Abstract
Shallow landslide, rapid sliding of topsoil or topsoil-weathered subsoil, is repeated periodically at a same site as the previous landslide scar on steep hill slope covered with forest vegetation through natural reforestation and soil-debris accumulation. A purpose of this study is to estimate the recurrence interval of shallow landslide at the same site on steep hill slopes in Yakushima island. Field work for recognition of land slide scars and Koya pyroclastic now deposits of 6300 years B.P. was carried out at the survey sites. Each landslide scar was dated using tree age of Cryptomeria japonica as indicator plant.
The landslide recurrence interval is estimated to be approximately at least 1000 to 1400 years from the age of the oldest scar on the steep hill slopes at the survey sites. It is probable that the landslide recurrence interval makes shorter the life span of Cryptomeria japonica on the steep slopes.
