Abstract 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.