抄録
Many mountain settlements in Japan have experienced rapid decreases of population since the beginning of the high economic growth period. In previous geographical studies of depopulated areas, the main concerns were to reveal the primary factors responsible for depopulation and to describe either the change of population or the industrial structure of the depopulated settlements. Though thirty years have already passed since depopulation was first regarded as a serious problem, few studies have considered regional segregation or differences in the depopulation processes. Hence it should be necessary to reveal regional differences in depopulation and the mechanisms which cause these differences as well.
The purpose of this paper is to make clear the regional differences in the depopulation processes in mountain settlements of Hiroshima Prefecture and to analyze the mechanisms of increasing regional differences in depopulation processes by using data of the settlements' population and its change. This is because population change is understood as the origin of depopulation problems and the criterion for the degree for depopulation. The statistics on settlements' population change employed in this paper is supplied from Investigation of Settlements in depopulated Areas. These statistics are very valuable data as they show the population change from 1960 to 1990 of each settlements.
The main results obtained are summarized as follows:
1) In the depopulated areas of Hiroshima Prefecture, the spatial patterns of depopulation processes show two zones. One is a gradually depopulating zone, and the other is a drastic one that shows there are remarkable differences of population change among each settlement. From the spatial differences obtained above, there are conspicuous differences in the depopulation processes among the regions or settlements that have been all considered heretofore as the same mountain settlements.
2) As a result of multiple regression analyses to estimate the factors causing depopulation, the author introduced six depopulation factors into the formula. This suggests that the distance from each settlement to the town office is the most important factor in the settlements' depopulation, while the agricultural factors are not so important.
3) The regional differences in depopulation are caused by various factors in each area. The municipalities can be divided into four types by the reasons for depopulation. These types form the zonal structure. This structure is defined mainly by the distance from urban areas like Hiroshima, Fukuyama, and Miyoshi.
4) The local authorities can be divided into two types according to the difference of population change among settlements. In one type, the differences in depopulation among settlements is remarkable, and in the other this is not so. The former is likely to be located in mountainous areas and in these local authorities public investments are concentrated around the settlements where the town offices are located. The latter type is located on the plateaus or near the plains and their areas are small, which makes town-office settlements not so advantageous.
5) The factors which caused the differences in the depopulation processes form a dual structure which consists of the district level centered on urban areas and the local authority level centered on town-office settlements. The population change of the depopulated areas so far has been restricted by this dual structure and the location of settlements has caused the differences in the mechanisms of depopulation.
