Relationship between the Type of Terraced Field Slopes and the Surface Geology

Abstract

Terraced field slopes is an element that gives the uniqueness of the area to the landscape of terraced fields. In the terraced field slopes, there are earth slopes and stone masonry. If the origins of the kind of terraced field slope is clear, when the farmland consolidation and the landscape conservation were planned in the terraced field areas, it may be also used to select the construction method of terraced field slope. This study quantitatively indicated the relationship between the type of the terraced field slopes and the surface geology. Rock classifications and geological epochs on 464 terrace field districts in Japan were analyzed. As the results, in the igneous rock, districts of stone wall have majority. However, in volcanic rocks, all districts that have surface geology before the late Pleistocene of the Cenozoic were earth slopes. In plutonic rocks, districts of stone wall have majority, too. However, districts of 27% that have weathered granitic rocks were earth slopes. In sedimentary rocks, 90% districts that have surface geology after the Paleogene of the Cenozoic were earth slopes. And 97% districts that have surface geology before the Paleogene of the Cenozoic were stone masonry. In the accretionary complex and metamorphic rocks terraced field slopes were almost stone masonry.