Use of multitemporal airborne lidar surveys to analyse post-failure behaviour of earth slides

Two helicopter-borne LiDAR surveys were conducted in August 2004 and May 2005 on a 2 km2earth flow that was totally reactivated in late winter 2004. Shaded view maps and differentialanalysis of terrain models from the two surveys allowed residual movements, as well as ruptureand accumulation features over the slope, to be assessed and mapped for the period between 2004and 2005. In particular, it has been made evident that residual movements involved about 20% ofthe whole landslide area. Retrogression of the crown zones, with a depletion estimated in theorder of maximum 20 m, was coupled with a more than 10 m advancement of the deeptranslational slide affecting earth and rock materials in the source area, that resulted in anapparent uplift of more than 15 m. Down slope, the upper accumulation lobe sector was loweredby about 10 m due to depletion and also by the progressive decrease in water content.This analysis proved the usefulness of LiDAR surveys for analysing post-failure behaviour ofthis type of mass movements.