Ground can settle as a result of many different processes.  If the watertable is lowered, frequently the ground above will settle slightly.  Sometimes this displacement can be several feet or more.  This situation is more significant if the area is composed of swelling soils.  These soils are predisposed to expansion and shrinkage.  Underground collapses of natural caves, or antique infrastructure such as pipes and drains, can also cause minor or major subsidence.

Water normally occupies the spaces between soil particles.  When the water is removed, or the pressure is released, the particles compact under the weight of surface layers and structures aboveground.

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* Pipkin, Geology and the Environment. p 194.


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Neighborhood Perceptions