Application of Multi-Temporal LiDAR for Gully Erosion Monitoring in Mediterranean Intensive Olive Groves

Monitoring the dynamics of gullies in Mediterranean agrosystems is critical but severely limited by agricultural practices that generate continuous machinery compaction and tillage of the soil, camouflaging topographic features and disturbing erosion analyses. This study discusses strategies to quantify erosion by distinguishing natural erosion from agricultural disturbance, integrating multitemporal LiDAR data (2014, 2020, 2024) with gully inventories using orthophoto maps (2011–2022). The volumetric changes were assessed using DoD for the periods 2014–2020 and 2020–2024, and the morphometric performance of the TNO index was further validated using ROC curves in R. Both approaches performed consistently higher in detecting permanent gullies. The TNO index has proven its usefulness for semi-automated delimitation in large or low-data areas. By intersecting DoD surfaces with the gully inventory, localized erosion processes were successfully isolated from the surrounding agricultural landscape matrix. The quantified rate of erosion in the gullies refers strictly to their internal dynamics, which have been close to the natural threshold for soil formation, indicating a risk of soil degradation.