The HySEA landslide-tsunami model implements the natural 2D extension of the 1D two-layer Savage-Hutter model presented in Fernández-Nieto et al. (2008), where Cartesian coordinates are used instead of local coordinates at each point of the 2D domain and where no anisotropy effects are taken into account in the normal stress tensor of the solid phase. The mathematical model consists of two systems of equations that are coupled: the model for the slide material is represented by a Savage-Hutter type of model (Savage and Hutter, 1988), and the water dynamics model is represented by the shallow-water equations (see Fernández-Nieto et al., 2008). One of the most important features of the model is that both the dynamics of the sedimentary fluidized material and the seawater layer are coupled and each of these two phases influences the other one instantly and they are computed simultaneously. These coupled effects were first studied in a 1D model by Jiang and Leblond (1992), who concluded that these effects are significant for cases of smaller slide material density and shallower waters. Nevertheless, the importance of numerically treating in a coupled mode phenomena that are physically coupled has been studied, for example, in Castro et al. (2011a) for the case of two-layer shallow-water fluids, and in Cordier et al. (2011) for sediment transport models. An uncoupled numerical treatment of these systems may generate spurious oscillations at the water surface or the interface.