[H-GG01] Dialogues on natural resources and environment between earth and social sciences

[HGG01-P01] Assessing the potential risk of land degradation in mountain area from the distribution of fine grained materials

★Invited Papers

*Hiromu Daimaru¹ (1.Forestry and Forest Products Research Institute)

Keywords:Hillslope conservation, land degradation in mountains, fine-grained materials, erosion

Japan's erosion control projects have been aimed at restoration of forests on degraded lands. A review of past erosion control projects reveals a common feature: most of the land where degradation has occurred is covered with fine-grained surface materials. "Hage-yama" that is a representative of the land degradation in Japanese mountains, have occurred on the low relief mountains with thick granitic weathering mantle in central to western Japan. Afforestation works in coastal area in Japan, was aimed at preventing movement of sand dunes whose vegetation covers had been destroyed by past human activities. Most of the degraded bare lands on the ridges of the Kitakami Mountains in northeastern Japan were caused by wind erosion of silty volcanic ash derived from Mt Iwate Volcano.
All of these land degradations are caused by the destruction of vegetation cover by past human activities, and the removal of surface fine-grained materials due to erosion by surface water, strong winds and frost heaves, and the presence of fine-grained surficial materials behind these land degradations can be mostly predicable by physical geography. The perspective of geography, which aims to clarify the relationship between human activities and the natural environment, can contribute to make clear the mechanism and predicting the risk of mountain land degradations in Japan.