Rainwater infiltration is the major cause of failure in unsaturated slopes. Analyses carried out to model groundwater flow in a partially saturated pyroclastic slope (Pirone, 2009) highlight the influence on the failure mechanism of the hydraulic condition at the upper boundary. Based on this consideration, slope stability may be reasonably increased by reducing water flow infiltrating into the subsoil. This objective can be pursued by reducing the permeability of the superficial soils through spraying a mixture of water, minerals and chemical additives, with a technique like hydro-seeding. The paper deals with this topic, analysing the hydraulic regime in an infinite slope consisting of the soil profile found in a test site monitored in southern Italy. Numerical analyses were carried out considering the slope both in natural conditions and treated with different types of mixtures sprayed on the soil surface. In the analyses, different rainfall histories were applied at the upper boundary. Soil hydraulic characterization was obtained by using suction and volumetric water content meas-ured in situ. Hydraulic characterization of the treated soil surface was performed by means of laboratory evaporation tests (Papa & Nicotera, 2011). The results of slope stability analyses are reported to quantify bene-fits due to treatments.