LANDSLIDES IN SOUTHERN CA.   Term Paper ID:21569 Click to get this paper

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Paper Abstract: Causes, examples, geologic process, types, materials, climate, vegetation, liability, remedies. Paper Introduction: Mass Wasting in Southern California More mass movement occurs in southern California than in any other region of the United States. Multiple factors contribute to this slope instability. Some of these include the area's steep hillsides, weak bedrock materials, adverse geologic structures, and heavy episodic precipitation. Recent landslides in Pacific Palisades, Palos Verdes, San Clemente, and Anaheim Hills have caused millions of dollars in damage. Moreover, as development continues to expand, southern California's landslide problem is only expected to worsen. Mass earth movements are highly variable. Typically, they occur within the following spectrum: e.g., from movements which are dependent upon some fluid, to those which are not. In subaerial environments, this spectrum comprises falls, slides, Text of the Paper: The entire text of the paper is shown below. However, the text is somewhat scrambled. We want to give you as much information as we possibly can about our papers and essays, but we cannot give them away for free. In the text below you will find that while disordered, many of the phrases are essentially intact. From this text you will be able to get a solid sense of the writing style, the concepts addressed, and the sources used in the research paper. For example, in Pacific Palisades andMalibu, mass movements comprise an inherent and very significant componentof the physical environment (USACE Appendix I). The risk formass movement may be particularly severe in areas that have been recentlysubjected to extensive wildfires. 1-27). Landslides along the bluffs in San Clemente rendered 14 homesuninhabitable; six of the homes eventually had to be destroyed. Unfortunately though, the caissonswere ripped from the ground, and transported all the way down to the surf. Below about 1,9 meters, many of southern California's slopesare covered with chaparral. In contrast, landslides occur when a sediment mass overcomes its owncohesion and internal friction. "Climate, Fire And Landslides In Southern California." Publications Of The Inland Geological Society 2 (1989): 91-1 .Overend, W. These were buried deep below the slide in the hope thatthey could stop the earth's advance. Onesuch mitigation effort involved caissons five feet in diameter, and 3 to4 feet in length. Rainfall infiltration and slope stability may additionally beinfluenced by the physical presence of plants. Then, within about 7 days, the slide hadmoved as much as 14 inches in some areas. Typical landslides span the range from "sudden andcatastrophic" to "slow and insidious." In the winter of 1969, for example,two intense southern California rainstorms caused 1 slip-debris flowevents on chaparral-, sagebrush-, and grass-covered slopes. Some of these include the area's steep hillsides, weakbedrock materials, adverse geologic structures, and heavy episodicprecipitation. Geology Of The Palos Verdes Peninsula And San Pedro Bay. Orange County, CA: National Association of Geology Teachers, 1986.Malnic, E. Department of the Interior, 1976.----------------------- 13 Among slides that move slowly over smooth basal slip surfaces,there may be relatively minor internal flow deformation. W.; Prior, D. Mass Wasting in Southern California More mass movement occurs in southern California than in any otherregion of the United States. Although Los Angeles County filed more than 3 countersuits againstthe Big Rock Mesa homeowners, a tentative settlement was reached in 1989.Under the agreement, Los Angeles paid the Malibu homeowners $35 million,CALTRANS paid $4 million, and various insurance companies paid $22million. Only through sucheffort may the cost of mass movements be minimized. Flowing and sliding may occur simultaneously. Two years later, in 198 , the city was hit once more. E. With such movementsthere is little or no shear displacement between the two originalmaterials. "Landslide Classification For Identification Of Mud Flows And Other Landslides." Publications Of The Inland Geological Society 2 (1989): 1-27.Dye, L. Repeated efforts to halt the Portuguese Bend slide have failed. Thatparticular landslide consisted of 25 slow-moving acres. Humanactivities tend to create new slope instabilities and reactivate ancientslides. Homeowners did manage to win a $9.5 million award fromthe County of Los Angeles though (Linden 32-39). Soil saturation maythe lead to slope failure. Otherdamage included cracked walkways, parking lots, and backyards. Lastly, tocompound these economic problems, most insurance companies excludelandslide coverage from their policies (Lait 1, 9). "Malibu Mesa Evacuees Are Caught Between A Rock And A Hard Place." Los Angeles Times 1 3 (1984, March 8): 1.Smith, D. Near the location of theformer Castle Rock, a new landslide destroyed both a residence and part ofPortomarina Way (USACE Appendix I). The slippage produced splitfoundations, broken walls, and cracked swimming pools. H.; Fleming, R. In this sense, the termsrelate to flow and depositional characteristics rather than composition.Finally, mud slides consist of slow-moving masses of "softened clayeymaterial" which slide along discrete basal and lateral boundary shearsurfaces. "Evolution of Landslide Repair In Southern California." Publications Of The Inland Geological Society 2 (1989): 28-4 .\Linden, K. In fact, Norton found 1961 and 1962 reports whichmapped the slide and warned that increased ground water could result inrenewed ground movement. Army Corps of Engineers (USACE). Specific disasters may or may not be associated with exogenoustriggering mechanisms. Denver, CO: U.S. 1-17). 176). J. Such phenomenacan produce long periods of steady rain (Minnich 91-1 ). A more recent slide occurred only a few miles north of PacificPalisades. The problems along this particular stretch ofhighway continued into 1984. Inaddition, the water is only 4 to 5 feet below the surface; whereas, thebentonite beds are over 1 feet deeper. The first large cracks in houses started to appear in aboutSeptember of 1984. Perhaps the most extensive damage during that particular winter,however, occurred in Castellammare Palisades. Because of differences in the physiognomy anddynamics of plant ecosystems, their different effects are difficult toisolate. In1969, for example, the largest landslide mass to undergo large movement inPacific Palisades involved the long-active Friends Street landslide. J.; Hampton, M. Nearly all ofsouthern California's rain falls in winter. Theyclaimed that the government was at fault for initially approving the mesadevelopment. Whenclosely spaced shear surfaces do occur they may be transient, and oftendisappear without leaving any evidence. Then, in 1978, another tworainstorms again triggered major debris flows and extensive flooding. ThePortuguese Bend slide plane is composed of soft, waxy bentonite beds.Bentonite is a volcanic ash. Ehlig believes that if the area's ground water can be lowered belowthe beds, the Portuguese Bend landslide will be less prone to failure (Dye1, 2, 3). A.; Brabb, E. 1-27). Theflows have "internal differential movements that are distributed throughouttheir mass (Campbell et al. E. "Anaheim Hills Homeowners See Their Dreams Slip Away." Los Angeles Times 112 (1993, February 22): A3.Leighton, F. This, he noted, proved that thecommunity's four horizontal drains were inadequate. E. Those slope displacements which exhibit more than one type ofmovement are called complex. Below Palos Verdes, bentonite may attainthicknesses of up to 7 feet. Origin of Sedimentary Rocks. R.; Varnes, D. Forexample, the area's ground water is replenished from several sources. 1-27). 1-27). There are many specific southern California areas which areparticularly prone to landslides. In 1983, the Pacific Coast Highway in Malibu was repeatedlyblocked by mass movements near Tuna Canyon Road (Smith 8). Rather, the Portuguese Bendslide is noteworthy for its duration. Richard Norton, a lawyer representing the Big Rock Mesafamilies maintained that the county had known the area was an ancient slidesite since the 196 s. In subaerial environments, thisspectrum comprises falls, slides, and flows (Blatt et al. This area experienced damageto streets, public utilities, and residences. For instance, soilfalls from the eastern part of Huntington Palisades have repeatedly blockedthe Pacific Coast Highway. Once detached, slides remain in constantcontact with the underlying slope materials. Translational slides, however,commonly involve rupture surfaces that are either planar or gentlyundulatory. Works CitedBlatt, H.; Middleton, G.; Murray, R. Heavy rains continue to reactivate younger slides. Although this particular abatement measurewas eventually abandoned, landslides in the Pacific Palisades/Malibu areacontinue to be a problem. Rockfalls typically result in piles of scree (Campbell et al. Recent landslides in Pacific Palisades, Palos Verdes, SanClemente, and Anaheim Hills have caused millions of dollars in damage.Moreover, as development continues to expand, southern California'slandslide problem is only expected to worsen. Viewed from above, the slide is roughlytriangular in shape: with one side of the triangle extending along thecoastline coincident with the landslide's toe (Linden 32-39). In southern California, slope failuresmost commonly occur in soils which have been saturated or otherwiseweakened by unusually heavy precipitation (Minnich 91-1 ). Perhaps the most famous southern California landslide though islocated in Palos Verdes. Relative movement within themass may take place on "discrete shear planes (Blatt et al. In southern California mass earth movement is a common. A. A second remedial measure proposed by Los Angeles consultantgeologist, Perry Ehlig, involves "dewatering" the area (Dye 1, 2, 3). Yet another major mass movement during the winter of 1993 occurred 12miles east of Disneyland in the upscale community of Anaheim Hills. Multiple factors contribute to this slopeinstability. The two terms tend to besynonymous, both involve the movement of extremely variable block sizesranging from large boulders to fine grains. It has beenestimated that the weight of all the material contained within thePortuguese Bend slide totals about 6 million tons. However, the slide'sshape and size are not what make it unusual. In addition, enlargement of preexistinglandslides has become widespread, particularly on Castellammare Palisadesand Porto Marina. Nearly all of southern California's precipitation comes fromsubtropical storms. Two other southern California landslides occurred in the Winter of1993. Thus, it could take years tolower the water table, and the project might not prove economicallyfeasible. The majority of debris flowsconsist of "poorly sorted material with cobbles and boulders embedded in afine muddy matrix (Blatt et al. A single series of storms candump half of the region's annual precipitation in as brief a time period asa couple of few weeks. Furthermore, as an additional part of the settlement, none of theparties involved had to admit responsibility and the homeowners agreed todrop any future claims (Garcia 1, 18). In fact, the main resistance toslide mass movements consists of frictional forces acting at these shearplanes. A.; Sangrey, D. Eventually the Big Rock Mesa homeowners sued Los Angeles County andthe state of California for more than $2 million in damages. Residents firstnoticed cracks forming in April. Mass earth movements are highly variable. Concave-upward rupture surfaces usually occur withinhomogenous sedimentary formations (Campbell et al. 14)." However, the terms "debris flow" and "mud flow" are alsocommonly used to refer to flowing slurries. During the early 193 s, an elaborate system of drainagetunnels was constructed along the cliffs bordering the coast. Despite this information though, the countyapproved seepage pits and horizontal drains in lieu of a sewer system.Norton additionally cited a 1973 county report showing that the mesa'swater table had risen to 2 feet. B.; Clark, B. These cyclonic cold fronts originate in the northernPacific Ocean. Overseveral decades, slide velocities have ranged from less than half an inchper day to as much as three or four inches per day. Sand flows, mud flows, or mud slides often occur inarid or semiarid environments. Landslides may besubdivided into both slides and slumps. In addition, mass movements often follow a sequence: falling, sliding,and flowing (Campbell et al. In reality, practically every landslide iscomplex to a certain extent. J. OnJanuary 2 , the head of this massive slide dropped suddenly about 2 to 45feet. Thesetunnels were connected to a hot-air furnace designed to remove soilmoisture (Leighton & Clark 31). Regardless though, LosAngeles County failed to take action. Englewood Cliffs, NJ: Prentice-Hall, Inc., 198 .Campbell, R. According to Lait (1993), residents hope to"sue the developer, the city, or somebody," in order to recoup theirsustained economic losses (Lait 1,9). In fact, such differential movementscan be intergranular; visible shear surfaces may not even form. Los Angeles, CA: The Society of Economic Paleontologists and Mineralogists & American Association of Petroleum Geologists, 1987.Garcia, K. Typically, they occurwithin the following spectrum: e.g., from movements which are dependentupon some fluid, to those which are not. Pacific Palisades Area, Los Angeles County, California. New slides since 1958 have generally occurredalong canyon walls and along the palisades themselves. "Another Huge Slide Closes Coast Highway." Los Angeles Times 1 2 (1983, May 15): 8.U.S. Such surfaces, for example, may involve pre-existingdiscontinuities (e.g., bedding planes, faults, or joints). In contrast,slumping occurs along rupture surfaces that are curved concavely upward.This movement typically involves fragment rotation and a greater amount ofinternal deformation. V.; Lindvall, C. A total of 25 homes were affected, of which 3 had to be condemned. "Slide, Winds Take Heavy Toll On Homes." Los Angeles Times 112 (1993, February 24): A1.Minnich, R. The control of future landslide damage requires careful managementof development. However, otherslides can involve considerable flow disruption. Mass movement is obviously a major problem for southern California.Moreover, it is only made worse by continued urban expansion. It resultsfrom the simultaneous occurrence of unstable slopes, fractured substrate, amediterranean climate, and chronic vegetal disturbances (e.g., fire)(Minnich 91-1 ). In addition, the homeowners claimedthat the California Department of Transportation (CALTRANS) was also atfault for cutting into the hillside to build Pacific Coast Highway.Norton, therefore, declared that both the state and county were responsiblefor the Big Rock Mesa landslide. Intense storms or rapidly melting wintersnow in these regions may impart mobility to accumulated sediment. "Effort To Halt Massive Slide Forms Mountain Of Dispute; Portuguese Bend Task Focuses On Valuable Land." Los Angeles Times 1 4 (1984, December 24): 1.Fischer, P. Over a period of 8 days, landslides and flooding resulting from a seriesof six major rainstorms cost the city $7 million (Campbell et al. The researchers foundthat the total economic loss from the movements totalled $45 million(Leighton & Clark 1982). Landslide damage included cracked walls, floors, driveways, tennis courts,and roads. Inaddition, slides buried a 1 -foot section of a railroad used by Amtrack(Malnic 1, 13). Thus, mostlandslides occur during or immediately after major storms. For instance,one slide on May 15, 1983 was estimated to contain about 3,5 cubic yardsof earth and large rocks. In addition, some houses completely collapsed (Garcia 1, 18). In all, a total of45 houses had to be evacuated. 1-27).Leighton & Poormand (1982) analyzed 5 destructive urban landslides whichoccurred in Orange County between 1966 and 1982. "The Portuguese Bend Landslide." In P. That was the year of Malibu's Big Rock Mesalandslide. Second Edition. Furthermore, while "disastrous landslides" maycertainly be expensive, the non-catastrophic landslide events actuallyresult in the greatest annual cumulative economic losses. B.; Nichols, D. When these beds become saturated with water,they form a slick, deformable surface upon which the ground above mayslide. On the southern side of Los Angeles' Palos VerdesPeninsula, the Portuguese Bend landslide extends over an area ofapproximately 27 acres. 176)." Theseplanes divide the mass into subunits. Variousstudies have shown that "denudation by fire temporarily exposes drainagebasins to rapid sediment yield and debris flow (Minnich 91-1 )." Further,such conditions may persist until a new layer of vegetation reestablishesitself. Nonetheless, the City of Rancho Palos Verdes has obtained a $2million grant from the state of California to, at least, initiate theremediation. While southern California's general climate is certainly conducive tolandslides, geomorphic processes such as slope failure are more typicallyrelated to "short-lived, extreme, precipitation events." These rainstormtriggered events commonly originate on slopes steeper than 3:1 (18degrees); whereas, mass movement depositional processes often begin onslopes less than 5:1 (11 degrees) (Campbell et al. However, the problem is actually quite complicated. The 1993 landslides eventually cost San Clemente severalhundred thousand dollars. Eventually, building and safety officials in the countyengineer's office had to post eviction notices throughout the area (Overend1,6). Bryant (eds), Guidebook: Geology and Landslides of the Palos Verdes Hills, California (pp. The impact of vegetationtends to be variable. This heavy rainfall, as well as the extended intervals ofrelative drought, tend to affect surface hydrological characteristics. Thirdly, subaerial debris flows typically consist of rapid and waterysediment movement. Forexample, in southern California, rainfall infiltrates soils immediately.Such absorption can readily exceed soil conductivity. Ehlig, M. All construction projects need to undergo thoroughinvestigation and analysis before being implemented. The differentincidents resulted in a total of 2 fatalities. This type of ground cover generally consistsof a contiguous, single layer of evergreen sclerophyllous shrubs. R. Rockfallsconsist of detached masses moving down steep slopes. Inthat particular year, storm-triggered landslide damage cost the City of LosAngeles $5 million. In and around PacificPalisades, landslide mitigation efforts date back to the first half of thetwentieth century. When some event can be associated with a landslide,they generally consist of such things as earthquakes, constructionprojects, snowmelt, and rainstorms. Moreover, when overland flow occurs, it mayresult in erosion (Minnich 91-1 ). Typically, a cool tradewind, marine layer in the cyclones'"warm sector" will cause the fronts to act like occlusions. In fact, southern California's subtropical stormshave produced some of the highest 24 hour precipitation intensities in theUnited States. 32-39). Although movement occurred between1931 and 1947, the landslide began historical movement in 1956. 186)." Varnes (1978) defines a mud flow asa "very slow to very rapid, wet flow of cohesive or noncohesive earthmaterial composed of at least 5 percent grains smaller than 2 mm (Campbellet al. In all, the PortugueseBend landslide has damaged or destroyed about 15 homes, a beach club, anda pier (Fischer 2). "$97-Million Settlement Over Malibu Landslide; Agreement Requires County, Caltrans, Insurers To Pay Homeowners For Big Rock Mesa Damage." Los Angeles Times 1 6 (1989, January 4): 1.Lait, M. If this paper is not what you are looking for, you can search again: Search for: or Click here to request an essay written just for you.