In this paper we present a discussion on the continuum approach to the
equations of motion for the gravity induced flow in a free surface of
a noncohesive granular material. We emphasize the usefulness of the c
ontinuum approach to describe the fully dynamic or grain-inertia and t
he quasi-static regimes. In order to justify the validity of the propo
sed equations, we introduce a model for the dissipative stresses occur
ring in the flow. We also discuss some of the analytical solutions of
these equations.