Quantitative estimation method for urban areas to develop compact cities in view of unprecedented population decline

摘要

In Japan, high economic growth after the war brought about disorderly urban sprawl. The government then enforced an "area division system," which divided city planning areas into "urbanization promotion areas" (UPA) and "urbanization control areas" (UCA). This system maintains the existing UPA size almost unconditionally and, in addition, aims to incorporate parts of UCA into UPA by the size corresponding to new housing demands, which is based on an incremental of the future population prediction. Therefore, there was no need for an objective judgment criterion to verify that the total size of the expanded UPA was suitable for the population size; there are also no related previous studies. Nevertheless, this was not recognized as a major problem when local government finances were abundant due to population increase. However, in Japan, the arrival of an era of unprecedented population decline is certain; maintaining a huge number of urban facilities at the current UPA size could seriously damage local government finance. Shrinking UPAs are an urgent issue and it is time to seriously discuss the appropriate UPA size for the size of the population. In this study, we developed a quantitative estimation method of UPA size, commensurate with population size, through regression analysis of the relationship between population and UPA size. This estimation method is based on the strong correlation between population and UPA size, therefore it can be used as a judgment criterion for local governments to reach appropriate UPA sizes when considering compact cities.