Empirical relationship for the estimate of pyroclastic soil thickness using slope steepness

The assessment of soil thickness plays a primary role in different areas of the geosciences, including landslide hazards and soil erosion assessment. Nevertheless, the thickness of the cover deposits is difficult to measure over large areas while the prediction with numerical models is still challenging. In this study, some topographic attributes, namely slope angle and profile curvature, are investigated as proxies for the estimate of soil thickness of pyroclastic cover through empirical relationships. The study area is the North-facing slope of the Lattari Mts. (Campania, Southern Apennines), which were historically affected by several flow-like landslides and flash floods. The dataset was collected with both direct and indirect measurements from field surveys and investigations in two test sites of the study area. The topographic parameters were derived from DEMs at three different cell sizes, respectively at 1 × 1 m, 5 × 5 m, and 10 × 10 m. The slope angle at 5 × 5 m resulted in the most fitting parameter with the soil thickness, whereas the curvature showed a low correlation at all the investigated scales. The relationship for the Pyroclastic Thickness Estimation (PTE) is defined by an exponential law, which was validated by an internal and external dataset and checked against other predictive models used in the literature for similar study areas.