Topography analysis of Houshanyue landslide

This study is a part of a long-term project near the Houshanyue hiking trail located in the Wenshan District of Taipei. The study site at Houshanyue first had a major landslide in September of 2008 triggered by Typhoon Sinlaku. For the next few years, the weather was relatively calm, and no major landslides occurred again. Vegetation began to recover gradually. The next heavy and concentrated rainfall did not arrive until August of 2012 (Typhoon Saola), and the study area had another major landslide. Before and after the 2012 landslide, a terrestrial laser scanner was brought to the site to scan the topography of the landslide surface. The data derived from the scans (three-dimensional point clouds) as well as a UAV (unmanned aerial vehicle) flight were used in the subsequent analysis. Slope gradients and slope orientations were calculated in grids of different sizes for all three sets of data, and maps of topography, slope gradient, and slope orientation were created. The change of terrain surface was easily seen in the resulting maps. Important observations were made from the analysis results.