C H A P T E R 1 0

Geomorphology of Natural Hazards

and Human-induced Disasters in Bolivia

Edgardo M. Latrubesse,a Paul A. Baker,b and Jaime Argolloc

aCentro de Investigaciones Geologicas-CIG and LATYR- CONICET, Universidad

Nacional de La Plata, Calle 1 N0 644, (1900) La Plata, ArgentinabDuke University, Division of Earth and Ocean Sciences, Durham, NC 27708, USAcUniversidad Mayor de San Andres, Instituto de Geologıa y Medio Ambiente, La Paz,

Bolivia

Contents

1. Introduction 1812. Volcanoes 1843. Earthquakes 1854. Floods and Droughts in Bolivia 1865. Landslides 1916. Conclusions 193

1. Introduction

Bolivia is a geographically and culturally diverse nation with an area of1,098,580 km2 and a population of approximately 9.5 million. Approximately63% of the population is urban, and 69% of this urban population resides inthree major cities: La Paz (including El Alto), Cochabamba, and Santa Cruz.The country is divided into seven main geologic-physiographic provinces,from west to east: the Cordillera Occidental of the Andes (Western Cordillera),the Altiplano, the Cordillera Oriental of the Andes (Eastern Cordillera), theSubandean belt, the Chaco-Beni plain, the Pando block, and the BrazilianShield (Fig. 10.1).

Corresponding author: Edgardo M. Latrubesse, Centro de Investigaciones Geologicas-CIG and LATYR- CONICET,Universidad Nacional de La Plata, Calle 1 N0 644, (1900) La Plata, Argentina, latrubesse@yahoo.com.br

Developments in Earth Surface Processes, Volume 13 � 2010 Published by Elsevier B.V.

ISSN 0928-2025, DOI 10.1016/S0928-2025(08)10010-4

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The Cordillera Occidental is the active volcanic arc formed by the eastwardsubduction of the Nazca seafloor plate underneath the South American continent.Thus much of this mountain chain is composed of Neogene-age magmatic andvolcanic rocks. The range contains at least 18 ‘‘potentially active’’ volcanoes alongthe frontier between Chile and Bolivia (de Silva and Francis, 1991). The highestmountain in the Cordillera Occidental of Bolivia is Nevado Sajama (it is also thehighest mountain in Bolivia, 6542 m above sea level, m.a.s.l.). It is not categorizedas ‘‘potentially active,’’ and its 25,000-year-old icecap (Thompson et al., 1998)suggests that it has not had a major eruption for at least the past 25,000 years. Sajamaand its neighboring volcanic peaks, Nevados Payachata and Quimsachata, are (as ofNovember 1984) the only Bolivian peaks in this range covered by active glaciers(Jordan, 1999).

Figure 10.1 Main morphotectonic units of Bolivia and cities.

182 Edgardo M. Latrubesse et al.

The Altiplano is a wide endorheic basin with an area of about 110,000 km2. It iselongated in a roughly north-south direction, parallel to the bounding ranges of theCordilleras Occidental and Oriental. The average elevation of the Altiplano is about3700 m.a.s.l. Despite its great elevation, for the most part the Altiplano is a relatively flatlandscape with a surficial cover of Quaternary lacustrine and alluvial deposits in lowerelevations between 3653 and 4000 m.a.s.l. The plain is interrupted by isolated rangesand hills with elevations from 4000 to 5300 m.a.s.l. The Altiplano is characterized by thepresence of large salt pans or salares such as Salar de Uyuni and Salar de Coipasa and largelakes such as the salty, shallow Lago Poopo and deep, fresh Lago Titicaca. Salar de Uyuniis one of the flattest surfaces on Earth, Earth’s largest salt flat (ca. 10,000 km2), the site ofseveral generations of large paleolakes (e.g., Fritz et al., 2004), and at 3653 m.a.sl. is thelowest point on the Bolivian Altiplano. The Altiplano was probably formed (meaningthat it became a topographically separate sedimentary basin) in the late Eocene (e.g.,McQuarrie et al., 2005) and was rapidly uplifted from near sea level around 11 millionyears ago (Ma) to near its present elevation by 6.7 Ma (Ghosh et al., 2006). Theimportant cities of La Paz/El Alto and Oruro are located on the Altiplano. Mining,government, tourism, and commerce are all important sectors of the economy; small-scale traditional agriculture remains a major livelihood and economic resource.

The Cordillera Oriental has a complex geological origin and character. Itcomprises part of the Andean fold and thrust belt and contains a variety of plutonic,volcanic, metamorphic, and sedimentary rocks with ages ranging from Proterozoicto Quaternary. High peaks of the Cordillera Oriental include Illampu(6421 m.a.s.l.), Illimani (6402 m.a.s.l.), and Huayna Potosi (6088 m.a.s.l.), amongothers. As of 1984, 16 peaks in the Cordillera Oriental were glaciated, with a totalglaciated area of about 550 km2(Jordan, 1999). All of these glaciers are retreatingrapidly (Francou et al., 2005). As 30 to 40% of the potable water of La Paz/El Altois derived from glacial meltwater of the Cordillera Real (the highest range in theCordillera Oriental), the retreat and eventual loss of the glaciers will represent alarge economic loss (Vergara et al., 2007). The cities of Potosi, Sucre, and Cocha-bamba are located in this range.

An east-west elevational cross section of the Cordillera Oriental is asymmetric: thewestern flank with the Altiplano has local relief up to about 2500 m, while the easternflank drops abruptly more than 5000 m from the highest peaks to the eastern lowlands.The Subandean zone is the easternmost, active frontal fold-and-thrust complexlocated between the Cordillera Oriental and the eastern lowlands. The majority ofthe drainage systems flowing to the Amazon Basin (comprising 720,000 km2) or to theLa Plata Basin (comprising 229,500 km2) have their headwaters in the CordilleraOriental and Subandean zones. The most important Bolivian tributaries to theAmazon include the Mamore, Madre de Dios, and Beni, Itenez. The main Bolivianriver draining to the La Plata Basin is the Rio Pilcomayo.

The Chaco-Beni plain lies east of the Subandean zone. This region is part of theAndean foreland basin: its sediment cover overlies the Precambrian Brazil Shield.The plain covers about half the area of Bolivia, and its drainage is either northwardtoward Amazonia or southward toward the La Plata Basin. This region containsBolivia’s most productive agricultural and pastoral lands as well as large natural gasreserves. The cities of Santa Cruz and Trinidad are located in this zone.

Geomorphology of Natural Hazards and Human-induced Disasters in Bolivia 183

Bolivia lies entirely inside the tropical region; thus all of the country is characterizedby a wet season ranging from October to April and a drier season from May toSeptember. Most of the wet-season precipitation derives from the South Americansummer monsoon (Zhao and Lao, 1998). In the north the Altiplano is wetter andwarmer (500 to 1000 mm/y; mean annual temperature �12� C), becoming progres-sively more arid and colder to the south (<100 mm/y; mean annual temperature�2� C). The eastern lowlands also have a north-south climatic gradient with semiaridto arid conditions (�350 mm/y) prevailing in the Chaco close to the Bolivia–Paraguayborder and much wetter conditions (>2000 mm/y) northward in the Amazon region.

The diversity of the topographic relief in Bolivia is a factor in the diversity of itsregional climatic conditions. For example, local relief produces orographic lifting inthe Andean and Subandean eastern flank, where the Yungas forests occur; localconvective rains in the Altiplano and Chaco; and rain shadow effects in inter-Andean valleys and on the Altiplano. Steep slopes also produce significant localvariations of solar exposure, a factor controlling locations of glaciers and arablelands. The eastern flank of the Cordillera Oriental of Bolivia is characterized bytemperatures that decrease with increasing elevation (lapse rate about 5�C/km) andprecipitation that peaks between about 1200 and 1800 m.a.s.l. Summertime rainrates are highest (>5000 mm/y) over the Chapare region in the foothills of theCordillera Oriental (Killeen et al., 2007).

Cold air incursions, called surazos in Bolivia and Peru and friagems in Brazil,begin as cold-core anticyclones in the South Pacific (Garreaud, 1999). These coldsurges penetrate northward from the Argentinean plains to the Chaco and Beniplains as far as the Amazonian region. They can produce abrupt drops of tempera-ture of as much as 10�C (Ronchail, 1999). Surazos can also reach up onto theAltiplano and the Andes. In the Cordillera Occidental, the arrival of surazos isaccompanied by winter snow in the higher peaks such as Nevado Sajama.

The largest source of interannual variation of precipitation in much of tropicalSouth America is related to the El-Nino-Southern Oscillation (ENSO). In general,El Nino events are registered as dry years on the Altiplano and in the CordilleraOriental (e.g., Garreaud and Aceituno, 2001), but some El Nino events bringwetter-than-normal conditions south of the Beni plain toward the Chaco. LaNina events, on the other hand, tend to produce wetter-than-normal conditionsacross much of Bolivia. There is some evidence that regional precipitation amountsalso vary on longer (decadal to multidecadal) timescales (e.g., Hastenrath et al.,2004) and that this variation is partly controlled by sea-surface temperatures in thetropical Atlantic (e.g., Liu, 2008).

2. Volcanoes

Modern volcanic activity in Bolivia is limited to relatively isolated regions ofthe Cordillera Occidental. Large explosive eruptions have been recorded in thePliocene and Pleistocene, forming pyroclastic and lava plateaus in the CordilleraOccidental. The most recent volcanic activity seems to belong to Volcan Parinacota

184 Edgardo M. Latrubesse et al.

(18� 100S and 69� 090W), which was active �8000 B.P. (Clavero et al., 2002). DaSilva and Francis (1991) judged its hazard to be mainly associated with mudflowsand debris flows that could threaten the nearby Arica-La Paz Highway and somesmall communities located nearby. Considering the low volcanic activity in recenttimes and their mostly isolated locations in areas with very low population density,volcanic hazards and vulnerabilities on the Bolivian side of the international borderare considered to be quite low.

3. Earthquakes

Because of the eastward-increasing depth of the Nazca lithospheric plate as itsubducts under the Pacific coast of South America, earthquakes in Bolivia do notoften attain magnitudes greater than 6 on the Richter scale. The predicted values ofpeak ground accelerations (a key indicator of susceptibility of buildings to damagingduring earthquake ground movement) due to seismicity also decrease eastward.Maps and descriptions of historical seismic activity in the country are availableonline through the San Calixto Observatory website (http://www.observatorio-sancalixto.org/). Here we summarize from that website some of the most signifi-cant earthquakes to have impacted Bolivia in historic times.

Most of the historically damaging earthquakes in Bolivia have occurred in theCordillera Oriental. In 1650 an earthquake destroyed the dome of the cathedral inChiquisaca. A quake damaged adobe buildings in Santa Cruz in 1871, in SanAntonio (now Villa Tunari) in 1871, and in Yacuiba in 1887 and 1899 (also causinginjuries). In 1909 an earthquake in Sipe Sipe destroyed several adobe buildings andcaused 15 deaths. In 1925, 1958, 1976, and 1998, earthquakes occurred in theregion of Aiquile. The last of these, on May 22, 1998, was also the most destructive.This magnitude 6.6 earthquake was at that time the largest shallow-focus temblor inBolivia in the past 50 years (Funning et al., 2005), and it caused damage over aregion of about 100 km diameter, including the villages of Totora, Aiquile, andMizque. More than 100 people were killed. In Cochabamba city, earthquakes in1942, 1943, 1959, and 1972 caused some damage to buildings. A strong earthquakedestroyed about half of the capital city of Sucre on March 27, 1948, killing 3persons and injuring several more. In 1957 an earthquake in Postrervalle (southwestof Santa Cruz) destroyed several adobe buildings. In 1947 an earthquake withmagnitude of 6.4 caused widespread damage in Consata (La Paz Department). Asecond, weaker quake was recorded in Consata in 1956.

On June 9, 1994, the largest deep-focus earthquake on Earth occurred 636 kmbeneath the Beni lowlands near Rurrenabaque. It is believed that the earthquakerupture occurred within the downgoing Nazca plate, deep under the SouthAmerican continental lithosphere (Silver et al., 1995). The earthquake was felt inalmost the entire country. In Cobija it caused cracks in walls and made tall buildingssway in La Paz. The earthquake is thought to be responsible for five deaths in themountains of Peru and for minor damage to many buildings in Brazil and Peru. Thequake was felt in many parts of South America and North America, as distant as

Geomorphology of Natural Hazards and Human-induced Disasters in Bolivia 185

Toronto, Canada (reported in ‘‘Significant Earthquakes of the World, 1994,’’ U.S.Geological Survey).

Because of its sparser population and smaller area, there has been less economicand human loss due to seismic activity in the Cordillera Occidental of Bolivia. In1995 a magnitude 5.3 temblor destroyed most of the adobe buildings of the town ofCumujo (just northwest of Salar de Coipasa). A second quake of magnitude 4.6revisited the region in 2001 and caused minor damage to adobe buildings in thetown of Coipasa. A much stronger earthquake of magnitude 6.9 occurred in PotosiDepartment along the frontier between Bolivia and Chile on November 17, 2005.The quake caused power outages in Tocopilla, Chile.

Minaya and co-workers (2005) considered possible damage to the city of La Pazfrom large earthquakes with epicenters in southern Peru or northern Chile. Theyconcluded that the probability of an earthquake of magnitude 9 (Mw) in those partsof Peru or Chile was high and that such a remote earthquake might result in anintensity of V on the Modified Mercalli scale (felt by nearly everyone), but thatthere was no chance that such earthquakes could generate intensities of VIII orhigher (causing damage even to well-built buildings) in La Paz or elsewhere inBolivia.

4. Floods and Droughts in Bolivia

In economic terms, floods and droughts are the most costly natural disasters inBolivia. Floods are induced by anomalously high precipitation and runoff, whereasdroughts are caused by anomalously low rates of precipitation. Of course, thehydrologic and economic impact of both flood and drought can be exacerbatedby direct human activities such as population growth in affected regions, deforesta-tion, the covering of regions of natural recharge by construction of impermeablebarriers (roads, buildings, and parking lots), and the construction of housing devel-opments in regions prone to landslides.

In Bolivia, the interannual variability of precipitation, beyond the range ofnormal wet-season/dry-season variability, is often ascribed to ENSO variability.Indeed, during El Nino events of the past few decades (Fig. 10.2), the Altiplano andAndes of Bolivia, as well as western parts of the lowlands, are often drier thannormal, especially during the DJF season (Fig. 10.3, 1950–2002). Farther east,precipitation during El Nino events often is above normal. However, during pastLa Nina events, DJF precipitation throughout Bolivia, on average, has not beensignificantly different than normal (Fig. 10.4, 1950–2002).

Whereas anomalous precipitation in Bolivia can sometimes be associated withENSO conditions, ENSO is clearly not the only cause of anomalous precipitation.For example, in both of the past two years (DJF, 2006–2007 and DJF, 2007–2008)there has been anomalously high precipitation (Figs. 10.5 and 10.6) and devastatingflooding in much of lowland Bolivia. Newspaper accounts (Keene, 2007; Claure,2008) quote meteorologists attributing both cases to El Nino conditions. In fact, asdescribed previously, El Ninos are most often associated with dry conditions in

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Bolivia. Moreover, although DJF, 2006–2007, was indeed a weak El Nino(Fig. 10.2), the period of DJF, 2007–2008, was actually a weak La Nina. Thus,either phase of ENSO can be associated with flooding conditions in lowlandBolivia; in fact, it seems likely that ENSO was not responsible for flooding ineither year.

No matter the distal cause of anomalously high or low precipitation, the resultcan be catastrophic. The 1982–1983 El Nino is a case in point. During that event,floods affected 700,000 people in lowland Bolivia, and drought affected 1,600,000in the Bolivian highlands. Economic losses totaled US$ 837 million, and 40 deathswere reported. Drought affected the Altiplano and Andes, with low dischargesrecorded in the Desaguadero, Iauca, Mauri, and Marquez rivers, as well as someminor rivers, such as Yanapollera, which provides water to the town of Uyuni. InPotosi rainfall during 1983 was half of the average, producing the worst drought in30 years (at that time). Water supply for the city was insufficient. In the lowlands,strong rainfall, 350 mm, fell on Santa Cruz Department in March, nearly threetimes the monthly average. On March 17 the total precipitation recorded was120 mm. The heavy rains caused extensive flooding of more than 150,000 km2,strong erosion in the upland areas, and sediment accumulation in valleys and low-lying regions affecting the public works, housing, and basic services. It is estimatedthat 9500 houses were affected by floods in Santa Cruz Department and 5000 morein rural areas. The floods of the Piraı River produced damage estimated at US$ 37million, and 900 people were reported missing (CEPAL, 1984).

Between 1990 and 1992, nearly 2 million people were affected in Bolivia byfloods and droughts. Flooding during 1991–1992 affected more than 40,000

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Figure 10.2 Nin‹ o 3.4-based index of El Nin‹ o (Red) and La Nin‹ a (Blue). From http://iri.columbia.edu/climate/ENSO/currentinfo/archive/200712/ENSO_Quick_Look

Geomorphology of Natural Hazards and Human-induced Disasters in Bolivia 187

inhabitants from 160 communities in northeastern Bolivia, causing agricultural andranching losses greater than US$ 16 million.

The very strong El Nino of 1997–1998 had significant impacts in Bolivia.Drought affected much of the Altiplano and the south of the country, andflooding was widespread in the eastern lowlands. Approximately 77,000 inhabi-tants were affected by flooding in eight of the nine Bolivian departments (the onlyexception was Chuquisaca) (PAHO, 2000). The incidence of malaria increased asa result of the flooding. In the highlands, dry conditions contributed to a 5-mrecession of the Chacaltaya glacier. In total, the results of flood and droughtcaused economic losses estimated at US$ 527 million (53% due to drought, 47%to flood).

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Figure 10.3 DJF precipitation in much of Bolivia is significantly lower than normalduring El Nin‹ o events. http://iridl.ldeo.columbia.edu/SOURCES/.IRI/.Analyses/.ENSO-RP/.ver1950-2002/.0p5deg

188 Edgardo M. Latrubesse et al.

The floods of 2006–2007 were dramatic. An intense rainy season started inJanuary 2006 and continued for about 112 days. An area of about 800,000 km2 wasflooded. Flooding was most severe along the Mamore River. The Beni capital cityof Trinidad was inundated, crops were destroyed, and 22,000 cattle drowned in theBeni. According to the Dartmouth Flood Observatory (http://www.dart-mouth.edu/�floods/index.html), 63,000 persons were displaced from theirhomes and 41 deaths were reported. The total damages throughout Bolivia wereestimated at US$ 90 million. The flood was described as the worst flood of the past30 years. One year later it was surpassed.

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Figure 10.4. DJF precipitation in Bolivia is not significantly greater than normal during LaNin‹ a events. http://iridl.ldeo.columbia.edu/SOURCES/.IRI/.Analyses/.ENSO-RP/.ver1950-2002/.0p5deg/

Geomorphology of Natural Hazards and Human-induced Disasters in Bolivia 189

During the last month of 2007 and the first three months of 2008 (as of March25, 2008), the eastern lowlands again underwent record flooding. Floodingextended over an area of about 870,000 km2. Again, Trinidad was the city thatsuffered the most. For much of the region, it was the third consecutive year ofserious flooding. An estimated 240,000 persons were displaced from their homesand 73 died. At this time, economic losses are estimated at US$ 200 million(Dartmouth Flood Observatory).

Water and sanitation systems were deleteriously affected by flooding(United Nations, 2008). The incidence of several diseases increased con-currently with the flooding: acute diarrheal diseases, acute respiratory dis-eases, dengue, leptospirosis, hemorrhagic fever, yellow fever, and malaria.Rates of malnutrition and psychological disorders also rose. Serious damageaffected roads and bridges, schools, and houses. Food resources were ser-iously damaged with loss of many cattle and crops. The total impacts ofthis latest and largest flood have not yet been fully accessed at the time ofthis review.

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Figure 10.5 DJF 2007 was also unusually wet in the lowlands and dry in the highlands. http://www.cdc.noaa.gov/cgi-bin/Composites/printpage.pl

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5. Landslides

Throughout many parts of Bolivia, landslides cause a large loss of life andproperty. We describe two case studies, the landslide in Chima town and thelandslides in La Paz city.

La Paz is the largest city of Bolivia with an estimated (2005) total population of1,640,000 (840,000 for La Paz and 800,000 for El Alto; data from InstitutoNacional de Estadıtistica, Bolivia). An estimated 60% of the urban population ofLa Paz proper is housed in self-built settlements (O’Hare and Rivas, 2005).

Landslides are a particularly important hazard in La Paz. The steep slopes andunconsolidated bedrock, the seasonality of precipitation and fluctuating water level,construction (often informal) on the unstable slopes, and deficient urban planning,all contribute to the city’s vulnerability (O’Hare and Rivas, 2005). Mass movementis typically triggered by ground saturation following intense summer convectiveprecipitation events. The unusual and spectacular geomorphological situation of thecity is another contributory factor. The city was founded in 1548 on the site of anindigenous community named Chuquiago, along the steep valleys of the

NCEP/NCAR ReanalysisSurface Preciptation Rate (mm/day) Composite Anomaly 1968–1996 climo

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Figure 10.6 DJF 2008 was anomalously wet in the lowlands and dry in the highlands ofBolivia (mm/day).

Geomorphology of Natural Hazards and Human-induced Disasters in Bolivia 191

Choqueyapa and Orkojahuira rivers. City growth spread up (to 4000 m.a.s.l.) anddown (to 3200 m.a.s.l.) the La Paz valley, a sedimentary basin filled with unconso-lidated, continental Cenozoic deposits. At the head of the valleys, the steep-sidedwalls of the Altiplano form huge natural amphitheatres that are now largely coveredby informal settlements. The latter are concentrated in the highest elevations and onthe steepest slopes of the city, those most vulnerable to large landslides; but floods,landslides, and other mass movements, can affect almost all parts of the city,including the affluent barrios of the Zona Sur.

O’Hare and Rivas (2005) discuss two particular events in detail. A landslidefollowing heavy rainfall produced a damaging landslide in the Cotahuma Barrio ofwestern La Paz on April 6, 1996. This slide killed 27 people and destroyed 80homes. Several days of heavy rain in March 2003 caused a series of mass movementevents at several locations around the city. Hardest hit was the barrio of Llojetawhere a landslide destroyed the homes of 75 families.

The peculiar setting of La Paz also subjects the city to flash flooding followingperiods of intense hail or rain. Such rainfall events are brought about by unusuallyheavy convective activity that can be produced during any summer wet season.Such a short, but intense, midafternoon storm brought torrential rain and hail to LaPaz on February 19, 2002. Drainage along small tributaries funneled into theChoqueyapu River. Hail and debris helped to block the drainage water system ofthe downtown, and the water overflowed along some streets, including the busymain thoroughfare (El Prado). The event caused 77 deaths, and one damageestimate exceeded US$ 60 million (Enever, 2002). In March 2002, the MunicipalGovernment of La Paz (GML) created the Permanent Committee of Attention andManagement of Disasters and in June 2002, with the support of the UNPD, set upprograms for flood management in La Paz city.

One of the more infamous landslides was that of Chima, a town located in theDepartment of La Paz. ‘‘Chima,’’ originally Chima Jaucata, in the Aymara languagemeans ‘‘castigated place.’’ The population of Chima is 2614, and its main economicactivity is gold mining. The gold occurs in Miocene conglomerates and modernalluvial deposits. The area is known as the Gold District of Tipuani, the richest andmost productive gold mining region of Bolivia, one that has produced 995 tons ofgold during its history.

Detailed studies of the disaster were undertaken by an international team of theCYTED Network XIII, and our discussion is culled from several publicationsproduced by that group (Orche 2003a, 2003b; Orche et al, 2003, among others).The area of Tipuani-Guanay is considered one of the most hazardous mining areasof Bolivia, having suffered repeated avalanches and floods. In 1952 a landslide killed400 inhabitants; in 1971 a landslide killed 20 inhabitants; another in 1991 killed 20more. In 2001 the area suffered from flooding. On March 31, 2003, a landslidekilled 169 persons and injured 11. Floods again afflicted the town on December 18,2003, destroying several houses.

The landslide of March 31, 2003 is illustrative. At the time of the landslide,the town of Chima had a population of about 2000 and contained 621 homes(Orche et al., 2003). The main mining activity by the Cooperativa AuriferaChima Limitada was concentrated on Cerro Pucaloma and produced a

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300-m-high, steep, unstable, and talus-covered face. Intense rainfall duringMarch infiltrated the artificial fissures on this face and exacerbated the unstableconditions. From March 26 to 28, 2003, a group of experts from CYTEDnetwork XIII visited Chima and, noting the risky situation of the town inrelation to the mining activity, alerted residents and local authorities. TheCYTED technicians further pointed out that overload produced by watersaturation of the adjacent mountain could cause its talus slope to fail. Onlythree days later, on March 31, a rotational slide, transformed downslope into adebris flow, advanced rapidly to the Rio Tipuani. The total volume of thedebris fan was estimated at 400,000 m3. A lobe of this flow swept away aportion of the city killing 169 inhabitants (including those missing), affectinganother 690 (35% of the total population) and destroying 149 houses (one-quarter of the town) (Fig.10.7). Economic losses were estimated at US$ 1.2million. As a consequence of this landslide, the Unit of Risk Management wascreated in La Paz Department with the support of UNPD.

6. Conclusions

Bolivia is subjected to a wide variety of natural hazards. The damaging effectsof these natural hazards are often exacerbated by human decisions and activities.The Bolivian government has only limited resources to plan for and to mitigateagainst disaster.

Figure 10.7. The town of Chima after the landslide disaster of March 31, 2003. (Photo byE. Orche).

Geomorphology of Natural Hazards and Human-induced Disasters in Bolivia 193

The most serious hazards facing the nation are hydrometeorological events,particularly floods, droughts, and landslides. In many of the cases that we havementioned, economic losses and loss of life could have been avoided or, at least,minimized with better planning and selective investment of resources into hazardmitigation.

Acknowledgment

The authors thank especially Professor E. Orche for providing valuableinformation on the Chima disaster.

194 Edgardo M. Latrubesse et al.