The development of the landforms in the Mihara Alluvial Plain is summarized as follows:
STAGE 0 (before about 22, 000y. B. P.)
The coarse materials were deposited in the valley of dissected Terrace I.
STAGE I (about 18, 000y. B. P.)
The alluvial fans were dissected by the rivers, and then Terrace II was formed.
STAGE II (about 7, 500y. B. P.)
When the sea invaded landward and it passed the location immediately below the present shoreline, the sea-level rose to -13m (T. P.).
STAGE III (about 6, 400y. B. P.)
The sea-level rose still more, and the sea invaded landward further. In this time, four main rivers did not join each other but flowed separately into the sea. Consequently, from this stage to the following stages, several characteristic landforms correspoding to the environmert of each river basin were formed.
STAGE IV (about 2, 600y. B. P.)
The inner bay changed into a lagoon because the sea-level fell and sandbars were formed. As the humic silt deposited in the fresh water environment existed about -60cm (T. P.) at point o, the author estimates that the sea-level fell below -60cm (T. P.).
STAGE V (Recent Age)
After the “early Kofun era” (the 4th C. A. D.), the occurrence of floods became more frequent, and the floodloam was deposited rapidly. Then, present landforms were completed. The landform classification map is drawn based on the development of landforms (Fig. 9). Each landform unit is arranged according to the time necessary for each landforming process and the geomorphological dendrogram is completed (Fig. 10). Finally, the Mihara Alluvial Plain is classified as follows: 3 surfaces in the order of 10⁴ years, 7 zones are in the order of 10³ years and 16 units in the order of 10² years or lers.

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　　　This study reveals interactions between agricultural production and actor’s relations in Kamihata settlements in Minami-Awaji City, Mihara Plain. Farm management in farm households is examined to determine whether farm activities, such as lending equipment, supplying compost, and establishing delivery routines develop the relationships among farmers or between farmers and other stakeholders, while identifying the kind of relationships formed. Moreover, the contribution of multi-layered network formed through relations between and among such stakeholders is considered.
　　　The research method adopts social network analysis. This approach allows a quantitative stand in analyzing human relations based on the presence or strength of ties between nodes, the distance between such nodes, and the node parameters. Economic activity and social life are inseparable in rural areas and villages, and ties among farm households are characterized by various roles existing in a multilayered structure. This study focuses on the extent and width of social ties among certain nodes.
　　　Results show that in Mihara Plain, the “ three crop” rotation system―a combination of paddy rice, onions,and cabbages or paddy rice, lettuce, or Chinese cabbages―has been widely promoted. The study area practiced intensive farming. The production of leafy vegetables served as an economic activity that could augment the income of farm households. Farm management, as practiced by every farmer household, progressed within the range of social groups such as settlements and districts, and did not become completely independent albeit done individually. Various territorial relations became a conforming frame, as seen in the sharing of equipment and supplying of compost. The network was selectively formed according to the purpose. In addition to the abovementioned relations, networks based on the delivery of crops was observed. These networks extended in various ways, according to every farmer household's management policy, and had various influences on every farmer's management practices.

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The purpose of this paper is to elucidate the change in the topographical environment of the plains after the end of the prehistoric age, and also to clarify the relationship between the change and the land use. Geomorphological analysis for environmental reconstruction is employed. It consists of four different analyses: landform surface analysis, landform zone analysis, micro landform analysis I and micro landform analysis II.
The purpose of landform surface analysis is to clarify the topographical change taking place in a time frame of 10⁴ years (for example, the formation of terraces). Landform zone analysis can clarify the topographical change on a scale of 10³ years order (for example, delta formation). These two analyses correspond to what was formerly called the history of topographical development. On the other hand, micro landform analysis I and micro landform analysis II are connected with the investigation of archaeological excavation. The purpose of micro landform analysis I is to clarify topographical change on a scale of 10² years. For example, a natural levee must have greatly influenced the location of a village. In micro landform analysis II, what is looked at is the topographical change which occurs every time a river floods. In geomorphological analysis for environmental reconstruction, we pay attention not to “natural topography” but to “topography of the human living environment”. In other words, geomorphological analysis for environmental reconstruction is not a mere history of topographical development; it includes the history of natural disasters and of land development.
As the subject of our research, we used the Mihara Plain on Awaji Island in Setonaikai. In Shichigawa Okitaminami site, part of delta I in the Mihara Plain, minute topographical changes and the appearance of the land used from the end of Yayoi era to the Kofun (old tomb) era-about 1, 700 years ago-can be clarified by geomorphological analysis for environmental reconstruction. The following is a summary:
1) The area surrounding the Shichigawa Okitaminami site was a shallow sea bed at the height of the Jomon transgression (stage III, about 6, 400y.B.P.). This sea area became a lagoon 2, 600y.B. P., when the sea level changed and a sand spit was formed at the inlet (stage IV).
2) The accretion of natural deposits progressed rapidly here from the end of the Yayoi era to the beginning of the Kofun era. This accretion caused the area where rice fields could be developed to spread down the river. The loam brought by the flood has a negative aspect in that it buries the rice field and a positive aspect in that it changes swampland into dry land with high productivity.
3) The rice fields are divided by a footpath in accordance with the level of the ground so that the difference in the height of each division would not exceed six centimeters. Where the incline is steep the rice field was smaller, where the ground is flat, the rice field is larger.
4) When floods or accumulation occur, the rice fields revert to their original state. Therefore it can be assumed that this process occurred without delay in the Mihara Plain.
5) Rice fields of stage IV₁₆ are of two different kinds: high and dry, and low and wet. The fields can also be classified as good or bad in terms of the water supply.

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It is the one of noteworthy things to see in the narrow mountanious island country like Japan, how and to what extent the high and gradient lands are actually cultivated. And this kind of investigation has been done hitherto largely in the central mountanious district and in the skirt of various volcanoes. As a result, apart from the mutual relation between the farming land and its height in which the latitude of the place plays a large part, it has been reported, in the case of gradient land, that the gradient of the land suitable for cultivation should be smaller than 15°. And the same kind of investigation was applied to that of the Island of Awaji, one of the islands in Inland Sea (Setonaikai) where the cultivation of gradient lands is highly developed. It has been proved that the greater part of the Island of the Island of Awaji which has the gradient of 20° or more and is used as paddy fields or orchards, as expected before the investigation, exceeds the average gradientof 15°. Of course, most paddy fields or orchards have the gradient of 10_??_15° or of less than that. Therefore, the limit of the gradient in the farming land of the islands in the Inland Sea where almost all islands are cultivated to their sum mits, has an eminent difference compared with that of the United States, little difference compared with the average limit of the gradient in our country. There was little difference between the limits of the gradient in the farming land and that of urban dwelling area in the city of Ashiya. In short, the limit of the gradient both in farming lands and dwelling areas in the steeply sloping cities is to be under 15° in our country.

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An "onion shed" is a wall-less storage house with only a beam, roof, and frame, where harvested onions are bundled and hung to be dried and stored. Onion sheds were a common feature in Minami-Awaji city in the beginning of summer; however, due to challenges related to hanging onions, the number of sheds has declined. In this study, the spatial characteristics and actual usage of rapidly disappearing onion sheds were investigated to determine an effective way to continue their succession. As per the findings, the district housed 1,093 sheds of three alignments- “spread style (in farmland)” “spread style (in village)” and “lined up style.” And traditional sheds with tiled roofs and wooden pillars accounted for 17.9% of all onion sheds, which were inclined to be lost with farmland consolidation. Moreover, it became clear that livestock farmers and double-cropping farmers are working together in a small village.

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This study aims at revealing how farmlands are managed by examining the roles played by the transfer of farmland rights in farm management and agricultural settlements; the study’s analysis is based on the social relationships among farmers that are involved in the process of transferring farmland rights for farmland maintenance. This study focuses on the spread and connection of social relationships among farm households. Past studies have often integrated the ties between farm households with territorial and kinship relations. This study focuses on the spread and connection of social relationships among farm households. This study classifies territorial relations on the basis of spatial spread as well as kin relations by degree of kinship. It also classifies various other social relationships after a careful consideration of each of their characteristics and analyzes them based on how these social relationships form layers, as explanatory variables, and who uses farmlands through the transfer of farmland rights as explained variables.

The following area was selected as study area: the Kamihata settlement in Minami Awaji City, Hyogo Prefecture, located on the Mihara Plain of Awaji Island, where even small farms in the settlement show an intensive use of farmland all year around. On the Mihara Plain, the “three crop” rotation system—a combination of paddy rice, onions, and cabbages, or paddy rice, lettuce, or Chinese cabbages—has been widely promoted.

On the Mihara Plain, the recipients did not attempt to increase profitability and the farmland transfers were motivated by non-economic factors. In the past, after a farm’s retirement, its farmland was generally transferred among farm households through kinship or same neighborhood relations in order to maintain the “farmland as a family property” and as “farmland of the settlement.” However, it gradually became difficult to secure farmland recipients solely through such relations. In order to sustain the farmlands within the settlement, farm households with a sufficient labor force were passively forced to take on the farmlands of landowners with whom they had no neighborhood or kinship relations. Consequently, full-time farmers with a sufficient labor force undertook the farming of additional farmlands simply because they were located in the same settlement. On the other hand, in the case of transfers of farmland rights extending to farms in other settlements, the main recipients were part-time farm households who took on these farmlands to sustain social relationships such as kesshaen or kinship relations with the landowners. In addition to transfers of farmland rights within the settlement, those outside the settlement were promoted based on the same district, kesshaen, or kinship relations. While same-settlement relations were the basis for sustaining farmlands within a settlement, territorial relations of a wider range than a settlement, kesshaen and kinship relations contributed to the sustainability of farmlands outside a settlement.

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　日本の農政において低迷する食料自給率の問題は，長らく政策的課題として掲げられ，国内での食料の増産が求められている。その対応策の一つとして，農地の流動化による遊休農地の有効活用が挙げられているものの，農地流動は円滑に進んでいない。平野部において農地流動の停滞する多くの地域は，小規模な稲作兼業農家が離農後も農地を手放すことなく保有する場合や，専業農家が施設園芸などの商品価値の高い作物生産に傾倒し，水田に十分な労働力を投下していないところである。また，このような地域では，耕地１枚当たりの面積は小さく，農地の受け手にとって条件が悪いことも農地移動の障害となっている。これらの地域では，稲作が経済活動として機能しておらず，兼業農家は農外就業，専業農家はその他の作物の生産によって世帯収入を支えている。 しかしながら，このように小規模兼業農家が多く，稲作以外の農業生産や農外就業により世帯収入を支えている農家が多い地域においても，農地が有効に利用されている事例も存在する。このような地域では，耕地１枚当たりの面積は小さいものの，農業生産の形態や段階に応じて，農業者の農地への関わり方を変化させている。これは，農業生産活動の場は農地で共通しているものの，その形態や段階によって，農地の果す経済的な役割が異なることに起因している。
農地が経済的な役割を果す段階においては，各農業者は最大限の利益を得られるように，個々の経営方針に則して農業生産を行っている。この場合，自身の耕作地での農業生産活動を，他の周辺農業者から干渉されることはなく，農地が私的な空間として，個々の農家が支配力を有している。
　一方で，農地は公的な側面も持ち合わせている。農地は各イエ（農家）に私有されるものであると同時に，各農家により構成されたムラ（集落）に属するものでもある。例えば，自身の農地を耕作放棄することは他の農家にとって迷惑行為となり，農地の継続的な利用を求められる場合などが挙げられる。これは，私有地である農地が，農家間の社会関係から形成される集落やその他の社会集団などの共同体によって，「共有」されるものであることを示している。集落営農や集団転作，「農地の景観保全」などは，この延長線上にある現象といえ，農業者個人の意向で農地の利用形態を決定できない側面をもつ。
このように農地の主たる利用形態である農業生産活動は，経済的行為として一様に扱うことはできない。多様な農業生産活動の形態や段階は，ムラ（集落）における農地の社会的・経済的役割を変化させている。農業者の社会生活上，農地は管理しなければならないものとなり，主体が「私有」と「共有」の間を変化するなかで，積極的にあるいは消極的に農業生産活動が展開している。
　これまで農村をフィールドにした研究においては，村落社会そのものや農業の経済的役割が，それぞれ個別の研究対象として扱われてきた。とくに農業を産業としてのみ扱う傾向が強かったため，農業がもつ社会的役割については，経済的役割と混同される傾向にあり，両者の役割に留意して議論されることは多くない。例えば集落営農は，ある地域の経済的役割のみならず農地管理という社会的役割も担っている。このような場合，農業生産を経済活動としてのみ扱うことは困難であり，私有の農地が集落などの社会集団内で，いかなる社会的役割を果しているのかを検討する必要があるといえる。
　農業の社会的役割について扱った研究では，個別もしくは複数の社会集団による共有地の管理について検討したものが多かった。これらの研究での主たる命題は，集落内部の主体間がもつ社会関係から，共有地である農地や林地，漁場の利用形態を明らかにするものであった。しかしながら現在の日本の農業において，農業生産活動をめぐる農業者間の社会関係は，集落内外に展開することは自明のものとなっている。そして近年では，このような農業者間の社会関係をネットワークとみなし，社会的ネットワーク分析を援用して，ネットワークが特定の農業生産活動に果たす役割を分析する実証研究が進められつつある。さらに，こうした社会関係が重層的に存在することによって構築される社会関係資本が，農業生産活動やそれに付随する諸現象に果たす役割を分析する必要性も，次なる課題として提示されている。
　そこで本発表では，大規模化とは異なるで，集約的に農地の有効的利用を行う地域として，三毛作農業が卓越する淡路島を事例にし，農業生産活動の形態や段階に応じて展開する重層的な農業者のネットワークを分析することから，個々の農業経営におけるそれぞれの農業生産活動にいかなる役割を果しているのかを明らかにする。

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