Volume estimation of small scale debris flows based on observations of topographic changes using airborne LiDAR DEMs

This paper describes a geographic information system (GIS)-based method for observing changes in topography caused by the initiation, transport, and deposition of debris flows using high-resolution light detection and ranging (LiDAR) digital elevation models (DEMs) obtained before and after the debris flow events. The paper also describes a method for estimating the volume of debris flows using the differences between the LiDAR DEMs. The relative and absolute positioning accuracies of the LiDAR DEMs were evaluated using a real-time precise global navigation satellite system (GNSS) positioning method. In addition, longitudinal and cross-sectional profiles of the study area were constructed to determine the topographic changes caused by the debris flows. The volume of the debris flows was estimated based on the difference between the LiDAR DEMs. The accuracies of the relative and absolute positioning of the two LiDAR DEMs were determined to be +/- 10 cm and +/- 11 cm RMSE, respectively, which demonstrates the efficiency of the method for determining topographic changes at an scale equivalent to that of field investigations. Based on the topographic changes, the volume of the debris flows in the study area was estimated to be 3747 m(3), which is comparable with the volume estimated based on the data from field investigations.