Imperviousness and imperviousness change

Indicator Assessment
Prod-ID: IND-368-en
Also known as: LSI 002
Created 21 May 2015 Published 05 Apr 2016 Last modified 13 May 2016, 03:54 PM
Between 2006 and 2009, soil sealing, or imperviousness, increased in all EEA-39 countries by a total of 4 364 k m 2 . This corresponds to an annual average increase of 1 454 k m 2 , or 0.027 % of the total EEA-39 area. During this period, the rate of increase in soil sealing relative to country area varied from 0.001 % to 0.48 %. In 2009, the percentage of a countries' total area that was sealed also varied greatly, with values ranging from 0.15 % to 15.23 %. The highest sealing values, as a percentage of country area, occurred in small countries with high population densities, while the lowest sealing values could be found in large countries with low population densities. The most problematic situation occurs in countries where there is already a high percentage of sealing and where the annual rate of increase relative to country area is high.

Key messages

Between 2006 and 2009, soil sealing, or imperviousness, increased in all EEA-39 countries by a total of 4 364 km2. This corresponds to an annual average increase of 1 454 km2, or 0.027 % of the total EEA-39 area. During this period, the rate of increase in soil sealing relative to country area varied from 0.001 % to 0.48 %. In 2009, the percentage of a countries' total area that was sealed also varied greatly, with values ranging from 0.15 % to 15.23 %. The highest sealing values, as a percentage of country area, occurred in small countries with high population densities, while the lowest sealing values could be found in large countries with low population densities.

The most problematic situation occurs in countries where there is already a high percentage of sealing and where the annual rate of increase relative to country area is high.

What are the extent, degree, dynamics and spatial pattern of surface sealing (imperviousness) in Europe?

Percentage soil sealing by country

Bar chart
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Table
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Imperviousness density in 2009

Note: The map shows the density of soil sealing in 2009, based on a 10 km2 reference grid. Green and light orange colors show areas with no or very limited sealing, while red and dark red colors show highly to fully sealed grid cells (mainly urban areas).

Data source:
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Annual change in soil sealing between 2006 and 2009, relative to sealed area in 2006

Bar chart
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Table
Data sources: Explore chart interactively

Annual average increase in soil sealing, 2006-2009, relative to country area

Bar chart
Data sources: Explore chart interactively
Table
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Average annual increase in soil sealing (imperviousness indicator)

Note: The map shows the yearly average imperviousness density change, relative to 10 km grid cells. The unit is the average percentage of newly sealed 10 km cells between 2006 and 2009.

Data source:
Downloads and more info

Between 2006 and 2009, the extent of soil sealing in the EEA-39 countries increased by 4 364 km2 to a total area of 112 614 km2 (or 1.9 % of the EEA-39 area), according to imperviousness data. This corresponds to an annual average increase of 1 454 km2, or 0.027 % of the total EEA-39 area.

Percentage of country area sealed: While on average, 1.85 % of the total area covered by the countries was sealed in 2006, this increased to 1.93 % in 2009. See Figure 1 for a comparison of country averages between 2006 and 2009 and Figure 2 for a map of sealing density in 2009, based on a 10 km grid.

In 2009, three groups of countries could be identified: 
a) Countries with very low sealed area as a percentage of total area (i.e. <1.0 %), e.g. Iceland (0.15 %), Norway (0.3 %), Sweden (0.5 %) and six other countries. 
b) Countries with medium high sealing values between 1.0 % and 3.0 %. There are 18 such countries.
c) A considerable number of countries with high sealing values between 3.0 % and 15.2 %. There are 12 such countries, including Germany (5.1 %), Liechtenstein (6.2 %), Belgium (7.4 %), the Netherlands (8.2 %) and Malta (15.2 %). See figure 1.

A more detailed spatial pattern of existing sealing in 2009, based on 10 km grid cells, can be seen in Figure 2. The main urban areas that have grid cells with high sealing levels are shown in dark red, while green areas represent grid cells without any sealing detected in the 2009 imperviousness product.

Percentage increase in sealing: Sealing increased in all countries between 2006 and 2009. The average percentage annual increase for the period was 1.35 % across the EEA-39, with annual values ranging from 0.53 % for the United Kingdom to 4.84 % for Norway. See Figure 3 for yearly increases by country. However, it should be noted that in countries with little relative and absolute sealing (e.g. Norway), even relatively modest (absolute) increases create high change rates.

Given that the imperviousness indicator does not capture land cover flows, it is not possible to monitor directly which land cover is mainly affected by an increase in sealing. The indicator can, however, be used together with Corine Land Cover (CLC) to establish in more detail which land cover strata are mainly affected by sealing increases.

On average, most of the sealing increases between 2006 and 2009 occurred in the CLC classes listed below. Most of the changes occurred in just a few of the CLC classes (the first four CLC classes listed below cover some 67 % of the total increase).

Percentage annual increase in sealing area (2006-2009) relative to country area (imperviousness indicator):

The imperviousness indicator shows that, on average, the annual rate of increase amounted to 0.027 % of the total EEA-39 area for the 2006-2009 period. The annual percentage increase in sealing relative to country area ranges from 0.001 % in Iceland to values above 0.1 % for Cyprus, Lithuania and Malta. See Figure 4 for a graph with results by country, and Figure 5 for a map with indicator results based on a 10 km grid.

CLC classes with the highest increase of imperviousness total area:

112 Discontinuous urban fabric (120 042 ha)

211 Non-irrigated arable land (85 829 ha)

242 Complex cultivation patterns (50 769 ha)

121 Industrial or commercial units (38 141 ha)

231 Pastures (19 653 ha)

243 Land principally occupied by agriculture, with significant areas of natural vegetation (16 439 ha)

 

CLC classes where highest share (percentage of area) is lost to imperviousness:

133 Construction sites (5.13%)

121 Industrial or commercial units (1.61%)

111 Continuous urban fabric (1.13%)

123 Port areas (1.01%)

122 Road and rail network and associated land (1.00%)

112 Discontinuous urban fabric (0.79%)


Indicator specification and metadata

Indicator definition

The imperviousness indicator is defined as the yearly average imperviousness change between two reference years, as measured by imperviousness change products. The change is aggregated for a certain reference unit, and expressed and relative to the size of said unit (as a percentage). The imperviousness change value for a 100 m raster cell is based on 100 m imperviousness change products, corresponding to the difference in imperviousness status values (e.g. IMD2009-IMD2006). The default reference unit is the country, but the indicator can be aggregated based on different spatial units. For example, for a certain country, an imperviousness indicator value of 0.2 %, means that an additional 0.2 % of this country's area has been sealed annually during the period between the two reference years in question. If above a certain rate of increase (threshold values), this value can be used as a warning sign. The aggregation of imperviousness values to reference units is performed using the LEAC CUBE method.

Units

The unit used for this indicator is the yearly average percentage change in imperviousness relative to the size of the reference unit. This was initially based on the total difference over the three reference years (2006-2009) divided by three, but it will be possible to calculate the indicator for different periods at a later stage (e.g. 2006-2012). It is important to note that the yearly average value is based specifically on the period 2006-2009.


Policy context and targets

Context description

The main policy 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 uses.

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 EU level, the 7th Environment Action Programme (7th EAP) includes a strong focus on unsustainable use of land and soil, including explicitly the issue of soil sealing. In this context the 7th EAP refers to a Commission Staff Working Document with the title "Guidelines on best practice to limit, mitigate or compensate soil sealing" (SWD/2012/0101).
In addition, land take is explicitly mentioned in chapter 23 of the 7th EAP, stating that "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."

In recognition of the importance of land in safeguarding natural resources, the Commission is considering a Communication on land as a resource.

Other important references can be found in 'A Sustainable Europe for a Better World: A European Union Strategy for Sustainable Development' (COM(2001)264) and the thematic documents related to it, such as the Commission Communication 'Towards a Thematic Strategy on the Urban Environment' (COM(2004)60), Cohesion Policy and Cities: the urban contribution to growth and jobs in the regions (COM(2006)385), Europe 2020 (COM(2010)2020), general provisions on the European Regional Development Fund, the European Social Fund and the Cohesion Fund Council Regulation (EC) No 1083/2006, as well as the concept of territorial cohesion.

Targets

Although, there are no quantitative targets for soil sealing/imperviousness at European level, different documents reflect the need for better planning to control urban growth and the extension of infrastructures. Policies relating explicitly to land-use issues, and especially physical and spatial planning, have, until now, generally been the responsibility of the authorities in Member States. The European Commission's Roadmap to a Resource Efficient Europe (COM(2011) 571) introduces, for the first time, a 'no net land take by 2050' initiative that would imply that all new urbanisation will either occur on brownfields or that any new land take will need to be compensated by reclaiming artificial land.

European policy, although it has no spatial planning responsibility, sets the framing conditions for planning. At European level, the 1999 European Spatial Development Perspective (ESDP), a non-binding framework that aims to coordinate various European regional policy impacts, already advocates the development of a sustainable, polycentric and balanced urban system with compact cities and a strengthening of the partnerships between urban and rural areas; parity of access to infrastructure and knowledge; and wise 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. Its environmental advantages are clear: relieving pressure on rural areas and greenfield sites, reducing pollution costs, more efficient energy use and natural resource consumption, facilitating economic diversification and emerging habitat (housing) requirements. Europe has several examples of regional strategies for economic regeneration and brownfield development (The OECD Territorial Outlook 2001) and recycling of artificial surfaces in several countries reach 30 % or more compared to the total land take area (CORINE LC 2006 results). Stronger links between EU urban and soil policies could encourage this further (e.g. following up respective 6th EAP Thematic strategies).

Related policy documents

Methodology

Methodology for indicator calculation

  • The 100 m imperviousness change product, produced as a deliverable in the 2006 and 2009 (and future) updates, is the basis for this indicator. 
  • Although imperviousness changes included in the 100 m change product could be summarised directly to certain reference units, the calculation of the indicator is performed via ingesting 100 m imperviousness change values in the EEA LEAC cube in order to create harmonised results with other spatial indicators using a similar methodology. The LEAC cube allows the extraction of statistics based on a system of grid-cells with a 1 km side length (an area of 100 ha). 
  • Reference units, such as countries, NUTS3 regions etc. are already included in the LEAC cube as so called “dimensions” and are used for the statistical aggregation of imperviousness changes corresponding to required reference units.
  • Yearly average imperviousness change values are calculated by dividing the average imperviousness change values by the number of years between two status years.

Methodology for gap filling

  • Known gaps were caused by image-gaps (input Earth observation data missing) in both 2006 and 2009 data. For 2009 gaps, the available 2006 values were used for the 2009 status layer. The production of imperviousness status layers (including reanalysis of 2006 and 2009 layers) will minimise the appearance of gaps by including additional satellite imagery (e.g. Sentinel2, Landsat-8). Where there are image gaps, primary status layers show the true status, thus avoiding the copying of values from another reference year. 

Methodology references

No methodology references available.

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 only valid for the three-year reference period under consideration. Possible variation within the three year period (for individual years) is currently not captured.

Data sets uncertainty

  • The indicator is based directly on the mapping of soil sealing/imperviousness using Earth observation data of about 20 m spatial resolution. Real sealing will differ from the values derived in this way for various reasons:
    • The spatial resolution of the input imagery (20 m) means that very small sealed surfaces will 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 real sealing.
    • As with all Earth observation derived products, the data contains 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).
    • There are some known issues in the 2006 and 2009 imperviousness data sets, which will only be corrected as part of a full reprocessing procedure, coinciding with the production of the 2015 reference year. For example, an area of large (apparent) sealing increases in southern Spain is in reality caused by greenhouses in this area being included as sealed in 2009, but (by mistake) excluded in 2006.
    • Where cloud gaps in 2009 were present, sealing values for 2006 were used in the 2009 product. This means that sealing increase for these areas is likely to be underestimated. This gap-filling will not be supported in 2015 and later updates (see section on "methodology for gap filling")
    • For imperviousness/soil sealing products, the term “reference year” must currently be understood to comprise a maximum of three years (the year before the reference year, the actual reference year, and the year after the reference year for gap-filling). This means that the Earth observation data used to produce the “2009 reference year” are, in reality, a mix of 2008, 2009 and 2010 acquisitions. This situation is likely to improve (imagery are more likely to come from one single year) with the future availability of new sensors, such as Sentinel2.

Rationale uncertainty

No uncertainty has been specified

Data sources

Generic metadata

Topics:

Land use Land use (Primary topic)

Soil Soil

Urban environment Urban environment

Tags:
imperviousness | imperviousness indicator | soil sealing | imd change
DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • LSI 002
Dynamic
Temporal coverage:
2006-2009
Geographic coverage:
Albania, Austria, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Kosovo, Latvia, Liechtenstein, Lithuania, Luxembourg, Macedonia, Malta, Montenegro, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, United Kingdom

Contacts and ownership

EEA Contact Info

Tobias Langanke

EEA Management Plan

2015 1.8.2 (note: EEA internal system)

Dates

Frequency of updates

Updates are scheduled every 3 years
European Environment Agency (EEA)
Kongens Nytorv 6
1050 Copenhagen K
Denmark
Phone: +45 3336 7100