Assessment of α and γ parameters in landslide volume estimation equations based on geological variability

This study targeted 15 geological sites in five regions of Japan where landslides occurred due to heavy rainfall between 2014 and 2019. The changes in elevation before and after each disaster were estimated using LiDAR DEMs, and the sediment volume (V) associated with each landslide was calculated. The α and γ coefficients in the landslide volume estimation equation, expressed as V = αAγ (where A is the landslide area), were investigated to clarify their dependency on landslide depth and geological factors, and the results were compared with those of previous studies. The findings showed that there is a negative correlation between the α and γ values, and that the γ value increases as the ratio of the increase in landslide depth to landslide area increases. In terms of geology, igneous rocks tended to have high α values and low γ values. This is hypothesized to be due to a function of the landslide morphology, wherein the landslide depth does not change markedly depending on the area of the landslide. The α and γ values for plutonic rocks and sedimentary rocks were widely distributed, and this was considered to be due to the diverse array of landslide morphologies and their underlying geologies. Metamorphic rocks tend to have a low α values and high γ values, which is suggestive of a landslide morphology in which the ratio of the landslide depth to the landslide area increases.