Sand dunes are wind forms elements on sandy coasts and represent a natural coastal protection measure. Natural processes like erosion and human interference (like coastal protection measures, changing coastal processes, tourism) can have a negative impact on dunes. Rehabilitation with feeding sand or planting vegetation can reinforce the dunes.
Based on the information provided by the Scottish Natural Heritage.
Dunes are a protective feature that provide sand buffer and protect the land from waves and flooding. Therefore they represent a buffer between sea and land, in a similar way to a seawall but are usually of natural origin. A distinct feature of dunes is their dynamic character, with a constantly undergoing change of their shape. Natural processes (waves and wind) and human interference (e.g. through tourism, housing or malfunctioning coastal protection measures) can have negative impacts on dunes and lower their natural protection abilities. For example Gómez-Pina et al. (2002) state that massive tourist development and road and boulevard constructions are two main reasons for severe damaging causes of dunes in Spain.
Dune rehabilitation refers to the restoration of dunes from a more impaired, to a less impaired or unimpaired state of overall function, in order to gain the greatest coastal protection benefits (Linham & Nicholls 2010). For example as part of beach nourishment, existing dunes can be reinforced or new ones can be created. The dredged sources for the nourishment can be placed on the beach followed by reshaping of the deposits into dunes, for example by bulldozers. Once, the dune has been provided by additional sand, there are several ways to stabilize the dune and help to keep the sand within the dune. One way could by building fences to trap the sand. Another way to stabilize the dunes is to plant vegetation that helps to trap and stabilize sediments. Dune fencing can additionally trap sand and also reduces reduce trampling in dune areas. Natural materials such as branches or reed stakes should be used for fence construction, because they “assure breakdown after the barriers have accomplished their trapping function or are eroded by waves” (Nordstrom & Arens, 1998: 171). One key barrier for implementing this measure is the conflict of different interests, since the dune rehabilitation could restrict other usage of the coastal area, especially tourism and housing.
Dunes are dynamic systems and the success of the rehabilitation will relay on the allowance of these dynamic natural processes. Wide sandy beaches are attractive for development and the phenomenon of coastal squeeze could lead to a problem if there is not enough space for the dunes to recover. The success of the rehabilitation depends also on the site specific circumstances, for example on the replenished sediments or the used plants.
Cost of implementation & maintenance
In general the costs for rehabilitating dunes are not seen as very high – assuming the area of land use is not a problem (Linham & Nicholls 2010). But maintenance costs could exceed the initial costs for the rehabilitation measures over the years. For a more detailed Cost-effectiveness evaluation see the RISC-KIT Case Study report.
One of the co-benefits of restoring dunes is the ecologically positive effect by increasing existing or establishing new coastal habitats. Ecological impacts could arise if bulldozer or other earth moving equipment for re-establishing the dunes is used. But while these are mostly temporarily effects, sand dunes provide a coastal coastal habitat for many highly specialised plants and animals (Linham & Nicholls 2010).
Different Ways of Dune strengthening, rehabilitation and restoration
Based on the information provided by the Scottish Natural Heritage in the following sections there are description of different ways of how to strengthen, rehabilitate or and restore dune systems.
These measures will not stop coastal erosion but lead to a more valuable coastal buffer zone. The success of the dynamic approach depends on the local settings – both from a natural and a social point of view. Factors to be considered are the use of proper construction material, planted dune vegetation, and campaigns to raise local commitment. If local stakeholders lack commitment, this could be a barrier for implementation of the measure. But this measure can also be seen as opportunity since the rehabilitation can lead to a more natural coastline and therefore to be considered as both ecologically and recreationally important.