Land subsidence in the Santa Clara Valley, California as of 1980

Abstract

From 1916 to 1966 in the San Jose area of Santa Clara Valley, California, generally deficient rainfall and runoff was accompanied by a fourfold increase in withdrawals of ground water. In response the artesian head declined 180 to 240 feet. As a direct result of the artesian-head decline, the land surface subsided as much as 12.7 feet in San Jose, due to compaction of the finegrained compressible confining beds and interbeds as their pore pressures decreased. The subsidence resulted in flooding of lands bordering the southern part of San Francisco Bay, and the compaction of the sediments caused compressional failure of well casings in several hundred water wells. The gross costs of subsidence to date are estimated to be $30 to $40 million.