“…Therefore, I point out some representative studies that treated single phase flow (Garg, 1971;Pride et al, 1992), and two-phase flow (Berryman et al, 1988;Santos, 1990;Tuncay, 1995;Tuncay andCorapcioglu, 1996, 1997;Lo et al, 2005Lo et al, , 2009) for a homogeneous medium. Recently, the two-phase work was extended to a medium containing smoothly varying heterogeneity in Vasco and Minkoff (2012). These papers dealt with large-scale, wave-induced flow, the so-called macroscopic flow.…”