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Berlin Environmental Atlas

01.02 Impervious Soil Coverage (Sealing of Soil Surface) (Edition 2017)

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Calculation of Degrees of Impervious Coverage at Block and Block Segment Level

The goal of the impervious-coverage mapping process is the derivation of the degrees of impervious coverage at block and block segment level in absolute and relative area numbers. Three degrees of impervious coverage (IC) were distinguished:

  1. IC - built-up impervious area (calculated from building data),
  2. IC - non-built-up impervious area (calculated from satellite data),
  3. IC - total (sum of 1 and 2)

For the calculations, the results of the pixel-based satellite-image classification were collated with the areas from the ISU5 block map 2015.

First, a summation by category of degree of impervious coverage and block (segment) area was carried out. Thus, the grid data of the classification system was no longer necessary for further analyses.

There were thus 15 area-referenced statements in sq. m. for each block and block segment:

  • Built-up area (from building data),
  • 12 categories of degrees of impervious coverage of the non-built-up area (corresponding to NDVI categories),
  • Track-gravel areas (optionally either 0 % or 100 % impervious), and
  • Shaded area (unclassified).

For the further improvement in the mapping results, the following additional calculations were carried out.

Optional Assignment of an Impervious-Coverage Value to Track-Gravel Areas

The class "Track gravel" has been maintained as a data field of its own, and can optionally be included in the calculations either as an impervious non-built-up (100 %) or pervious built-up area (0 %). This ensures the different evaluation of gravel according to the subject matter at hand. In the map shown, track gravel is considered 100 % impervious.

Classification of Shaded Areas

Shaded areas have been assigned impervious-coverage values at block level in a follow-up classification procedure at block (segment) area level using ISU or BWB data.

For this, the shaded areas were analyzed depending on area type. For area types with predominantly residential use and adequate BWB data, the latter was used for the classification of the shaded areas. For all other area types, shaded areas were classified in accordance with their block-specific surroundings.

Evaluation of Built-Up and Non-Built-Up Impervious Areas in the Category "Allotment Garden"

Due to the improved data base for buildings, it was possible to record the built-up impervious area share more accurately than was the case still for the 2005 and 2011 mappings. However, as there are still gaps in the building data, especially in this category, e.g. due to unmapped cottages and sheds, shares of the non-built-up impervious area were also counted as part of the built-up area in the current impervious coverage mapping, based on the mean values laid down in the Bundeskleingartengesetz (Federal Allotment Garden Law) and those specific to Berlin (SenStadtUm, I C 2009). A degree of impervious coverage for built-up areas of 9.6 % for West Berlin and 8.6 % for East Berlin was assumed.

Application of Corrective Factors

To further improve the mapping results, so-called corrective factors were employed. The BWB data on impervious soil coverage was used for this purpose. The principle of area-type-referenced corrections is based on the following well-founded assumptions:

  • the BWB data was still largely up-to-date at the time corrective factors were developed,
  • the BWB data was adequately precise, due to the ascertainment methods (terrestrial inspection, aerial-image interpretation, building-owner information),
  • the one-time calculation of corrective factors makes them transferable to future evaluations, since they describe systematic trends in a city-wide comparison.

Due to a lack of topicality, overlap problems, differing definitions of impervious coverage, and gaps in impervious coverage ascertainment of some use types by the BWB, corrective factors could be calculated only for 5 area types (cf. Table 3).

Corrective factors were only applied to non-built-up areas.

Tab. 3:Corrective factor by area type
  Area type
(TYPE)
BWB data
non-built up area
impervious
[sq. m.]
Classification result
non-built area
impervious
2005 [sq. m]
Corrective factor
21 Village-like mixed development 447,806 598,469 0.75
22 Row houses and duplexes with yards 830,718 1,315,616 0.63
23 Detached single-family homes with yards 4,129,760 6,349,315 0.65
24 Villas and town villas with park-like gardens 1,353,980 1,411,935 0.96
25 Densification in single-family home area, mixed development with yard and semi-private greening 1,133,823 1,367,805 0.83
Tab. 3: Corrective factor by area type

Excel
[Table is also available as Excel-File (MS-Excel is required).]

Adoption of the Pavement Types from 2001

The pavement types of the non-built-up impervious block segments (walkways, courtyard areas etc.) were grouped into four pavement-type classes, from concrete to grass trellis stones. Their respective distribution was investigated via selected test areas, and the results transferred to all areas of the same area type. The type-specific pavement type distribution was not updated for the current map, but is based on a survey from 1988 (AGU Arbeitsgemeinschaft Umweltplanung (Environmental Planning Working Group) 1988). The pavement types are not shown on the map; however, they can be shown in the Geoportal via the factual data display by block (segment) area.


Tab. 4: Pavement classes in non-built-up impervious areas by area type (Goedecke & Gerstenberg 2013)


Excel
[Table is also available as Excel-File (MS-Excel is required).]

Degrees of Impervious Coverage of Roads

The degree of impervious coverage of roads is based on the evaluation of road statistics from the Senate Department for Urban Development and the Environment, Grundsatzangelegenheiten der Straßenbautechnik und der Straßenerhaltung, Tabelle Fahrbahndecken und Beläge der Straßen und Gehwege in der Baulast Berlins (Policy matters of road construction technology and road maintenance, table of road surfaces and pavement types of roads and walkways subject to maintenance by Berlin) (as of January 1, 2016), covering 8,950 ha of roads excluding motorways (SenStadtUm 2016b). The data for these statistics is available for each borough. The degree of impervious coverage per borough resulting from these statistics was assumed to be valid for all road areas within the respective boroughs.

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