Urban sprawl is a multi-layered concept that includes topics ranging from the outward expansion of a city to the development of auto-dependency in surrounding rural areas. This diffusive structure has become the root of numerous economic, social and environmental problems. Therefore, many local governments have shifted their focus onto a compact city policy, which is a more effective urban structure. Numerous studies have focused on overall effectiveness of the so-called hub city. However, two pertinent issues remain to be studied. The first is the details of political costs for such a concept, and the second is the inclusion of surrounding suburban and agricultural communities in large-scale land uses. This study examined the influence of the compact city concept on the surrounding areas. In particular, we established a scale of policy that consists of two points: the scale of the hub area and the scale of the size of the population settling into the hub. This was achieved by employing the existing “effectiveness of land use” to simulate changes in such uses.
Our framework for describing the effect of such a policy implementation is as follows: First, we utilized a scatter diagram that consisted of the size of the population and rate of land use in a 1 km2 area. The first variable was designated as “urbanization area” in which an increase in population can shift rural land use to urban land use, and the second variable was “regeneration area” in which a decrease in population can shift urban land use to rural land use. The angle of the line represented the scale of the hub area. Second, we established the aggregation point for each area in the scatter diagram. In this case, the point of urbanization was called “size of the population.” Third, we controlled the movement of plots in each area, which simulated population migration and change in land use to calculate the political costs.
Next, to evaluate the surrounding area, we described the spatial population and land use after policy implementation. In this case, we focused on the regeneration area and calculated the percentage of land use needed to establish the relationship between the scale of policy, political costs and degree of isolation.
This study provided four overall findings. First, larger hub area and higher population density in the hub lead to higher political costs. Second, the degree of isolation in agricultural communities geographically far from the city center is basically high. Third, the degree of isolation in suburban communities increases as the hub area and population density of the hub area rise. Fourth, low scale of the hub area in terms of size of population settling into the hub impacts the relationships between political costs and degree of isolation in the surrounding region. These results show that the compact city policy influences isolation in the surrounding areas.
JEL Classification: R11