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Berlin Environmental Atlas

01.02 Impervious Soil Coverage (Sealing of Soil Surface) (Edition 2012)

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Calculation of Degrees of Impervious Coverage

The goal of the impervious-coverage mapping process is the derivation of the degrees of impervious coverage at block level. The absolute and relative section information was calculated. Three degrees of impervious coverage (IC) were distinguished:

  • IC "Built-up impervious sections" (calculated from the Automated Map of Properties/ ALK data),
  • IC "Non-built-up impervious sections (calculated from satellite data),
  • IC Total (sum of the above).

For the calculations, the results of the pixel-based satellite-image classification were collated with the areas from the block map ISU 5.
First, a summation by category of degree of impervious and block area was carried out. Thus, the grid data of the classification system was no longer necessary for further analyses.

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

  • Built-up areas (from the ALK),
  • 12 categories of degrees of impervious coverage - for non-built-up areas (corresponding to the 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 respective question at issue. 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 using ISU data or BWB data. The shaded areas were evaluated depending on section type. For section types with predominantly residential use and adequate BWB data, the latter were used for the classification of the shaded areas. For all other section types, shaded areas were classified in accordance with their block-specific surroundings.

Evaluation of Built-Up and Non-Built-Up Impervious Sections in the Category "Allotment Gardens"

For the category "Allotment Gardens," the data on impervious soil coverage usually showed only the overall degree of impervious coverage. Since the ALK mapped no summer cottages and hardly any functional buildings, the non-built-up impervious areas could only rarely be distinguished from the built-up impervious areas. Therefore, the degree of impervious coverage was ascertained almost entirely via satellite-image evaluation.
For this impervious-coverage map, the differentiation between built-up and non-built-up areas was carried out with the help of average values from the Department of Urban Development and the Environment, Section I C, Allotment Gardens. 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 Correction Factors

For the further improvement in the mapping results, so-called correction factors were used. The BWB data on impervious soil coverage was used for this purpose. The principle of section-type-referenced corrections is based on the following well-founded assumptions:

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

Due to topicality, overlap problems, differing definitions of impervious coverage, and gaps in impervious coverage ascertainment of some types by the BWB, correction factors could be calculated only for 5 section types (cf. Table 3).
Correction factors were only used on the non-built-up areas.

Tab. 3: Correction Factor by Section Type
  Section type
(TYPE)
BWB-Data
impervious
non-built-up area
[sq. m]
Classification result
impervious
non-built-up area
[sq. m]
Correction-
factor
21 Mixed village type 447,806 598,469 0.75
22 Row houses and duplexes with gardens 830,718 1,315,616 0.63
23 Single-family homes with gardens 4,129,760 6,349,315 0.65
24 Villas and townhouses with park-like gardens 1,353,980 1,411,935 0.96
25 Densification in single-family home areas Gardens, semi-private green space 1,133,823 1,367,805 0.83
Tab. 3: Correction Factor by Section Type

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

Adoption of the Surface Types from 2001

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

Table 4
[approx. 20 KB size]

Tab. 4: Impervious Coverage Classes in Non-built-up Impervious Areas

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

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