A new method for determination of most likely landslide initiation points and the evaluation of digital terrain model scale in terrain stability mapping

摘要

This paper introduces a new approach for determining the most likelyinitiation points for landslides from potential instability mapped using aterrain stability model. This approach identifies the location with criticalstability index from a terrain stability model on each downslope path fromridge to valley. Any measure of terrain stability may be used with thisapproach, which here is illustrated using results from SINMAP, and fromsimply taking slope as an index of potential instability. The relativedensity of most likely landslide initiation points within and outside mappedlandslide scars provides a way to evaluate the effectiveness of a terrainstability measure, even when mapped landslide scars include run out zones,rather than just initiation locations. This relative density was used toevaluate the utility of high resolution terrain data derived from airbornelaser altimetry (LIDAR) for a small basin located in the Northeastern Regionof Italy. Digital Terrain Models were derived from the LIDAR data for arange of grid cell sizes (from 2 to 50 m). We found appreciable differencesbetween the density of most likely landslide initiation points within andoutside mapped landslides with ratios as large as three or more with thehighest ratios for a digital terrain model grid cell size of 10 m. This leadsto two conclusions: (1) The relative density from a most likely landslideinitiation point approach is useful for quantifying the effectiveness of aterrain stability map when mapped landslides do not or can not differentiatebetween initiation, runout, and depositional areas; and (2) in this studyarea, where landslides occurred in complexes that were sometimes more than100 m wide, a digital terrain model scale of 10 m is optimal. Digitalterrain model scales larger than 10 m result in loss of resolution thatdegrades the results, while for digital terrain model scales smaller than 10m the physical processes responsible for triggering landslides are obscuredby smaller scale terrain variability.