The study on method to draw large-scale soil map in diluvial soil area in Hokkaido, using digital elevation data for a 10 m grid.

摘要

To understand the detailed soil distribution of a terrace with a diluvial deposit, the method to draw a large-scale soil map was studied in Urausu Town of Sorachi district (Hokkaido, Japan) by combining soil survey and digital elevation data for a 10 m grid. Based on the soil survey, soils in the research area were classified into 3 soil series groups according to 'Classification of Cultivated Soils in Japan, Third Approximation,' which were 'skeletal terrace brown forest soils,' 'fine-textured aquic brown forest foils' and 'fine-textured haplic gray upland soils'. In addition, 'fine-textured haplic gray upland soils' were classified into 2 categories based on the abundance of gravel in the subsoil. A slope map in the research area was made with digital elevation data for a 10 m grid. From the relationship between soil types and slope, it was clear that 'skeletal terrace brown forest soils' were distributed in the areas with more than 4 degrees slope. 'Fine-textured aquic brown forest soils' were distributed in the areas with slope of 2 to 4 degrees . On the other hand, without regard to abundance of gravel, 'fine-textured haplic gray upland soils' were distributed in the areas with less than 2 degrees slope. Precise soil distribution of each soil series group was drawn based on the above relation and the slope map. The obtained map reflected exactly the precise soil distribution for each soil series group, except for the areas of topographical modification. The abundance of gravel in subsoil of 'fine-textured haplic gray upland soils' increased in the terrace whose slope was mainly middle or high. It is suggested that the characteristics of topography for each target terrace must be clarified to draw a large-scale soil map based on precise soil classification in a diluvial soil area using digital elevation data for a 10 m grid..