2. Theory
3.3. MCA‐Step 2: Assessment of QoL and UES
3.3.1. Housing‐Scenarios
Socio‐environmental impacts, and impacts on the environment itself, accompany each change of the built environment and of changing land use patterns. Within this study, housing‐scenarios, which represent different housing‐densities, were defined. They were used to quantify the intensity of socio‐environmental impacts and land‐use change due to new housing‐development. Accordingly, the intensity of these impacts differs according to the altered provision with urban green and open spaces. For instance, ALBERTI ET AL. (2005) state clear interactions between humans and biophysical processes, which are mediated by patterns of urban development and a change in land cover. A quantification scheme based on a set of indicators combines the concepts of QoL and UES and is an integral part of the scenario‐based assessment of this thesis.
According to FÜRST & SCHOLLES259 (2004), scenario‐technique is applied to develop realistic pathways or corridors of a development. This development depends on framework conditions for a comparable distant future and according to relatively high uncertainties. This method is applied as especially quantitative forecasting methods fail or as uncertainties forbid a simulation. In contrast, the probability or accuracy of an event is less important compared to the derivation and description of distinct factors and interdependencies. Scenarios present many of the possible future developments without prescribing any likelihood to any of the outcomes. Each scenario should present a plausible future in its own right.
259 Original German expression p. 206
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Following ROTMANS ET AL. 2000260 scenarios are defined by the following characteristics:
• Scenarios are hypothetical and describe possible future pathways
• Scenarios consist of states and derived forces, events, consequences and actions, which are causally related
• Scenarios start from an initial state (usually the present) and depict a final state
Figure 20 shows three defined scenarios for each single‐family homes and multi‐story housing. The allocation of scenarios of single‐family‐homes or multi‐story‐houses was executed according to specifications by the City of Essen261. Additionally, the current land uses at each site are named
“status‐quo‐scenario”.
Each following scenario (1, 2, and 3) represents a distinct housing‐type and its associated housing‐
density. The density is defined according to planning‐standards262. The housing‐density increases from scenario 1 to scenario 3 (see figure 20). This leads to altered land use structures as well as to a modified provision with patterns of urban green spaces and associated socio‐environmental impacts.
Figure 20 Housing‐scenarios and associated housing‐densities (author´s draft)
Land use structures and the provision with urban green spaces react sensitively towards altered housing‐densities and land‐use patterns. As a consequence, the provision with UES and their contributions to QoL alter. According to JAMES ET AL. (2009, p. 68) “ecosystem services provided by urban green spaces are related to the physical aspects of these spaces”. These interrelations also include the physicality and ecological performance of green spaces263. Defined indicators (see ch.
260 cit in. LOBO ET AL. 2005, p. 3
261 See SCHAUERTE 2007
262 a.o. KORDA 2005; PRINZ 1995
263 See definition of green spaces according to JAMES ET AL. (2009, p. 66).
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63 3.3.2.) will be used to quantify and assess the modification of land use patterns and its effects on QoL and UES due to housing‐development.
Table a5 (see annex) indicates, to what respect QoL/UES‐indicator‐values change within each scenario. As mentioned, a status‐quo‐scenario was calculated264. It is used as a reference‐scenario in order to quantify the intensity of each altered indicator‐value throughout the following scenarios 1 to 3. This intensity will be represented by the percental deviation in chapter 4.
As housing‐sites are still subject of preparatory land use planning, their display in the draft (status 2008) of the regional land use plan is executed at a scale of 1:50.000 and does not provide lot‐sharp limits of each site. Therefore the application of gross housing‐density compared to net housing‐
density is the most appropriate way.
3.3.1.1. Quantification of Housing‐Scenarios
The system of scenario‐quantification and indicator‐calculation will be presented in the next paragraphs (see figures 21 and 22).
The first step of the quantification represents the attribution of land use data and initial standard‐
calculation, in order to get a closer insight into their socio‐environmental performance (see fig. 21).
Closer information on that will be given within the indicator‐explanation (chapter 3.3.2). This enables the calculation of the status‐quo‐scenario.
The second step comprises these GIS‐based allocation of indicator‐values for each land use class (see also table a5 in annex A) in accordance to varying housing‐densities. The third step comprises the calculation of weighted mean values, in order to quantify the modified indicator‐performances.
The spatial extensions of scenario‐analysis refer the future housing‐sites together with their closer living surroundings (see fig. 21). This follows the anthropocentric approach in this second step of the MCA compared to physiocentric direction of the QoP‐assessment as outlined in chapter 3.1.
According to planning literature265 “closer living surroundings” are defined as a radius of 500m which are adequate to 5‐10 min walking distance266. Therefore, a buffer of 500m (including a walking distance coefficient of 1.2) was created around each analyzed housing‐site. All presented results of impact assessment in chapter 4 refer to these spatial extensions. (see fig.21).
264 Note: The scenarios do not refer to the most appropriate housing‐structure to achieve an optimum of QoL and UES. The
housing‐scenarios refer to standardize mono‐structural housing types. The optimum to what they are compared is marked by the status‐quo‐scenario.
265 CITY OF LEIPZIG 2004
266 See also CITY OF BERLIN 2009 defining a distance to open spaces of closer living surroundings of 500m and the definition of the URGE‐RESEARCH TEAM (2001‐2004).
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Figure 21 Quantification of scenarios (author´s draft)
Looking back at the first step of figure 21, we see that two different types of indicators are mentioned. This aspect needs special attention, because it influences the quantification of socio‐
environmental impacts and the calculation of indicator‐values.
The first indicator‐group (regulation, biotope quality, sealing rate, seeping rate, surface run‐off and evapotranspiration) is subject to data‐attribution. That means, an allocation of values indicating the individual contribution of each cadastral land use class to its indicator value was executed in advance. In doing to, look‐up tables referring to the reference‐values of cadastral land use data and their individual performance of climate regulation, biotope quality (SINGER 1995267) or hydrological standards such as characteristic sealing rates, seeping rate, surface run‐off and evapotranspiration
268.
267 The study of SINGER (1995) aims at assessing the ecological performance of urban open spaces associated to cadastral
land use data. In doing so, elaborated reference values focusing on the regulative function, biotope quality, sealing rate, recreational values and soil quality for most of the cadastral land use classes (ALK). These reference values have been applied in attributing cadastral land use data of the City of Essen provided on lot‐level. Singer defines three classes ranging from 0 (no performance) to 4 (very high performance).
268 City of BERLIN 2007 (www.stadtentwicklung.berlin.de/umwelt/umweltatlas) It provides hydrological reference values of
characteristic land use structures within the city of Berlin. A distinction between different housing types and open space structures has been made even though it refers to a very rough spatial resolution. Therefore the calculation of individual standards for the City of Essen is necessary.
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65 The second indicator‐group covers all indicators of green provision per resident. It is based on the calculation of local standards of green provision, which is based on own green‐mapping (see the following excursus). In doing so, standard values on green shares per gross building‐land were calculated according to comparable housing types within the city of Essen. The additional residents, who will be attracted by new housing construction, were calculated according to the outlined housing structure types of the scenarios with reference to planning literature. Factors such as household‐size, living space per resident and gross housing‐density269 were taken into account.