Dichte und Schrumpfung - Leibniz-Institut für ökologische ...

24 IÖR Schriften │ Band 49 • 2008 Dichte und Schrumpfung – Christiane Westphal
- Declining densities lead to an increase of per-capita-costs of water supply,
sewage disposal and district heating. When population densities decline, fixed
costs have to be shared by a smaller number of inhabitants so that per-capita
costs rise. Again dispersed shrinkage may cause approximately 15 to 20 %
higher costs for the provision of public utilities than compact shrinkage.
Resulting from those strong impacts of urban shrinkage and declining densities on
water supply, sewage disposal and district heating, operators of public utilities have
stressed the need for compact shrinkage and therefore for consequently demolishing
vacant flats from the urban fringe.
Based on analyses of statistical data as well as on model calculations this study
proposes corridors of minimum densities that are required for cost effective and operable
public utilities.
Minimum densities are calculated according to three different criteria:
- the threshold value of disproportionately high per-capita-efforts (in m network
length of water provision / sewage disposal per capita),
- the threshold value of loss of technical operability and
- the threshold value of cost effectiveness.
Table II: Corridors of minimum densities for housing in shrinking cities from the point
of view of public utilities
Type of housing and
urban character
Turn of the twentieth
century block
High rise housing
estate
Mid rise housing estate
(from the 1920/30ies
and 1950/60ies)
Modern apartment
block (built after 1990)
Detached family homes
Picture
(photos: IÖR) Floor
space
ratio
Infrastructural
effort
Inh. per
net ha
Technical
operability
Floor
space
ratio
Inh. per
net ha
Cost
effectiveness
Floor
space
ratio
Inh. per
net ha
0.4-1.3 90-270 0.5-1.4 100-310 0.4-1.1 80-250
0.4-0.8 100-200 0.5-0.8 110-230 0.4-1.0 90-270
0.3-0.7 80-160 0.3-0.7 80-160 0.3-0.7 70-180
0.3-0.6 60-130 - - 0.2-0.65 50-110
>0.3 >60 0.2-0.4 30-80 0.1-0.3 30-70
However, it has to be considered that – as shrinking processes are in their initial
stage and experiences are still scarce – there were hurdles in developing these corridors
such as lack of data availability. Also minimum densities are closely related to
the question which standards shall be provided in shrinking cities. Therefore their
development needs to be integrated into a broader public discussion.