La Conchita (1995) La Conchita landslide, Ventura County. Official websites use .gov Days later, on March 10, a subsequent debris flow from a canyon to the northwest damaged five additional houses in the northwestern part of La Conchita. La Conchita landslide verdict - The Landslide Blog - AGU Blogosphere The following summary of the 1995 La Conchita landslide is extracted from O'Tousa (1995) and Anderson (Robert Anderson, RJR Engineering, 2005, personal commun.). During and just after storms, existing coastal landslides may become reactivated and seemingly stable coastal cliffs may erode and fail rapidly. Hemphill, J.J., 2001, Assessing landslide hazard over a 130year period for La Conchita, California, in Association of Pacific Coast Geographers Annual Meeting, Santa Barbara, Calif., September 1215 2001. 3H). Agenda What is a landslide? The upper part of the slope consists of interlayered siliceous shale, siltstone, and sandstone of the Middle to Upper Miocene Monterey Formation. Eyewitness accounts indicate, however, that similar to 2005, dust was in the air and much of the deposit included relatively dry material. The two formations are in fault contact along the active Red Mountain Fault, which extends across the slope face. Do you know what type of landslide occurred in La Conchita? A .gov website belongs to an official government organization in the United States. In southern CA, the USGS has also identified the rainfall conditions required to trigger post-wildfire debris flows. copyright Engineering Applications Figure 5. In 2005, after a 15-day period of near-record rainfall, a larger area failed rapidly, remobilizing part of the 1995 slide. Many areas of coastal California are subject to cliff erosion and coastal landslides (see new research onEl Nio coastal hazardsin California). Heavy rains of January 1995 led to a March 4, 1995, landslide in the La Conchita Community of Ventura County (County), California. Even in the absence of additional significant rainfall this year (2005), the remainder of the 1995 landslide could still remobilize, most likely as a deep slumpearth flow similar to that in 1995. There are generally three types of creep: (1) seasonal, where movement is within the depth of soil affected by seasonal changes in soil moisture and soil temperature; (2) continuous, where shear stress continuously exceeds the strength of the material; and (3) progressive, where slopes are reaching the point of failure as other types of mass movements. https://pubs.usgs.gov/fs/2004/3072/fs-2004-3072.html, Combination or two or more principal types of movement. The USGS has conducted hazard assessments forpost-wildfire debris flowsfor four recent fires in southern CA, as well as numerous fires across the Western U.S. including central and northern California. Below are publications associated with this project. The volume of material moved by the landslide was 2.8 cubic kilometers (0.67 mi 3) . Types of Landslides The term "landslide" describes a wide variety of processes that result in the downward and outward movement of slope-forming materials including rock, soil, artificial fill, or a combination of these. Debris flow: A debris flow is a form of rapid mass movement in which a combination of loose soil, rock, organic matter, air, and water mobilize as a slurry that flows downslope (fig.
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