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Adaptation option

Beach and shoreface nourishment (2015)

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). Beach nourishment also often aims at maintaining beaches (beach width for tourism and recreational purposes). The process involves dredging material (sand, pebbles) from a source area (offshore or inland) to feed the beach where erosion is occurring. 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 area between the mean low water mark and the fair weather wave base). 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.
  • Medium-scale (of the order of 5 million m3 – depending on the local context) nourishments of channel walls, on locations where tidal channels erode the coast. This type of nourishment has successfully been applied in among others the Netherlands to keep the channels away from the coast.
  • Large scale nourishment. This has been tested in the Netherlands in the so-called ‘Sand Motor’. The Sand Motor involves 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 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 or can 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.
Additional Details
Reference information

Adaptation Details

Category
Green

Stakeholder participation

Stakeholder participation will depend on the specific case and on the national context. For example, beach nourishment measures may be included in ICM plans, which may be developed via stakeholder consultation.

In the Netherlands, the implementation of traditional small scale nourishments and the construction of the Sand Engine resulted in very different public participation processes. While small scale nourishments have been a more technical issue, not involving stakeholders outside the coastal engineering community, the creation of the Sand Engine, 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 EIA was carried out, which involved a further stage of public consultation. The project was approved and work was carried out from 2009 to 2011.

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, as long-term design criteria usually are not taken into account, something necessary for hard construction. If conditions change in a negative way, additional nourishment can be simply added.
  • Beach nourishment can complement other grey measures such seawalls or groynes and green measures such as dune reinforcement. Dune construction and reinforcement can even improve beach resilience and act as sand reservoirs, thus improving effectiveness of beach nourishment.
  • 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 Anglet (France), sediment dredged in the port of Bayonne to facilitate navigation is used for beach nourishment.

Limiting factors:

  • Beach nourishment potentially can 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.
  • Finding a source with sufficient quantities and good-quality sand can be challenging. The dredged sand should match the sand present on the site in terms of grain size, colour, and composition, unless it is a shoreface nourishment. In Hel Peninsula (Poland), the grain size of dredged sand from a nearby bay was much smaller than the grain size of sand taken in the open sea and was consequently easily dispersed, even in low energy wave currents. Consequently, erosion continued even though a large amount of sediment was spread over the beach. After research, sand from open sea sites and a nearby breakwater was preferred as more effective against erosion. Using a similar type of sand (in terms of colour and composition) is also important for public acceptance of beach nourishment interventions. In addition, the source site should be close enough to the nourishment site to keep costs reasonable.
  • Sediment availability could be an issue if the demand for nourishment projects rises. Offshore sand deposits may be a limited resource, especially in some areas such as the Adriatic sea, that should be carefully used taking in consideration key priorities and also future needs. This also implies that beach nourishment, in a long-term perspective, must be integrated within a wider approach, e.g. including managed realignment, setback definition, re-planning and zoning of coastal areas, etc.

The Sand Motor in the Netherlands seeks to address these problems by reducing the frequency of replenishment and therefore the number of disturbances of the ecosystem. The Sand Motor is designed to be a solution for twenty years. In addition, the distribution of the sand by the currents will create a more natural coastal profile and avoid the destruction of habitats. The Sand Motor could also bring a number of environmental benefits such as the creation of new habitats, such as mud-rich areas and extra dunes in the coastal zone until the complete distribution of the sediment.

Costs and Benefits

Beach nourishment typically needs regular application. It is advised to compare the costs (which also depend on the availability of sand) with the costs for hard constructions and their maintenance, to ensure an optimal choice. Estimates of unit costs presented in the UK AVOID report (2010) on Costs of adaptation to the effects of climate change in the world’s large port cities  range from US$ 5-8 (4-6 €) per cubic meter of sand (DIVA model) for Europe; other estimate show a wider variation: US$ 3 to 46 per cubic meter. In the UK, higher estimates were found: US$ 4.6 to 46.4 (3.5-35€)/m3. In the Netherlands, lower estimates were found, around US$ 3 to 8 (2-6€) per cubic meter. However, prices there have recently risen due to the lack of contractors available to undertake nourishment works. Since 2000, the average volume of sand supplied to nourish the entire coast in the Netherlands is 12 million cubic meter per year. According to the AVOID report, a key factor influencing nourishment costs appears to be the transport distance between the source area to the deposit site. The frequency of replenishment times the volume per nourishment will affect the long-term costs.

Scottish Natural Heritage (2000) provides cost information per length of nourished beach: GBP 5,000-£200,000 (6,300-251,700€)/100m frontage, not including control structures, ongoing management and minor works.

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 2.5€/m3 compared to up to 6€/m3 for traditional nourishment. This is extremely low because contractors were eager to do this innovative project. The total cost in 2011 was thus about 50€ million, and the Motor is expected to be in place for 20 years.

Key EU Legislation:

  • Extraction of minerals through marine dredging falls into Annex II of the EIA Directive (codified as Directive 2011/92/EU): 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, it is often requires 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 Habitats Directive (92/43/EEC).
  • The Directive on Maritime Spatial Planning (2014/89/EU) 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

1-5 years.

Life Time

Nourishment of beaches can remain in place for intervals that vary from 2 to 10 years.

Reference information

Websites:
Source:
Fact sheet provided by the OURCOAST II Project.

Keywords

Beach nourishment, dredging, replacement, sand, shoreface

Sectors

Coastal areas, Disaster Risk Reduction

Climate impacts

Flooding, Sea Level Rise, Storms

Governance level

Local (e.g. city or municipal level)
Sub National Regions

Geographic characterisation

Global

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