Evolution of large-scale paleo-landslides in volcanic area reconstructed based on LiDAR technology

The key information of landslide, including the range of landslide, morphological features, volume estimations, etc., is important when analyzing the triggering mechanism, hazard assessment and mitigation. For a paleo- landslide, however, these features could often be masked by the successive surface processes after sliding. To alleviate this difficulty, this research proposes a topological reconstruction method to enable the assessment of the key information based on the DEM derived from high-resolution LiDAR images. Two large-scale landslides in volcanic terrain were studied. Accordingly, the paleo-morphology of the slide area before landslide was reconstructed based on the originally undisturbed dome-shaped topography, by supposing the volcano kept an ideal conic shape and comparing with the nearby un-eroded hillslopes of the same volcanic cone. The morphology of the studied landslides is characterized by very gentle slope profile within the slide area and a steep cut-off slope situated around the toe indicating a surface singularity. By employing proposed reconstruction method, the landslide volume was then estimated from two different DEM, before and after the landslide. The total removed volume of these two paleo-landslides is about 820 ± 20 × 106 m3. The incision of creeks is accordingly obtained from the discrepancies between the current DEM and its envelope surfaces. By comparing to the current creek profiles, it shows that the maximum amounts of incision are situated in the middle to lower slope within the slide area, implying the effect of normal faulting as an important factor for triggering landslides and for topographic evolution. The maximum amount of incision could be as high as 15 m, which indicates the observed event(s) from the LiDAR topographic data are indeed ¡§paleo¡¨ landslide(s). As a result, this study demonstrates the LiDAR technique as a powerful tool for landslide analysis and also provides methods for analyzing paleo-landslide of various categories.