Sealing of Soil Surface 1990



Sealing soil surfaces negatively affects the ecosystem and the human habitat. Ground surfaces will be considered sealed in this study when they are covered with impervious materials. Sealed surfaces can be divided into built-up and non-built-up sealed (impervious) surfaces, along with surfaces sealed by built-up structures which are either completely sealed by asphalt and concrete, or covered by materials of varying permeability. These are also defined as sealed, although some, such as grass trellis stones and widely-spaced cobblestones or flagstones, do allow a limited growth of vegetation and access of water into the soil.

The greatest effects of surface sealing are found in urban and metropolitan areas where large portions of total area are sealed. Continued development increases the degree of sealing. This is particularly true of Berlin. The reunification of Germany and the transfer of the government to the new capital has increased the demand for construction and the development of new property areas.

Effects of Surface Sealing

The following text describes the effects of surface sealing on climate, water, soil, plants, animals and the human habitat.

Sealing contributes to an urban climate. Air is warmed by the high heat storage capacity of buildings and asphalt streets. This reduces cooling in the night, especially during summer (cf. Fig. 1).

Fig. 1: Temperature Range above Various Surfaces

Fig. 1: Temperature Range above Various Surfaces

Relative humidity is decreased at the same time because vegetal surfaces and their cooling evaporation (evapotranspiration) are lacking (cf. Maps 04.04, 04.05, 04.06, 04.07 SenStadtUm 1993) (SenStadtUm – Berlin Department of Urban Development and Environmental Protection). This can produce extreme levels that considerably reduce human quality of life.

Non-sealed surfaces, such as parks, exert a great influence. Positive climate effects on human well being can be documented beginning with areas as small as 1 ha. Vegetal areas also influence dust and pollutants in the air, for the large surface area of leaves can bind dust and other air pollutants.

Sealing reduces surfaces available for infiltration (absorbing precipitation). This results in far-reaching changes in the water balance. Groundwater recharge (formation of new groundwater) necessary for the water supply, is reduced. Rain water on sealed surfaces is polluted by tire residue, dust and dog faeces. This polluted water is transported by sewers either directly into drainage canals or discharged by way of sewage plants (cf. Map 02.09 SenStadtUm 1992b). In urban areas with two-pipe drainage systems (separated rain water and sewage), rain water flows directly into surface waters. Small bodies of water are particularly affected by these loads of filth. In areas with combined rain water and sewer systems, heavy rainfall can overload the sewage drainage system or the pumping stations. Untreated mixed effluents can then also flow directly into surface waters. Increased sealing levels can also increase dangers of flooding in certain areas; this was a great influence in the collecting (catchment) area of the Panke River (Geiger 1992).

Sealing and density greatly impair soil functions. The reduction of water and oxygen entrance into the earth destroys organisms in the soil. Because water cannot infiltrate into the ground, pollutants transported by air and precipitation cannot be held in the soil. They are washed into surface waters.

Complete sealing of soil causes complete loss of flora and fauna. Even partial surface sealing causes a loss of habitat. Biotopes are cut up or isolated. Sensitive species are displaced to the advantage of a few more adaptable species.

The sealing of urban area directly effects the human habitat. A high degree of sealing is usually paired to a disparity between population size and available open spaces. The construction of buildings tightly rowed onto each other, often separated only by asphalt or concrete surfaces, can exert an oppressive, monotonous effect on those who live there. Nature, even in the change of seasons, cannot be directly experienced in dense residential areas. Long distances to the city’s edge or into surrounding areas have to be traveled in order to make up for missing contacts with nature.

Development of Sealing

The development of sealing is reflected in the expansion of residential areas and traffic areas. Residential areas include the attendant open spaces within residential blocks, such as yards, parks and playgrounds, following the definition of the Federal Agency for Statistics. These areas are differentiated in the Map of (Impervious) Sealing.

The percentage of developed property and traffic areas (not including train facilities) in West Berlin rose by 2.4% from 1979 to 1989, primarily at the cost of agricultural areas. That corresponds to a daily loss of open spaces of 3,400 sq. meters, about the size of half a soccer field. An average of 115 ha per year was taken for settlement in West Berlin during that period of time. The Britz Garden, in comparison, has an area of 85 ha; the recreational center Wuhlheide has an area of 114 ha.

No precise figures for the development of residential areas in East Berlin are available. Construction within settlement areas was minimal up to the middle of the 70s. Large areas formerly used for sewage farms and agriculture at the edge of the city were taken for construction of the residential areas of Marzahn, Hellersdorf and Hohenschönhausen (including gigantic high-rise housing blocks) at the end of the 70’s and beginning of the 80’s. Residential construction in West Berlin in recent years was much lower. About 148,350 residential units were constructed in East Berlin from 1981 – 1990. About 64,100 residential units were built in West Berlin in the same time period (cf. Map 06.03, SenStadtUm 1995c).