Imperviousness and imperviousness change in Europe

Assessment versions

Published (reviewed and quality assured)

• No published assessments

Rationale

Justification for indicator selection

Environmental relevance

Data and indicators on the extent of, and change in, soil sealing or imperviousness (used synonymously) are important for a number of highly relevant policy issues. Imperviousness is defined as the covering of the soil surface with impervious materials as a result of urban development and infrastructure construction (buildings, constructions and layers of completely or partially impermeable artificial material (e.g. asphalt, metal, glass, plastic or concrete).

Changes in imperviousness can indicate land use intensification or land cover/land use change due to urban or industrial development and related increases in traffic infrastructure. All these changes have potentially significant implications for biodiversity, soil functions (including carbon storage and sequestration), hydrological properties, provision of ecosystem services and nature conservation. In particular, exchanges of energy, water and gases are restricted and pressure on adjacent, non-sealed areas is increased. Until recently, the only European data set available to indirectly document changes in imperviousness was the Corine Land Cover (CLC) data set. However, the associated ‘land take’ indicator covers a lot of surface area that is not actually sealed. The imperviousness indicator supplements this indicator on land take by providing information with higher spatial resolution, based on a more direct measurement of imperviousness, and with more frequent updates.

Scientific references

• Assessment of Soil Sealing Management Responses, Strategies, and Targets Toward Ecologically Sustainable Urban Land Use Management Artmann, M., 2014.  AMBIO, 43:530-541. DOI 10.1007/s13280-014-0511-1
• The anthropogenic sealing of soils in urban areas Scalenghe, R. and Marsan, F.A., 2008. Landscape and Urban Planning, V.90, Issues 1-2, p.1-10. DOI: 10.1016/j.landurbplan.2008.10.011
• Soils: Basic Concepts and Future Challenges Bouma, J., 2006. Soil functions and land use. In: G. Certini, R. Scalenghe (Eds.), Cambridge University Press, Cambridge, EU (2006), pp. 211–221
• Urban sprawl in Europe European Environment Agency (2006): Urban Sprawl. The ignored challenge. EEA Report 10/2006. ISSN 1725-9177
• Identification and quantification of the hydrological impacts of imperviousness in urban catchments: A review Jacobson, C.R., 2011. Journal of Environmental Management, Volume 92, Issue 6, 1438-1448. doi:10.1016/j.jenvman.2011.01.018 
• Overview of best practices for limiting soil sealing or mitigating its effects in EU-27 Prokop, G., Jobstmann, H., & Schönbauer, A. (2011). Overview of best practices for limiting soil sealing or mitigating its effects in EU-27. European Communities, 227. Broken link: http://ec.europa.eu/environment/archives/soil/pdf/sealing/Soil%2520sealing%2520-%2520Final%2520Report.pdf
• Progress in Physical Geography: Earth and Environment Sutton, P.C., Anderson, S.J., Elvidge, C.D. (2009) Paving the planet: impervious surface as proxy measure of the human ecological footprint. Progress in Physical Geography. 33: 510-527.
• Place Based Territorially Sensitive and Integrated Approach Zaucha, J. and Świątek, D. (2013), Place Based Territorially Sensitive and Integrated Approach Broken link: http://www.stfk.no/Documents/Nering/Kysten%20er%20klar/Report_place-based_approach_29_03_2013.pdf

Indicator definition

This indicator measures the covering of the soil surface with non-permeable materials, hence indicating imperviousness. The aggregation of imperviousness values to reference units, such as urban areas, floodplains, coastal zones or protected areas is performed using the integrated spatial data platform of the EEA.

Units

The unit used for this indicator is the percentage and km² of imperviousness surfaces relative to the size of the reference unit. 

Policy context and targets

Context description

The main policy-relevant objective of this indicator is to measure the extent and dynamics (change) of soil sealing, resulting from the development of urban and other artificial land.

At the United Nations Conference on Sustainable Development held in Rio in 2012 (Rio+20), world leaders identified land and soil degradation as a global problem and committed to ‘strive to achieve a land degradation-neutral world in the context of sustainable development’. At the EU level, the Seventh Environment Action Programme (7th EAP) includes a strong focus on the unsustainable use of land and soil, including the issue of soil sealing explicitly (EU, 2013a). In this context, the 7th EAP refers to the Commission Staff Working Document ‘Guidelines on best practice to limit, mitigate or compensate soil sealing’ (EC, 2012).

In addition, land take is explicitly mentioned in Chapter 23 of the 7th EAP:

‘Every year more than 1,000 km² of land are taken for housing, industry, transport or recreational purposes. Such long-term changes are difficult or costly to reverse, and nearly always involve trade-offs between various social, economic and environmental needs. Environmental considerations including water protection and biodiversity conservation should be integrated into planning decisions relating to land use so that they are made more sustainable, with a view to making progress towards the objective of 'no net land take', by 2050’ (EU, 2013a).

In recognition of the importance of land in safeguarding natural resources, the Commission is considering publishing a communication on ‘land as a resource’.

Other important references can be found in the Communication from the Commission ‘A sustainable Europe for a better world: a European Union strategy for sustainable development’(EC, 2001) and the thematic documents related to it, such as EC (2004, 2006, 2010) and EU (EU, 2013b), as well as the concept of territorial cohesion.

Targets

Although there are no quantitative targets for soil sealing/imperviousness at EU level, different documents reflect the need for better planning to control urban growth and the extension of infrastructure. Policies relating explicitly to land use issues, and especially physical and spatial planning, have, until now, generally been the responsibility of authorities in individual Member States. The European Commission’s roadmap to a resource efficient Europe (EC, 2011) introduced, for the first time, a ‘no net land take by 2050’ initiative that aims to ensure that either all new urbanisation occurs on brownfields or any new land take is compensated for by reclaiming artificial land.

EU policy, although not establishing requirements for spatial planning directly, provides a framework for planning. At the EU level, the 1999 European Spatial Development Perspective (ESDP) (EC, 1999), a non-binding framework that aims to coordinate various European regional policy impacts, advocates the development of a sustainable, polycentric and balanced urban system with compact cities and the strengthening of partnerships between urban and rural areas, as well as parity of access to infrastructure and knowledge, and evidence-based management of natural areas and cultural heritage. The 2008 Green Paper on territorial cohesion and the 2007 EU territorial agenda and action plan by the Territorial Agenda of the EU and the action programme for its implementation (COPTA, 2007) build further on the ESDP. Specific, relevant actions in the field of land in particular are Action 2.1d ‘Urban sprawl’ and Action 2.2 ‘Territorial impact of EU policies’.

Demand for new urban areas may be partly satisfied by brownfield remediation. The environmental advantages of this are clear: relieving pressure on rural areas and greenfield sites, reducing pollution costs, enabling more efficient energy use and natural resource consumption, and facilitating economic diversification and emerging habitat (housing) requirements. There are several examples of European regional strategies for economic regeneration and brownfield development (The OECD Territorial Outlook 2001). On average, land recycling increased steadily between 1990 and 2012 on an annual basis, with considerable variation between and within countries. Stronger links between EU urban and soil policies could encourage this further (e.g. following up relevant 6th EAP thematic strategies).

Related policy documents

• COM(2010) 2020 final, Europe 2020: A strategy for smart, sustainable and inclusive growth
  European Commission, 2010. Europe 2020: A strategy for smart, sustainable and inclusive growth. COM(2010) 2020 final. 
• European Spatial Development Perspective (ESDP)
  European Spatial Development Perspective (ESDP). Towards Balanced and Sustainable Development of the Territory of the European Union. Informal Council of Ministers responsible for Spatial Planning in Potsdam, May 1999.
• General Union Environment Action Programme to 2020 - Living well, within the limits of the planet
  7th EAP. ISBN 978-92-79-34724-5 doi:10.2779/66315
• Guidelines on best practice to limit, mitigate or compensate soil sealing
  Commission Staff Working Document SWD (2012) 101
• Roadmap to a Resource Efficient Europe COM(2011) 571
  Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions. Roadmap to a Resource Efficient Europe.  COM(2011) 571  

Methodology

Methodology for indicator calculation

• The 100-m imperviousness product of 2018, aggregated from the 10-m 2018 imperviousness data set for analytical performance, is the basis for this indicator.
• The calculation used to obtain the data presented in the indicator is performed by ingesting the 100-m imperviousness data set into the EEA’s integrated data platform to create harmonised results with other indicators based on spatial data sets and using a similar methodology.
• The data cube approach used for the data platform enables the extraction of statistics based on a system of grid cells with a side length of 100 m (an area of 100 ha).
• Statistics are calculated in the data cube as regional aggregates, such as NUTS-0 to NUTS-3, land cover classes, protected areas, floodplains and coastal zones.
• All data sets used for the aggregation are registered in the EEA’s Spatial Data Infrastructure (SDI) under the reference layers node of the integrated data platform: https://sdi.eea.europa.eu/catalogue/idp/eng/catalog.search#/home 

Methodology for gap filling

No gaps.

Methodology references

No methodology references available.

Data specifications

EEA data references

• Copernicus aggregated Imperviousness change information 2009-2012 provided by European Environment Agency (EEA)
• Copernicus Land Monitoring Service - High Resolution Layers - Imperviousness provided by European Union

Data sources in latest figures

Uncertainties

Methodology uncertainty

The methodology for deriving the indicator is simple and introduces very little uncertainty. However, it needs to be fully understood that the yearly averages are valid for only the 3-year reference period under consideration. Possible variation within the 3-year period (for individual years) is currently not captured.

Data sets uncertainty

This indicator is based directly on the mapping of soil sealing/imperviousness using Earth observation data at about 10-m spatial resolution. Real sealing will differ from the values derived in this way for various reasons:
• The spatial resolution of the input imagery means that very small sealed surfaces will sometimes not be captured, e.g. small buildings and small paved roads, and other sealed surfaces with a very small footprint. This can lead to an underestimation of sealing.
• As with all Earth observation-derived products, the data contain omission errors (sealed surfaces not detected) and commission errors (areas wrongly classified as sealed). The distribution of these errors depends on the quality of the input data, calibration during production and local differences in spectral contrast (which makes sealing in some locations ‘easier’ to detect than in other locations, depending on the context).

Rationale uncertainty

No uncertainty has been identified.