Beach and shoreface nourishment

Beach nourishment or replenishment is the artificial placement of sand on an eroded shore to maintain the amount of sand present in the foundation of the coast, and this way to compensate for natural erosion and to a greater or lesser extent protect the area against storm surge. Nourishment may also use gravel and small pebbles, in particular for the shoreface (the nearshore area within the low water mark and the limit where fair weather waves interact with the seabed). Beach nourishment also often aims at maintaining beach width for tourism and recreational purposes. The process involves dredging material (sand, gravel, small pebbles) from a source area (offshore, near-land or inland) to feed the beach where erosion is occurring. Beach nourishment does not halt erosion. It rather addresses sediment deficit by providing additional sediment from external sources, often requiring repeated interventions. The technique has been used in the United States since the 1920s and in Europe since the early 1950s. Beach nourishment is common practice in the Netherlands, Germany, Spain, France, Italy, the UK and Denmark. Several beach nourishment techniques can be used: 

• Beach nourishment, in which the sand is spread over the beach where erosion is occurring to compensate shore erosion and restore the recreational value of the beach. Wind will then distribute the sand onshore and in the dunes. 
• Backshore nourishment, in which sand is stockpiled on the backshore (part of the beach above the foreshore, which is only exposed to waves under extreme events) to strengthen the dunes against erosion and breaching in case of storm. The sand may deplete greatly during storms. 
• Shoreface nourishment. The reduction of wave energy leads to enhanced accumulation at the beach. This can be combined with beach nourishment to strengthen the entire coastal profile. 

Large scale nourishment has been tested in the Netherlands in the so-called ‘Sand Motor’. The project involved the placement of sand in the shoreface and above. It is supposed to function as a source of sediment supply re-distributed by waves and currents to beaches and dunes over distances of several kilometres. It is meant to function over a period of some twenty years. The Sand Motor differs from traditional techniques both in terms of scale and by the sand redistribution technique mainly using the natural forces of wind and waves rather than mechanical energy. 

Techniques also differ according to the origin of the sand deposit: 

• Inland or nearshore sources: the sand is excavated from accumulating areas close to the shore and transported to beach by trucks. This technique is more suited for small scale nourishment. 
• Offshore dredging: the sand is dredged from the seafloor. Dredged material can be pumped through pipelines directly to the beach. It can also be suction-dredged from source, transported and dumped by ship or pumped ashore to build up beach profiles. Offshore dredging should be used carefully and should not be done in the submerged beach close to the coast to avoid impacting beach dynamics. 

In order to enhance the protection of coastal resources in a sustainable way, beach and shoreface nourishment can be part of broader integrated coastal management zone management (ICZM) plans, Coordination at different spatial levels of governance is required. Indeed, ICZM includes principles that are also important for coastal erosion management, such as the involvement of all relevant parties and taking a long term perspective. An example of beach nourishment adopted within a ICZM can be found in the coastal area of Marche region in Italy. Beach nourishment can complement other grey measures such seawalls or groynes and green measures such as dune strengthening. Dune construction and reinforcement can even improve beach resilience and act as sand reservoirs, thus improving the effectiveness and long-term sustainability of beach nourishment. 

IPCC categories

Structural and physical: Ecosystem-based adaptation options

Stakeholder participation

Stakeholder participation depends on the specific case and on the national context. Beach nourishment measures may be included in ICZM plans, which generally require stakeholder consultation. 

In the Netherlands, the implementation of traditional small scale nourishments and the construction of the Sand Motor resulted in very different public participation processes. While small scale nourishments dealt with specific technical issues, not involving stakeholders outside the coastal engineering community, the creation of the Sand Motor, because of its greater impact on coastal environment, tourism and recreation and land use, involved a larger community of stakeholders. Awareness-raising of flood protection issues was one component of the project. 

In the region of Le Marche, Italy, regional authorities held extensive discussions of plans for beach nourishment in the municipalities of Sirolo and Numana with local officials and stakeholders (including fishing and tourism interests) as well as inhabitants. An Environmental Impact Assessment was carried out, which involved a further stage of public consultation. The project was approved and the work was carried out from 2009 to 2011. In 2019, a new ICZM Plan was built together with public and private stakeholders, constantly informed and consulted about the planned activities. 

Success and Limiting Factors

Success factors: 

• Beach nourishment is a flexible and fast coastal management option compared to hard construction, and it is adaptable to changing conditions. Due to its flexibility it is also a relatively cheap measure to prepare compared to hard construction works. If conditions change in a negative way, additional nourishment can be simply added. 
• Besides flood and erosion protection, beach nourishment can provide benefits for coastal tourism, recreation activities and coastal habitats preservation. 
• In some cases, beach nourishment can use material extracted for another purpose, allowing it to be productively reused: in the region of Emilia Romagna (Italy) sediment dredged in ports to facilitate navigation is used for beach nourishment. However, sediment quality needs to be properly assessed to avoid any contamination of the destination site. 
• Beach nourishment has been applied around the world for many years and consequently a broad experience can support its correct design and implementation.  

Limiting factors: 

• Beach nourishment can potentially negatively affect foreshore ecosystem with the burial of biota, the loss of habitats in nearshore sandbars, or the disruption of bird and other animal nesting, if it is not carried out properly. Some species, such as sand-dwelling invertebrates, are sensitive to a change of sediment types. Studies show that the impact depends on the frequency of nourishment in a given area. 
• Beach nourishment is usually an ongoing process, which leads to higher costs over time and repeated disturbance of the ecosystem. Nourishment does not end erosion; it only provides additional sediments on which erosion will continue. Therefore, traditional small-scale onshore nourishment has to be repeated regularly because the sand stock is depleted either by coastal erosion or storm surges. 
• Although beach nourishment is usually based on a working with nature approach, it is not totally impact free. In particular, the extraction of materials from the quarry site, the transport route and the potential impact of new imported material on coastal and marine habitats need to be carefully assessed and planned.  
• Finding a source with sufficient quantities of sand that is also compliant with chemical-physical requirements of the destination site can be challenging. The dredged sand should match the sand present on the site in terms of grain size, colour, and composition. For sandy beach and dune systems, the placement of significantly finer sediment may result in quick loss of nourished sand. Using less mobile (coarser) sediment typically helps that the added sand remains in the project area longer and performs better during storms. However, overly coarse sediments may result in the formation of a steeper beach (i.e., a change in beach state) which may have negative impacts on recreation, safety, and the environment.  
• Sediment availability could be an issue if the demand for nourishment projects rises. Offshore sand deposits may be a limited resource. Offshore sand dredging can create conflicts with other maritime activities, especially in some restricted sea basins such as the Adriatic Sea where many sea uses coexist in a limited space. Adequate marine spatial planning that considers both current and future needs as a response to climate change can help solving these issues. This also implies that beach nourishment, in a long-term perspective, must be integrated in broader coastal defence interventions targeted to find a more stable solution to the issue of coastal erosion (see also Retreat from high risk areas, Restoration and management of coastal wetlands).  

The Sand Motor intervention in the Netherlands, carried out in 2011, seeks to address some of these problems by reducing the frequency of replenishment and therefore the number of disturbances of the ecosystem. The project was designed to have a lifespan of 20 years. An independent assessment carried out 10 years after the construction indicated that the Sand Motor’s objectives in  long-term coastal protection have been achieved and that its lifespan will be even longer.  Moreover, new habitat for local flora and fauna as well as spaces for recreation were created and their quality is being assessed. 

Costs and Benefits

Beach nourishment typically needs regular application. It is advised to compare the costs of nourishment (which also depend on the availability of sand) with the costs for hard constructions and their maintenance, to ensure an optimal choice. Costs for beach nourishment can vary widely between and within countries.  

Costs presented in a UNEP-DHI report (2016) vary in Europe from €5 to 7/m3if transportation costs are not included. Indeed, the most important determinant of nourishment costs appears to be the transport distance and the number of journeys between dredge and target sites. Several other factors can affect unit costs of nourishment such as amounts of sand needed and frequency of nourishment, estimated material losses, availability (and size) of dredgers, etc. Interventions in remote locations can increase up to 34€/m3.  

Nourishment interventions protect the inland from flooding in a flexible way. In addition they offer important synergies with economic activities related to coastal tourism, by keeping adequate beach width. 

The Sand Motor in the Netherlands involved the use of 20 million of cubic meter of sand. In this case, the estimated unit cost was 3.3€/m3, which was lower than the cost of traditional nourishment (up to 6€/m3). Along with increasing coastal safety in the long-term, the intervention also allowed to improve natural surroundings and create new space for recreation activities. 

Legal Aspects

• Extraction of minerals through marine dredging falls into Annex II of the EU Environmental Impact Assessment Directive on the assessment of the effects of certain public and private projects on the environment). Member States decide whether projects in Annex II should undergo an EIA procedure, either on a case-by-case basis or in terms of thresholds and criteria. If not subject to impact assessment, the implementation of beach nourishment may require prior declaration or authorisation.  
• Any project likely to have a significant impact on a Natura 2000 site must be reviewed via an ‘appropriate assessment of its implications for the site’, to determine whether the project will adversely affect the integrity of the site, as per Art. 6(3) of the EU Habitats Directive. 
• The EU Directive that establishes a framework for Maritime Spatial Planning refers to the extraction of raw material as one of the activities to be covered by maritime spatial plans. Consequently, the use of offshore sand or other aggregates for beach nourishment may need to be addressed under such plans. Additional national legislation may apply, such as permitting requirements. 

Implementation Time

Implementation time can vary depending on the scale of intervention (small-scale versus large scale), on the source of sediments (distance to site) and on the related transport route. The actual process of dredging, transport and redistribution of sand along the beach usually requires a short implementation time (e.g. some months). However, the complete process of designing the intervention, selecting the proper site, evaluating sediment compatibility and potential impacts, can require longer time. Implementation may require more planning time if the measures are conceived as part of a ICZM plan and require an active and broad stakeholder engagement. Finally, time should be devoted to beach monitoring in the months and years following the intervention to assess its effectiveness and the potential additional need of new sand replenishment actions.

Life Time

Nourishment of beaches can remain in place for intervals that vary from 2 to 10 years. Depending on local conditions, replenishments and maintenance may need to be carried out regularly. Beach nourishment is a continuous process and the beach erosion won’t be fully stopped with this option. Sea level rise and increase in extreme events will probably reduce the lifetime of such projects, increasing the need and frequency of supplementary nourishment if a project relies exclusively on this measure.  

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