Openness methods can visualize the topographic character of angular measure between surface relief and horizontal distance; it is a useful tool for determining geomorphic fractures. We adopted the high-resolution Airborne LiDAR (Light Detection And Ranging) DEM to obtain the positive and negative values. Positive shows reflect ridge, scarp and terrace, whereas negative describe valley, river and gully. Red Relief Image Map (RRIM) can identify fine-scale geomorphic change when it is combines the positive and negative values. Many of the characteristics that obtained from the negative calculation (marked in gray-scale) and an analysis of stacked slope (marked in red-scale), to interpret the position of eroded gullies in the Tsaoling sliding area. In this study, we investigated the distribution of erosion gullies and calculated the bedrock incision rate for the Cholan Formation and Chishui Shale for 1999 and 2011, which were 31 to 39 cm/year and 54 to 89 cm/year on average, respectively. These results indicated that the Cholan Formation has a higher resistance to erosion than the Chishui Shale, where the erosion was more serious.

The paper draws the topographic characteristics of the landslide induced by Chi-Chi Earthquake and Typhoon Morakot in Ai-Liao catchment, in slate stratum. The result from topographic analysis on the DEM shows 90% landslides induced by earthquake are small than 10 ha, the average slope is 30-50o, and 75% of landslide locates at the ridge or the mountainside of the slope. Oppositely, the 52% landslides induced by typhoon are large than 10 ha, the average slope of landslide is gentle to the one of earthquake landslides and 81% of landslides locates at the mountainside or the toe of slope. The analysis result also demonstrated that a certain degree of deflection usually occurs before a sliding initiation that suggests the deformation (and the subsequent damage) of the massive landslide is progressive. Moreover, the profile curvatures of landslide cases are close to the curvature 1×10-4 (1/m), the landslide possibility rises up at where curvature beyond the value.

The heavy rainfall of Typhoon Morakot caused severe damage to infrastructures, property and human lives in southern Taiwan in 2009. The most atrocious incident was the Hsiaolin landslide which buried more than 400 victims. Consequently the airborne LiDAR survey was carried out from 2010 to 2012 by Central Geological Survey, MOEA in Taiwan to produce 1m x 1m high resolution DEM and aerial ortho-photo images in order to build up post-disaster high resolution DEM database and apply to such as investigate and analysis for geologically sensitive areas, Geological and Topography characteristics, Potential geological disaster, River system analysis. the key projects is to investigate and analysis large-scale landslides, the result shows that there are hundreds of large-scale landslides area in central, southern and eastern Taiwan. For those potential landslides site near villages, monitoring instruments such as single-frequency GPS, rainfall recorder and electro-optical theodolite have been set up to detect the surface displacement. More monitoring instruments such as tiltmeter, inclinometer, rain gauge, extensometer and Time Domain Reflecometry (TDR) will be deployed in high susceptibility landslide area in the near future.

The typhoon Morakot in 2009 August caused lots of deep-seated landslides in southern Taiwan, especially the most serious ones in Hsiaolin village. In order to prevent this kind of serious disaster, interpretation of potential deep-seated landslides is an important work that leads to disaster prevention and mitigation of future important information. During the develop of deep-seated landslides movement process, some characteristics often can be found from terrain data. We use different resolutions of the digital terrain data and images to interpret the sites of potential deep-seated landslides, the results show that high precision digital terrain data from airborne LiDAR (Light Detection And Ranging) can provide more subtle topographic characteristics, greatly improving the capability to interpret the potential deep-seated landslides, with aerial photos during the interpretation. Results of the interpretation are validated through field work to ensure the accuracy.

Taiwan is located on the circum-Pacific seismic zone, the active tectonic actions, steep terrain, and geological structures provide abundant debris material. The seasonal typhoons with heavy rainfall often cause landslides and debris flow .The aerial photos or satellite images are often used for interpretation of landslides, debris flow, and other geohazards, but the results are affected by topography, shades, cloud cover, and vegetation. With the development of high resolution LiDAR technique, this study uses aerial photos and satellite images as well as LiDAR shading map for identification of landslides and debris flow. Comparisons of the results from LiDAR shading maps and aerial photos are made, and differences of the interpretation results are discussed. Using LiDAR for interpretation of landslides and debris flow provides accurately large-scale landslides identifications of and can exclude unfavorable factors in using aerial photos or satellite images. The landslides interpreted by LiDAR are mostly large-scale landslides. By LiDAR also provides good results of debris flows interpretation along with river channels, and alluvial fan. However, the small-scale landslides are difficult to identify using LiDAR shading map.