Impervious Soil Coverage (Sealing of Soil Surface) 2005
In the map, the degree of impervious coverage, i.e. the coverage of the earth’s surface with impermeable materials, is represented in percent of the reference area (statistical block or block segment). Generally, the degree of impervious coverage declines from the center toward the outskirts, since the building structure toward the outskirts is less dense, and the outskirts areas are either completely undeveloped (forest or farmland), or characterized by detached homes. The exceptions to this are the traditional centers of boroughs like Spandau and Köpenick, which were separate cities prior to 1920. There, impervious coverage degree is about 60 %, and more than 90 % in their core areas. The large new development areas at the outskirts, such as Marzahn, Hellersdorf and Hohenschönhausen, or Gropiusstadt in Neukölln and the “Thermometer Estate” in Lichterfelde, are between 50 % and over 80 % impervious.
The following table shows the average degrees of impervious coverage and the mean precision levels per section type.
The highest overall degrees of impervious coverage are shown for the section types “Closed Courtyard” with 83 %, and “Airport” with 86 %. The lowest degrees of impervious coverage, with 0 % each, are listed for the section types “Forest” and “Farmland.”
For a better overview, the degrees of impervious coverage are also summarized for each land-use type (ISU categories). Residential areas have an average degree of impervious coverage of 38 %. The core areas have the highest mean degree of impervious coverage, with 77 %, while “Forest” and “Farmed fields” have the lowest.
The statistical blocks and partial blocks of Berlin (without streets and waters) are 27 % impervious, on the average. Of this, 13 % are on the impervious built-up areas, and 14 % on the impervious non-built-up areas. Including bodies of water and streets, Berlin is thus 32 % impervious. Of this, 11 % are on the impervious built-up area, and 21 % on the impervious non-built-up area. Berlin is thus one third impervious. The impervious area in turn consists of roughly equal parts of buildings, of streets, and of non-built-up impervious areas.
Impervious Coverage in the Boroughs
For the borough-referenced evaluation, the average degree of impervious coverage of the road surfaces was calculated. For this purpose, statistics on the pavement and road surfacing of Berlin’s streets, bicycle paths and sidewalks were evaluated (SenStadt 2006).
The borough with the lowest degree of impervious coverage is Treptow-Köpenick, with 21 %, while Kreuzberg-Friedrichshain and Mitte have the highest degrees, with 66 and 60 %, respectively. These two boroughs also have the highest shares of built-up areas, as a proportion of their total areas.
Data on Impervious Soil Coverage in 2005 Compared with 1990 and 2001
Due to different ascertainment methods, a direct comparison between the impervious coverage values of 2001 and 2005 is possible only to a limited degree. No change in the impervious area over the course of this period of time can be ascertained from these figures.
In 2001, the degree of impervious coverage in Berlin amounted to 34.7%, incl. streets and bodies of water. These data are to some extent based on evaluations of satellite images and other sources from the ‘80s (only in West Berlin). These mapping system were expanded to include East Berlin in 1990, and partially updated, in 2001 by means of aerial photography and topographical maps of the area. Here, use-specific flat values were assumed in some cases. Overall, the ascertainment methodology was non-uniform.
The current set of maps now provides a data set obtained according to a considerably improved methodology which is uniform and completely automated. The result is that the degree of impervious coverage in 2005 amounts to 31.8%, and is thus approx. 3% below the values of 2001. However, this does not under any circumstances imply any reduction in impervious area.
It is notable that the values ascertained for the impervious built-up area over the years are almost identical. This indicates that the old ascertainment methods yielded values that were quite good on the average, since the ALK survey in 2005 can be considered very precise.
For the non-built-up impervious areas, the picture is somewhat different. Here, the values ascertained have decreased by 3 percentage points compared with 2001. This may on the one hand be due to the fact that on the old maps, some green and open-space categories (e.g. Forest and Farmland) were assigned flat values for their non-built-up impervious portions, values which we today recognize as too high. Since these areas constitute a major share of the municipal area, the degree of impervious coverage was overestimated for the non-built-up impervious areas overall. On the other hand, due to the problems mentioned above regarding the interpretation of the satellite data, the non-built-up impervious areas were more likely to be underestimated under the new method. These assumptions are rather more plausible than the supposition that any reduction in impervious areas has actually taken place in the municipal area.
With regard to the ascertainment of impervious roadways, the roughly estimated values available in 1990 could be replaced by values from the Road-Building Authority only in 1997. These were used for the evaluations in 2001 and updated in 2005. A slight increase in the degree of impervious coverage caused by roadways, due to road-building measures, primarily in East Berlin, certainly seems plausible.
In case of a future repetition of the procedure, e.g. in the context of a monitoring process, the new method will now permit the ascertainment of changes relevant at the block level, and then their incorporation into a city-wide balance sheet.