Landscape Creep

Primary reference(s)

Hutchinson, J.N., 1968. Mass movement. In: Fairbridge, R.W. (ed), Encyclopedia of Geomorphology. Reinhold Publishers, pp. 688-695.

Varnes, D.J., 1978. Slope movement types and processes. In: Schuster, R.L. and R.J. Krizek (eds), Landslides, Analysis and Control. Special report 176: Transportation Research Board, National Academy of Sciences, pp. 11-33.

Additional scientific description

Extremely slow movement of surficial soil layers on a slope (typically less than 1 m deep), commonly as a result of climatedriven cyclical volume changes (wetting and drying, frost heave). There are generally three types of creep: seasonal creep, where movement is within the depth of soil affected by seasonal changes in soil moisture and soil temperature; continuous creep, where shear stress continuously exceeds the strength of the material; and progressive creep, associated with slopes that are reaching the point of failure due to other types of mass movement. Creep is indicated by curved tree trunks, bent fences or retaining walls, tilted poles or fences, and small soil ripples or ridges (HIghland and Bobrowsky, 2008).

Metrics and numeric limits

Creep can be regional in nature (tens of square kilometres) or confined to small areas. The rates of movement are extremely slow, usually less than 0.5 m per decade (0.5 to 15 mm/yr) (Saunders and Young, 1983).

Examples of drivers, outcomes and risk management

Rainfall and snowmelt are typical triggers for landscape creep, whereas for other types of creep there could be numerous causes, such as chemical or physical weathering, leaking pipes, poor drainage, destabilising types of construction (Highland and Bobrowsky, 2008).

Because it is hard to detect in some places owing to the slowness of movement, creep is sometimes not recognised when assessing the suitability of a building site. Creep can slowly pull apart pipelines, buildings, highways, and fences, and can lead to more significant ground failures that are potentially more destructive and faster moving than those resulting from creep alone. The most common mitigation for creep is to ensure proper drainage of water, especially for seasonal creep. Slope modification such as flattening or removing all or part of the landslide mass, can be attempted, as well as the construction of retaining walls (Highland and Bobrowsky, 2008).