Usoi Landslide Dam and Lake Sarez, Pamir Mountains, Tajikistan

Usoi Landslide Dam and Lake Sarez,Pamir Mountains, Tajikistan

ROBERT L. SCHUSTER

Engineering Geology/Geotechnical Engineering Consultant,1941 Golden Vue Drive, Golden, CO 80401

DONALD ALFORD

Geoscience Advisor, Focus Humanitarian Assistance, 7777 Leesburg Pike,Suite 303S, Falls Church, VA 22043

Key Terms: Early Warning, Earthquake, Lake, Land-slide, Landslide Dam, Outburst Flood, Overtopping,Rock Slide

ABSTRACT

In 1911, a 2-km3 (0.5-mi3) earthquake-triggeredrock slide blocked the Murgab River, southeasternTajikistan, forming a still-existing, 600-m-high (1,970-ft-high) natural dam—the highest dam, natural orman-made, in the world. Lake Sarez, impoundedby this blockage, is 60 km (37 mi) long, with a maxi-mum depth of 550 m (1,800 ft) and a volume ofapproximately 17 km3 (~4 mi3). This lake, which hasnever overtopped the dam, exits the downstream faceas a series of large springs that regroup as theMurgab River. Freeboard between lake surface andthe lowest point on the dam crest currently isapproximately 50 m (~165 ft), and the lake is risingat an average rate of 18.5 cm/yr (7.3 in./yr). Ifthe blockage were to fail, a worst-case scenario couldendanger tens or possibly hundreds of thousands ofpeople in the Murgab, Bartang, Panj, and AmuDarya valleys downstream. Dam failure potentiallycould result from: 1) seismic shaking, 2) catastrophicovertopping caused by a landslide entering the lakefrom the valley wall at high velocity, 3) surfaceerosion caused by natural overtopping by the risinglake, 4) internal erosion (piping), 5) instability causedby lake pressure against the dam, or 6) slope in-stability of the dam faces. Occurrence of an over-topping wave resulting from a potential landslidehigh on the right bank of Lake Sarez seems to be themost realistic of these slight possibilities for failure.Because of the high cost of installing physicalremediation to the dam in this rugged mountain area(no roads lead to the site), the main protectivemeasures now being undertaken are hydrological

monitoring at the dam and installation of a floodearly warning system downstream.

INTRODUCTION

On February, 18, 1911, a Ms 7.6 earthquake (Abe andNoguchi, 1983) struck the Pamir Mountains of south-eastern Tajikistan north of the Murgab River (Figure 1),triggering a huge landslide (Figure 2) in Carboniferousquartzites and schists and Permian-Triassic marbles andshales (Preobrajensky, 1920; Gaziev, 1984; Hanisch,2000, 2002a; Papyrin, 2002; and Schuster, 2002). Thisapproximately 2.0-km3 (;0.5-mi3) landslide, whichaccording to the classification of Cruden and Varnes(1996) would best be classified as a massive rock slide,dammed the Murgab River, impounding Lake Sarez(Figures 2–6) and its smaller tributary impoundment,Lake Shadau (Figure 7). Above water, the landslide hasa surface area of 9.9 km2 (3.8 mi2); its total area isapproximately 12 km2 (;4.6 mi2) (Papyrin, 2002).

This rock slide, named after the village of Usoi, whichwas completely buried by the slide, apparently wasa high-velocity, catastrophic event. As shown in Figure 2,the slide originated on a very steep slope (inclination,358–408 or greater). The crest of the head scarp was at anelevation of approximately 4,500 m, and the rock massfell as much as 1,800 m (5,900 ft) to an elevation of 2,700m (8,860 ft) in the valley of the Murgab River (Gaziev,1984). According to Papyrin (2002), Soviet scientistsViktor Lim, Yusuf Akdodov, and Yuri Kazakov haveestimated the velocity of the Usoi rock slide at 24 to 25m/second (;90 km/hour; ;55 mi/hour). The location ofthe slide was determined by a combination of unfavorabletectonic and structural factors (Hanisch, 2000):

� A high degree of rock fracturing from previoustectonic activity.

� A major thrust fault with an unfavorable orientation.� A series of intensively sheared zones forming the

geometric setting for a typical wedge failure.

Environmental & Engineering Geoscience, Vol. X, No. 2, May 2004, pp. 151–168 151

Lake Sarez (named after the village of Sarez, whichwas drowned by the rising water) rose rapidly behind the600-m-high (1,970-ft-high) landslide dam. The lake isnow approximately 60 km (37 mi) long, with a maximumdepth of approximately 550 m (1,800 ft) and a totalvolume of approximately 17 km3 (;4 mi3). The surfaceof the lake currently lies slightly above 3,200 m (10,500ft) a.s.l., surrounded by mountain peaks that rise toelevations of more than 6,000 m (19,700 ft). The Usoilandslide dam is the highest dam, natural or man-made, inthe world, approximately twice as high as the 300-m-high(985-ft-high) Nurek Dam (Figure 1), also in Tajikistan,the world’s highest man-made dam. In a worst-casescenario, a catastrophic outburst flood from Lake Sarezwould destroy many villages and much infrastructure inthe Amu Darya river basin, which is populated by morethan 5 million people, tens or possibly hundreds ofthousands of whom live on floodplains downstream fromLake Sarez and could be endangered by the flood.

The Usoi landslide dam and Lake Sarez are located inthe Gorno-Badakhshan Autonomous Oblast (Province)of the Central Asian Republic of Tajikistan, in a regionslowly emerging from many years under the formerSoviet Union. This remote region is defined by some ofthe highest mountain ranges on earth—the Pamir, TienShan, Karakoram, and Hindu Kush Mountains—and theproblems concomitant with these high mountain areas,such as the social, economic, and political isolation ofthe peoples living there. The topographic complexity andgeneral inaccessibility of these high mountain ranges,coupled with the many political and economic difficultiesassociated with the transition from Soviet rule, havealso hindered the application of engineering solutionsto geologic hazards, such as those posed by the Usoilandslide dam.

The Usoi landslide dam and Lake Sarez presenta major dilemma, both to the governments of the riparianrepublics of the Amu Darya river basin (Tajikistan,Afghanistan, and Uzbekistan) and to the internationaldevelopment assistance agencies and banks that are thesource of most of the available economic aid in the regiontoday. The Central Asian republics themselves do nothave the necessary resources for even the most modestremedial engineering efforts on the dam, the lake, and thedrainage basin.

A conference, convened by Focus HumanitarianAssistance, USA (FOCUS), in Washington, D.C., duringthe summer of 1998 and attended by Western geo-scientists and representatives from the U.S. Agency forInternational Development (USAID), the World Bank,and the U.S. Geological Survey (USGS), concluded thatinsufficient information was available concerning manyaspects of the Usoi/Sarez hazard. The recommendation ofthis conference was a reconnaissance of Usoi/Sarez andthe Murgab/Bartang river valley downstream from thedam. This reconnaissance, undertaken in October 1998,led to the conclusion that no obvious signs of instabilitywere present in the landslide dam and to a recommenda-tion that installation of monitoring instrumentation onthe dam and lake and an early warning system fordownstream villages should be given high priority(Alford, 1998; Alford et al., 2000). This reconnaissancewas followed in June 1999 by an interagency risk-assessment mission to the site that was organized by theUnited Nations International Decade for Natural DisasterReduction (IDNDR) Secretariat with direct support fromthe USAID, FOCUS, and the United Nations Develop-ment Programme (Alford and Schuster, 2000a). Thismission consisted of a combined group of Western andTajik scientists who studied both the dam and the lake as

Figure 1. Map of Tajikistan showing location of the Usoi landslide dam, Lake Sarez, the Murgab and Bartang rivers, and villages in the area.

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well as the environment and inhabitants of the Murgab/Bartang/Panj river valley for approximately 200 km(;125 mi) downstream. The mission participants con-cluded that, in the near- to mid-term, the probability ofa massive outburst flood from Lake Sarez was very low(Alford et al., 2000). However, it was fully realized that,should such a flood occur, the impact on downstreamvalleys could be catastrophic.

In 1999, the World Bank began preliminary plan-ning to implement the recommendations of these mis-sions, resulting in organization of the Lake Sarez RiskMitigation Project (LSRMP), managed by the WorldBank and receiving financial support from the govern-ment of Switzerland, USAID, FOCUS, and the Aga KhanFoundation. The LSRMP, which is run by the govern-ment of Tajikistan, has begun quantifying the risk facedby the inhabitants of the valleys below the lake and hasprepared caches of emergency supplies for those villageswith the greatest vulnerability. It will also oversee theinstallation of monitoring and early warning instrumen-tation at Lake Sarez and in the villages of the upperBartang river valley.

A major problem faced by Western scientists andengineers in evaluating the conflicting approaches pro-posed for dealing with the problems of Lake Sarez hasbeen the lack of information available in English-language technical publications before the reconnaissance

missions of 1998 and 1999. Most Soviet-era studies ofthe Usoi landslide dam and Lake Sarez either remainunpublished or are available only in Russian. It is there-fore considered to be reasonable to ensure that a synthesisof the best-available information concerning Usoi/Sarez,derived from studies undertaken during the past 80 years,be available in the event that continuing engineeringstudies or efforts are warranted. Thus, it is the purpose ofthis paper to present an overview of the informationavailable regarding the Usoi landslide dam and LakeSarez from the time of formation of the dam to the present.

LONGEVITY OF LANDSLIDE DAMS

Landslide dams and the lakes they impound may existfor periods of time ranging from several minutes toseveral thousand years, depending on many factors,including: 1) size and shape of the dam, 2) volume andrate of water and sediment inflow to the newly formedlake, 3) character of the geologic materials comprisingthe dam, and 4) volume and velocity of flow through thedam (Schuster and Costa, 1986; Costa and Schuster,1988; and Schuster, 1995).

Figure 8 shows the time between dam formation andfailure for 187 landslide dams, as documented by Costaand Schuster (1991) and by Schuster (1995). Becauselandslide dams are heterogeneous masses of landslide

Figure 2. Usoi landslide dam and Lake Sarez. The steep source area of the 1911 Usoi rock slide is in the left background; the north end of the

landslide dam is in the foreground. The light-colored, post-1911 debris flow has mantled the north end of the rock slide and flowed into Lake Sarez at

the center-right and downstream into the Murgab River drainage at the left. (Photo taken August 1992 by S. F. Cunha, Department of Geography,

Humboldt State University, Arcata, California.)

Usoi Landslide Dam and Lake Sarez


materials rather than engineered structures, many of thesestream blockages fail within short periods of time—oftenonly a few hours to a few days after formation. The hazardfrom failure of landslide dams is emphasized by the shortlives of most such dams: 35 percent of those shown inFigure 8 failed within 1 day, 55 percent lasted 1 week orless, 68 percent failed within 1 month, 83 percent lastedless than 6 months, and 89 percent failed within 1 year.These data indicate that, among landslide dams, the Usoiblockage is a distinct anomaly in terms of longevity.

Stability of landslide dams is critically dependenton resistance to erosion, either at the dam surface (fromsurface-water runoff) or inside the dam (from seepage-caused piping). Landslide dams composed mainly of soft,low-density, fine-grained, or easily liquefiable materialsare more hazardous, because they are easily susceptible tofailure by erosion. Mud-flow and debris-flow dams areparticularly prone to rapid failure, because they usuallyare low dams that are quickly overtopped and very sus-ceptible to surface erosion.

Conversely, landslide dams consisting of significantmasses of large rock fragments or blocks, such as the Usoiblockage, are apt to resist failure for long periods of time.Probably the world’s outstanding example of a long-termlandslide dam that still exists, although it no longerimpounds a lake, is the Sımareh landslide in southwestIran (Harrison and Falcon, 1937, 1938; Watson andWright, 1969). Composed of limestone debris, this hugeprehistoric landslide, which was probably triggered by anearthquake approximately 10,000 to 11,000 years B.P.

(Watson and Wright, 1969), has a surface area of 166km2 (64 mi2) and an estimated volume of 24 to 32 km3

(6–8 mi3), making it one of the world’s largest subaeriallandslides (Shoaei and Ghayoumian, 2000). This lime-stone mass dammed the Sımareh and Kashkan Rivers,forming a blockage as much as 400 m high. Two majorlakes, now filled with sediment, were impounded by thelandslide (Watson and Wright, 1969). ‘Lake Sımareh’extended 40 km (25 mi) up the Sımareh River to sub-merge a 200-km2 (77-mi2) area. The smaller ‘Jaidar Lake’covered a 90-km2 (35-mi2) area of the landslide debrisat the mouth of the Kashkan River.

Another outstanding example of a long-lived landslidedam is the 2,200-year-old Waikaremoana blockage ofthe Waikaretaheka River, North Island, New Zealand.This 2.2-km3 (0.5-mi3) landslide (approximately the samevolume as the Usoi landslide) in Tertiary sandstonesimpounds the 250-m-deep (820-ft-deep) Lake Waikar-emoana, which has a volume of 5.2 km3 (1.2 mi3) (Readet al., 1992). Unlike the Usoi landslide dam, theWaikaremoana blockage probably was overtopped withinapproximately 10 years of formation of the dam. It owesits long-term survival to the erosion-resistant nature of therock mass that forms the rock-slide dam.

Another interesting long-lived landslide dam wasthe rock- and debris-fall blockage that impounded LakeYashinkul on the Tegermach River in the Republic ofKyrgyzstan in 1835. This natural dam failed catastroph-ically in 1966 because of piping, after having been stablefor 131 years (Glazyrin and Reyzvikh, 1968; Pushkar-

Figure 3. View of Usoi landslide dam (arrows) and the downstream (west) end of Lake Sarez from the right (north) valley wall of the lake. (Photo

taken June 1999 by Jorg Hanisch, German Federal Institute for Geosciences and Natural Resources, Hanover, Germany.)

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enko and Nikitin, 1988). This example illustrates thata landslide dam can fail after having existed under stableconditions for many years.

PHYSICAL CHARACTERISTICS OF THE USOILANDSLIDE DAM

Landslide dams are commonly much wider (dimensionparallel to the stream) than man-made embankment damsof equal height. Gaziev (1984) indicated that the basalwidth (above lake level) of the Usoi blockage wasapproximately 4 km (2.5 mi) (Figure 5), a figure agreedon by Adushkin (1991) (Figure 9). Papyrin (2002, p. 46)found that the width was 3.75 km (2.3 mi) ‘‘from theupper pool to tail-water,’’ and Hanisch (2000) estimatedits width at 5 km (3 mi). This large basal dimensionprotects the natural dam against failure because of basalsliding or piping.

Hanisch (2000, 2002a) has divided the Usoi landslidedam into three sectors: northern, central and southern.

Northern Sector

This sector includes the lowest part of the dam crest,with a minimum freeboard of approximately 50 m (;165ft). The surface is covered almost continuously with rockblocks averaging approximately 2 to 3 m (;7–10 ft) indimension; some are as large as 20 m (65 ft). Practicallyno fine-grained geologic materials exist in the area closestto the source of the rock slide; however, rock avalanches,

debris flows, and mudflows actively deposit rock and soildebris on the surface of this sector of the dam (Figure 2).

Central Sector

This part of the dam rises an average of approximately100 m (;330 ft) above lake level. The surface of thissector differs from the rest of the dam in that no largerock blocks are present. Instead, the surface is covered byfines (mostly silt). Apparently, this material was origi-nally colluvium on the pre-landslide slopes before thelandslide occurred. However, the downstream slopeincludes large rock blocks.

Southern Sector

This is the toe of the Usoi rock slide and the highestpart of the dam, with a maximum crest height ap-proximately 270 m (;885 ft) above current lake level.The surface is covered by rock blocks (Figure 10) ofvarious sizes, the largest with dimensions as great as 20 m(65 ft). Virtually no fines are present on the surface.

CHARACTERISTICS OF LAKE SAREZ

Lake Sarez rose rapidly after the Murgab River wasdammed in 1911, soon submerging the village of Sarez.As indicated by Berg (1950), by October 1913 the lakewas 28 km (17 mi) long and 280 m (920 ft) deep, and byAugust 1915 it was 350 m (1,150 ft) deep. As the lakewidened as the surface rose, the rate of rise slowed(Figure 11). From 1949 to 1988, the average annual

Figure 4. NASA Landsat image of 60-km-long (37-mi-long) Lake Sarez. Arrow indicates location of the Usoi landslide dam.



increase in lake level was 18.5 cm/yr (7.3 in/yr) (StuckyConsulting Engineers Ltd., 2001). Schaeren and Raetzo(2003) estimated that today’s 60-km-long (37-mi-long)lake was rising at an average rate of approximately 10cm/yr (;4 in./yr). Apparently, this trend is continuing;however, it is difficult to predict what effects globalwarming may have on the future water regime of the lake.The maximum lake level reached was approximately3,270 m (;10,730 ft) a.s.l. in 1994, and the currentmaximum yearly level is approximately 3,260 to 3,265 m(10,695–10,710 ft) a.s.l., indicating a current maximumdepth of approximately 550 m (;1,805 ft). Averageannual fluctuation of lake level is 10 to 12 m (33–39 ft).In the late summer (as the result of snowmelt runoff), thewater level rises 5 to 6 m (16–20 ft) above the meanannual level, and it drops approximately the same amountbelow normal by the following spring (Papyrin, 2002).The current volume of water in this 60-km-long (37-mi-long) lake is approximately 17 km3 (4 mi3).

Based on Soviet records, Stucky Consulting EngineersLtd. (2001) have noted that inflow to Lake Sarez averages45.7 m3/s (1,630 ft3/s). Lake Sarez drains by dischargethrough the dam; thus, the dam has never beenovertopped. Soviet hydrograph records (Figure 12) from1943 to 1988 at the village of Barchidiv (Figures 1 and13) at the confluence of the Murgab and Bartang rivers,some 20 km (12 mi) downstream from Lake Sarez,

indicated an average flow in the Murgab River of45.8 m3/s (1,635 ft3/s), or approximately the same asthe outflow from Lake Sarez. (This flow rate reflects bothlake evaporation and minor tributary input between thedam and Barchidiv.) The flow exits the dam as a series ofapproximately 45 large springs that regroup to form thelower Murgab River (Stucky Consulting Engineers Ltd.,2003) (Figure 14).

RIGHT VALLEY SLOPE ABOVE LAKE SAREZ

The right valley slope above Lake Sarez approxi-mately 5 km (3 mi) upstream from the landslide dam hasbeen characterized by Soviet geologists as a ‘dormant’landslide (called the ‘right-bank landslide’), with a volumeestimated at from 0.35 to 2.0 km3 (0.1–0.5 mi3) (StateCommittee on Emergencies, 1997, 1999). This ‘land-slide’ has a width along the lake shore of approximately 1km (0.6 mi); its approximate upper boundary is shown inFigure 15. The huge range in the estimate of volumeexists both because the thickness of the landslide is veryuncertain and because it is not clear whether potentialmovement would be associated with a single, large,monolithic landslide or would be made up of smallerindividual landslides. The one drill hole bored by Russianscientists indicated a deep-seated failure surface, but theevidence is problematic. More drilling is needed toresolve the issue. If the failure surface is shallow in thearea of potential landslide activity, the landslide (whichmay be local) most probably can be classified asa shallow debris slide, mainly in colluvium. If the failuresurface is deep, however, the mass movement could bea massive rock and debris slide. If this ‘dormant’landslide is indeed a deep-seated rock slide, a worst-casecatastrophic failure scenario brings to mind the 1963Vaiont landslide disaster in Italy (Kiersch, 1964; Muller,1964, 1968; and Semenza and Ghirotti, 2000), whichpossibly could lead to an overtopping failure of the Usoilandslide dam.

Recent field studies by geologists from Stucky Con-sulting Engineers Ltd. (Schaeren and Raetzo, 2003),however, contradict the concept of a single, monolithic,pre-existing landslide on this slope. Instead, the rightvalley slope (Figure 15) can be divided into four in-dividual areas, each of which is subject to separatelandslide processes. In general, the upper part of the slopeis subject to debris slides in colluvium formed fromsandstone talus. The lower part may be at risk from rock-slide activity with failure surfaces projected to be at depthsof no more than 100 m. Schaeren and Raetzo (2003, p. 31)have estimated that the total volume of landslide-susceptible material on the right-bank slope is approxi-mately 1.2 km3 (;0.3 mi3), but they also note there is littlechance that all this material would fail simultaneously asa monolithic landslide. Thus, they believe any landslide

Figure 5. Map of the Usoi area showing location of the 1911 Ms 7.6

earthquake epicenter, source area of the Usoi rock slide, and rough

outline of the Usoi landslide dam. (After Gaziev [1984].)

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that might trigger a wave in Lake Sarez would havea volume on the low end of the original 0.35 to 2.0 km3

(0.1–0.5 mi3) estimate, or might be even smaller.Numerous open cracks have been monitored on this

slope for many years by Russian and Tajik observers.Movements of as much as 10 cm/yr (4 in./yr) have beennoted (State Committee on Emergencies, 1997).In August 1998, a set of modern extensometers wasinstalled on the slope (Hanisch, 2000, 2002b). One rodextensometer indicated movement of 2 cm (0.8 in.)over a 9-month period; another showed movement of1 cm (0.4 in.) over the same period. However, surficialgeologic evidence probably indicates that these move-ments reflect local deformation rather than movement ofa monolithic mass.

RISKS TO USOI LANDSLIDE DAM

Although the Usoi landslide dam has been stable formore than 90 years, it is not an engineered structure, andit impounds a very large volume of water upstream frompopulated valleys. Thus, consideration must be given toits long-term safety. Several elements of risk must beconsidered, most of which have been noted by Hanisch(2000):

� Risk of failure caused by geotechnical slope instabilityof the landslide dam. This includes instability of theentire dam mass against sliding on its base and localslope instability within the body of the dam.

� Risk of failure as a result of surface erosion followingovertopping caused by natural rise of the lake level.

� Risk of failure caused by impact and overtopping bya massive wave resulting from catastrophic activation(or reactivation) of a landslide (or landslides) on theright valley slope above the lake.

� Risk of failure as a result of internal erosion (piping).� Risk of failure caused by seismic impact on the land-

slide dam and lake.

In addition, Yuri Kazakov, a Russian geologist whoconducted geological studies at Usoi/Sarez from 1985 to1993, has observed ice (from a pre-landslide mountainglacier) in the landslide dam that he feels was in-corporated in the landslide mass during the 1911 event(Renouf, 1999; Kazakov, 2001). Kazakov believes thisice is melting and ‘‘threatening to weaken the structure ofthe dam’’ (Kazakov in Renouf, 1999, p. 13).

The possibility of failure by each of these mechanismshas been studied as a research effort of the LSRMP,a major undertaking that will be discussed below. Someof the factors involved in considering the possible failuremodes are discussed in detail here.

Failure by Sliding of the Dam Mass Along Its Base

The driving force that might cause failure by sliding ofthe dam mass along its base is the hydrostatic load ofapproximately 500 m (1,640 ft) of reservoir water. Theresisting force is the frictional resistance acting on the

Figure 6. Aerial oblique view of Lake Sarez looking upstream from the Usoi landslide dam. (Photo taken June 2001.)



total area of dam base. Hanisch (2000, 2002a) obtaineda factor of safety of approximately nine against the oc-currence of such sliding.

Failure by Slope Instability Within the Bodyof the Dam

At present, it is difficult to estimate the factor of safetyagainst sliding within the dam for either static or dynamiccases, because it currently is not possible to assign valuesfor shear-strength parameters for the internal structure ofthe dam. Based on arbitrary estimates of shear strengthand seismic acceleration, Hanisch (2000; 2002a) obtainedfactors of safety of 2.48 and 1.15 for the upstream slopeof the dam for the static and dynamic (pseudo-static)cases, respectively, for current lake levels. However,Hanisch noted that his estimates for the strength andacceleration parameters are crude, because little is knownregarding the internal structure of the dam or of the flowpattern through the dam. Because of the lack of suchknowledge, he did not attempt to analyze the slopestability of the downstream face of the dam.

Failure by Surface Erosion Caused byNatural Overtopping

The current minimum freeboard for the dam at thenorth end is approximately 50 m (165 ft) (Alford and

Schuster, 2000a; Schaeren and Raetzo, 2003). The rateof rise in lake level will decline in the future with con-stant inflow, because the surface area of the lake will in-crease as the stage rises. Thus, at the current averagerate of lake-level rise of 18.5 cm/yr (7.3 in/yr) (StuckyConsulting Engineers Ltd., 2001), a conservative estimateof time to overtopping is at least 250 to 300 years. Inaddition, as noted in the description of the northern sectorof the dam, the surface of the northern sector is coveredwith large boulders, similar to those shown in Figure 10,which will not be susceptible to erosion in the event ofovertopping.

Failure from Overtopping Caused by CatastrophicActivation of a Large Landslide on the

Right Valley Slope

Although the general opinion (Stucky ConsultingEngineers Ltd., 2001; Schaeren and Raetzo, 2003)currently is that the true volume of the landslide-susceptible material on the right-bank slope is on thelow end of the estimated range of 0.35 to 2.0 km3

(0.1–0.5 mi3), there remains a slight possibility of a deep-seated, ‘dormant’ landslide on this slope, for whicha worst-case, catastrophic-failure scenario brings to mindthe 1963 Vaiont landslide disaster in Italy (Kiersch 1964;Muller, 1964, 1968; and Semenza and Ghirotti, 2000), inwhich a landslide-caused wave overtopped Vaiont Dam.

Figure 7. Aerial oblique view from the head of the Usoi landslide looking southward across Lake Sarez toward the tributary Lake Shadau. Arrow

indicates the current location of the Tajik government meteorological observatory, which serves as a base for studies of the area. (Photo taken in 1984

by A. Strom, Institute for Dynamics of the Geosphere, Moscow, Russia.)

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For this reason, the State Committee on Emergencies(1997, 1999) has calculated a wave height and floodvolume overtopping the dam of 180 m (590 ft) and 225million m3 (8 billion ft3), respectively, for the 2.0-km3

(0.5-mi3) landslide. These same calculations showed thata 0.35-km3 (0.1-mi3) landslide would not cause anovertopping wave and, thus, would not harm the dam(Hanisch, 2000). More-detailed flood-scenario analysesare presented below.

Failure by Internal Erosion (Piping)

For the following reasons, risk of failure caused byinternal erosion is considered to be very low (Hanisch,2000, 2002a; Stucky Consulting Engineers Ltd., 2001):

� The lake has been flowing through the dam since about1911 without failure having occurred by piping. Thus,little reason exists to expect failure by this process inthe future.

� Discharge has remained essentially constant duringthe period of measurement from 1943 to the present(Figure 12), an indication that the rate of internalerosion must be very low.

� Seepage-water discharge is clear. Thus, no sediment isbeing carried from the dam, an indication that sig-nificant erosion is not occurring.

� In general, the Usoi landslide dam is composed ofa heterogeneous mass of large blocks of rock, ap-parently without significant, interconnected pocketsof fine-grained materials that might be susceptible topiping. Where pockets of finer materials occur, theyapparently are not continuous.

� As indicated by Stucky Consulting Engineers Ltd.(2001, 2003), the hydraulic gradients through the Usoilandslide dam range from 0.10 to 0.13 for 50 m (165ft) of dam freeboard (current value) to 0.12 to 0.14 for10 m (33 ft) of freeboard (a possible future freeboard).These possible gradients are far below the usuallyacknowledged critical gradient of 0.30 for piping infine-grained materials.

� Dye-tracer experiments conducted by Stucky Consul-ting Engineers Ltd. have indicated that flow velocitiesthrough the landslide dam range from 0.01 to 0.1 m/s(0.03–0.3 ft/s), values too low to result in internalerosion (Wernli, 2003).

Based on the above factors, it appears that the risk offailure by internal erosion is very low. At the same time,at many points the existing vehicle track in the BartangValley is less than 1 m above the existing river surface.Thus, only a small increase in river level caused byinternal erosion in the blockage could inundate the lowerportions of the track and render access to the upperBartang Valley problematical.

Failure by Seismic Shaking

The Pamir Mountains in southeastern Tajikistan areamong the world’s most tectonically active regions, domi-nated by a series of active thrust faults and associ-ated wrench faults (Fan et al., 1994; Lukk et al., 1995).As a consequence of this high level of tectonic activity,the Lake Sarez area is frequently struck by earthquakes,commonly attaining Richter-scale magnitudes as greatas 6 (Fan et al., 1994). Historically, earthquakes with

Figure 8. Length of time that landslide dams survive based on 187

historic cases of failed dams. (After Costa and Schuster [1991] and

Schuster [1995]).

Figure 9. Comparative cross-sections (parallel to stream) through the Usoi landslide dam (Adushkin, 1991); the 1986 Bairaman River landslide dam,

Papua New Guinea (King et al., 1989); and the large, constructed earthfill Oroville Dam, California, USA. Crest heights and dam widths for the three

dams are indicated at the left, and the approximate current surface level for Lake Sarez is shown at the right. (After Schuster [1995]).



magnitudes greater than 7 have occurred in the Pamirsand vicinity (Kristy and Simpson, 1980). However, thegeometry (very broad base with fairly flat slopes) andmaterial properties (composed mostly of large rockfragments and blocks) of the Usoi landslide dam masswill protect it against seismically induced slope failuresand liquefaction even under these extreme loadingconditions. Realistically, little chance exists for a seismi-cally induced failure of the dam.

Dam Collapse Caused by Melting of Internal IceFollowed by Overtopping

At present, the extent and nature of ice in the bodyof the landslide dam is unknown. Geologic field studyis needed to determine where such ice crops out. Ifit appears to occur as massive bodies, a drilling orgeophysical exploration program should be consideredto determine if potential melting of the ice mass con-stitutes a threat.

FLOOD SCENARIOS

If the Usoi landslide dam were to be overtopped andbreached by a flood wave, the floodwaters could flow asfar as 2,100 km (1,300 mi) down the Murgab, Bartang,Panj, and Amu Darya rivers into the Aral Sea (Figure 16).However, the people most endangered would be those inthe villages and towns along the lower Murgab River andthe Bartang River in Tajikistan and along the Panj River,which forms the Tajik–Afghan border, because thesemountain valleys are narrow and the people in themwould have short warning times.

The two most probable modes of outburst-floodinitiation from failure of the Usoi landslide dam probablywould be a breach flood, resulting from overtopping anddowncutting of the blockage, and a seiche flood, result-ing from a wave generated by a large landslide (mostprobably on the right-bank slope) issuing into LakeSarez. Alford (2000) has modeled these two arbitraryfloods for a 180-km (110-mi) reach of the Bartang andPanj rivers downstream from the Usoi landslide dam.

Alford assumed a flood discharge through a rectan-gular breach outlet in the dam with a width and depth of500 m (1,650 ft). His flood produced by the seichewave was assumed to have overtopped the blockagewith an average depth of 50 m (165 ft) over a damlength of 2,000 m (6,560 ft). Both these assumptionswere arbitrary, but reasonable. For both cases, impactson villages along the banks of these rivers would bedevastating. For both models, predicted flood depthsranged from a maximum of nearly 200 m (650 ft)immediately downstream from the Usoi landslide damto a minimum of 37 m (121 ft) for the seiche scenarioand 55 m (180 ft) for the breach option at the village ofShojan, 147 km (91 mi) downstream from the dam and8 km (5 mi) upstream from Rushan (Figure 1). Asmight be expected, local flood depths would becontrolled by valley topography, largely the width ofthe valley floor and the slope of the valley walls. Amaximum depth encountered at a populated site wasmodeled at the village of Suponj (Figure 1), 102 km (63mi) downstream from the dam, where flood depth wasestimated to be 160 m (525 ft) by the breach option and114 m (374 ft) by the seiche option. For several reasons,these preliminary results must be considered as grossestimates only:

� A major flood from Lake Sarez probably will becomea debris flow within a distance of a few kilometers orless, thus altering flood hydraulics unpredictably.

� Both dynamic flood-routing models used by Alfordwere sensitive to cross-section placement. Valley crosssections vary widely within short distances. However,they were represented in this modeling effort bya spacing of approximately 15 km (9 mi), providing

Figure 10. A 10-m-high example of the boulders on the surface of the

southern sector of the Usoi landslide dam.

Schuster and Alford


only a gross representation of the complex valleygeometry.

� The modeling of complex seiche waves is poorlyunderstood, particularly for the case where a very largelandslide falls at high velocity into a very deep body ofwater.

� The models used in this study simulated erosion-basedbreaching using a simplified, one-dimensional ap-proach in which the breach shape was predefined as aninput parameter. Such a model is best suited tosimulate breaching of a man-made earthfill dam, notbreaching of a complex, heterogeneous landslide dam.

More recently, the USGS has modeled a potentialdam-overtopping flood produced by a seiche waveassociated with catastrophic landslide failure of theright-bank slope into Lake Sarez at a location 5 km (3mi) uplake from the Usoi landslide dam (Risley et al.,2003). In these studies, flood-routing simulations weremade for three theoretical landslide-induced overtoppingfloods over a 530-km (330-mi) reach of the lowerMurgab, the Bartang, and the Panj rivers downstreamfrom the Usoi landslide dam. For landslide volumes of200, 500, and 1,000 million m3 (0.2, 0.5, and 1 km3; 7.1,17.2, and 35.7 billion ft3), estimated flood overtoppingvolumes were 2, 22, and 87 million m3 (71, 785, and3,105 million ft3) water, respectively. Estimated peakdischarge at the dam for these three flood scenarios was57,000, 245,000, and 790,000 m3/s (2.0, 8.8, and 28.2million ft3/s) based on triangular hydrographs of 70-, 90-,and 110-second durations, respectively. A constant, 50-m-wide (165-ft-wide), rectangular channel, which repre-sented mean channel width, was used for the entire 530-km (330-mi) reach, as was a roughness coefficient of0.038, which was deemed to be appropriate for steepmountain streams.

Based on simplifying assumptions concerning channelgeometry, for the 87 million m3 (3,105 million ft3) flood

scenario, flow volumes were estimated by the USGS tobe 1,100, 800, and 550 m3/s (39,200, 28,600, and 19,600ft3/s) at locations 50, 100, and 150 km (31, 62, and 93 mi)downstream from the dam, respectively, producingmodeled flood crests of approximately 8, 7, and 6.5 m(26, 23, and 21 ft) above the channel bed at thoselocations. The impact of such a flood at specific pointsalong the rivers downstream from the dam cannot bedetermined with any specificity from the USGS study,but it is apparent that such a flood could have a majoreffect on the villages located along the lower MurgabRiver and the Bartang River. In addition to these villages,which would be either totally or partially inundated bysuch a flood, the only road connection between Khorog(Figure 1), the capital of Gorno-Badakshan, and Dush-anbe would be interrupted by the probable destruction ofthe bridge crossing the mouth of the Bartang River,located 150 km (93 mi) downstream from the Usoi dam.The only remaining roads into Khorog would be a road tothe south, into the Afghan province of Badakshan, andthen linking to another road across the Murgab Plateau toKyrgyzstan. This would significantly increase thealready-existing political and economic isolation of theprovince. The population of the villages in the Murgab/Bartang/Panj valleys affected directly by such a floodprobably does not exceed 25,000, and that of Gorno-Badakshan as a whole is nearly 250,000 (Centre forDevelopment and Environment, 2002).

The USGS model was also used to simulate themuch less likely scenario of an instantaneous dam breachand subsequent draining of the total 17 km3 (4 mi3) ofthe lake. Simulated peak flows in this scenario wereapproximately 64,000, 52,000, 40,000, and 20,000 m3/s(2.3, 1.9, 1.4, and 0.7 million ft3/s) at locations 50, 100,

Figure 11. Rate of rise of the surface of Lake Sarez, 1911 to 1991.

(After Berg [1950] and Stucky Consulting Engineers Ltd. [2003]).

Figure 12. Discharge of the Murgab River at the village of Barchidiv,

16 km (10 mi) downstream from Usoi landslide dam, 1947 to 1988.

The flows very closely equal discharge from Lake Sarez. (After

Papyrin [2002]).



150, and 530 km (31, 63, 93, and 330 mi) downstreamfrom the landslide dam.

POSSIBLE INSTALLATION OF REMEDIALMEASURES TO PREVENT DAM FAILURE

The possibility of installing engineered remedialmeasures to reduce the risk of dam failure resulting fromany of the above-mentioned factors was given consider-able thought by Soviet scientists and engineers. Zolotarevand others (1986, p. 156) noted that the two most rationalmethods of protecting the dam were:

� ‘‘[C]ontrolled 100–150 m [330–490 ft] water leveldrawdown in the lake to eliminate overtopping by highwave, through construction of a tunnel spillway on theleft bank for irrigation in dry years and for powergeneration.’’

� ‘‘[R]aise the crest of the lowered section [i.e., lowestpart of the dam crest] at the right bank [by] movingthe boulder material over the obstruction using theconstruction machinery or by the blast fill method fromthe exposed scarps located above.’’

Zolotarev and others also recognized, however, that‘‘The engineering protection activities at preventing theUssoi [sic] obstruction from break-through with a view ofa highly mountainous region, remoteness and compli-cated engineering geology are difficult to realize and arerather costly.’’

Another suggestion for improving the safety of thedam has recently been made by Papyrin (2002), who sug-gested lowering the current level of the lake by removingmud and rock debris from transverse fissures across thesurface of the dam at its crest, thus allowing water to seepthrough these fissures. Papyrin (2002, p. 48) believes thatthe debris can be removed by ‘‘overburden mining andexplosives,’’ which provide ‘‘a simple and nonexpensivemethod of solving the Sarez problem by lowering thewater level 40 to 50 meters [130–165 ft]—in a naturalway, mind you.’’

Papers presented at a regional conference convenedin Dushanbe, the capital of Tajikistan, during late 1997 bythe International Organization for Migration and byFOCUS to consider the Usoi/Sarez problem, and attendedprimarily by representatives from the Central Asianrepublics, were based largely on 80 years of studiesby Soviet geologists and engineers. This conferencereflected an agenda centered on need for constructionof a road to Lake Sarez to enable access by heavyconstruction equipment for remedial efforts. Without sucha road, the actual engineering measures proposed—ranging from draining the lake through increasing thefreeboard of the dam to building structures to permit thecontrolled release of water for irrigation or hydroelectricgeneration—would not be possible. Even preliminarystudies necessary to assess the feasibility of suchengineering measures would be difficult without heavyvehicles being able to access the dam and the lake by road.

The major engineering required to lessen the hazard

Figure 13. Village of Barchidiv (see Figure 1), which is located on alluvial deposits along the Murgab River, 16 km (10 mi) downstream from the

Usoi landslide dam.

Schuster and Alford


posed by Lake Sarez—and advocated by the CentralAsian republics—has been judged by the developmentagencies as far too expensive to be realistic. The Usoilandslide dam is located approximately 200 km (125 mi)by road and track from the village of Khoroq (Figure 1),the capital of Gorno-Badakhshan Province, which liessome 2,000 km (1,250 mi) by all-weather road fromDushanbe, the capital of Tajikistan. Approximately 60km (37 mi) of this distance is two-lane road, to the villageof Rushan, at the confluence of the Bartang River withthe Panj River (Figure 1). The distance from Rushanupstream to the dam is approximately 150 km (;93 mi),of which 130 km (80 mi) consists of an undeveloped,one-lane track to the village of Barchidiv. Access to thedam and lake over the final 20 km (12 mi) upstream alongthe Murgab River from Barchidiv is currently by footpaththrough a very rugged canyon or by helicopter. It hasbeen estimated by Periotto (2000) that rehabilitation of theexisting 130-km, one-lane road from Rushan to Barchidivthrough the gorge of the Bartang River to permit transit ofheavy construction equipment would cost fromUS$300,000 to US$600,000 per kilometer. Periotto notedthat the feasibility of constructing a road over the 20 km(12 mi) of the Murgab river canyon between Barchidivand the Usoi landslide dam had not yet been established,

so the cost of such a road could not even be estimated.Thus, it is clear that the great distances involved, plus thecosts of road construction through this extreme, moun-tainous terrain, currently render major remedial modifi-cations to the dam and/or lake financially impractical.

EARLY WARNING SYSTEMS

It has long been recognized that a ‘fail-safe’ systemhas been needed to warn the downstream populationof an outburst flood if the Usoi dam were to failcatastrophically. As noted above, the flood could carrydown the Murgab, Bartang, Panj, and Amu Darya riversas far as the Aral Sea (Figure 16); however, the greatestdanger undoubtedly would be to the towns and villageslocated relatively near the dam along the Murgab,Bartang, and Panj rivers. At present, monitoring of thedam and the right-bank landslide is conducted by Tajikobservers based at the government meteorological ob-servatory at Lake Sarez (Figure 17). The system has beendesigned to provide a warning to government officialsin Dushanbe by short-wave radio, who will then transmitthe warning to Khorog, and to villages in the BartangValley, by telephone. Radio links have been installed and

Figure 14. Oblique aerial view northeastward across the Usoi landslide dam toward Lake Sarez (upper right). Arrows indicate a line of springs along

the downstream face of the landslide dam that discharge from Lake Sarez to form the Murgab River. This is the only evident outlet from Lake Sarez.

The light-toned area on the surface in the upper left is the post-1911 debris-flow material that covers the north end of the Usoi landslide. (Photo taken

June 2001.)



evacuations practiced under the tutelage of the Tajikgovernment and FOCUS.

The current system has three shortcomings. The firstis that, because of the harsh winter climate, on-siteobservations cannot be conducted consistently duringthose months. The second and main shortcoming is thatthe warning time under any system probably will not begreat enough to allow people in the downstream villagesclosest to the dam to escape a possible flood. The closestand most vulnerable downstream village, Barchidiv(Figure 13), is at the mouth of the Murgab River, only16 km (10 mi) from the Usoi dam. It has been estimatedthat an outburst flood caused by a landslide-triggeredseiche wave would take only 25 to 30 minutes to reachBarchidiv (Zaninetti, 2000). A proposed televisionsatellite warning system will have an estimated responsetime of 54 minutes, and experience gained in flood-escape exercises has shown that it takes the residents ofBarchidiv approximately 2 hours to evacuate to higherground. Obviously, it will be difficult for an earlywarning system to help the people of the Murgab rivervalley or the upper part of the valley of the Bartang River.Hopefully, monitoring of the dam and right-bank land-slide will allow prediction of dam failure, which will aidin providing any necessary warning to the downstreampopulation. The third problem with the current warningsystem is its lack of reliability. The satellite connectionsystem (now more than 10 years old) does not alwaysoperate continuously (Zaninetti, 2000).

It should be noted that an automatic system based

on detection of a sudden rise in the level of the BartangRiver was installed, but this system is now inoperativebecause of a lack of maintenance since the end of theSoviet era. In any case, this system is located too fardownstream from the dam to be completely effective,because four villages are located upstream from theexisting system (Zaninetti, 2000).

ONGOING EFFORTS TO REMEDYTHE USOI/LAKE SAREZ PROBLEM

Major ongoing efforts related to problems of theUsoi landslide dam and Lake Sarez are being conductedthrough the LSRMP under management of the SarezAgency, Ministry for Emergencies, Government ofTajikistan, and funded by the State Secretariat forEconomic Affairs, Switzerland; the Aga Khan Founda-tion; the International Development Association; the U.S.Agency for International Development; FOCUS; and theGovernment of Tajikistan (Republic of Tajikistan, 2000).The World Bank advises the project in a supervisory role.The LSRMP is comprised of three components:

� Monitoring and early warning systems (StuckyConsulting Engineers Ltd.): Design and installationof a monitoring system and an early warning system.

� Long-term solutions component (Stucky ConsultingEngineers Ltd.): Strengthening of local communitiesfor emergency preparedness planning and provision ofsafety-related supplies.

Figure 15. Area of possible landslide activity along the right valley wall of Lake Sarez. The volume of potential landslide activity in this area has been

estimated at from 0.35 to 2.0 km3 (0.1–0.5 mi3). The approximate upper margin of the landslide-susceptible area is indicated by the dashed line.

(Photo taken June 2001.)

Schuster and Alford


� Social component (FOCUS): Strengthening of localcommunities for emergency-preparedness planning andprovision of safety-related supplies.

The technical efforts for design and installation of themonitoring and early warning systems of this program arebeing led by personnel of Stucky Consulting EngineersLtd. of Renens, Switzerland. In addition to the technicalstudies related to monitoring of the dam and the right-bank slope being conducted by Stucky ConsultingEngineers Ltd., FOCUS has made considerable progressin emergency preparedness and training, and the USGShas completed a major flood-routing study for the im-mediate downstream valleys (Risley et al., 2003).

SUMMARY AND CONCLUSIONS

With a height of approximately 600 m (;1,970 ft), theUsoi landslide dam is the largest dam in the world, twiceas high as Nurek Dam, the world’s highest man-madedam. Although this natural dam has existed for morethan 90 years without overtopping and with no sign ofsignificant instability, it is not an engineered structure,and it impounds a very large volume of water upstreamfrom populated valleys. In addition, a few other landslidedams have failed after long periods of stability. Thus,

because this natural dam is located in a highly seismicarea, which is prone to landslide activity, reason exists toremain vigilant concerning dam overtopping and/orfailure, possibly resulting in a catastrophic outburst flood.

In our opinion, such a failure would be most aptto follow earthquake-triggered landslide activity on thesteep north valley slope above Lake Sarez, approximately5 km (3 mi) uplake from the dam. In a worst-casescenario, if this slide (estimated volume, 0.35–2.0 km3

[0.1–0.5 mi3]) were to enter the approximately 550-m-deep (;1,800-ft-deep) Lake Sarez at high velocity, itcould cause a huge wave that could overtop the landslidedam, possibly causing it to breach because of erosion andresulting in a disastrous outburst flood down the Murgab,Bartang, and Panj rivers. We consider this an outsidepossibility, not a probability. However, we feel that thispossibility demands continued study regarding the land-slide susceptibility of the right-bank slope and installa-tion of an effective early warning system.

At an international symposium on problems of theAral Sea that was convened in Washington, D.C., inApril 1993, A. Dostiev, Vice President of the SupremeSoviet of the Republic of Tajikistan, noted that anoutburst flood from Lake Sarez would influence a pop-ulation of 5 million people in 52,000 km2 (20,000 mi2) ofthe Amu Darya river basin in Tajikistan, Afghanistan,

Figure 16. Map of the Aral Sea drainage basin indicating the path of a potential outburst flood from Lake Sarez down the valleys of the Murgab,

Bartang, Panj, and Amu Darya rivers to the Aral Sea.



Uzbekistan, and Turkmenistan, destroying property,arable land, vegetation, and livestock (A. Dostiev inLim et al., 1997). However, the most recent flood-routingmodels produced by the USGS (Risley et al., 2003) andby Stucky Consulting Engineers Ltd. (2002) suggest thatthe most probable dam failure and flood—an overtoppingof the Usoi landslide dam caused by a right-banklandslide (or landslides) into the lake—would mostprobably impact only the lower Murgab River and theupper reaches of the Bartang River, with less than 10,000inhabitants being endangered. The IDNDR mission toUsoi/Sarez recognized the formidable cost of construct-ing a road access to Lake Sarez that would enableconstruction of remedial measures at the lake/dam. Theythus recommended establishment of monitoring and earlywarning instrumentation as a realistic, near-term alterna-tive to these measures (Periotto, 2000; Zaninetti, 2000).

ACKNOWLEDGMENTS

We would like to acknowledge the information andadvice we have received from Jorg Hanisch, BrunoPeriotto, Attilio Zaninetti, and others of the 1999 UnitedNations IDNDR mission to Lake Sarez; from Col.Anvarjon S. Abdulloev and R. Babadjanov, Directorsof the Sarez Agency, Tajik Government; from PatriceDroz and his colleagues of the Stucky Engineering Ltd.project team; from Rita Cestti and Alessandro Palmieri ofthe World Bank; from Paul Hearn of the USGS; and fromYuri Kazakov, Russian geologist, who spent several fieldseasons at Usoi/Sarez and provided us with valuable

advice concerning the field geology of the site. In addi-tion, we would like to personally thank Professor SobitNegmatullaev, Director, and Dr. Anatoly Ischuk, DeputyDirector, Tajik Institute of Earthquake Engineering andSeismology, for their hospitality and technical advice.(Professor Negmatullaev also serves as Chairman of thePanel of Experts for the LSRMP.)

In addition to the organizations mentioned above,which are directly supporting the LSRMP, two othershave had continuing recent involvement in studies of theUsoi/Sarez problem. The first of these was the IDNDR,headquartered in Geneva, Switzerland. As noted above,in June 1999 the IDNDR, with the cooperation of theUnited Nations Office for the Coordination of Human-itarian Affairs, the United Nations Development Pro-gramme, the United Nations Environment Programme,the World Bank, the CIS (Commonwealth of IndependentStates) Interstate Council for Emergency Situations,FOCUS, the U.S. Agency for International Development,and the USGS, sponsored the United Nations ScientificReconnaissance Mission to Usoi/Sarez, which led to thecurrent LSRMP. (Note that IDNDR is now the In-ternational Strategy for Disaster Reduction [ISDR].) TheJune 1999 mission resulted in publication of the valuableUnited Nations report, Usoi Landslide Dam and LakeSarez—An Assessment of Hazard and Risk in the PamirMountains, Tajikistan (Alford and Schuster, 2000b),which provided considerable information on which thispaper is based.

A very important non-governmental organizationin the continuing saga of Usoi/Sarez is FOCUS, an

Figure 17. Tajik government meteorological observatory on Lake Sarez at the south end of Usoi landslide dam. Lake Shadau (see Figures 5 and 7),

a tributary lake to Lake Sarez, is in the background. (Photo taken June 2001.)

Schuster and Alford


organization that works directly with the people in thevalleys downstream from the Usoi dam in providingtechnical assistance. FOCUS sponsored a workshop onthe problem of Lake Sarez in early 1998 as well asa reconnaissance of Usoi/Sarez later that year, and itcollaborated in the June 1999 United Nations mission.FOCUS continues to provide technical assistance andadvice to the people of Gorno-Badakhshan Provincethrough the social component of the LSRMP—with fund-ing provided by the Aga Khan Foundation and the U.S.Agency for International Development—and collaborateswith professional personnel of Stucky ConsultingEngineers Ltd. and officials of the Tajik governmentSarez Agency as part of the overall LSRMP effort.

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Documents

Usoi Landslide Dam and Lake Sarez, Pamir Mountains, Tajikistan