Forest vegetation recovery process on a landslided hillslope for 75 years

in Nakanosawa watershed, the western Tanzawa

Abstract

The Tanzawa mountains is important water source forest area in Kanagawa Prefecture. However, it is the place where the landslide and mudflows occurred frequently by the Great Kanto Earthquake in 1923, and subsequent heavy rainfalls, etc. It is thought that sufficient water and soil preservation function is not exhibited because many landslides remain still now. The purpose of this study is to clarify the vegetation recovery process of landslides in Nakanosawa watershed(370 ha), Kurokura basin. Changes of the landslide feature by aerial photographic analysis and field survey which investigated the vegetation recovery of remained landslides were performed. The difference of landslide area between the recovered landslide by vegetation for a short period and the remained landslide is not found. Slope angle, slope direction and altitude of the landslide were greatly involving as a factor of vegetation recovery.