Groundwater rise and hydrocollapse: technical and political implications of ‘Special Geologic Report Zones’ in Riverside County, California, USA : R. J. Shlemon, in: Land subsidence. Proc. international symposium, The Hague, 1995, ed F.B.J. Barends & others, (IAHS; Publication, 234), 1995, pp 481–486

Abstract

Rapid urbanization in the semi-arid southwestern part of Riverside County, California is made possible only by the large-scale importation of water for domestic use. The resulting irrigation run-off and infiltration has caused groundwater levels to rise over 20 m within the past few years, particularly in former, alluvium-filled channels. Soil hydrocollapse, differential settlement and ground fissures are now occurring, causing extensive damage to houses, schools and related infrastructure. Alleged property damages exceed 50 million (US) dollars, and litigation has ensued. For public safety, the County of Riverside established two Special Geologic Report Zones, each about 500 ha, deemed CaliforniaOaks and Silverhawk, respectively. Inretrospect: the formation of the zones has proven to be administratively time- consuming and expensive; the litigation between home-owners, builders, geotechnical firms and reviewing agencies is divisive; home values, even for undamaged structures, have been reduced owing to disclosure laws; and the geotechnical community now recognizes, from sad experience, that rapid urbanization and related water level rise accelerates the potential for soil hydrocollapse and extensive property damage.