The interfacial flow simulations using a robust interface-tracking method are presented. The method is based on one fluid formulation, where a single set of governing equations for the whole computational domain with variable material properties is solved. Interfacial terms, at the boundary separating the phases, are accounted for by adding the appropriate sources as δ functions. The representation of the moving interface and its dynamic restructuring, as well as the transfer of information between the moving front and the fixed grid, is discussed. This method has been applied to density stratified flows, and interfacial movements are then presented. An experimental study on salt wedge movement, conducted in the University of Dundee, has been simulated using the above algorithm. The numerical results are compared with the experimental results and those of a semi-empirical model developed earlier by the authors. © 2007 International Association for Hydraulic Engineering and Research, Asia Pacific Division.