11 de setembro de 2012

Monitoring Urban Sprawl in Germany - Towards a GIS-based Measurement and Assessment Approach

S. Siedentop
Leibniz Institute of Ecological and Regional Development (IOER) – Weberplatz 1, D-01217 Dresden, Germany. e-mail: s.siedentop@ioer.de


During the 1990’s, the phenomenon of urban sprawl received growing attention in the international urban policy debate. In a recent report, the European Environmental Agency addressed sprawl as one of the major challenges facing urban Europe in the next decades (EEA 2006). However, a survey of the literature yields no agreement in terms of defining and measuring urban sprawl. Some scholars denote sprawl simply as ongoing urbanisation or low density development, others stress the level of suburbanization and deconcentration or characteristics of land use patterns. The absence of a common understanding constrains the analysis of sprawl’s causes, costs and consequences as well as the formulation of planning strategies towards economically, ecologically and socially acceptable land use patterns. Urban and environmental planning aiming to combat sprawl must have an agreed-upon way to measure it in order to evaluate the progress of planning strategies and programmes (Siedentop 2004).

Alongside the lacking definition and measuring convention, the specific process character of urban land use change hinders more effective anti-sprawl-policies. Environmental, social and economical problems caused by urban sprawl tend to be cumulative in nature. They build up over a period of time and usually have more than one cause. In contrast, the legal framework regulating the use of environmental resources generally addresses a single pollutant or a single project but ignores multiple actions that can add up or interact to cause cumulative effects. It has to be acknowledged that the mismatch between the scales at which sprawl-related environmental degradation occurs and the scales at which regulatory decisions are made is a significant obstacle to a more effective environmental management. Therefore, the development of a multi-dimensional and multi-temporal measurement approach is of crucial importance for urban and regional development policies.

Measurement Approach

On this background, a methodological framework for the measurement and assessment of land use patterns and dynamics is presented. First, the approach should be able to indicate the multiple driving forces and causative agents of land use change associated with urban sprawl. Secondly, this framework should be qualified for considering and assessing different impacts of land use and land use dynamics concerning ecological, social and economical objectives of urban and regional development policies. It also should recognise direct, indirect and cumulative cause and effect relationships. A third important requirement is that the selected indicators should be applicable with available data sources. And last but not least the approach has to deal with the varying scales on which land use policies are carried out.

The GIS-based measurement tool is based on the assumption that urban sprawl is a multidimensional phenomenon which can only be measured with a multiple-indicator approach. Three general process characteristics of urban sprawl are being discerned: the conversion from natural to artificial surfaces (surface-related impacts); the change of land use patterns from a compact urban form to irregular, dispersed land use patterns (pattern- related impacts) and the reduction of urban density (density-related impacts). Each sprawl- dimension is related to specific environmental impacts as well as unintended social and economic outcomes (Figure 1). These very different kinds of impacts can be addressed in terms of their specific impact pathway (direct, indirect, cumulative impacts), their spatial and temporal scale (local, regional and global impacts; short-term and long-term impacts) and particularly affected environmental components, social groups or economic subsystems.

Figure 1. Three dimensions of urban sprawl and impacts explained by one or more dimensions (examples)

The proposed indicator system contains about 20 core indicators. Some indicators can be applied to the measurement of the (aggregate) land use pattern. Due to their low level of elasticity, “pattern-indicators” are suitable for “global” sustainability appraisals of land use in larger time intervals. Other indicators aim to address land use changes within a specific period of time on patch level (see Table 1 with examples). The latter are notably qualified for the continuous controlling of land use development in order to assess the success of regulatory policies.

Table 2. Categorisation of selected sprawl indicators


European Environment Agency (2006) Urban Sprawl in Europe. The ignored challenge. EEA Report No 10/2006. Copenhagen.
Siedentop, S. (2004) Urban Sprawl – verstehen, messen, steuern. DISP 160: 23-35.

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