High-Resolution Soil Erosion Assessment in Mediterranean Olive Orchards Using Drone-Based Digital Elevation Models and Surface Runoff Monitoring

Soil erosion is a critical environmental issue in Mediterranean regions, caused by climate change and unsustainable farming practices. The combination of intense rainfall, extended drought periods, and conventional farming techniques significantly degrades topsoil, creating risks for soil fertility and crop productivity. This study aims to assess soil erosion risks in hilly olive orchards using cutting-edge technologies -drone-based digital elevation models (DEMs) and surface runoff monitoring- to quantify soil loss with high precision.

In the first phase of our research, we focused on direct measurements of soil loss collected from an experimental setup. An experimental area allowed for the collection of sediment samples after rainfall events, which were analyzed to estimate soil loss. Simultaneously, we employed an advanced drone equipped with a LiDAR camera (DJI MATRICE 350 RTK) to create high-resolution DEMs before and after rainfall events. The Difference of DEMs (DoD) methodology was used to calculate soil displacement, with millimeter-level accuracy. These values were then validated using direct soil loss measurements from the experimental runoff collection system.

The second phase of our study explored the use of a more affordable, commercial drone (DJI Phantom 4) for soil erosion analysis. This drone, equipped with an RGB camera, offers a cost-effective alternative but requires orchards with low density vegetation. A newly planted 0.2-hectare olive orchard with low tree density provided an ideal test site. Preliminary findings indicate that tractor operations such as tillage and plowing in combination with intense rainfall events caused the displacement of approximately 80 m³ of soil. As we continue to monitor the site, we are awaiting the end of the rainy season in late spring to use the drone again and estimate additional erosion caused by rainfall events.

By combining both high-resolution LiDAR-based DEM analysis and direct measurements of soil loss, this study demonstrates the potential of drone technology -both advanced and commercial- to accurately assess soil erosion. These methodologies offer valuable insights into the effects of different land management practices and can inform sustainable farming strategies in Mediterranean olive orchards facing the challenges of climate change.