The evolution of a hillslope when the slope angle remains constant. Ellis et al. (1999) Basin Res. 11, 1 argue that parallel slope retreat requires some mechanism to remove weathered material from the foot of the slope in order to maintain the existing topography. See Leeder et al. (2002) Basin Res. 14, 1 on parallel slope retreat by earthquake-induced collapse failure. Jackson et al. (2005) Sedimentol. 52, 5 find parallel slope retreat on beaches, when breaking waves on the upper foreshore are lower; enhanced when waves approach at large angles to the beach.