Settlement system has a hieralchical structure which consists of national, regional and daily system. Inter-settlement migration is one of the most useful measures analyzing national and regional system structure. Because of the complexity of interactions between cities, towns and villages in these days, the complex structure of settlement system, which could not be elucidated with methods heretofore in use, has to be analyzed. In Hiroshima Prefecture prefectural area almost coincides with the area of tightly combined regional system. In this paper the author analyzed the structure of regional settlement system and its change between 1967 and 1983 in Hiroshima Prefecture. The main findings are summarized as follows. 1. Migration pattern in 1983 were analyzed with Modified Weaber Method and it appeared that 12 centers of in-migration existed in the regional system of Hiroshima Prefecture. Hiroshima City is the dominant center of tightly combined regional system. Fukuyama and Kure are centers of local system consisted of their neighbouring cities, towns and villages and subordinate to Hiroshima City. Another centers are more loosely combined with their neighbouring cities, towns and villages than Hiroshima City or Fukuyama with them and these centers are tightly combined with Hiroshima City. Accordingly these centers and their neighbouring cities, towns and villages construct loosely combined sub-systems which are included in Hiroshima City or Fukuyama system, and which could not be elucidated with methods heretofore in use. 2. Generally speaking the regional settlement system of Hiroshima Prefecture changed a little from 1967 to 1983. However Hiroshima City was more tightly combined in 1983 than in 1967 with cities, towns and villages in eastern part of Hiroshima Prefecture. In this area Fukuyama system reduced from 1967 to 1983. The areas of sub-systems centered Fuchu-cho and Shin'ichi disappeared in 1983. In the northern part Miyoshi system expanded and encroached Shobara ssystem. In central area Higashihiroshima system also expanded. Accordingly it is interpreted that sub-system are being weeded out and integrated in Hiroshima Prefecture. 3. Calculating average distance that in-migrants moved from previous residences to each center of sub-system, the locational characteristics of each center in the prefectural area and effect of distance from Hiroshima City to the center were analyzed. Particularly the average distances of Fuchu-cho, Itsukaichi and Shin'ichi are shorter than others. Because Fuchu-cho and Itsukaichi are satellite town of Hiroshima City, Shin'ichi that of Fukuyama and there are many migrants from Hiroshima City to Fuchu-cho and Itsukaichi and from Fukuyama to Shin'ichi. 4. For the purpose of analyzing the relation between number of in-migrants and distances which they moved, spatial interaction model was applied to migration data and distance parameter of each center was estimated. The distance parameter estimates of Hiroshima City is least-negative than all other centers. Accordingly the accessibility of Hiroshima City is exceedingly high and it is explained that many migrants move from almost all cities, towns and villages in Hiroshima Prefecture to Hiroshima City. Fuchu-cho, Itsukaichi and Hatsukaichi have also less-negative-estimates. These three towns has turn into satellite towns of Hiroshima. They and Hiroshima City have tightly combined like one region and act as a center of prefectural-wide regional system. The parameter estimates of another centers are less-negative than that of Hiroshima City and this fact proves that these are centers of limited local sub-systems. Variations of the estimates explain the detailed characteristics of centers which could not be explained by the analysis of migration pattern.

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In Higashi-hiroshima City, machinery industries such as electric machinery, automobile and the like has been growing since the latter half of higher economic growth period after the Second World War. Today, this city has a considerable agglomeration of factories and forms a industrial region. Agriculture, which was a former main industry, has been forced to change by the impact of such industrialization. Moreover, a lot of laborers from other area are inflowing to this city and so the structure of labor force tends to be complex. The objects of this paper are to clarify the relationship between the industrialization and the changing structure of local labor force. Therefore the author tried to analyse the following points: 1) The feature of the location in two major manufacturing industries, automobile and electric machinery. 2) The structure of labor force in each of two industries. 3) The process of the labor outflow from agriculture to these industry. 4) The relation with such outflow and the change of agriculture. The following results were obtained. 1) In machinery factories, the quality of labor force shows the different characteristics in proportion to the number of their workers, typically, larger ones absorb new graduates from wider areas inside or beyond Hiroshima pref. , middle class ones absorb them from Hiroshima pref. and young laborers in this city, the small ones employ middle or high-aged laborers from the neighboring areas. Subcontract factories of electric machinery acquire cheap housewife laborers. However, the supply of industrial labor in this city tends to be in short, so some large factories induce laborers from neighboring towns in Kamo county (Gun), most of which are transported by companys' microbuses. 2) Under such conditions, the outflow of agricultural population has increased. In the first stage (1955-1964), many young laborers outflew into Hiroshima city and its suburbs. In the second stage (1965-1974), young and middle aged laborers outflew into the factories which moved to this area. In the third stage (1975-), middle and high aged laborers were absorbed into small factories in this city. And housewife laborers of farm household were employed by the factories which have moved to this area for acquiring less-paid labor. 3) Agricultural production developed till about 1965 by the effort of the farming management, but after which it gradually began to decline. Many part-time farm household have remarkably increased and continue to subsist agriculture (monoculture of rice cultivation). On the other hand, only a few upper class farmers grow fruit or keep dairy farming. 4) In the case of Nishi-shiwa area, agricultural population was absorbed in other industrial sectors according to the status of farm and in every stage. Recentry, housewife laborers of farm were employed by subcontract factories produce automobile parts. Consequently, the structure of labor force in this area was newly organized.

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Streamflow reflects variable land conditions in the drainage area, such as landform, subsurface geology. But there are many indefinite matters about its mechanism. So the purpose of this paper is to clarify the relation between runoff and land conditions, using the "tank model",which is one of the runoff analysis models. The study areas are the catchment areas of Koyagawa-Dam, Sabagawa-Dam and Mukunashi-Dam. The author compares the hydrographs with the outputs from the tank models, mainly to clarify seasonal influences of land conditions, and the parameters of the tank models with the scores of the land conditions given in proportion to the importance for runoff in each study area. The results are summarized as follows; 1) The influence of irrigation water is remarkable in Koyagawa and Mukunashi, which have many paddy field. In these area the discharge lowers about 1 mm from April to September. The influence of irrigation ponds is evident in Mukunashi. In a dry year the discharge continues to lower for a short period even after the paddy cultivation in this area. 2) The influence of snowfall is predominant in Sabagawa. During winter the hydrograph does not coincide with the output from the tank model in this area. The maximum difference is about 15-20 mm. 3) The "time lag" caused by the local precipitation, Is related to the relief, the shape and the size of the catchment area. 4) Highly vegetation stabilizes the fluctuation of the direct runoff, and gentle inclination decreases the direct runoff. Humic soil and deeply weathered crust restrains the intermediate runoff. Pored subsurface geology and faults check the fluctuation of the base runoff.

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