In this paper we present direct numerical simulations of a sliding avalanche in aerosol regime. The second scope of this study is to get more insight into the interaction process between an avalanche and a rigid obstacle. An incompressible model of two miscible fluids can be successfully employed in this type of problems. We allow for mass diffusion between two phases according to the Fick's law. It is shown that the present model is consistent in the sense of kinetic energy. Some connections with Brenner-Navier-Stokes and Kazhikhov-Smagulov systems are revealed. The governing equations are discretized with a contemporary fully implicit finite volume scheme. The solver is able to deal with arbitrary density ratios. Encouraging numerical results are presented. Impact pressure profiles, avalanche front position and velocity field are extracted from numerical simulations and discussed. The influence of the bottom boudary condition onto propagation and impact processes is discussed. Finally we give some ideas of how this methodology can be used for practical engineering problems.