  Variable-coefficient Korteweg - de Vries equation is applied to describe the
interfacial wave transformation in two-layer fluid of variable depth. The
soliton dynamics in this fluid is studied. The solitary wave breaks in two
transient points. One of them is the point when two-layer fluid transforms to
the on-layer flow. The second one is the point where layer thickness are
equaled. The soliton amplitude dependence on the thickness of lower layer is
found.
