Rock Slope Denudation Processes at Mt. Shakushi in the Hakuba Mountains

The denudation processes at the rockwall of Mt. Shakushi (Hakuba Mountains) were investigated by examining the recent retreat (1976-2023) of a slope linked to a rock slope failure in 2005, using multi-year 3D topography models created from SfM-MVS software together with aerial photographs and UAV images. The results show that denudation occurred frequently on rockwalls with high joint density. Two parallel cracks were observed in the head area of the rockwall before the collapse in 2005. The collapse occurred along one of the two cracks. The remaining crack expanded between 2019 and 2023, such that the rockwall is now in an unstable state. In addition to the observed denudation processes and their joint density dependence, crack expansion along one of the dominant joints was revealed, indicating that gravitational deformation plays an important role in denudation.