学際的な手法を用いた近世後期における新田開発の進展過程の復元 : 広島県西条盆地南部，三升原を事例として

広島県東広島市西条盆地南部の段丘面上にある三升原を対象に，古文書や古絵図の読解，SfM-MVS技術を活用した圃場整備前の地形復元，現地調査といった学際的な手法を用いて，近世後期における新田開発の進展過程を実証的に明らかにした。三升原の新田開発は，1808年から1819年の12年間において，唐櫨の植え付けと失敗までの前半の3年間，3年の空白期間を挟んで，稲作と畑作を進めた後半の6年間という流れであった。三升原では，地表の高さよりも用水路の底面が高い「揚溝」の割合が大きい。これは，集落より上流側にあたる地域が低かったためである。三升原の新田開発の進展は，同様に広島藩が主導した柏原の進展と一致し，藩の国益事業の一環とみなせる。両地区の住民の就業を比較すると，柏原は純農村的な集落であるが，三升原は農村・商業・原料指向型製造業が混合した集落である。地形・交通などの地理的条件によって，集落の性格が分かれたと見なせる。

We studied the process of new field development in the late Edo period in Sanjobara, located on a fluvial terrace in the southern part of the Saijo Basin in Higashi-Hiroshima City, central Hiroshima Prefecture. For this purpose, we used interdisciplinary methods such as reading old documents and drawings, reconstructing the topography by the SfM-MVS technology using aerial photographs before post-war land reform, and field surveys. The development of new fields in Sanjobara lasted for 12 years, from 1808 to 1819. The first half of the period comprised three years of failure due to the planting and death of the wax tree, and the second half consisted of six years of rice and field cultivation after a three-year gap. In Sanjobara, the percentage of “lift ditches,” where the irrigation channel was higher than the surrounding ground surface, was high. This was because the area to the east, upstream from the village, was lower than that of Sanjobara, and hence the irrigation channels were raised. The timing of the development of new rice paddies in Sanjobara was consistent with that in Kashobara, also led by the Hiroshima Domain, and can be regarded as part of the domain’s interest project. A comparison of the employment of both villages’ residents shows that Kashobara was a purely rural settlement, while Sanjobara was a mixture of farming, commerce, and raw material-oriented manufacturing. The differences in geographical conditions, such as topography and transportation, have resulted in different characteristics of both villages.