Regional investigation on seasonality of erosivity in the Mediterranean environment

The rainfall erosivity, playing a decisive role into erosion and degradation of soils, is a relevant factor for land-use planning and environmental risk assessment. Its decisive role must be studied by also taking in mind the outlook of climate change. The observations needed to determine the erosivity with adequate temporal and spatial detail, however, are rarely available. The aim of this study consists in assessing the spatial and seasonal distribution of rainfall erosivity in the Mediterranean environment. A regional analysis of erosivity was conducted considering more than 45 thousands erosive rainstorms in Calabria (Southern Italy). A network of 155 rain gauges, well distributed over the region, provided the necessary information with a time detail of 5 min between 1989 and 2008. After a concise review of the literature, three time scales were considered: monthly, daily and "single event" scale. A power law relationship between the values of rainfall and erosivity, obtained by analysing the erosive rainstorms, was applied, showing systematic seasonal variations. The climatic control on erosivity was well described by regression equations formed by a constant value (wet period) and a cosine curve (dry months). This seasonal trend testifies that a greater erosivity per unit of rainfall has to be expected in the driest months. In addition, altitude ranges in Calabria from sea level to over 2,000 m a.s.l., affecting the rainfall regime. Considering this aspect, the regression equations were slightly improved by including the influence of the altitude in the analysis of erosivity. The erosivity maps, achievable in the Mediterranean climate area through the methods and equations proposed in this paper, can provide a significant contribution towards the modelling of detachment and transport of soil particles at the catchment scale. © 2014 Springer-Verlag Berlin Heidelberg.