Using Airborne Laser Scanning to Assess Forest Protection Function against Rockfall

Forests situated on slopes in mountainous areas can provide protection against natural hazards such as avalanches and rockfall. Quantifying this mitigating effect requires accurate mapping of forest stands and estimation of their dendrometric characteristics. However, steep terrain and lack of accessibility hamper field surveys. Airborne Laser Scanning (ALS) is a remote sensing technique whose potential for the retrieval of forest parameters has been widely investigated in the past ten years. The objective of this study is to assess the potential of ALS for estimating stand parameters required as input data for rockfall simulation models or more generally for quantifying the rockfall protection function of forests. ALS data was acquired over an 8.6 km area including coppice stands and deciduous stands on poor quality sites. Multiple regression models were established between laser-derived metrics and forest variables from 31 field plots. The coefficients of determination for stem density, mean diameter, dominant height and basal area ranged from 0.43 to 0.80. Comparison of cross validation results showed that laser-derived estimates are more accurate than values obtained by interpolation of field data.