A straight, sloping element of a hillslope, located either in the middle of a slope profile, or at the base of the free face. Burt (2003) PPG 27, 4 finds that a constant slope is characteristic of valley incision, but that it cannot survive at its original angle once downcutting stops. Calvache et al. (1997) Geomorph. 21, 1 note that particle size influences the longitudinal constant slope profiles of alluvial fans.