it can become self-sustaining. Regular monitoring and re-planting are necessary.  
  • Dune thatching: covering the face of the dune with plant debris and branches to stabilise sand, encourage sand accretion and protect dune vegetation. Materials can be put on the ground manually or mechanically. The input of organic material favours the development of plants and grass. 
  • Dune fencing: construction of fences along the seaward face of the dune to reduce wind speed on the surface and encourage foredune deposition of transported sediment. Fences are often constructed of wood. Depending on local circumstances they can also use other material (including, for example, used fish netting). Dune fencing  can also increase the deposit of organic matter and the resulting growth of grasses and other plants. Fences can also act as barriers against wave impact. This technique is not suited for all types of dunes: the installation of fences is difficult on steep slopes, and in very instable areas. Also, maintenance can be complex in touristic areas welcoming a lot of visitors.  
  • Hybrid combinations of a dyke-core in a dune: this is a combination of hard man-made structures topped with sand, dunes and vegetation. This mimics natural landforms in aesthetic and most functionalities, and it is much more resistant to erosion and flood resistant 

These methods are complementary and are usually combined: grass planting usually requires fencing and thatching to succeed. Interventions on dunes are more effective when they are integrated with the restoration or strengthening of the complete coastal transect. This includes  retro-dune wet areas and consolidated dunes with shrub and tree vegetation. Grass planting can be useful to conceal hard defences such as gabions, timber or rock structure. 

Artificial dunes are engineered structures reproducing the form of natural dunes, often in a chain-like manner. They are built with sand brought from an external source area. They are shaped into dunes using bulldozers, dune nourishments or other means. This is often carried out at the same time as beach nourishment and can be even integrated in larger intervention projects for coastal defence, combining different green and grey solutions and requiring coordination at different levels of governance (see also Adaptation of integrated coastal management plans). 

Additional Details
Reference information

Adaptation Details

IPCC categories

Structural and physical: Ecosystem-based adaptation options

Stakeholder participation

Dune construction can provoke conflicts of interest over land use. Landowners may be eager to preserve sea views without hampering tourism along the coast. Conversely dune construction or restoration often requires that areas close to the coast are protected against massive tourism. Fencing to avoid disturbance from people or minimise sand transport may be needed. Fencing and thatching can have a negative impact on the landscape esthetic and therefore can be controversial in touristic places. Another concern is that sand from dune construction can be undesirably deposited in nearby residential or commercial areas. Stakeholder engagement at an early stage of the project (involving local authorities and economic operators) can help minimizing these conflicts. The involvement of tourism operators in dune restoration initiatives can boost the development of new initiatives of sustainable tourism or eco-tourism that in their turn can help the preservation of dunes. 

Conversely, dune construction, strengthening and rehabilitation projects can also provide an opportunity to raise awareness of local stakeholders and visitors. Dune construction and strengthening do not necessarily include a public participation process. This depends on the conservation aims of the site - which do require owners, land managers or conservation NGOs – to be involved in the process of setting conservation goals. If the area behind the dunes is a natural area, nature managers may want to be involved in dunes formation or strengthening to ensure that the nature conservation goals of the site are being met by the process. Participation in flood risk management is required by the Floods Directive (2007/60/CE). Dune construction and strengthening can be included among measures set in the flood risk management plans under this directive, thus requiring participation in the planning process. 

Success and Limiting Factors

Success factors: 

  • If they are well managed, dunes can offer a high degree of protection against flooding and erosion. 
  • They also provide valuable habitats for animal and plant species. Dune rehabilitation or the construction of artificial dunes is beneficial to the beach ecosystem. In some cases, artificial dunes can restore the recreational value of the beach.  
  • Dune thatching, fencing and grass planting are low cost solutions to reduce dune erosion.  
  • Materials used for thatching can be biodegradable as well can contributes to a circular or eco-friendly maintenance strategy.  
  • Sand and vegetation creates a natural appearance to man-made structures as they integrate with the dunes. 
  • Dune construction and strengthening can be combined with beach nourishment, to improve coastal resilience and natural landscape of the coastline.  
  • Dune construction can include walkways and confined paths which can bypass fortified or fragile areas and contribute to eco-tourism or local ecosystem services. 

Limiting factors:  

  • Grass planting and thatching less likely to succeed if erosion is very severe, and methods are also labour intensive. This option has a limited lifetime and require frequent maintenance (replacing plants, put fertiliser, replacing branches blown away, repair after vandalism etc.).  
  • Thatching must be limited as transport by machines leads to deterioration; although fences are usually made of degradable timber, they also use wires and sometimes plastic that can be a long term nuisance.  
  • Thatching is conducive to invasive plant species which can grow in nutrient rich grounds and overtake native species. 
  • Construction of fences and thatching can limit access to the dune and the beach 
  • Thatching and fences also alter the natural visual aspect of the dune, which may have a negative influence on tourists’ flows and recreational activities, so adequate information panels and awareness raising initiatives should be implemented in the site to help visitors understanding the environmental value of these interventions 
  • The natural dynamics of both the dunes and the areas behind them may be hindered by strong wind or water erosion. Combining planting with creating landscaping with controlled wind drifts that allow inland sand drift may greatly counteract such erosion losses and generate an exciting landscape for the visitors. This requires, however, sufficient land area, and knowledge of the local wind patterns in the planning process.  

Costs and Benefits

Implementation costs depend on the dune construction strategy. Thatching and planting costs can be  low as material used is cheap. However, their limited lifetime implies on-going maintenance costs, involving in particular labour costs. Costs also depend on site location and accessibility. The unitary price for dune reconstruction (sand transport and nourishment) could range from 6.90–17.10 €/m3 , depending on the origin of the sediment, location of dune and the operations of transport. Conversely, it is more difficult to estimate the maintenance cost and the cost of revegetation, because it strongly depends on plant typology and the strategy used. Protective planting with herbaceous local, non-invasive plants to control surface erosion can cost 11-28 €/m2 (Fernández-Montblanc,et al., 2020). 

Dune construction and strengthening costs are low compared to the costs of hard defence solutions, such as dykes and seawalls. Moreover, a wide range of co-benefits, beyond coastal defence, are expected from this option. Sand dunes provide a valuable coastal habitat for plants and animals, preserve biodiversity and encourage the sustainable development of coastal area, with special reference to eco-tourism.  

Certain types of natural dunes are classified under Annex I of the EU Habitats Directive as a natural habitat of EU interest. Dune strengthening and rehabilitation, and in some cases dune (re)construction as well, may be part of the management plan for sites protected under the EU Natura 2000 network. The EU Floods Directive applies to inland waters as well as all coastal waters across the whole territory of the EU. The Directive requires that Member states take into consideration long term developments, including climate change, as well as sustainable land use practices in their flood risk management plans. Dune construction and strengthening can be included in these plans as measures to reduce the impact of coastal flooding. 

Implementation Time

Implementation time depends on the dune reconstruction option chosen. It can take approximately 1 to 5 years. More integral changes in the landscape may take longer due to implication for the local landscapes and discussion with the stakeholders. All of the options should include maintenance time after the implementation to ensure the planted or placed elements are still intact.  

Life Time

Lifetime is highly variable (5-25 years). Biodegradable elements used in the interventions need to be regularly replaced, while dunes may need to be periodically replenished with new sand and periodical re-planting can be necessary to strengthen their barrier function against erosion. 

Reference information

References:

Fernández-Montblanc, T., Duo, E., and Ciavola, P. (2020) Dune reconstruction and revegetation as a potential measure to decrease coastal erosion and flooding under extreme storm conditions, Ocean & Coastal Management, https://doi.org/10.1016/j.ocecoaman.2019.105075 

Gao, Jinjuan & Kennedy, David & Konlechner, Teresa. (2020). Coastal dune mobility over the past century: A global review. Progress in Physical Geography: Earth and Environment. 44. 030913332091961. 10.1177/0309133320919612. https://journals.sagepub.com/doi/10.1177/0309133320919612 

de Winter, R.C., Ruessink, B.G. Sensitivity analysis of climate change impacts on dune erosion: case study for the Dutch Holland coast. Climatic Change141, 685–701 (2017). https://doi.org/10.1007/s10584-017-1922-3 

Brown, S., Hanson, S. & Nicholls, R.J. Implications of sea-level rise and extreme events around Europe: a review of coastal energy infrastructure. Climatic Change122, 81–95 (2014). https://doi.org/10.1007/s10584-013-0996-9 

Published in Climate-ADAPT Sep 03 2016   -   Last Modified in Climate-ADAPT Dec 18 2023

Document Actions