Landslide site reconstruction with terrestrial laser scanning

The study of a landside site involves many aspects of data collection and data analysis activities. Among the data to be collected are the site location, the landside orientation, the soil profile, and the vegetation cover. Although these data (such as the topography and the distribution of trees) are 3-dimensional in nature, they are usually collected and examined in a 2-D fashion to simplify the data collection process and to facilitate the subsequent stability analysis. While this is adequate in many landslide problems, it may be too limiting in dealing with complex situations and sliding scenarios. To refine the data collection methodology and apply it to challenging filed environments, a fast and reliable surveying system is required. This paper reports a recent experience in using a terrestrial laser scanning system to perform terrain and vegetation mapping. The study site is located in the Wen-shan district of Taipei City, Taiwan. Because roughly half of the city's area is mountainous area, many landslides occur during the typhoon seasons. The case study site is a part of the challenging Mt. Houshanyue hiking trail that collapsed after the Kalmaegi typhoon (July 2008) and the Sinlaku typhoon (September 2008). It is north to a tea plantation and near a Taipower 345 kV transmission tower. The total area affected by the landslides is about 10 hectares and the elevation change is quite significant, about 80 meters in the study area. Using a terrestrial laser scanning system, the landside site was scanned and mapped in a very short amount of time and the results reached the level of detail never before achieved by the traditional surveying methods.