| The M 6.7 Hokkaido eastern Iburi earthquake, occurred in September 2018 at a depth of ca. 35 km, caused numerous landslides in the hilly area of ca. 20 km N-S and ca. 20 km E-W in the western edge of the Yubari Mountains. Some of the distinct features of the earthquake-induced landslide event were the extremely high density of landslide occurrence, which created the large area of bared slopes, and the large amount of sediment which accumulated at the footslopes and in the stream valleys. The large amounts of sediment at the footslopes and in the stream valleys, as well as soils and sediments remaining on the bare slopes, are supposed to be eroded and discharged from the catchment over time. Some of the key questions here should be how the catchment responds to such altered (disturbed) geomorphic conditions, and how long it takes to reach a steady state of sediment discharge after disturbance, given the geo-ecological conditions in northern Japan.
An important finding through field-based observation of a disturb catchment was that revegetation on bared slopes appeared slow, which was at least partially attributed to strong solifluction in early winter and early spring. Slow revegetation seemed affecting steady erosion of and efficient sediment transport through gullies on the bared slopes.
We report our 2-year measurement of solifluction, gully erosion and revegetation processes on the bared slopes, and 5-year monitoring of sediment discharge at the outlet of a ca. 5 km2 landslide disturbed catchment, which should provide useful field-based data for examination of: 1) the mechanism of erosion and sediment discharge (in other words, slope and stream connectivity) on the disturbed slopes by landslide under the geo-ecological conditions in northern Japan, and 2) catchment-scale geomorphic response to the major landslide event over time. |
