ON THE DISTRIBUTION OF “SHIMA-BATAKE” (ISLAND-LIKE OR MICRO-BUTTE-LIKE UPLAND FIELD) LANDSCAPE

Abstract

By “shima-batake” landscape is meant landscape in which upland fields of various shapes, approximately 50-80 cm. above the ground of paddy-fields, are distributed among paddy-Melds, much as micro-buttes are scattered over a plain, or numerous small flat islands are scattered over the sea. In regions where “shima-batake” are densely distributed, there are cases in which the area of upland fields is larger than that of paddy-fields. The purpose of the present paper is to clarify in which regions such landscapes are found. In the first place, after making a detailed inquiry into the relationship between the distribution of “shima-batake” and micro-land forms as well as irrigation in the Hamana and Iwata Plains in the downstream region of the Tenryu River, consideration was given to the origin of “shima-batake.” By a similar method of investigation, inquiry was made into the downstream plains of the Kiso River, the Yahagi River, the Toyo River, the Sagami River, the Kuji River, the Naka River, the Shinano River, the Agano River, the Kariyata River, etc., and also the coastal plains of the Tone River, the Kinu River, and the Naka River, as well as the downstream plains of the Yoro River, the Obitsu River, and the Koito River, on the west coast of the Boso Peninsula, the Kujukuri coastal plain, and two other regions. Approximately 40 years ago, Prof. Glenn T. Trewartha expressed his opinion concerning the “shima-batake” in the downstream plain of the Tenryu River (Annals of American Geographers, Vol. 18, 1928, pp. 127-257). In a recent work, he has expressed the same opinion as before (Japan, a Geography, 1965, p. 652). His opinion is as follows: As a result of the flooding of the Tenryu River, large deposits of detritus were made in the paddy-fields, and the irrigation canals were buried. In their work of restoration following the disaster, the farmers removed the detritus from the paddy-fields and irrigation canals, and piled it up in one part of the paddy-fields, which they later leveled out to make upland fields. These up-land fields formed the “shima-batake.” The present writer, however, cannot agree with this opinion in view of the fact that “shima-batake” are distributed even in diluvial tablelands that are entirely free from any danger of flooding, as well as for other reasons. The present writer holds the following view: In regions where “shima-batake” are distributed, the slope of the land surface is extremely gentle, and the surface abounds in micro-relief. (In general, the difference in height between the high parts and the low parts is less than about 80cm.) Again, the water-level of the irrigation canals in such regions is approximately the same as the height of the lowest part. Moreover, the source of irrigation water is far from abundant. In such a region, in the days before pumps could be used, the farmers had no choice but to level down the high parts and make paddy-fields in order to expand their paddy-fields. The present writer thinks that it was as a result of the expansion of paddy-fields in these regions by individual farmers that the complex distribution pattern of paddy-fields and upland fields was formed. Recently, in regions where plentiful irrigation water has been made available by the use of pumps, “shima-batake” have been leveled out, and the whole region has been made into paddy-fields. Again, in regions where the area of paddy-fields cannot be expanded because of the limitation of irrigation water, and in other places where it was felt desirable that the upland fields should be left as they were, numerous small “shima-batake” have been combined to form upland fields with large areas.