The Geomorphometry of Rainfall-Induced Landslides in Alishan Area Obtained by Airborne Lidar and Digital Photography

For understanding the distribution of slope angles, OHM and roughness of the rainfall-induced landslides in Alishan Area of Central Taiwan, a survey was carried out with airborne Lidar and aerial digital camera to obtain DEM and DSM of 1 m grid and color orthophotos of 50 cm grid. DEM, DSM and orthophotos are georeferenced and co-registered. The 106 landslide polygons derived from photo-interpretation are used for extracting slopes, OHM and roughness. Results show that the average slope angle of landslides is 41 degrees with a standard deviation of 14 degrees; average OHM is 4.4 m with a standard deviation of 6.3 m; average roughness is 2.05 m with a standard deviation of 2.56 m. It is also observed that scale effects are obvious for roughness but not for slope and OHM when the grid is larger than 40 m, which is the average dimension of landslides. These morphometric parameters can be further applied in the automation of landslide inventory.