The 2005 La Conchita landslide occurred at about 12:30 p.m. on January 10. The 2005 landslide mobilized the south flank of a larger landslide that occurred in March 1995, and destroyed 9 homes. 7). Science 238:921–925 . Also, the video shows dust in the air as the landslide flowed downslope. 2014, Oso Landslide, Washington: On March 22, 2014, a landslide of approximately 18 million tons (10 million yd 3) traveled at 64 kph (40 mph), extended for nearly a 1.6 km (1 m), and dammed the North Fork of the Stillaguamish River. We … 1B, p. S319—S332. In addition, large and small ravines that incise the bluff have produced debris flows recently and in the past. Currently, we have insufficient data and understanding of the failure mechanisms of this landslide to adequately answer these questions, but it is clear that the hazard from renewed landslide movement is considerable. Several smaller, more recent slumps and earth flows also are visible, as is the 1995 slump—earth flow (terminology after Varnes, 1978). Prudence would certainly dictate, however, that we anticipate renewed landslide activity during or after future periods of prolonged and(or) intense rainfall. John Morgan, 56 . A .gov website belongs to an official government organization in the United States. What was the immediate cause of the 2005 La Conchita landslide? LA CONCHITA, CA - DECEMBER 07: A man bicycles past bluffs burned in the Thomas Fire on December 7, 2017 in La Conchita, California. In 2005, a landslide in La Conchita, California killed 10 people and destroyed or damaged three dozen homes. The La Conchita landslides that occurred in 1995 and 2005 form only a small percent of a much larger landslide complex, according to the geologists. Arrows show other landslides in the area. Incipient movement of the upper part of the slide was reported as early as the summer of 1994, when surface cracks were observed in the upper part of the slope (O'Tousa, 1995). The 1995 slide was 120 m (400 ft) wide, 330 m (1100 ft) long, and covered approximately 4 ha (10 acres). Since that time, landslides frequently have inundated roads, … The 1995 landslide is outlined in blue and the 2005 landslide in yellow, while a red line overhead outlines the main scarp of an ancient landslide that involved the entire bluff. After covering the road with 7-8 feet of debris, the slide stabilized. The KCAL–TV video indicates that the landslide material mobilized simultaneously and nearly instantaneously into a highly fluid, rapidly moving debris flow. VENTURA, Calif -- La Conchita is an area of concern for mudslides during this week's storm, and many living there have a mix of different emotions as they wait for the rain. The La Conchita area has experienced, and will likely continue to experience, a rather bewildering variety of landslide hazards. The 2005 landslide occurred at the end of a 15–day period that produced record and near–record amounts of rainfall in many areas of southern California. A few things, however, can be said. 2005 La Conchita Landslide ¾Landslide occurred early afternoon on 10 January ¾430 mm of rainfall from 27 December to 10 January (record 15-day rainfall) ¾About 200,000 m3(15%) of the 1995 deposit mobilized and flowed rapidly into the community There is no reason to believe this pattern of landsliding will stop. Law enforcement officers and media representatives were in the area, which facilitated capturing the moving landslide on video. Figure 3 shows LIDAR and false–color infrared images of the bluff above La Conchita and the surrounding area, and several sizes, types, and ages of landslides are visible. La Conchita Landslide Hazard During the second week of January, the media spotlight focused on a deadly landslide in the small seaside town of La Conchita, California. Isolated parts of the Rincon Mountain landslide are active in the La Conchita area, but no evidence exists that the entire slide mass is moving as a unit. Historical accounts dating back to 1865 have reported landslides in the area around La Conchita as being a regular occurrence (Hemphill, 2001). The 1995 and 2005 landslides in the 200-m high sea cliff above the community of La Conchita, California, are known to be part of a reactivated Holocene prehistoric landslide. 3). (cc) photo by Metro Centric on Flickr Double click to crop it if necessary Introduction Research Budapest San Francisco Results (cc) photo by Metro Centric on Flickr Stockholm Notes Place your own picture behind this frame! Little or no newly failed material was involved in the landslide; rather, it consisted of a remobilization of the southeastern portion of the 1995 landslide deposit, involving about 200,000 m3 (250,000 yd3) (James O'Tousa, RJR Engineering, personal commun., 2005). La Conchita lies on a narrow coastal strip about 250 m (800 ft) wide between the shoreline and a 180–m (600–ft) high bluff having a slope of about 35°; above the top of the bluff is a gently rising terrace surface covered by avocado and citrus orchards (fig. The 2005 landslide mobilized the south flank of a larger landslide that occurred in March 1995, and destroyed 9 homes. LA Cochita Landslide (cc) photo by jimmyharris on Flickr The La Conchita landslide then occurred on March 4. Several smaller landslides occurred between the summer of 1994 and March 1995, when the large slide occurred. Why did the landslide material not mobilize into a rapid debris flow in 1995? How and why the same material failed twice in 10 years by fundamentally different mechanisms certainly will be the object of future research, and it is much too complex to analyze in detail at this time. 2005 La Conchita landslide. On January 10, 2005, a landslide struck the community of La Conchita in Ventura County, California, destroying or seriously damaging 36 houses and killing 10 people. The arcuate bench at the top of the bluff is the head of a very large prehistoric landslide that affected the entire bluff. The Southern Pacific rail line that extends along the coastal strip was inundated by landslide debris in 1889 and again in 1909, when a train also was buried (Hemphill, 2001). However, this still leaves some troubling questions unanswered. The lower part of the slope is siltstone, sandstone, and mudstone of the Pliocene Pico Formation (O'Tousa, 1995). 10—12. The 2005 La Conchita Landslide occurred at the end of a 15–day period of near-record rainfall levels. At Ventura (20 km [12 mi] southeast of La Conchita) seasonal antecedent rainfall from October 1, 2004 through January 10, 2005 totaled 493 mm (19.4 in) as compared to the mean value of 122 mm (4.8 in). 13, 52 p. National Oceanic and Atmospheric Administration, 1995b, Climatological data—California, January—March 1995: National Climatic Data Center, v. 99, no. The 1995 landslide had a horizontal length, vertical length, and depth of 120 x 330 x 30 m and covered approximately 10 acres with a volume of 1.3x106 m3. Which of the following is NOT one of these conditions? An official website of the United States government. Landslides occur when gravitational and other types of shear stresses within a slope exceed the shear strength (resistance to shearing) of the materials that form the slope. A wall built after the 1995 landslide to keep minor landslide debris off the road was tilted forward and(or) overtopped in places by debris from the 2005 landslide (fig. February 1995 produced only about one–third of the normal rainfall, but a modest storm on March 2—3 produced 21 mm (0.81 in) of rain. Keefer DK, Wilson RC, Mark RK, Brabb EE, Brown WM, Ellen SD, Harp EL, Wieczorek GF, Alger CS, Zatkin RS (1987) Real-time landslide warning during heavy rainfall. In 1995, after a very wet January, the landslide did not move until more than a month later, during which time very little rain fell (fig. The 1995 landslide was a deep, coherent slump—earth flow that deformed plastically and moved slowly enough that people could get out of its way. Details. This is the location of two destructive landslides that hit the community of La Conchita. These tools convert Adobe PDF documents into HTML or ASCII text, which then can be read by a number of common screen–reading programs that synthesize text as audible speech. Daily Dosage Subscribe Unsubscribe 943. In addition, an accessible version of Acrobat Reader 6.0, which contains support for screen readers, is available. A Fun Waste Of Champagne. The Regional Director goes on to state that "the La Conchita landslide is a large, deep-seated and ancient landslide complex that has undergone repeated movements in the years preceding the most recent slide." 5 and 6). Explore {{searchView.params.phrase}} by color family {{familyColorButtonText(colorFamily.name)}} Detailed Description An oblique LIDAR image of La Conchita, Calif., reveals the community’s grim landslide history. Different landslide scenarios are more or less likely to occur as a result of different specific rainfall conditions, and no part of the community can be considered safe from landslides. On March 10, a subsequent debris flow from a canyon to the northwest (see canyon on left part of figs. T2 - La Conchita, Ventura County, California. The January 2005 landslide was a debris flow that killed 10 people, and damaged 36 residential homes. The 2005 landslide pushed many of the houses off their foundations and into each other at the toe of the landslide (figs. Ten people died in the 2005 La Conchita landslide: Tony Alvis, 53 . The slide covered 300 feet of Vista Del Rincon (VDR) Drive. These recent landslides spilled over U.S. Highway 101 in the Ventura County community that is located 25 miles south of Santa Barbara. 1—3. This was not the first destructive landslide to damage this community, nor is it likely to be the last. The video shows relatively intact vegetation being rafted on the surface of the rapidly flowing mass, which indicates that much of the landslide mass simply was being carried on the fluidized layer at depth, which presumably was much more saturated. This also is consistent with the shallower, fluid mode of failure: shallow, rapid debris flows most commonly occur during periods of prolonged, intense rainfall with little or no lag time (Campbell, 1975; Keefer and others, 1987; Jibson, 1989). Researching houses in SB and came upon this video of La Conchita landslide. In late 2004 and early 2005, an intense series of rainstorms impacted southern California, causing flooding and innumerable landslides throughout the region. Aug 15, 2014 - Explore Vision Aerie's photos on Flickr. The landslides in the area around La Conchita have been a regular occurrence, according to the historical accounts dating back to 1865. The surface of the bluff above the town of La Conchita was barren and allowed for plentiful water infiltration. AU - Gurrola, Larry D. AU - DeVecchio, Duane E. AU - Keller, Edward A. PY - 2010/1/15. Morton, D.M., and Campbell, R.H., 1989, Cyclic landsliding at Wrightwood, southern California, in Sadler, P.M., and Morton, D.M., eds., Landslides in a semiarid environment with emphasis on the inland valleys of southern California: Inland Geological Society, Riverside, Calif., v. 2, p. 174—182. The ZIP Code is 93001, and the community is inside area code 805.. On January 10, 2005, a major landslide occurred in La Conchita. The timing of the two landslides with respect to the triggering storms is of primary interest. Tweet Share on … Document Accessibility: Adobe Systems Incorporated has information about PDFs and the visually impaired. R.L. During the second week of January, the media spotlight focused on a deadly landslide in the small seaside town of La Conchita, California. Future landslide activity could move into the same areas that recently have been damaged or could mobilize in other directions that could damage any or all of the developed area. The movement of the same landslide mass in 1995 and 2005 by two very different mechanisms, and with markedly different results, is difficult to explain. The main mass that failed is on the southeastern margin of the larger ancient landslide that encompasses the entire front of the bluff (see fig. La Conchita Landslide. Parise, Mario, and Jibson, R.W., 2000, A seismic landslide susceptibility rating of geologic units based on analysis of characteristics of landslides triggered by the January 17, 1994 Northridge, California, earthquake: Engineering Geology, v. 58, p. 251—270. Wallet said he moved to La Conchita, 70 miles northwest of Los Angeles, from Ventura in search of an easier life. 12). VIDEOS GALLERIES. Eyewitness accounts indicate, however, that similar to 2005, dust was in the air and much of the deposit included relatively dry material. The landslide scenarios sketched above potentially could impact any part of the La Conchita community. The developed part of the slope where the houses were impacted has a flatter slope, and so the flow probably slowed to no more than 5 m/s (15 ft/s) in the neighborhood. The upper part of the slope consists of interlayered siliceous shale, siltstone, and sandstone of the Middle to Upper Miocene Monterey Formation. The following summary of the 1995 La Conchita landslide is extracted from O'Tousa (1995) and Anderson (Robert Anderson, RJR Engineering, 2005, personal commun.). La Conchita Landslide Hazard. Since only about 15 percent of the 1995 deposit remobilized in 2005, could the remainder also mobilize into a rapid debris flow, or is it more likely to remobilize as a deep slump? From December 27, 2004 through January 10, 2005, the nearby city of Ventura received 378 millimeters (14.9 inches) of rainfall, only slightly less than its mean annual total of 390 millimeters (15.4 inches). 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 slump—earth flow similar to that in 1995. Y1 - 2010/1/15. These recent landslides spilled over U.S. Highway 101 in the Ventura County community that is located 25 miles south of Santa Barbara. The two formations are in fault contact along the active Red Mountain Fault, which extends across the slope face. Wofford, Michael, 2005, Ventura, California weather conditions. On January 10, 2005, a landslide struck the community of La Conchita in Ventura County, California, destroying or seriously damaging 36 houses and killing 10 people. This area has experienced two massive landslides in the past decade: March 4, 1995, and January 10, 2005. A memorial to some of them can be seen at the bottom of the slide. From December 27, 2004 through January 10, 2005, Ventura received 378 mm (14.9 in) of rainfall, only slightly less than its mean annual total of 390 mm (15.4 in) (Wofford, 2005; National Oceanic and Atmospheric Administration, 1994a, 1995a). URL: https://pubs.usgs.gov/of/2005/1067/508of05-1067.html This was not the first destructive landslide to damage this community, nor is it likely to be the last. Landslides from the 200-m high slope behind La Conchita will reoccur and future development on the proposed Rincon Mountain slide should be very carefully evaluated to avoid reducing slope stability and reactivation of the …

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