A Method for Identifying Retreat and Re-concentration Residential Areas
toward Sustainable Urban Structure based on Triple Bottom Line
Noriyasu KACHI*, Takuya TOGAWA**, Yuta SUZUKI**, Hirokazu KATO** and Yoshitsugu HAYASHI**
* Toyota Transportation Research Institute; 1-1, Wakamiya-cho, Toyota Aichi, 471-0026, Japan
Tel: +81-565-31-7543, Fax: +81-565-31-9888, E-mail: [email protected]
** Graduate School of Environmental Studies, Nagoya University
Keywords: Sustainability, Triple Bottom Line, Environment Efficiency, Cost Efficiency, Compact Urban Area
The total population reached its peak in the year 2005 but subsequently it started declining in Japan. The current urban
structure, which has been sprawled by rapid population growth and motorization, has increased the maintenance cost of
unnecessarily expanded built-up area and also increased the environmental load. It is difficult to keep living
environment in such the condition. Therefore, compaction policy by restricting inefficient urban area usage is required.
However, there is a fear that excessive compaction leads to deteriorate residential quality of life due to congestion and
the additional environmental load. Thereby, the examination of suitable urban structure, which is able to improve the
land productivity toward higher residential quality of life and to tackle the constraints of global environment and public
finance, and its switching process, is needed.
This study aims to develop a model system for identification of retreat and re-concentration areas applying the
environment and cost efficiency indicators based on the triple bottom line (environment, economic and social aspects)
and the feasible conditions for population migration by a logic model. Retreat is defined as restricting the supply of
new houses and infrastructure, and re-concentration is defined as the guided migration of population to high-capacity
districts with enough infrastructure. Retreat and re-concentration areas are identified according to the following
procedure. Firstly, environment and cost efficiency of quality of life in each residential district are calculated base on
carbon dioxide emission, built-up area maintenance cost and quality of life indicator estimated by using SURQUAS
(Smart Urban area Relocation model for sustainable QUAlity Stock) system, which has been developed by the authors’
study group. Secondly, residential areas with low environment and cost efficiency are identified as a potential retreat
area and ones with high environment and cost efficiency are identified as a potential re-concentration area. Thirdly,
retreat and re-concentration areas are extracted considering the feasible conditions for population migration by a logic
model, which is a tool to describe the conditions to achieve a final goal according to ‘if–then’ rule. Finally, the
changes in quality of life indicator and environment and cost efficiency of the whole area by implementation of retreat
and re-concentration are examined.
Applying the developed model system to an actual Japanese local city implies that concentration of residential area to
central area will be more sustainable in terms of triple bottom line under the constraint of carbon dioxide emission, and
the feasible conditions for population migration from a retreat area to a re-concentration area examined.