MONITORING AND MODELING FOR CITY SHRINKAGE IN JAPAN : PHENOMENA, MANAGING AND REVIVING STRATEGIES

City shrinkage means that an area with minimum population of 10,000 residents that has faced population losses in large parts for more than two years and is undergoing economic transformations with some symptoms of structural crisis (Hollander et al., 2009). City shrinkage is gradually becoming a common phenomenon wide around the world. Over the last fifty years, 370 cities throughout the world with population over 100,000 have shrunk at least 10% (Oswalt and Rieniets, 2007). Wide swaths of the U.S., Canada, Europe, and Japan are projecting double-digit decline in population in the coming decades (Hollander et.al, 2009). In Japan, over 90% of the municipalities are losing their population. How to deal with the shrinking issue and problems caused by its chain effects still remains a challenge for researchers from various disciplines. In a shrinking city, depopulation due to out-migration and/or lower fertility, and residential preferences change leads to a shift of inhabitants from city core to the suburb, which will give rise to city sprawling in the city fringe as well as lower density of population near city core area (Kabisch et.al, 2006). In the inner city, problems like large dwelling vacancy even demolition and underuse of infrastructures will occur due to low population density, which will lead to large brownfield and land wastage in the near city core area. While in the suburb, there is new demand for dwellings and infrastructures construction caused by urban sprawling, which will occupy arable land and forest in the suburb and have negative influence on the natural ecosystem. Both house vacancy/demolition in the city core and urban sprawling will lead to a dispersed city structure, which will cause problems in infrastructures and welfare services, at the same time, local residents will gradually lose the sense of community and cause social segregation, as the consequence, there will be negative impact on the life quality of local residents. The main negative influences of city shrinkage can be categorized into two aspects. On one hand, in the sense of environment and eco-system, large brown field and land wastage will be left in the city core, and new expansion in suburb will occupy forest and arable land and destroy the natural ecosystem. On the other hand, in the sense of local residents, negative influence on quality of life may be generated by difficulties to access to infrastructures, losing the sense of community and social segregation. In the paper, the shrinking phenomena in Japan are well analyzed based on a case study in Katsuura city. Land use map, census data, questionnaire survey etc. are used to detect changes in land use, population, industry and residential preference. Interview is made with officers in the department of urban construction and department of planning in local government to get further information about current situation and policy intentions. On the basis of analysis of current situation in Katsuura city, an innovative simulation model combined land use change model generated by rent-gap theory based Cellular Automata with residential migration decision model based on multinomial logistical model is built to project current trend of shrinking pattern in the case study area and compare various policy scenarios. The case study area, Katsuura city, is a typical shrinking city. According to the statistical survey, in Katsuura city, the industry is stagnated even slightly decreasing, the population is constantly declining but residential area is still expanding. A dispersed city structure with over low population density and large land wastage is not a sustainable way of development. Local government has realized some of the negative influences of city shrinkage caused in Katsuura city in the aspects of environment and life quality of residents. For example, due to the low efficiency of infrastructure caused by the low density of population, the frequency of the buses has dropped, which gives inconveniences for residents especially the aged who cannot drive. In order to take response to the shrinking situation, local government has been trying to revive the fishing industry and tourism in Katsuura city, but until now the effect is limited. Comparing to reviving the industry, maintaining the life quality of residents and preserving the environment are more urgent and realistic. According to the analysis of residential satisfaction by ordered logistical model, density, safety, accessibility and natural environment are key factors for the residential satisfaction. The four factors are used as the criterion to compare the policy scenarios in the simulation model. With the simulation model that combining the land use change model and residential migration decision model, three scenarios are made and compared. Scenario 1 is the trend projection. In the scenario 1, the new residential development will gradually sprawl into suburb to occupy the arable land and forest. And the residential decision remains preferring suburb to near city core area. If the trend continues, the whole urban structure will more dispersed than before. Scenario 2 is residential redevelopment in the city core area, in this scenario. In scenario 2, by limiting the new expansion in suburb, the infrastructure and welfare will be improved in the city core area to attract the population back to the city core. In scenario 2, the city structure will be more compact than scenario 1. But with the concerning of tsunami, since part of the existing city core is quite near the coastline with very low elevation, the feasibility of the scenario 2 is still with consideration. Scenario 3 is the new development and residential redevelopment in the near city core area. In scenario 3, by properly limiting the new residential expansion on arable land and forest in suburb, to achieve the new development near the city core with highest rent gap value, and part of the residential redevelopment in the city core to re-concentrate population in the near city core area with higher elevation and proper distance to coastline. With the policy comparison in the simulation model, for shrinking cities sharing the similar situation with Katsuura city in Japan, setting proper regulation or charge tax to limit the new expansion on arable land and forest to protect the natural environment, planning with the concern of natural disaster like earth quake, tsunami, etc. and cutting subsidy to develop a proper sized area to re-concentrate the population will be an possible effective way to protect the environment at the same time maintain the residents\u27life quality. For Katsuura city, concerning for the tsunami is one of the most important things associated with the safety, the residential land in the planning should be have proper distance to coastline and with at least 8.5 meter elevation. Concerning with tsunami, developing new land with higher elevation in the city core area is necessary and at the same time redeveloping part of the existing residential land in the city core will be an effective way to manage the Katsuura city. Developing old center for aged residents and improving nursery and primary school for young children in the inner city, at the same time preserving space for park and green land is very important to re-concentrate population to achieve higher life quality and protect the arable land forest in the suburb