Landslides and avalanches in reservoirs represent one of the main risks threatening the safety of territories interested by hydroelectric power plants. The consequences of such events are affected by several variables like type of landslide (rigid, granular, mud, etc.), energy and volume of the landslide, reservoir water level and bathymetry, dam geometry and so on. A numerical model based on the SPH technique, has been developed to simulate water dynamics fully coupled with landslide dynamics, in variable depth reservoirs. The numerical model solves the complete Navier-Stokes equations; viscous terms have been generalized to describe non-newtonian fluids with various rheological behaviours, in order to simulate the propagation of different kinds of landslides (granular, mud, debris, etc.). The model is able to deal easily with irregular boundaries like ground surfaces in natural topography and man made structures; in fact it includes a new methodology to model the terrain morphology that allows to overcome the difficulties which can arise with more “ad-hoc” methods like "ghost-particle" and "guard-particle" techniques. The correct behaviour of the fluid at the terrain interface is proved by several tests. The model architecture, beside multi-phase problems (simultaneous computation of landslide and water dynamics), can manage 3-D problems in order to forecast the reservoir fluid-dynamics in a wide range of practical situations. The activity has been carried out in the framework of a Research Program funded by the Italian Ministry of Industry to improve the electric system in Italy. PUBBLICATO A5009134 (PAD – 615787)PUBBLICATO A5009134 (PAD – 615787)PUBBLICATO A5009134 (PAD – 615787)PUBBLICATO A5033673 (PAD – 698408)