“…Since the number of scalar unknowns is six (h, u and three independent components of P), the system is not in conservative form. The definition and computation of discontinuous solutions for non-conservative hyperbolic equations is a challenging problem (see examples of non-conservative systems in compressible turbulence [7,2], multi-layer shallow water flows [34,4,32,5,1,30], multi-phase fluid flows [3,24,40,41,42,19,14], solid-fluid systems [17,33]).…”