Abstract
Large-scale landslides often cause severe damage to lives and properties; therefore, their identification is essential in order to adopt proper mitigation measures. The objective of this study was to set up a methodological approach to help identify large-scale landslides using Lidar data, aerial photos and field investigation. The selected study areas were the Namasha and Liuoguey Areas in Kaohsiung City, Taiwan, both of which were severely hit by the Typhoon Morakot in 2009. The identification of large-scale landslides was performed based on Lidar high-resolution topographic information. The linear structures were mapped according to the shading map, with aspect in different azimuth to show good details of the structures. The scarps of the landslides were also identified. Validation of the results was done using both aerial photos and field investigations. In addition, stability analyses were performed on designated cases to further validate the results of Lidar identification.
Highlights
Due to the fragile geologic structures and steep terrains, the heavy rainfall carried by typhoons often causes landslide and debris flow in Taiwan
It is observed that the scars/linear structures identified using Lidar data are similar to the identified landslides from the aerial photo
Due to the high geomorphologic resolution, Lidar data proved to be very helpful in identifying the scars/linear structures associated with large-scale landslide in comparison to using aerial photos, especially for the vegetated sites
Summary
Due to the fragile geologic structures and steep terrains, the heavy rainfall carried by typhoons often causes landslide and debris flow in Taiwan. Other large-scale landslides were observed in both the Chishan and the Laonong River watersheds. These landslides that occurred upstream of the debris flow torrents often contributed to debris transport, thereby increasing debris flow, and causing severe hazards and secondary hazards such as landslide dam and dam burst, or further debris transportation in subsequent rainfall events. An example of a large-scale landslide near the Tai-27Jia Highway next to the Laonong River is shown, where its head scarp can be identified. Investigation and identification of potential large-scale landslides is crucial for hazard reduction
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