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Downhill creep, also known as soil creep or commonly just creep, is the slow, downward progression of rock and soil down a low grade slope; it can also refer to slow deformation of such materials as a result of prolonged pressure and stress. Creep may appear to an observer to be continuous, but it really is the sum of numerous minute, discrete movements of slope material caused by the force of gravity. Friction, being the primary force to resist gravity, is produced when one body of material slides past another offering a mechanical resistance between the two which acts to hold objects (or slopes) in place. As slope on a hill increases, the gravitational force that is perpendicular to the slope decreases and results in less friction between the material that could cause the slope to slide.

Creep has caused the soil to spread over this pavement.

Creep can also be caused by the expansion of materials such as clay when they are exposed to water. Clay expands when wet, then contracts after drying. The expansion portion pushes downhill, then the contraction results in consolidation at the new offset.

Objects resting on top of the soil are carried by it as it descends down the slope. This can be seen in churchyards, where older headstones are often situated at an angle and several metres away from where they were originally erected.

Vegetation plays a role with slope stability and creep. When a hillside contains many trees, ferns, and shrubs their roots create an interlocking network that can strengthen unconsolidated material. They also aid in absorbing the excess water in the soil to help keep the slope stable. However, they do add to the weight of the slope giving gravity that much more of a driving force to act on in pushing the slope downward. In general, though, slopes without vegetation have a greater chance of movement.

Design engineers sometimes need to guard against downhill creep during their planning to prevent building foundations from being undermined. Pilings are planted sufficiently deep into the surface material to guard against this behavior.

## Modeling regolith diffusion

For shallow to moderate slopes, diffusional sediment flux is modeled linearly as (Culling, 1960; McKean et al., 1993)

${\displaystyle q_{s}=k_{d}S\,\!}$

where

Objects resting on top of the soil are carried by it as it descends down the slope. This can be seen in churchyards, where older headstones are often situated at an angle and several metres away from where they were originally erected.

Vegetation plays a role with slope stability and creep. When a hillside contains many trees, ferns, and shrubs their roots create an interlocking network that can strengthen unconsolidated material. They also aid in absorbing the excess water in the soil to help keep the slope stable. However, they do add to the weight of the slope giving gravity that much more of a driving force to act on in pushing the slope downward. In general, though, slopes without vegetation have a greater chance of movement.

Design engineers sometimes need to guard against downhill creep during their

Objects resting on top of the soil are carried by it as it descends down the slope. This can be seen in churchyards, where older headstones are often situated at an angle and several metres away from where they were originally erected.

Vegetation plays a role with slope stability and creep. When a hillside contains many trees, ferns, and shrubs their roots create an interlocking network that can strengthen unconsolidated material. They also aid in absorbing the excess water in the soil to help keep the slope stable. However, they do add to the weight of the slope giving gravity that much more of a driving force to act on in pushing the slope downward. In general, though, slopes without vegetation have a greater chance of movement.

Design engineers sometimes need to guard against downhill creep during their planning to prevent building foundations from being undermined. Pilings are planted sufficiently deep into the surface material to guard against this behavior.

For shallow to moderate slopes, diffusional sediment flux is modeled linearly as (Culling, 1960; McKean et al., 1993)

where ${\displaystyle k_{d}\,\!}$ is the diffusion constant, and ${\displaystyle S\,\!}$ is slope. For steep slopes, diffusional sediment flux is more appropriately modeled as a non-linear function of slope[1]

${\displaystyle q_{s}={\frac {k_{d}S}{1-(S/S_{c})^{2}}}\,\!}$

where ${\displaystyle S_{c}\,\!}$ is the critical gradient for sliding of dry soil.

On long timescales, diffusive creep in hillslope soils leads to a characteristic rounding of ridges in the landscape.[1][2]