  We consider Navier-Stokes equations for compressible viscous fluids in one
dimension. We prove the existence of global strong solution with large initial
data for the shallow water system. The key ingredient of the proof relies to a
new formulation of the compressible equations involving a new effective
velocity $v$ (see \cite{cras,para,CPAM,CPAM1}) such that the density verifies a
parabolic equation. We estimate $v$ in $L^\infty$ norm which enables us to
control the vacuum on the density.
