Home Database Adaptation options Raising and advancing coastal land
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Adaptation option

Raising and advancing coastal land

For centuries, coastal communities have used rocks and soil to raise coastal land as a defence against storms and rising sea levels. Similarly, coastal advance has a long history around the world, especially in densely populated areas, with a limited land extension. 

In major coastal cities, raising and extending coastal land have been especially targeted at the creation of new port and harbour areas and safer urban embankments. In natural areas, coastal advance can be favoured by planting vegetation with the specific intention to support natural accretion of land and surrounding low areas. Coastal advance can also include the extension of beaches beyond the natural coastline, reducing coastal risks for the hinterland. In this case, beach advance differs from beach nourishment that is aimed to compensate shore erosion by artificial placement of sand, maintaining the pre-existing beach width.  

A historical example of raising coastal land can be seen in the Wadden Sea coast and barrier islands (now part of Denmark, Germany and Netherlands): here, small settlements were built on small man-made hills, called warften in German and tierpen or wierden in Dutch, to protect against storm surges. The first artificial hills identified date to the Bronze Age. Some hills were still used in the 1800s, by which time the construction of dikes had largely replaced this form of coastal protection. Many of these mounds remain and some are heritage sites. In more recent times, some examples of raising and advancing coastal land can be found in urban areas: 

  • Bilbao (Spain), as part of an urban regeneration project, where the surface of Zorrotzaurre peninsula was planned to be elevated by 1.5 meters, so that new buildings can be constructed on a higher and safer level.  
  • Venice, within the integrated system for the protection of the city and its lagoon against flooding. Mobile barriers operating at the three lagoon outlets to safeguard the city from flooding, are integrated with local defence measures. These measures are aimed at increasing the elevation of embankments and pavements of lower areas of urban settlements located in the lagoon and in the littorals. Where possible, embankments and streets were raised up to the designated protection height of 110 cm above the local reference sea level. This measure significantly reduces the number of tides that cover the street. About 12% of the city is still located below the safeguard level of 110 cm, including the iconic and low-lying St. Mark’s Square. A much wider and articulated design to protect the entire square and the surrounding area has been conceived (including the elevation of urban pavements as well as on the reorganisation of the entire sewage and drainage system). 

Other examples pertain to port areas: 

  • The Port of Rotterdam, largely built outside the flood defence system of the city and in open connection to the North Sea. Though areas are currently well protected against flooding and already built well above mean sea level, preventive adaptation strategies  are under assessment by the Port Authority in collaboration with local governmental institutions and private companies. Adaptation strategies include further raising of ground level and placing valuable assets on raised construction. 
  • Biomass fuel supply chain in United Kingdom, by structurally raising power plant equipment above potential storm surge water levels, to ensure energy provision without interruption in the long term also in adverse conditions.  

Raising and advancing coastal land are generally part of broader intervention plans to protect coasts, cities and valuable infrastructures from flooding. Plans can include other grey (seawalls, breakwaters, storm surge gates/flood barriers) or green adaptation measures (dune construction and strengthening, restoration and management of coastal wetland). Higher elevation areas can also be required when the existing defences do not ensure adequate protection from flooding, for example due to dike or seawall overtopping of storm surges. 

The implementation of this adaptation option should be coordinated at upper levels of government and integrated in holistic coastal management plans (Adaptation of integrated coastal management plans), to ensure that the associated costs do not preclude the implementation of other, more relevant measures.  

To be effective in the long term, interventions of raising and advancing coastal land should be planned taking into considerations climate change scenarios, especially local projections of relative sea level rise and of the frequency and intensity of storms and storm surges. 

Whenever coastal advance is expected to subtract natural areas and cause biodiversity loss, damaging natural ecosystem, it should be carefully considered by assessing the full scope of the intended measures in terms of time and space and preferably avoided. Advancing coastal land can require other physical protection measures. Indeed, the new gained land or the raised land can be exposed to flooding in the long term, due to sea level rise and to more frequent storm surges.  

In past centuries, land reclamation through filling of wetland and near-shore areas below the high-tide level had become another commonly used technique to gain new space, also to build new urban or industrial sites. Such practice, highly transforming coastal ecosystems, causing loss of biodiversity and increasing long- term vulnerability to flooding, is not included in this adaptation option.  

Additional Details
Reference information

Adaptation Details

IPCC categories

Structural and physical: Engineering and built environment options

Stakeholder participation

Stakeholder participation is especially required if raising or advancing coastal land is part of larger coastal plans. Such plans that include defence structures might be the subject of Environmental Impact Assessment, depending on national laws and regulation. When this measure is implemented in protected sites such as Natura 2000 sites (under the EU Birds and Habitat Directives), claiming new natural land, an “appropriate assessment” that necessarily involve stakeholders in a structured public participation process, is usually required. Similarly, the EU Floods Directive calls for public participation processes for risk management plans. Moreover, proposals to raise urban land will most likely require public consultation under national and local laws. 

Conflicts can arise between stakeholders that can directly or indirectly benefit from coastal raising or advance. Tourism stakeholders and port authorities can benefit from beach extension and construction of new harbour areas respectively. Conversely, local communities can be worried about modification of the coastal landscape, habitat and biodiversity loss and environmental impacts in general. Such conflicts call for an active involvement of all interested actors, including local authorities, coastal communities, private companies, research institutions and/or NGOs. 

Success and Limiting Factors

Like other grey measures for coastal defence, raising and advancing coastal land can provide predictable levels of safety. If the entire land area is raised above the highest projected sea level, only low residual risks still exist. Moreover, compared to other hard protection measures (such as seawalls and storm surge barriers), there is no risk of catastrophic failure. With projected increases in coastal zone populations, gaining new land can be a leverage for the advance or raising of coastal areas, providing new opportunities of coastal development.  

As other grey options, raising and advancing coastal land is poorly flexible and requires periodical maintenance or upgrade to ensure adequate protection level in the face of climate change and progressive sea level rise. Raising coastal land can be technically challenging, especially in urban and industrial areas hosting complex or highly vulnerable infrastructures. This is also the case for fragile historical areas, such as St. Mark’s Square and the whole city of Venice. In these cases, raising land is possible only till a certain level and technical constrains of different nature (e.g. the preservation of the artistic value of historical buildings) can prevail. 

Advancing coastal land can alter coastal ecosystems. It can also require other seaward physical preventive measures against flooding, with associated construction and maintenance costs, and impacts (e.g. alteration of coastal solid transport). This option is especially suited for small-scale interventions (e.g. to reduce the vulnerability of small ports or urban areas or of specific equipment to be put on safer areas). Raising or advancing large coastal areas can require disproportionate costs, be technically challenging and cause several environmental impacts. 

 

Costs and Benefits

The main benefit associated to this option is the reduction of flooding, especially for areas or infrastructures affected by sea level rise and increasing frequency of storm surge events. It ensures full protection of the area at predictable safety levels without risks of failure sometimes associated to other grey protection measures. By creating new usable land, raising or advancing coastal areas can help preserving key economic activities (e.g. safe port areas), expanding land usability by citizens (elevation of urban pavements) and enhancing tourism and recreational activities (beach extension). 

The costs greatly depend on the specific location, the adaptation needs and the extension of the areas to be raised. Cost can also include the requirement for hard protection measures to defend reclaimed land from coastal flooding and erosion. Cost assessments should properly include both the construction phase and maintenance cost. The latter can progressively increase considering the increasing pressure from sea level rise and storminess. Synergies with other defence works already in place should be maximised to reduce the costs associated to this adaptation option, extend its effectiveness and increase the overall resilience of coastal areas. Synergies can also be created with dredging interventions: raising or advancing land can offer an opportunity for material disposal from ports, harbours and navigation channels (after proper assessment of contamination level). This could reduce the overall cost and eliminate the need to identify offshore disposal sites for dredged material. 

The construction of coastal works to mitigate erosion and hard sea defences ‘capable of altering the coast’ fall into Annex II of the Environmental Impact Directive (EIA): 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. However, this requirement does not affect the maintenance and reconstruction of these works. 

Under the EU Habitats Directive, an appropriate assessment will be needed if works to raise or advance coastal land affect protected species or natural habitats.

Implementation Time

Implementation time is highly variable, depending on the scale of the intervention. Small-scale interventions involving limited areas can require limited time (< 1 year), while large-scale interventions, raising wide coastal areas, as part of broader intervention plans, can require much more time. Technical constrains related to the complexity, fragility and value of the urban system (and buildings) usually increase the implementation time. 

Life Time

A medium life time is expected for this option (more than 15 years). However, periodical maintenance and efficacy re-assessment must be ensured, especially to progressively adapt to the sea–level rise and the possible intensification of storms and storm surges. 

Reference information

References:

IPCC, (2019). Special report on the Ocean and the cryosphere in a changing climate. Chapter 4: Sea Level Rise and Implications for Low-Lying Islands, Coasts and Communities. 

UNEP-DHI (2016). Managing climate change hazards in coastal areas. The coastal hazard wheel decision-support system. United Nations Environment Programme & Lars Rosendahl Appelquist 

Published in Climate-ADAPT Jun 07 2016   -   Last Modified in Climate-ADAPT Dec 12 2023

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