Terrane mapping on the dip-slope based on high-resolution DTM and its geological implications at the Huafan University campus in northern Taiwan

Analyses of slope stability is a critical issue in mountainous areas in Taiwan, for slope failure often causes great damage to local and even regional communities. A dip-slope about 20° toward southwest has been confirmed, on which the Huafan University campus is founded in the northern end of the Western Foothill belt in northern Taiwan. Continuous monitoring systems for the dip-slope by means of inclinometers and groundwater gauges have been set up within the campus for 15 years. Furthermore, a numerical three dimensional modeling for the landslide runout of the dip-slope has also been achieved and proposes potential failure mechanisms. Nevertheless, geomorphic and geological conditions which may be related to the slop failure in the study area were unclear owing to dense vegetation and artificial objects. A 3-D GIS mapping method on the basis of a high-resolution digital terrane model (DTM) derived from LiDAR technology is applied to this area. The high-resolution DTM can be used to distinguish small-scale natural morphology of geomorphic and geological features and structures. Results of the analyses reveal several bulges existing at lower part of the dip-slope, implying potential creeping behavior. In addition, narrow and small gullies are also found on one of the flanks of the dip-slope, and may raise instability if erosional processes continue within the gullies on both lateral sides of the slope mass. On the other hand, traces of a potential fault striking NNE-SSW through the campus is also proposed. The existence of the potential fault can explain the phenomena of groundwater exudation in some places within and outside the campus. Furthermore, bedding plane traces of the bedrock formations by the 3-D mapping method perform inconsistent attitudes within the campus and adjacent regions, resulting in a concave morphology of the landform. It is thus assumed that the potential fault and fold-like structures probably resulted from tectonic stress coming from the southeast due to tectonic plate movements.