Slope instability can result in ground loss or ground movement that could affect structures or natural features at the top or bottom of the slope. When development is directed away from slopes it is usually because the development is likely to change the soil strength or a slopes natural resistance to sliding.
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Increased water in the pores of a soil, for example septic systems, leaking pools and heavy rainfalls, generally has a weakening effect on soil strength and thus its ability to support itself at a certain angle and to support any weight bearing structures
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Changes in surface flow from downspouts and other concentrated flow sources can cause severe erosion and gullying on the slope face
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Trees, shrubs and vegetation that provide natural stability can be removed by well intentioned owners
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Toe erosion from flowing water at the base of the slope can over-steepen the natural angle, and the slope may respond by cutting further back to regain a natural angle. Falling trees on a slope may be evidence of this back cutting as are the exposed soils at the place where the toe erosion is occurring
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Rapid decrease in stream or lake water levels can remove soils through suction like processes and can decrease soil strength
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Ice moving through stream systems can scour the bed and banks of the stream
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Loads such as buildings, filling and excavations can increase the pore pressure of a soil and a decrease in the soil strength can occur
