Impact of the 1992–1993 winter storms on hydroconsolidation, differential settlement, and ground fissures, Murrieta area, southwestern Riverside County, California
Roy J. Shlemon, Mack Hakakian, 1997. "Impact of the 1992–1993 winter storms on hydroconsolidation, differential settlement, and ground fissures, Murrieta area, southwestern Riverside County, California", Storm-Induced Geologic Hazards, Robert A. Larson, James E. Slosson
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The 1992-1993 winter storms in Murrieta, California, produced rainfall that exceeded 200% of normal. This water infiltrated into buried channels filled with up to 30 m of alluvium and thus added to rising water levels caused by accelerating urban runoff during the previous 5 yr. Downstream valleys in the California Oaks area of Murrieta, now modified to support golf courses, were little affected by the rainfall, for most of the underlying sediments had already been saturated. Upstream, however, nar-row alluvium-filled valleys were subjected to 3 to 4 m of groundwater-level rise in a 2-month period. Depending on local channel geometry and presence of fill loads, the 1992-1993 storms accelerated alluvial saturation, hydroconsolidation of collapsible soils, differential settlement, and formation of ground fissures. This combined natural and man-induced rise in regional groundwater levels damaged many houses and streets and locally impaired underground utilities. Alleged damages exceed $50 million, and litigation continues unabated. The Murrieta (California Oaks) hydroconsolidation, dif-ferential settlement, and ground fissures provide a case study of new challenges to the engineering geologist in California.
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A multidisciplinary volume of case histories presenting the work of professionals who investigated catastrophic damage caused by the 1992—1993 winter storms in southern California and Arizona. Papers in this volume discuss topics such as: why severe winter storms occur and how the resulting floods fit into the context of the geological record; flood-damaged infrastructure development and mining operations in river channels; storm damage to four counties in southern California; ground settlement intensified by rising ground water caused by infiltrating rain, and the subsequent litigation; warning the public of imminent debris-flow hazards and how to set the moisture and rainfall thresholds that must be reached to issue a warning; and major infiltrating-rainfall-activated landslides that damaged homes in southern California. The release of this volume marks the 50th anniversary year of the Engineering Geology Division.