Comparative Analysis of Ice Break Damage in Two Börzsöny Mountain Valleys in Hungary in 2014 Based on Airborne Laser Scanning

Severe mechanical damage from frost and ice on trees occurred in the Börzsöny Mountains in Northern Hungary during 1–2 December 2014. The frost and ice affected 10,000 hectares overall; however, the two examined valleys suffered conspicuously different extents of damage. While the Rakottyás Valley study area had severe damage, the Pogány-Rózsás Forest Reserve suffered only moderate damage. Airborne Laser Scanning (ALS) and a field survey were utilised to assess the damage. Digital Surface Modell (DSM), Digital Terrain Model (DTM), and Normalised Digital Surface Modell (nDSM) were calculated from the dense point cloud in 3D. Elevation, slope and aspect were derived to describe site conditions. Damage thresholds were set for the ALS data (tree height < 5 m) and the ground-based damage (frequency > 90%). These were compared in a confusion matrix on a pixel scale, which showed partial agreement due to different sampling methods and ranges but also indicated that Rakottyás was more damaged (54.35% of the area) than Pogány-Rózsás (36.7%). The Total Accuracy was 0.54.