A new strategy to assure compliance with soil loss tolerance at a regional scale

The relevant erosive effects of extraordinary rainfall events due to climate change require establishing soil conservation strategies to prevent damages due to hydrogeological instability. The “tolerable” soil loss, i.e., the maximum soil loss compatible with sustainable soil use, represents a quantitative target to establish the effectiveness of actions to control soil erosion. In this paper, a new approach to defining the condition corresponding to a tolerable soil loss is proposed. At first, using the statistical analysis of the measured annual values of the rainfall erosivity factor, the cover and management factor CT, for which the maximum tolerable soil loss is equal to the annual soil loss of given return period T, is defined. Then, for the Sicilian region, a relationship between the CT factor obtained for T = 1000 years and the mean annual value of the rainfall erosivity factor, R, is established. For a given value C of the cover and management factor, this relationship allows for the establishment of the corresponding mean annual rainfall erosivity factor, named Rland-use. The result C ≤ CT for T = 1000 years is obtained for areas with R ≤ Rland-use, and the compliance with soil loss tolerance is then assured. Conversely, for areas characterized by R > Rland-use, the reduction of C to a value less than CT for T = 1000 years is required to obtain a tolerable soil loss condition. Finally, for the Sicilian region, the overlay between the C spatial distribution for arable lands (mainly cereals and legumes) and areas covered by vineyards, derived from the land use map, and the CT spatial distribution allowed to define areas in which tolerable soil loss conditions occur or soil conservation strategies are required.