Deadly Debris Flows on I-5 Near Grapevine, CA

by Vincent S. Cronin, Univ of Wisconsin-Milwaukee, Milwaukee, United States,
James E. Slosson, Univ of Wisconsin-Milwaukee, Milwaukee, United States,
Thomas L. Slosson, Univ of Wisconsin-Milwaukee, Milwaukee, United States,
Gerald Shuirman, Univ of Wisconsin-Milwaukee, Milwaukee, United States,

Document Type: Proceeding Paper

Part of: Hydraulics/Hydrology of Arid Lands (H²AL)


A series of debris flows inundated the southbound lanes of interstate Highway 5 (1-5) approximately 110 km (70 mi) NW of Los Angeles, California, between Fort Tejon and Grapevine, early on February 5, 1978. These flows resulted in the death of a motorist and damage to several trucks and autos. The design of the highway and its drainage systems is insufficient to guarantee the public safety, because it fails to address the debris flow hazards that are present. An adequate geological site investigation undertaken during the design phase would have shown that landslides are ubiquitous along this segment of 1-5, and that a series of Holocene debris fans extend into Grapevine Canyon. The steep topography, fractured bedrock and loose soil conditions are quite favorable for the continued development of debris flows. Although there were no recorded debris flows along this segment of 1-5 or its predecessor (US 99) between 1933 and 1978, it was unreasonable to assume that slope failures would not occur in the future as they had in the past. Lack of adequate mitigation since 1978 makes it highly probable that debris flows will inundate 1-5 in the future, with similar results.

Subject Headings: Debris | Solids flow | Traffic flow | Public health and safety | Highways and roads | Drainage systems | Landslides | Highway and road design | United States | California | Los Angeles

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