LAND SUBSIDENCE

The sinking or settling of land to a lower level in response to various natural and man-caused factors, for example: (1) earth movements; (2) lowering of fluid pressure (or lowering of ground water level); (3) removal of underlying supporting materials by mining or solution of solids, either artificially or from natural causes; (4) compaction caused by wetting (Hydrocompaction); (5) oxidation of organic matter in soils; or (6) added load on the land surface. With respect to ground water, subsidence most frequently results from overdrafts of the underlying water table or aquifer and its inability to fully recharge, a process termed Aquifer Compaction. Also see Subsidence.