parallel slope retreat

The evolution of a hillslope where the angle remains constant for each part of the slope. Parallel retreat assumes uniform lateral erosion over the whole hillslope. The length of the slope element is also constant except for the pediment which increases in length over time. The concept was first introduced by W. Penck, who accepted the process would depend on the efficient removal by streams of slope-foot debris, and that parallel retreat would take place only on parts of a slope. It is now generally conceded that no single model of slope evolution can explain all the features of hillslopes.