Effects of the 1993 storms on the west Castellammare Mesa landslide, city of Los Angeles, California

The storm of January 18, 1993, triggered or reactivated an older landslide that destroyed nearly a dozen homes in the Castellammare mesa area of Los Angeles, California. The catastrophic slope failure was the end result of the 1992-1993 rains and more than 100 years of local development that included construction and maintenance of coastal and local roads, construction of hillside homes, and maintenance of the mesa. Residential development started in the mid-1920s. Unimproved lots were sold and residences constructed, starting in 1926, without consideration of geologic hazards. The presence of large ancient landslides was determined from mapping started in the 1950s. However, lot by lot development continued without proper consideration of regional hazards. Remedial repairs were conducted by the city of Los Angeles, Caltrans, and private home owners in a non-integrated fashion, generally in response to catastrophic failures. Significant slope failures were observed during the rains of 1938, 1941, 1952, 1969, 1978, and 1983. By late 1992, the region had deteriorated significantly because of slope creep and poor maintenance. Site reviews during and following the rains of January 18, 1993, indicated the need for (1) an understanding of regional geologic hazards and geotechnical problems associated with the development on and maintenance of a relatively large, paleolandslide; (2) an integrated, geotechnical approach to the development of an area of small, individually owned lots; and (3) a single government agency working with the home owners" association to coordinate geotechnical studies, local government improvements, development and maintenance of private lots, and the maintenance of streets, utilities, dewatering wells, and other infrastructure.