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In this study, the main focus is the application and improvement of four empirical models, which account for the pyroclastic cover deposit thickness (PCDT) spatial distribution with respect to the bedrock surrounding the Somma-Vesuvius volcano(Campania, southern Italy). Three models, which are already known in the literature, link the depth to bedrock to the morphologicalfeatures of a slope. An original model called SEPT (slope exponential pyroclastic thickness) is presented in this manuscript and combinesthe initial total thickness of ash-fall pyroclastic cover with the slope gradient. All models were applied and validated using field measurements derived from this and preceding studies in the study area. The main finding is that the spatial distribution of the depth to bedrock in mountainous peri-volcanic areas mainly depends on the initial thickness of air-fallen material at a given position and slope angle. These findings allowed for the recognition of an ash-fall pyroclastic depositional environment that is characterized by different processes from those existing in other geomorphological frameworks and in which the soil thickness along the slopes is controlled by the weathering of bedrock and the formation of soilin situ. Finally, in this research, a reliable approach is proposed that is also applicable to other peri-volcanic areas of the world to assess the spatial distribution of the depth to bedrock, which is a fundamentally important parameter in distributed geomorphologic and hydrologic modeling.