A problem that has resulted in damage to many structures throughout California is a problem known as "Slope creep." Slope creep does not refer to an unsavory character that hangs out on the nieghboring hill. Slope creep refers to the process whereby soil that is part of a slope slowly moves downhill. Slope creep can be caused by a number of natural factors, such as weathering, but is typically more problematic when it is caused by poor development of a fill slope. The process can involve very slow movement of the soil, but the accumulation of the movement over time can result in considerable damage. The slow rate of movement creates a condition where there may not be a dramatic change in conditions over a short period of time. In other words, the damage resulting from slope creep may take a substantial amount of time to develop.
Slopes comprised of compacted fill may experience more rapid movement, with more dramatic results. As is common in other soil movement problems, the introduction of water to a newly constructed fill slope can result in dramatic changes to the soil strength. Soil that is wetted, and then dries out, can result in expansion and contraction of the soil. When the soil strength is weakened, the slope may gradually creep downhill due to gravity. This creep may result in a surficial movement, where it is actually visible to see the soil on the surface of the slope sloughing downhill; or the creep may be deeper in the slope, which may result in a gradual movement of the entire slope, or in worst case scenarios, the failure of the entire slope.
The taller and deeper the slope, the more danger of slope creep, particularly with respect to manufactured fill slopes.
If your home or building is at the top or bottom of a slope, particularly a fill slope, look for the signs of slope creep. If a significant amount of surficial soils moves downslope, this may be a slope creep indication. If there are cracks observed in the slope, this could also be an indication of a potential problem.