We consider a model for the flow of granular matter which was proposed by Hadeler and Kuttler (Granular Matter, 1999). The original model uses the height of the standing layer and the thickness of the moving layer as the unknowns. By introducing the slope the standing layer, one arrives at a 2 by 2 system of balance laws. This system is weakly linearly degenerate at a point. With suitable conditions on the initial data, one can prove the global existence of smooth solutions. Furthermore, we prove the global existence of large BV solutions, for a class of initial data with bounded but possibly large total variation. This is partly a joint work with Debora Amadori, Italy.