Sediment Generation from Numerous Shallow Landslides Related with Clear Cutting at Granite Mountain, Mt. Ichifua, Japan : Veränderungen im Natur- und Kulturhaushalt und ihre Auswirkungen : INTERPRAEVENT

2000

8 Lit. Ang.

Unselbständiges Werk

13124

200084951

A large number of shallow landslides occurred on Mount Ichifusa (Granite, catchment are: 223.7 ha and averaged slope: 36°). Kyushu Island, Japan, due to the clarcutting of broad-leaf forest between 1960 and 1970. We measured the expansion of the landslide area and determined the volume of sediment generated since clear-cutting began 25 years ago. Measurement of landslide area and averaged depth of landslide scar were used to calculate the gross volume of sediment generated from landslides. Temporal changes in landslide areas were determined by interpretation of aerial photographs taken in 1976, 1979, 1984, 1989 and 1994, and the average depth of landslide scars was measured by field survey. The landslide area was 21 ha in 1979, cumulatively increasing to 47 ha (1984), and 96 ha (1994), which accounts for about 60 % of the entire hill slope area. The average depth of landslide scars was 1.12 m. Since 1973, the rate of sediment generation was 300-490 mßha®Üy®Ü, with interuptions between 1984 and 1989. The volumetric change of sediment generated from 1976 to 1994 was 1.13x10 hoch 6 mß.