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The urban climatic consequences of soil capping have already been described in Chapter 2. The degree of soil capping (Figure 6/3) within a development is defined by the proportion of property area that has been built over. Relevant structural data include:
Detailed information about limits on soil capping is found in BUNZEL (1992) and RISCH (2005), continue the EUROPEAN COMMISSION (2012) has issued guidelines to limit soil sealing. A large number of smaller green spaces with their sum effect can contribute to a reduction in the thermal burden or the heat-island effect, as long as these green spaces are closely networked and exhibit a sensible arrangement from the perspective of the urban realm (e.g. corresponding with main ventilation corridors). The planting of trees and shrubs along streets leads to a reduction of ambient heating (especially in built-up areas) and thus serves to balance out overheated city structures. Large-crown trees and their corresponding shade create comfortably-shaded spaces. On the other hand, plantings can lead to a reduction in wind velocity and thus reduce the removal of pollutants. Outside of built-up areas, forests and strips of planting create (under some circumstances) hindrances for cold air flow (cf. Chapter 6.2.2). A measurable long-distance climatic effect is created only by very expansive green spaces of sizes at least 50 hectares. The effect of smaller green spaces, meanwhile, is based on the "placeholder effect" of displacing other land uses unfavorable to the urban climate. Table 6/1b provides an overview of global investigated parks.
Table 6/1b: Overview of the size, location , maximum cooling effect (PCImax), range of urban parks (compilation of Kuttler (2010) after Bongardt (2006)) Legal Bases: The regulatory possibilities named in Section 6.1.1 come into question here, as their validity depends considerably on the need of urban development to fulfill greening functions. The establishment according to § 9 (1) 3 BauGB of minimum sizes of property to be developed can work against an undesirable densification of the built environment and soil capping. A clause for the preservation of trees, shrubs, and water can be established in a site plan for existing bodies of water and their plant cover (§ 9 (1) 25.(b) BauGB). Bodies of water can be depicted according to § 5 (2) 7. BauGB in a land use plan or confirmed according to § 9 (1) 16. BauGB in a site plan. In a site plan it can also be established that parking lots and garages outside of coverable property areas can only be constructed underneath the surface (§ 9 (1) 4 BauGB and § 12 (4) BauNVO) or that they may not be constructed on non-coverable property areas (§ 23 (5) BauNVO). According to § 19 (4) BauNVO, surfaces for parking lots and garages (including underground garages) inclusive of their access roads are taken into account in the determination of the permissible surface area. The BauNVO makes a limited provision for possible exceptions for these types of structures. The municipality will have to deal with the question of regulations deviating from this standard in individual site plan processes, on the one hand to leave as much uncapped surface area as possible, and on the other to preserve through concentrated building and parking connected open spaces that are especially important for the urban climate. According to § 74 (1) 3. of the State Building Ordinance (LBO), it is possible to establish localized construction specifications for the design and usage of unbuilt surfaces on developed property. According to this, further specifications for the greening of construction sites and for parking areas can be reached. Rulings according to § 74 LBO can be decided upon together with the site plan. |
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6.1.3 Avoidance of Soil Capping by Green Spaces and Water
