Landslide geomorphology: An argument for recognition, with examples from New Zealand

The role and significance that have been ascribed to landsliding within geomorphology were examined with respect to some of the influential historical concepts of landform evolution. Landsliding was almost completely ignored as a geomorphic process in the earliest models of landform evolution. While there has been a growing acknowledgement of landsliding as a hillslope process capable of performing significant erosion and transportation, it has received only sparse recognition as a formative process in its own right. Notable exceptions are the rarely referenced model of relief development of Skempton, A.W., 1953. Soil mechanics in relation to geology. Proceedings of the Yorkshire Geological Society 29 (3), 33–62 Pt.1 and the reply of Selby, M.J., 1974. Dominant geomorphic events in landform evolution. Bulletin International Association of Engineering Geology 9, 85–89 to the frequency–magnitude findings of Wolman, M.G., Miller, J.P., 1960. Magnitude and frequency of forces in geomorphic processes. Journal of Geology 68 (1), 54–74. Together, these two contributions provide a sound basis of geomechanical theory and ample empirical evidence to indicate that landslides have the potential to control landform evolution. It is proposed that landslide geomorphology systems exist, within which landslides dominate form and process by governing the mechanisms, rhythm, and pace of geomorphic change, in time and space. A review of New Zealand terrain suggests that these criteria are met in six distinctive landslide geomorphology systems. Each of these can be characterised not only by the landslide regime but also by the fundamental pre-conditions of tectonic setting and geology. It is argued that the existence of such systems and the complex interrelations involved require the recognition of a landslide geomorphology in its own right.