Hillslope form and process: history 1960–2000+

The study of hillslopes has been dominated by the expansion of studies into process rates and mechanisms. Perhaps the greatest volume of work has been on the ‘wash’ processes of soil erosion, but there has also been significant work on the diffusive mass movements of linear and non-linear ‘creep’ that shape the convexity of hilltops, on more rapid mass movements and on solution processes. There has also been fresh work on distinctive processes in coastal, arid and cold-climate environments. Accompanying and integrated with process understanding, and made possible by ubiquitous computational power, modelling has developed from soluble mathematical simplifications to complex simulations that incorporate much of our understanding of process and climate. Particular topics that have seen significant advance include a more complete understanding of drainage density and texture, and a broadening of interest to encompass the ‘critical zone’ that constructively unifies the land surface with the lower atmosphere, the biosphere and the regolith. There has also been a change of focus towards steeplands, dominated by mass movements, supply-limited removal and tectonic activity. Most recently, and now incorporated into the concept of the ‘Anthropocene’, human impact is now receiving increasing attention as we acknowledge its accelerating role in changing landscapes and their relationships.