Survey method of debris flow traces using airborne LiDAR data for peak discharge estimation

Abstract

In this study, we propose a method to estimate the peak discharge of debris flow by surveying debris flow traces using digital elevation model (DEM) and DEM of difference (DoD) generated from airborne LiDAR data. The accuracy of the DoD was affected by slope and point density. In particular, areas with slopes greater than 40°or point densities less than 10 points / 25 m² showed an increase in the DoD error, with the error of at least 0.2-0.3 m. When areas with topographic changes greater than the DoD error were considered as trace areas, these areas were close to the areas considered by conventional field survey. Hence, it is likely that topographic changes beyond the DoD error have occurred in the area where debris flow occurred. At the survey points in this study, we considered areas where the topographic change on the DoD was 0.2-0.4 m or greater as trace areas. When peak discharges were estimated from these trace areas, the probability that peak discharges were in the range of half to twice that of conventional field surveys was about 50%. Furthermore, the probability was about 70%, when peak discharges were estimated only from the survey points where the superelevation was 1 m or higher. In the future, it is necessary to study the method of setting the radius of curvature and to verify the validity of the results of estimating flow velocity and peak discharge.