U.S. Department of the Interior

U.S. Geological Survey

Professional Paper 1723 

Interaction of Dams and Landslides—Case Studies and 

Mitigation

By Robert L. Schuster 

0 100 METERS

Left abutment

Chloritic schist

Glacial deposits

Lacustrine silts

Slide in 

schist Sand and gravel
Cover.—Aerial view of Swift Dam, Lewis River, western Washington State, United States 

(photograph taken by Lynn Topinka, U.S. Geological Survey). 

Top inset.—Bonneville Dam, Columbia River Gorge, Washington and Oregon, United States 

(photograph taken by Derek Cornforth, Landslide Technology, Portland, Oregon). 

Bottom inset.—Cross section through rock slide, Durlassboden Dam, Austria (modified from 

Záruba and Mencl, 1982).
Interaction of Dams and Landslides—Case 

Studies and Mitigation

By Robert L. Schuster

Professional Paper 1723

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2006

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Suggested citation:

Schuster, R.L., 2006, Interaction of dams and landslides—Case studies and mitigation: U.S. Geological Survey 

Professional Paper 1723, 107 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Background............................................................................................................................................1

Presentation of Data ............................................................................................................................2

Sources of Information ........................................................................................................................3

Summary of Data...................................................................................................................................3

Selected Case Histories of Dams on Landslides (by Landslide Type)...................................................4

Rock Fall (Including Talus Deposits) .................................................................................................4

Slides in Competent Rock....................................................................................................................6

Slides in Incompetent rock ...............................................................................................................13

Massive Rock Slides and Glide Blocks...........................................................................................13

Earth and Debris Slides......................................................................................................................15

Rock and Debris Avalanches............................................................................................................16

Debris, Mud, and Earth Flows...........................................................................................................17

Cambering and Valley Bulging..........................................................................................................22

Problems Encountered Due to Interaction Between Dams and Landslides .....................................22

Abutment and Foundation Instability...............................................................................................22

Abutment and Foundation Seepage ................................................................................................24

Mitigative Measures ...................................................................................................................................25

Planning Measures.............................................................................................................................25

Avoidance of Landslides...........................................................................................................25

Relocation of Site..............................................................................................................25

Site Abandonment ............................................................................................................27

Redesign of Dams Because of Landslide Problems ............................................................27

Lowering Reservoir Level or Reducing Rate of Filling.........................................................28

Physical Measures for Foundation and Abutment Stabilization..........................................................28

Removal of Landslide Deposits ........................................................................................................28

Total Removal of Landslide.......................................................................................................28

Partial Removal of Landslide ...................................................................................................28

Partial Removal of Talus Cover ...............................................................................................29

Partial Removal of Landslide Deposit Following Construction or

 Postconstruction Slope Failure ...........................................................................................29

Flattening Abutment Slopes..............................................................................................................29

Earthfill or Rockfill Berms Serving as Buttresses .........................................................................29

Dam Serving as Buttress...................................................................................................................30

Cutoffs or Keys ....................................................................................................................................30

Retaining Walls ...................................................................................................................................30

Piles and Caissons..............................................................................................................................30

Anchors ................................................................................................................................................30

Moving or Reinforcing Spillway .......................................................................................................30

Guniting.................................................................................................................................................31

Dental Work .........................................................................................................................................31
iv

Physical Measures for Reducing Abutment and Foundation Seepage..............................................31

Impervious Cutoffs..............................................................................................................................31

Impervious Curtains, Membranes, and Blankets ..........................................................................31

Drainage Systems...............................................................................................................................32

Multiple Mitigation Methods ............................................................................................................32

Breaching as a Remedy.....................................................................................................................32

Summary and Conclusions.........................................................................................................................33

Acknowledgments.......................................................................................................................................33

References Cited..........................................................................................................................................33

Appendix........................................................................................................................................................51

Figures

1. Original sketch map and cross section showing landslide conditions 

at Farmers Union (now Rio Grande) Dam, southwestern Colorado, 

United States .................................................................................................................................2

2. Photograph of Mammoth Pool Dam, San Joaquin River, California, United States ..........5

3. Cross section through the narrow gorge in the foundation of Waterbury Dam, 

Little River, Vermont, United States ...........................................................................................5

4. Views before and after construction of Taylor Park Dam, central Colorado, 

United States .................................................................................................................................6

5. Gross Dam, Colorado, United States.........................................................................................7

6. Gravity-slip surfaces in granitic foundation rocks at Gross Dam, 

Colorado Front Range, United States ........................................................................................7

7. Photograph looking upstream at the remains of St. Francis Dam, 

southern California, United States.............................................................................................8

8. Cross section through the 1928 left-abutment landslide at St. Francis Dam, 

California, United States..............................................................................................................8

9. Cross section through the pre-existing rock slide that forms the left abutment 

of Beauregard Dam, northwestern Italy ...................................................................................8

10. Simplified cross-valley cross section through Dalešice Dam, Jihlava River, 

Czech Republic..............................................................................................................................9

11. Oblique view of Tablachaca Dam, Peru..................................................................................10

12. Photograph looking upstream at the right-abutment landslide at 

Tablachaca Dam, Peru...............................................................................................................10

13. Map of rock slide at the right abutment of Tablachaca Dam, Peru ...................................10

14. Photograph of Lake Harriet Dam, Cascade Range, Oregon, United States......................10

15. Major Holocene landslide deposits in the Columbia River Gorge, Washington 

and Oregon, United States ........................................................................................................11

16. Oblique aerial view of Bonneville Dam in the Columbia River Gorge, 

Washington and Oregon, United States .................................................................................12

17. Map of the Cascades landslide complex and its components, United States.................12

18. Simplified cross section through the rock slide in schist that forms the 

right abutment of Durlassboden Dam, Austria ......................................................................12

19. Photograph of Fruitgrowers Dam, western Colorado, United States ................................13
v

20. Locations of 18 dams on landslide bench and slump-block landslides 

derived from the basalt plateau of the Grand Mesa, western Colorado, 

United States ...............................................................................................................................14

21. Photograph of Grand Coulee Dam, eastern Washington State, United States................15

22. Cross section through the Parangana Dam site, Victoria, Australia .................................16

23. Oblique aerial view of Cheakamus Dam, British Columbia, southwestern Canada........17

24. Cross section through the site of Cheakamus Dam, British Columbia, 

southwestern Canada................................................................................................................17

25. Aerial-oblique view of Mud Mountain Dam, western Washington State, 

United States ...............................................................................................................................18

26. Cross section through the site of Mud Mountain Dam, Washington State, 

United States ...............................................................................................................................18

27. Aerial view of Swift Dam, Lewis River, western Washington State, 

United States ...............................................................................................................................18

28. Geologic map of the area around Swift Dam, Washington State, 

United States ...............................................................................................................................19

29. Geologic map of the area around Yale Dam and Yale Saddle Dam, 

Washington State, United States.............................................................................................20

30. Sketch of the earthfill sediment-retention dam on the North Fork 

Toutle River, southwestern Washington State, United States ............................................21

31. Photograph of Medeo Dam, a debris-flow retention structure on the Malaya 

Alma-Atinka River, Kazakhstan ................................................................................................21

32. Photograph of construction of a cellular reinforced-concrete debris-retention 

dam on the Bolshaya Alma-Atinka River, Kazakhstan..........................................................21

33. Cross section through B.F. Sisk (San Luis) Dam, California, United States ......................23

34. Photograph of Cheurfas Dam ...................................................................................................23

35. Photograph of Star Mountain Dam, southeast Oregon, United States .............................24

36. Oblique-aerial view of Ochoco Dam, central Oregon, United States ................................24

37. Cross section through the site of Howard Hanson Dam, western 

Washington State, United States.............................................................................................25

38. Photograph of Scott Dam on the Eel River, northern California, United States ...............26

39. Cross section through a narrowed section of the Romanche River valley, 

France...........................................................................................................................................27

40. Oblique view of the left end of Mojave River Dam................................................................29

41. Photograph of the remains of Mystic Lake Dam, southwestern Montana, 

United States ...............................................................................................................................32

Tables

Appendix Table A. Dam characteristics, relation to landslides, mitigative measures, 

and cited references..................................................................................................................51
Abstract

In the first half of the 20th century, engineering geology and geotechnical engineering were in their infancy, 

and dams were often built where landslides provided valley 

constrictions, often without expert site investigation. Only the 

most important projects were subjected to careful geologic 

examination. Thus, dams were often built without complete 

understanding of the possible geotechnical problems occurring in foundations or abutments. Most of these dams still 

exist, although many have undergone costly repairs because 

of stability or leakage problems. Today, however, every effort 

is made in the selection of damsites, including those sited 

on landslides, to provide foundations and abutments that are 

generally impervious and capable of withstanding the stresses 

imposed by the proposed dam and reservoir, and possible 

landslides. 

By means of a literature search, technical interviews, and 

field inventory, I have located 254 large (at least 10 m high) 

dams worldwide that directly interact with landslides; that is, 

they have been built on pre-existing landslides or have been 

subjected to landslide activity during or after construction. 

A table (Appendix table A) summarizes dam characteristics, 

landslide conditions, and remedial measures at each of the 

dams. Of the 254 dams, 164 are earthfill, 23 are rockfill, and 

18 are earthfill-rockfill; these are flexible dam types that 

generally perform better on the possibly unstable foundations 

provided by landslides than do more rigid concrete dams. 

Any pre-existing landslides that might impinge on the 

foundation or abutments of a dam should be carefully investigated. If a landslide is recognized in a dam foundation or abutment, the landslide deposits commonly are avoided in siting 

the dam or are removed during stripping of the dam foundation and abutment contacts. Contrarily, it has often been found 

to be technically feasible and economically desirable to site 

and construct dams on known landslides or on the remnants of 

these features. In these cases, proven preventive and remedial 

measures have been used to ensure the stability of the foundations and abutments, and to reduce seepage to acceptable 

levels. 

Introduction

This paper presents case histories of dams that have interacted with landslides in abutments and/or foundations. It uses 

these case histories to discuss problems caused by different 

types of landslides and mitigative measures used to alleviate 

these problems. Note that interactions between reservoirs and 

landslides are beyond the scope of this paper. Thus, wellknown cases of reservoir-induced landslides such as those at 

Vaiont Dam and Grand Coulee Dam’s Lake Roosevelt are not 

included.

Background

“Many major slides have in the past blocked up river 

valleys, the resulting constrictions giving dam sites 

which appear at first sight to be admirable. In view 

of the of the nature of the material in slides, and 

its unconsolidated and often disturbed conditions, 

sites of this kind may often prove to be very far 

from ideal. Dams have, however, been successfully 

founded at such sites” (Legget, 1939, p. 225–226).

“No structure grips the ground so closely as a dam. 

It holds on at its base and at its flanks***. In other 

words, a dam is made up of two parts: the artificial 

dam, man-made, and the natural dam, which continues it, surrounds it, and on which it is founded. 

The more important of the two is the latter which is 

unnoticed” (Martin, 1974, translated from Coyne, 

1939). 

From Coyne’s statement it can be further inferred that 

any movement, or potential movement, of the foundation or 

an abutment1 is critical to the stability and effectiveness of the 

dam itself. Thus, the possibility of gravitational 

1

I will use dam “foundation” as being the rock/soil in direct contact with the 

base of the dam, and dam “abutments” to be the parts of the valley side slope 

that are in direct contact with the ends of the dam. Together, the foundation 

and abutments form the “footprint” of the dam.

Interaction of Dams and Landslides—Case Studies 

and Mitigation

by Robert L. Schuster
 Interaction of Dams and Landslides—Case Studies and Mitigation

movement (landslide2 activity) in the foundation or an abutment of a dam is of critical importance. Because many (if not 

most) such movements are reactivations of all or parts of preexisting landslides, it is extremely important to identify these 

morphological elements and to realize their possible effects on 

the dams involved. As noted by Weaver (1989), “Landslides, 

if recognized prior to construction, presumably are avoided or 

are removed during stripping of the dam foundation. However, landslides of significant size sometimes occur during the 

course of stripping operations for a dam on weak rock foundations, and must be left in place.”

In the early part of the 20th century, a few experts 

recognized and presented the problems posed by pre-existing 

landslides in dam foundations or abutments (see for example, 

Clarke, 1904; Lapworth, 1911; Atwood, 1918, (his fig. 1); 

Willis, 1928; Bromehead, 1936; and Legget, 1939). However, in spite of this technical expertise and warning, many, 

if not most, dams were built without expert examination of 

damsites; only the most important projects were subjected to 

careful geologic studies. Thus, dams were often built without 

complete understanding of the possible geotechnical problems 

inherent in their abutments or foundations. Today, however, 

every effort is usually made to select a damsite in which 

the abutments and foundation are relatively impervious and 

capable of withstanding the stresses imposed by the proposed 

dam and reservoir under all probable loading conditions. Thus, 

permeability and stability of dam abutments and foundations 

must be considered during site selection, site preparation, 

construction, and operation of dam structures (Záruba, 1979; 

Weaver, 1989).

Many post-World War II geologists and engineers have 

discussed in depth the importance of understanding the 

existence of landslides at damsites. Among the most noteworthy works have been those of Burwell and Moneymaker 

(1950), Gignoux and Barbier (1955), Richey (1959, 1964), 

Walters (1971), Desio (1973), Barbier (1974), Martin (1974), 

Anderson and Trigg (1976), Záruba and Mencl (1976, 1982), 

Mencl (1977), Záruba (1979), Hobst and Zajíc (1983), Legget 

and Karrow (1983), Legget and Hatheway (1988), Galster 

(1989a,b), Fell and others (1992), Skempas and Chandler 

(1993), Tolmachev (1994), and Riemer (1995).

It has often been found to be technically feasible and 

economically desirable to site and construct dams on known 

landslides or on their partial remnants after most of the material has been stripped from the site. The stability of the landslide or its remnant can be enhanced by the buttressing effect 

of the dam itself, which can be augmented by berms acting as 

buttresses, by anchors, or by retaining structures. In addition, 

problems caused by seepage through the landslide materials 

usually can be remedied by means of surface or subsurface 

drains, grout curtains, impervious membranes, or other preventive or remedial measures.

2

“Landslide” will include all types of gravitational mass movements, such 

as falls, slides, avalanches, and flows, according to the landslide classifications 

of Varnes (1978) and Cruden and Varnes (1996).

Presentation of Data

Appendix table A presents the cases of 254 large3 dams 

that were identified in this worldwide survey of dams built on 

(1) pre-existing landslides, (2) remnants of partly excavated 

landslides, and (3) construction-caused or post-construction 

landslides. It includes only cases in which part or all of the 

landslide was left in place as part of the foundation or an abutment. The table includes data for a few dams that no longer 

exist. Each case includes the location, dam and stream names, 

dam type and purpose, year of dam completion and owner, 

dam and reservoir dimensions, landslide type and position, 

comments regarding the landslide and remedial measures, and 

3

For cases in which “the dam had specially difficult foundation conditions,” 

the International Commission on Large Dams (ICOLD) defines a “large” dam 

as one that is at least 10 m high (International Commission on Large Dams, 

1977). Because most dams constructed on landslides fit this specification, I 

will use 10 m as the minimum height for “large” dams. All dams in Appendix 

table A are 10 m high or higher, and thus all are “large” dams.

LAVA

FARMERS UNION

RESERVOIR

FLOWS

DAM

SPILLWAY

TUNNEL

ROAD

LAVA FLOWS

DAM

TUNNEL

A

A

A

B

B

LANDSLIDE

B

Road

Road

LANDSLIDE 

pr

Figure 1. Original sketch map (A) and cross section (B) 

along the line A–B, showing landslide conditions at Farmers 

Union (now Rio Grande) Dam, southwestern Colorado, 

United States (Atwood, 1918, p. 19).
references and other information sources. The purpose of this 

tabulation is to provide observations and conclusions to aid in 

future dam-siting decisions.

Some, but not all, of the dams in Appendix table A are 

also discussed as examples of the basic types of landslides on 

which dams have been built, as examples of the common problems encountered from interaction of dams and landslides, or 

as examples of the types of mitigation measures that have been 

used to solve or reduce problems related to dam and landslide 

interaction.

Sources of Information

The data presented in Appendix table A have been 

obtained from the following sources:

Technical papers, reports, and textbooks appearing in 

the international geological, geotechnical, and damengineering literature

Government dam-building agencies and consulting 

companies, mostly in North America

Geotechnical consultants and colleagues with experience on dams and landslides, mostly in the United 

States

Local, State, and Federal dam-safety agencies in the 

United States

Personal experience of the author, including visits to 

nearly all of the U.S. dams listed, as well as several of 

the foreign dams

Information on dams located outside the United States 

has been obtained mainly from a detailed search of the 

international landslide and dam literature. Especially valuable 

were proceedings of congresses and specialty conferences 

of the International Commission on Large Dams (ICOLD), 

the International Association for Engineering Geology and 

the Environment (IAEG), the International Society for Soil 

Mechanics and Geotechnical Engineering (ISSMGE, formerly known as the International Society for Soil Mechanics 

and Foundation Engineering), the American Society of Civil 

Engineers (ASCE), the Association of Engineering Geologists 

(AEG), and other sources. Also perused were professional 

journals, such as Geotechnique, The Quarterly Journal of 

Engineering Geology, the Journal of Geotechnical Engineering, Environmental and Engineering Geoscience, and Engineering Geology. United States proceedings included those 

of the annual meetings of the U.S. Society on Dams (USSD, 

formerly known as the U.S. Committee on Large Dams) and 

the Association of State Dam Safety Officials (United States). 

Physical data on dams in the United States were obtained 

from the CD-ROM, National Inventory of Dams 1996 (Federal Emergency Management Agency, 1996), which includes 

76,000 U.S. entries. Landslide information on U.S. dams came 

partly from published technical papers, partly from the files of 

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Federal dam agencies and State dam-safety organizations, and 

partly from interviews with professional colleagues in government agencies, universities, and consulting companies. In 

addition, the author visited nearly all of the U.S. dams entered 

in the table, as well as several foreign dams, often in the 

company of local dam officials and personnel. The source(s) 

of information for each dam is indicated in the last column of 

Appendix table A.

Summary of Data

Of the 254 dams in the study, 153 are located in the 

United States; 142 of these are in the conterminous Western 

States (including, or west of, the Rocky Mountains). The 

State of Colorado leads the list with 56 dams on landslides 

(Schuster, 2003), followed by California with 21, Oregon with 

18, Utah with 16, and Washington with 14. For the rest of the 

world, Italy leads with 11 dams, followed by Australia with 

7, India, Japan, and the United Kingdom with 6 each, and the 

Czech Republic and Spain with 5 each. This seeming bias in 

gathering of data for the Western United States (as compared 

to that for the rest of the world) probably occurs because of 

(1) the very large number of dams that have been built in the 

Western United States, (2) the great number of landslides in 

the mountains of the Western United States, and (3) the fact 

that I have closer technical and professional contacts in the 

Western United States than elsewhere in the world—contacts 

who have been willing to supply research data to this study. 

In addition, in the United States, many data were obtained as 

public information from State dam-safety agencies, an opportunity that did not present itself for other countries. Instead, 

almost all non-United States case histories were obtained 

from published papers in technical journals and proceedings. This latter fact also resulted in a preponderance of big 

dams (as compared to fairly small dams) for foreign countries 

because incidents involving smaller dams were not as apt to 

be reported in technical publications. Notable was the lack of 

available data from the republics of the former U.S.S.R.

Of the 254 cases in Appendix table A, 165 are earthfill, 

23 are rockfill, 19 are earthfill and rockfill, 24 are concrete 

gravity, 13 are concrete arch, 7 are concrete arch-gravity, 2 are 

masonry/stone, and 1 is unknown. Interestingly, 120 of the 153 

U.S. dams are earthfill, probably because of the large number 

of relatively small (10–50 m high) irrigation dams that have 

been built in the Western States. The outstanding examples 

of this earthfill bias are the States of Colorado, where 52 of 

the 56 dams are earthfill, and Utah, where all 16 dams are 

earthfill.

With regard to the primary purposes of the 254 dams, 

108 are for irrigation, 56 for hydroelectric power, 48 for water 

supply, 20 for flood control, 12 for recreation, 5 for debris 

retention, and 5 for tailings or waste disposal. Within the 

United States, 85 of the dams are for irrigation, 27 for water 

supply, 14 for flood control, 14 for hydroelectric power, 11 

for recreation, 1 for debris retention, and 1 for fly-ash storage. 

Introduction 
 Interaction of Dams and Landslides—Case Studies and Mitigation

Colorado, the State with the most dams in this study, includes 

42 irrigation dams, 7 recreation dams, 6 water-supply dams, 

and 1 dam for electric power. Of course, many of the dams 

also have secondary functions in these same categories.

The structural heights of the 254 dams range from the 

prescribed minimum of 10 m to a maximum of 170 m. The six 

highest dams in the study are as follows: Thissavros, Greece 

(170 m); Upper Gotvand, Iran (170 m); Grand Coulee, United 

States (168 m); Daniel Palacios, Ecuador (167 m); Thomson, 

Australia (166 m); and Trinity, United States (164 m). The 

worldwide distribution of dams by height is as follows: 153 

are 10–50 m high, 62 are 51–100 m high, 29 are 101–150 m 

high, 9 are 151–170 m high, and 1 dam had no height information. This distribution is to be expected because many more 

dams exist in the lower part of this range than in the upper 

part. Also, it is to be expected that smaller dams commonly 

have not been as carefully sited as the larger dams and, consequently, are more apt to be sited on landslides. The large 

number of relatively small (10–50 m high) dams on landslides 

worldwide, however, is more specifically a result of the fact 

that 115 of the 153 U.S. dams in Appendix table A fall in this 

category.

It is not easy to categorize the 254 tabulated dams by 

landslide type because authors of the papers cited often did not 

indicate what type of landslide was present and because many 

of the landslides are “complex;” that is, more than one type of 

slope movement occurred. For each case, I arrived at a “best 

estimate” of landslide type based on a simplified approximation of the “Varnes landslide classification” (Varnes, 1978; 

Cruden and Varnes, 1996). In the case of complex landslides, 

I have noted the primary type of movement at the dam site. In 

cases where I have not been able to determine the specific type 

of movement, I have designated the type as “landslide.” Nearly 

all of these “general” cases are located outside the United 

States because I was able to visit nearly all the U.S. sites to 

personally evaluate the landslide types. I have broken down 

the distribution as follows:

Rock falls (including talus deposits)—20

Slides in competent or “hard” rocks—60

Slides in incompetent or “soft” rocks—109

Earth and debris slides—25

Rock and debris avalanches—3

Debris/mud/earth flows, including lahars (volcanic 

debris or mud flows)—23

Cambering and valley bulging—1

“Landslides” (type unknown)—13

Typical well-indurated, competent, or “hard” rocks 

include igneous rocks; most metamorphic rocks; hard sedimentary rocks, such as limestones and hard sandstones; and 

competent volcanic rocks, such as andesite and basalt. Typical 

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poorly indurated or incompetent rocks include shales, soft 

sandstones, soft volcanic tuffs, and weathered schists. Note 

that 169 of the 254 cases involve rock slides, in either competent (60 cases) or incompetent (109 cases) rocks. The large 

number of “soft-rock” slides is largely because of the great 

number of 10–50 m high dams that have been built on shales 

and other relatively incompetent sedimentary rocks in the 

Western United States. In the United States, the number of 

dams associated with “soft-rock” landslides is 78, as compared to 36 associated with “hard-rock” landslides. Outside 

the United States, 36 dams have interacted with “hard-rock” 

slides, versus 31 associated with “soft-rock” landslides. In the 

United States, numerous dams have been built on very large 

landslide masses or glide blocks that consist of hard rocks, 

usually basalts, that have slid intact on underlying softer volcanic or sedimentary materials. The largest of these areas is the 

Grand Mesa landslide complex in western Colorado, which is 

the site of dozens of dams and reservoirs, including 19 of the 

dams in this study.

Selected Case Histories of Dams on 

Landslides (by Landslide Type)

This section discusses notable cases in which dams 

have been built on landslides or landslides have occurred in 

foundations or abutments either during construction or after 

completion of the dam. Individual cases are organized by type 

of landslide.

Rock Fall (Including Talus Deposits) 

Of the 20 cases in this category, only two (Mammoth 

Pool and Waterbury Dams, both in the United States) are dams 

that have been sited on large rocks that had fallen to the bottom of steep-walled gorges. The other 18 were cases in which 

a significant thickness (at least a few meters) of talus on an 

abutment slope was not removed, or was only partly removed, 

during construction. In most of these cases, an impervious 

core zone or trench was dug through the talus, but the mass 

was left in place under the outer shells of the dam. In several 

other cases that were reviewed, but not included in Appendix 

table A, existing talus was removed from the entire footprint 

of the dam. The main reason for removal of the talus was usually its high permeability. Selected examples of the 20 cases 

are discussed below.

Mammoth Pool Dam—Mammoth Pool Dam (fig. 2) 

on the San Joaquin River in the Sierra Nevada Range 

of central California, United States, is a 125-m-high 

earthfill dam, which was completed in 1959 to 

produce hydroelectric power. As was obvious during 

early planning for the dam, the canyon originally 

•
was dammed naturally by rock-fall deposits related 

to exfoliation of the granodiorite that formed the 

upper canyon walls. Some individual boulders in 

the bottom of the gorge were as large as 5,000 m3 in 

size. Professor Karl Terzaghi served as the primary 

geotechnical consultant for this dam; his main function 

was to evaluate whether a water-tight dam could be 

built on these rock-fall deposits, and to decide what 

types of mitigative measures would control rock fall 

during construction or future operations of the dam. 

To ensure safety from rock fall, the remaining sheets 

of granodiorite on the upper slopes were removed or 

bolted to the canyon walls (Terzaghi, 1962; Goodman, 

1993, p. 242–243). Blocks in or near the location of 

the cutoff trench at the core of the dam were removed 

or broken up by means of explosives. The cutoff 

trench was constructed through the rock-fall detritus to 

bedrock. Most boulders and rock fragments under the 

outer shells of the dam were left in place. Mammoth 

Pool Dam is performing satisfactorily with only minor 

seepage loss.

Waterbury Dam—Waterbury Dam is a 57-m-high 

earthfill dam on the Little River, Vermont, United 

States. The dam was completed in 1938 but has been 

subject to foundation seepage since. Unknowingly, the 

dam was founded on detached rock slabs in a narrow gorge at the base of the dam (fig. 3). As noted by 

Saber and others (2001), “Detached rock slabs along 

the right (west) side of the gorge form a roof over a 

piping tunnel known to have been a piping path in the 

past, and capable of being a piping path in the future 

if injected filter materials are destabilized.” A grouting 

program to prevent seepage through the rock-fall zone 

was completed in 1985, but, apparently, some seepage 

continues.

•

Ancipa Dam—Ancipa Dam, a 105-m-high cellular 

concrete gravity dam on the Troina River of Sicily, 

Italy, was completed in 1953 to provide hydroelectric 

power and irrigation water. The dam’s right foundation 

and abutment have a thick talus cover. “At the right 

bank, the bedrock is reached by a concrete cut-off wall 

driven through the talus” (ANIDEL, 1961, v. 1, 

p. 300–306).

Marmorera Dam—Marmorera (Castilleto) Dam in 

Graubünden Canton of southeastern Switzerland is a 

91-m-high earthfill dam that was completed in 1954 

to produce hydroelectric power. The valley wall that 

forms the left abutment and left end of the dam foundation is a large talus fan (mainly serpentinite fragments) 

underlain by alluvium and moraine material. Because 

of the heterogeneity of this foundation and abutment, 

three separate remedial measures were introduced 

during the original construction to reduce seepage 

(Rambert and Gavard, 1961; Schnitter, 1961):

An underground curtain wall of concrete was placed 

to bedrock through the alluvium and morainal deposits in the lower part of the foundation.

A cutoff grout curtain was placed through the pervious talus fan that formed the upper foundation and 

abutment. The grout was a mixture of colloidal clay 

and cement stabilized by a chemical agent. As would 

•

•

1.

2.

Figure 2. Mammoth Pool Dam, San Joaquin River, California, 

United States. Note the exfoliation sheets and blocks in the 

granodiorite that forms the right abutment. Photograph taken

in 1998.

Figure 3. Cross section through the narrow gorge in the 

foundation of Waterbury Dam, Little River, Vermont, United 

States. The detached mica schist slab formed a “roof” 

over a potential piping path in the sand and gravel below. 

Modified from U.S. Army Corps of Engineers unpublished 

report (1988).

135

0 5 10 15 20

140

145

150

ELEVATION IN METERS

 IN METERS

Mica schist

Sand and gravel

Mica schist slab

Mica schist

Selected Case Histories of Dams on Landslides (by Landslide Type) 
 Interaction of Dams and Landslides—Case Studies and Mitigation

be expected, the talus was found to be much more 

pervious near the surface than at depth.

A grout curtain was placed in the bedrock under the 

core of the dam.

Two successful examples of dams that have been built 

on talus-covered abutments in the Rocky Mountains of the 

Western United States are Taylor Park Dam in Colorado and 

Anderson Ranch Dam in Idaho.

Taylor Park Dam—Taylor Park Dam is a 63-m-high 

earthfill dam on the Taylor River in the Rocky Mountains of Colorado, which was completed in 1937 to 

provide irrigation water for the area. It was recognized 

before construction that the right abutment of the dam 

3.

•

was covered by a thick talus cone derived from overlying sedimentary rock cliffs (fig. 4). The talus mass 

consisted predominantly of boulder-to-cobble-size rock 

fragments with some fine-to-coarse gravel and sand. 

During construction, the talus was removed from under 

the center and upstream parts of the dam, but was left 

in place in the area extending from ∼25 m downstream 

from the centerline to the downstream toe of the dam. 

The foundation was prepared by constructing three 

concrete cutoff walls, one located roughly along the 

centerline and the other two upstream. The remaining talus in the downstream part of the right abutment poses a very minimal threat of piping; however, 

thus far, in spite of some seepage, there has been no 

evidence of piping. The dam has had a long history of 

satisfactory performance.

Anderson Ranch Dam—Anderson Ranch Dam on 

the South Fork Boise River in southern Idaho is a 

139-m-high earthfill dam completed by the Federal 

government in 1971 to provide irrigation water. Before 

construction, the right abutment was covered by a thick 

layer of basalt talus, which was removed under zone 1 

(the interior, relatively impervious zone) of the dam, 

partially removed (“engineered”) under the upstream 

shell, and left in place under the downstream shell. 

Seepage from the right valley wall downstream from 

the dam apparently passes through this talus. In addition, in recent years a small landslide has occurred into 

the reservoir at the upstream edge of the “engineered” 

talus slope.

Slides in Competent Rock

As noted by numerous authors (for example, Wentworth, 

1929), concrete dams, and especially arch dams, require 

competent rock foundations; while earthfill and rockfill dams 

can be founded satisfactorily on less-competent materials. 

However, this study notes 43 concrete dams that were built on 

pre-existing landslides or had landslides occur during or after 

construction. As would be expected, most of these concrete 

dams were built on what was originally thought to be competent rock. A total of 61 of the 254 dams in Appendix table 

A interact with slides in competent (“hard”) rock. Selected 

examples of these 61 dams are described below.

Gross Dam—Gross Dam (fig. 5), Colorado, United 

States, is an example of a concrete-gravity dam that 

was founded on a pre-existing deep-seated slide in 

competent rock. Completed in 1955, this 104-m-high 

municipal water-supply dam is seated on deep-seated 

“gravity-slip surfaces” in both granite abutments 

(fig. 6) (Wahlstrom, 1974, p. 78–79). Although these 

“gravity faults” were closely watched during construction, they pose no hazard to the completed dam, which 

•

•

Figure 4. Views before (A) and after (B) construction of 

Taylor Park Dam, central Colorado, United States. Note 

the talus deposit that serves as the right abutment of the 

dam and the chalk line (marked by arrow) in photograph 

(A), which marks the location of the right end of the 

future dam on the talus cone. Photographs taken in 1937 

by A.A. Whitmore, U.S. Bureau of Reclamation.

A.

B.
Figure 5. Gross Dam, Colorado, United States, which 

supplies water to the city of Denver. The cross section in 

figure 6 shows gravity-slip surfaces in both abutments of 

the dam. Photograph taken in 2003.

is expected to buttress any possible future movement. 

Thus, even though the dam is a relatively inflexible 

concrete structure, this type of slide was primarily a 

“textbook” case that posed no danger to the dam, and 

the dam continues to perform well.

St. Francis Dam—Possibly the best known, and most 

infamous, of dams that have been built on what was 

thought to be competent rock, but was actually the toe 

of a pre-existing landslide, was St. Francis Dam in 

southern California, United States, a 62-m-high archgravity dam completed in 1926 to supply water to the 

city of Los Angeles. The presumed stable left abutment 

of this dam actually was the toe of a large, prehistoric 

•

lll ll ll ll ll ll lll lll ll ll ll ll ll l ll llll lll lll lllll lll lll lll ll ll ll ll ll llllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll ll lllll

llllllllllllllllllllllllllllllllll ll ll ll llll ll ll ll llllllllllllll ll lllllllllllllllllllllllll ll llllll ll llll ll llllllllllll ll l ll ll ll ll lll lllll ll ll ll lll ll llllllll ll ll ll ll llllll ll llll ll

0 100 METERS

DAM CREST

Figure 6. Gravity-slip surfaces (marked by thick arrows) in granitic foundation rocks at Gross Dam, 

Colorado Front Range, United States. Other faults of tectonic origin are geologically much older 

than the gravity-slip “faults.” Modified from Wahlstrom (1974).

landslide in schist bedrock. As the reservoir neared 

capacity in 1928, the dam suddenly failed, releasing a 

catastrophic flood that drowned 450 people (Outland, 

1977). Preliminary investigations pointed to a fault in 

the right abutment as the cause of failure. Later, more 

comprehensive studies (Willis, 1928; Rogers, 1992, 

1995, 1997) showed fairly conclusively, however, 

that failure began as reactivation of the schist slide in 

the left abutment (figs. 7 and 8). This is the only case 

noted in this study of a catastrophic dam failure caused 

by dam construction on a pre-existing landslide. The 

dam was never rebuilt.

Beauregard Dam—Another major concrete dam that 

has experienced reactivation of a rock slide in an abutment is Beauregard Dam, a 132-m-high arch-gravity 

dam on the Dora di Valgrisenche River in northwestern 

Italy, which was completed in 1960 (ANIDEL, 1961, 

v. 1, p. 313–314). The left abutment for this dam is a 

massive rock slide in mica schist, which before construction overlaid a deep pocket of glaciofluvial sediments (fig. 9) (Desio, 1973, p. 901; Záruba and Mencl, 

1982, p. 243–244). During the first filling of the reservoir, the landslide reactivated, attaining a displacement 

rate of 20 mm/month. As a remedial measure, some of 

the sediments were replaced by concrete. In addition, a 

watertight membrane was placed through the left abutment by cement injection. The dam is performing well.

Dalešice Dam—Dalešice Dam, a 100-m-high hydroelectric-power rockfill dam on the Jihlava River in 

the Czech Republic, which was completed in 1979, 

•

•

Selected Case Histories of Dams on Landslides (by Landslide Type) 
 Interaction of Dams and Landslides—Case Studies and Mitigation

Figure 7. Looking upstream at the remains (center of photograph) 

of St. Francis Dam, southern California, United States, soon after its 

1928 failure, which resulted in a catastrophic flood that killed about 450 

people. The failure began in the toe of a large prehistoric landslide that 

formed the left abutment (right side of photograph); note fresh landslide 

scarps. Photograph taken in 1928, courtesy of Department of Geography, 

University of California at Los Angeles.

Figure 9. Cross section through the preexisting rock slide that forms the left abutment of 

Beauregard Dam, northwestern Italy. Modified 

from Desio (1973, p. 901)

Figure 8. Cross section through the 1928 

left-abutment landslide at St. Francis Dam, 

California, United States. Modified from 

Rogers (1995).

NATURAL FLATS

1928 RESERVOIR

SLIDE MASS REACTIVATED BY DRAW DOWN

OF ST. FRANCIS RESERVOIR

TOPOGRAPHIC BENCH FORMED

BY PALEOLANDSLIDE

PELONA SCHIST

PALEOSLIDE

QUATERNARY

LACUSTRINE SEDIMENTS

Left abutment

Slope debris

Excavation

line

Depth of grout curtain

0 50 100 m

Mica-schist slide

Firm mica schist

Glaciofluvial

gravel
was founded on supposedly stable amphibolite and 

granulite. However, during excavation for the right 

abutment of the dam, failure occurred in schistose 

mylonite along a fault contact between the amphibolite and the granulite. The failure resulted in sudden 

movement of a 150,000 m3 block of amphibolite along 

the mylonite zone (Mencl, 1977; Záruba and Mencl, 

1982, p. 245–246) (fig. 10). As remedial measures, 

a temporary stabilizing berm was built at the toe of 

the slope and material was removed at the head of the 

slide. Subsequently, the slope was further stabilized by 

making horizontal benches from which anchors were 

installed into the firm granulite (Hobst and Zajíc, 1983, 

p. 399–401). 

Tablachaca Dam—Another well-known example of 

a concrete dam built on a pre-existing slide in competent rock is Peru’s Tablachaca Dam (figs. 11 and 

12), an 80-m-high concrete arch-gravity dam on the 

Mantaro River, a tributary of the Amazon River. This 

dam was placed in service in 1972 to produce about 

one third of Peru’s electric power. During the late 

1970s, it was noted that part of an ancient rock slide 

in phyllite, which formed the right abutment of the 

dam, had reactivated (probably because of the reservoir) and was moving slowly toward the dam (fig. 13) 

•

(Novosad, 1979; Novosad and others, 1979). A system 

of remedial measures, which included an earth berm 

at the toe of the slope (the toe of the berm is underwater), prestressed rock anchors, and drainage adits, were 

installed during the 1980s (Morales Arnao and others, 

1984; Repetto, 1985; de la Torre and others, 1997) at 

an estimated cost of U.S. $40 million (1985 dollars). 

Since then, the dam has generally performed well; 

however, recently there has been renewed creep in the 

right abutment (Garga and de la Torre, 2004).

Lake Harriet Dam—Another interesting concrete-arch 

dam case is that of Lake Harriet Dam, a 21-m-high 

dam (fig. 14) that was completed in 1923 to produce 

electric power for western Oregon, United States. The 

left abutment of this dam was thought to be stable 

basalt. However, this basalt abutment is part of the 

reactivated toe of a 50-km2 landslide mass. During 

the early 1980s, cracks were noted in the dam due to 

compression from the left abutment. The problem was 

solved in 1985 by using the tremie process (underwater pumping through a pipe) to place a soil-bentonite 

“membrane” against the upstream face of the dam, and 

by constructing rockfill buttresses against both faces 

of the dam (Schroeder and others, 1988). Although 

the dam is currently performing well, the compressive 

•

Figure 10. Simplified cross-valley cross section through Dalešice Dam, Jihlava River, Czech Republic. Construction caused 

reactivation of a rock slide of the amphibolite in the right abutment. This cross section shows locations of remedial excavations 

and rock anchors. Modified from Záruba and Mencl (1982, p. 246).

0 50 METERS

260

280

300

320

340

360

ELEVATION IN METERS

Excavation for intake tunnels

Anchors

Mylonite zone

Original ground surface

Amphibolite block

Excavated

surface

Anchors

Granulite

Selected Case Histories of Dams on Landslides (by Landslide Type)   
10 Interaction of Dams and Landslides—Case Studies and Mitigation

Figure 11. Oblique view of Tablachaca Dam, Peru. The preexisting rock slide in the right abutment is outlined by arrows. 

This slide was reactivated in the 1970s, probably because of 

infiltration from the reservoir. Photograph taken in 1982.

Figure 12. Looking upstream at the right-abutment 

landslide at Tablachaca Dam, Peru. Photograph taken 

in 1982.

0 300 METERS

Ancient

rock slide

Recent

rock slide

Reservoir

Dam

Outlet

2,800

2,900

3,000

3,100

3,200

2,800

2,700

2,700

N

Figure 13. Map of rock slide at the right abutment of 

Tablachaca Dam, Peru. Shown is the recent, active slide that is 

a reactivation of the toe of a larger, ancient rock slide. Modified 

from Novosad (1979).

Figure 14. Lake Harriet Dam, Cascade Range, Oregon, 

United States. The basalt that forms the left abutment 

of this dam is part of the reactivated toe of a 50-km2

landslide mass. Photograph taken in 1999.
force of the landslide continues to act against the dam 

through the basalt abutment.

Bonneville Dam—Another well-known example of 

a dam on a major rock slide is Bonneville Dam, a 

60-m-high concrete gravity dam in the Columbia River 

Gorge of Washington and Oregon, United States. It 

was completed in 1937 for purposes of hydroelectric 

power production, navigation, and recreation. The 

Columbia River Gorge includes several large Holocene 

landslides in basalt underlain by less-competent volcanics (fig. 15) (Palmer, 1977). The right (Washington) 

abutment of this dam is part of the toe of the Bonneville landslide (figs. 16 and 17), the youngest element 

of the huge Cascade landslide complex (figs. 15 and 

17) (Sager, 1989; Keech and Sanford, 1998; Schuster 

and Pringle, 2002). Although there have been minor 

surficial movements of the Bonneville landslide, its 

mass is so large and well-seated that the dam abutment 

and foundation are stable, and the dam continues to 

perform well.

•

Figure 15. Major Holocene landslide deposits in the Columbia River Gorge, Washington and Oregon, United States, 

including the Cascades landslide complex, the youngest element of which is the Bonneville landslide (figs. 16 and 17). 

Note the location of Bonneville Dam. Modified from Palmer (1977).

Durlassboden Dam—A European example is Durlassboden Dam, an 83-m-high structure in Austria, which 

was built on a large rock slide. The right abutment of 

this hydropower dam is on a large block of graphitic 

schists and quartzites that had slid down the right valley wall and sunk into valley deposits of glaciofluvial 

sands and gravels and lacustrine silts (Mignon, 1968; 

Záruba, 1974; Rienössl and Schnelle, 1976) (fig. 18). 

The abutment and foundation were subsequently sealed 

by a grout curtain that extends into silts about 50 m 

beneath the valley floor.

Platoro Dam—Another example in the Western United 

States is Platoro Dam, a rockfill/earthfill dam on the 

Conejos River in the San Juan Range of southwestern 

Colorado, which was completed in 1951 to provide 

irrigation water for the area. The left end of this 

50-m-high dam rests on a massive andesite slump 

block (length >1 km). Because of the large, wellseated mass of the block, there have been no stability

or seepage problems, and the dam continues to perform 

well.

•

•

0 10 20 KILOMETERS

OREGON

WASHINGTON

MAP LOCATION

OREGON

WASHINGTON 

Washougal

Stevenson

Skamania

COLUMBIA RIVER

BONNEVILLE

DAM

WIND MOUNTAIN

LANDSLIDES

FOUNTAIN

LANDSLIDE

CASCADES LANDSLIDE

COMPLEX

SKAMANIA

LANDSLIDE

WASHOUGAL

LANDSLIDE RUCKEL

LANDSLIDE

45° 45 ́

122°

Selected Case Histories of Dams on Landslides (by Landslide Type) 11
12  Interaction of Dams and Landslides—Case Studies and Mitigation

Figure 16. Oblique aerial view of Bonneville Dam in the 

Columbia River Gorge, Washington and Oregon, United 

States. The right (Washington) abutment is the toe of the huge 

Bonneville landslide, which is the most recently active part 

of the Cascades landslide complex. Photograph by Derek 

Cornforth, Landslide Technology, Portland, Oregon.

0 5 KILOMETERS

OREGON 

WASHINGTON 

BONNEVILLE DAM

Bonneville landslide

Moseley Lakes

landslide

Red Bluffs landslide

TABLE

MOUNTAIN

RED BLUFFS

COLUMBIA RIVER

Stevenson

Cascade Locks Carpenters Lake

landslide

N

Figure 17. Map of the Cascades landslide complex and its 

components, which include the Bonneville landslide. Note 

the location of Bonneville Dam. Modified from Wise (1961). 

0 100 METERS

Right abutment

Chloritic schist

Glacial deposits

Lacustrine silts

Slide in 

schist Sand and gravel

Figure 18. Simplified cross section through the rock slide 

in schist that forms the right abutment of Durlassboden Dam, 

Austria. Modified from Záruba and Mencl (1982, p. 243).

Occasionally, movement along pre-existing joints or 

faults in seemingly competent rock abutments is reactivated by 

dam construction. In many cases, any movement is halted by 

the buttressing effect of the dam itself. Movement of masses of 

competent rock along joints and fractures in this manner does 

not traditionally characterize the slipped rock masses as landslides. However, such movement of competent rock masses 

in this manner may create problems for dams similar to those 

caused by landslides. Two cases of dams that interact with this 

type of movement of rock masses are included in Appendix 

table A and are discussed below.

Meishan Dam—An example is Meishan Dam, an 

88-m-high concrete multiple-arch dam on the Shihe 

River, Anhui Province, China. This dam, which was 

completed in 1956 for purposes of flood control, irrigation, and hydropower, was founded on jointed granite, 

and, in 1962, movement occurred along joints in the 

right abutment (Qi, 1986; Chinese National Committee 

on Large Dams, 1987, p. 134–138). Apparently, these 

joints had exhibited some movement before construction. Remedial measures included installation of a 

grout curtain, an impervious membrane upstream of 

the abutment, anchors, and berms that served as buttresses.

Tooma Dam—An Australian example is Tooma Dam, 

a 67-m-high, earthfill/rockfill dam constructed on the 

Tooma River of southeastern Australia to produce 

hydroelectric power. After completion of the dam 

in 1961, sliding was noted along joints in both abutments (Hunter, 1982; Fell and others, 1992). Remedial 

measures included rockfill buttresses, “dental” work 

in open joints (filling voids with cement grout or 

concrete), addition of a downstream grout curtain, and 

adding to the impervious zone of the embankment. 

•

•
Slides in Incompetent Rock

One hundred and nine of the dams in Appendix table 

A were built on landslides in poorly indurated, relatively 

incompetent rocks. Most of the slides in this category have 

occurred in soft sedimentary rocks, mainly shales, mudstones, 

siltstones, and poorly indurated sandstones, and in weathered 

schists and weak volcanics. Embankment dams have commonly been constructed at sites where incompetent materials 

form dam foundations or abutments.

Slezska Harta Dam—In the Czech Republic, Nechranice, Slezska Harta, Terlicko, and Zermanice Dams have 

all encountered problems with “soft rock” abutments. 

Especially well known are the problems in the shale 

left abutment of Slezska Harta Dam, a 65-m-high rockfill structure on the Moravice River, which was completed in 1997 for purposes of water supply and flood 

control. During construction of this dam, movement 

occurred in shale slide deposits that made up the left 

abutment (Novosad, 1990; Torner and Novosad, 1991). 

The stability problem was mitigated by excavation of 

slide material from the upper left slope, construction of 

a berm at the toe of the slope, and installation of surface and underground drains (Novosad and Novosad, 

1993).

Fruitgrowers Dam—An interesting example of a dam 

in the Western United States that was built on soft 

rocks is 17-m-high Fruitgrowers Dam, an earthfill dam 

built to provide irrigation water in western Colorado. 

The original Fruitgrowers Dam (11 m high) was constructed in 1898, but failed in 1937 due to “saturation 

and slipping” in the embankment at the spillway, which 

caused considerable flood damage to the small town 

of Austin, the Denver & Rio Grande Western Railroad, and a State highway (Engineering News-Record, 

1937). The current dam was built in 1939, and its left 

abutment is on a large landslide in shale (fig. 19). Slow 

movement began in this shale mass in the late 1990s. 

This abutment is currently being closely monitored 

to determine if remedial measures will be needed, but 

otherwise the dam is performing well.

Soft sedimentary rocks form the abutments or foundations of several major dams in the Great Plains of central 

North America. In a few of these cases, pre-existing slides in 

soft sedimentary rocks of the valley walls have affected design 

and construction of major Canadian and U.S. dams. Two outstanding examples follow.

Gardiner Dam—Especially well known in Canada 

is the case of Gardiner Dam, an earthfill dam on the 

South Saskatchewan River in the central province of 

Saskatchewan. This 69-m-high dam was completed 

in 1968 for purposes of irrigation, water supply, and 

•

•

•

production of hydroelectric power. The shale left 

abutment of the dam included a large prehistoric slide 

(Ringheim, 1964; Jaspar and Peters, 1979). Local 

failure occurred in this abutment during construction, 

which led to excavation of much of the unstable shale 

under the central zone of the dam. To increase the 

stability of the abutment, the slopes of the remaining 

landslide deposit were flattened, and extensive berms 

were added as buttresses. The dam is performing satisfactorily.

Oahe Dam—In the United States, several large dams 

on the upper Missouri River have been built on soft 

sedimentary rocks. One of these is Oahe Dam, a 

75-m-high earthfill dam in South Dakota, which was 

completed in 1966. During construction, problems 

were encountered that were caused by pre-existing 

shale slides in the right abutment, and construction 

triggered a slide in the left abutment (Engineering 

Division, 1958; Knight, 1963). After the left-abutment 

slide occurred, 5.0 million m3 of slide material was 

removed; of this, 3.5 million m3 was placed at the toe 

of the slope as a berm that acts as a buttress. Part of a 

small slide remains in the right abutment. Both abutments are now completely stable because of the buttressing effect of the dam itself, and the dam continues 

to perform well.

Massive Rock Slides and Glide Blocks

In the Western United States, numerous dams have been 

built on massive landslides and glide blocks; these are cases 

in which entire dams and reservoirs lie on the large landslide 

masses. The best known of these cases are dams on landslides 

adjoining the Grand Mesa in western Colorado, on huge 

•

Figure 19. Fruitgrowers Dam, an irrigation dam in western 

Colorado, United States, showing apparent landslide 

topography in shale of the left abutment. Photograph taken 

in 1999.

Selected Case Histories of Dams on Landslides (by Landslide Type) 13
14  Interaction of Dams and Landslides—Case Studies and Mitigation

landslide masses in the mountains of north-central Colorado, 

and on the Malaga landslide in central Washington State.

Grand Mesa landslide area—Rising to an elevation 

of 3,300 m, the Grand Mesa is an ∼130-km2 plateau remnant in western Colorado that is capped by 

continuous undisturbed upper Tertiary basalt flows 

that slope gently to the west. The basalt flows are 

underlain by a sequence of claystone, conglomerate, 

and sandstone, which overlies the Tertiary Green River 

Formation. Where these relatively weaker sedimentary 

rocks have failed, they have formed steep basalt cliffs, 

30–150 m high, which surround the upland surface of 

the Grand Mesa (Yeend, 1969, 1973). A very irregular surface, produced by huge slumps and modified 

by glaciation, extends outward from the base of the 

basalt cliffs (Baum and Odum, 1996, 2003). Numerous 

lakes formed on this irregular surface as a result of the 

slumping and subsequent glaciation. The surface levels 

of many of these natural lakes have been raised by the 

addition of man-made dams. East of today’s Grand 

Mesa, the landslide bench is extensive. Overall, this 

huge area of slump blocks extends about 70 km from 

east to west and 20 km from north to south, most of 

it lying to the east of the basalt remnant of the Grand 

Mesa (fig. 20). 

As became obvious early in the 20th century, the 

irregular surface topography of this large landslide 

•

bench was well-suited for the easy impoundment of 

snowmelt by dams and reservoirs. Thus, many dams 

and reservoirs were built on these landslides and intermingled glacial deposits. Appendix table A lists 19 

irrigation, water supply, and/or recreation dams that are 

founded on the Grand Mesa landslide bench, ranging 

in structural height from 10–26 m (there are no larger 

dams in the Grand Mesa area). Noted in Appendix 

table A as being on this landslide bench or on rockfall deposits from Grand Mesa cliffs are the following Colorado dams: Atkinson, Big Beaver, Bonham, 

Cedar Mesa, Eggleston, Goodenough #2, Granby #12, 

Hogchute, Kehmeier, Kennicott Slough, Kiser Slough, 

Knox, McKoon, Monument #1, Overland #1, Park, 

Vela, Ward Creek, and Young’s Creek Nos. 1 and 2. 

Several of these dams have had foundation or abutment 

seepage problems, often requiring repairs, but none 

has manifested stability problems or pose downstream 

hazards.

Mountains of north-central Colorado—North-central 

Colorado includes several subranges of the Rocky 

Mountains, in which large rock slides consisting of 

resistant rocks (usually volcanics) overlying softer 

rocks (usually shales, siltstones, and soft sandstones) 

are common. These rock slides often occurred as 

massive landslides from the valley walls upon retreat 

of late Pleistocene valley glaciers. They have formed 

•

0 10 KILOMETERS

39° 39°

108°

108°

EXPLANATION

Area of “in-place” basalt 

Margin of landslide bench 

GRAND MESA

Figure 20. Locations of 18 dams (solid circles) on landslide bench and slump-block landslides 

derived from the basalt plateau of the Grand Mesa, western Colorado, United States. One other dam 

(Overland Dam) is located on these landslide deposits, less than 2 km east of the eastern border of 

this figure. The landslide map has been modified from Yeend (1969).
constrictions in high mountain valleys, resulting in 

seemingly opportune sites for the location of dams. 

Examples of these in Appendix table A include Stillwater #1, Upper Stillwater, Yamcolo, Poose Creek, 

and Sheriff Dams, which are irrigation and recreation 

dams located in valleys that drain from the northeast 

slopes of the Flattop Mountains that consist of Tertiary 

basalts overlying shales and sandstones. A similar 

example from Appendix table A, Joe Wright Dam, 

is a large water-supply dam on eastward-flowing Joe 

Wright Creek in the Colorado Front Range. These 

dams are all performing well.

Three other dams and their reservoirs in north-central 

Colorado, which are included in Appendix table A, are located 

entirely on large glide blocks in soft rocks. Jones #2 Dam, a 

12-m-high earthfill dam built in 1887, which impounds the 

main water-supply reservoir for the town of Kremmling, lies 

on a massive prehistoric 16-km2 glide block in shales and 

sandstones of the Niobrara and Dakota Formations (Barclay, 1968, p. 157; Izett and Barclay, 1973; Madole, 1991a). 

D.D.&E. Wise (Aldrich Lake) Dam, a 12-m-high earthfill irrigation dam, lies on the eastern edge of a massive 16-km2

 landslide in Mancos Shale (Madole, 1989). Lower Cogdill Dam 

is a 12-m-high earthfill irrigation dam that was constructed in 

1956. The dam and reservoir lie entirely on an 18-km2 glide 

block overlying Lewis Shale and Mesaverde Group sandstones 

and shales on the west slope of the Elkhead Mountains in 

northwestern Colorado (Madole, 1982). Minor seepage issues 

from toe drains at Jones #2 Dam. Lower Cogdill and D.D.&E. 

Wise Dams have shown no distress related to their landslide 

foundations and abutments, and overall all three dams continue to perform satisfactorily.

Matheson Dam, an 18-m-high irrigation dam, was built 

in 1951 on the northeast edge of an 18-km2 landslide mass 

(Tertiary volcanics overlying Morrison Formation shales and 

sandstones) in the Rabbit Ears Range northeast of Kremmling 

(Madole, 1991a). There has been some seepage through the 

landslide right abutment of this dam, probably related to the 

landslide materials; otherwise the dam is performing well.

Malaga landslide area—The Malaga landslide, a large 

glide block on the west side of the Columbia River 

near Wenatchee, Washington, United States, consists 

of basalt that overlies softer volcanics and sedimentary 

rocks. Its irregular surface has served as a site for several small dams. Qualifying as large dams are Stemilt 

Main Dam (height, 20 m) and Upper Wheeler Dam 

(height, 20 m), two irrigation dams that are founded 

entirely on this large glide block. The Stemilt Main 

Reservoir leaked considerably through the landslide 

material until an impervious geosynthetic membrane 

was successfully emplaced in 1986. Minor leakage at 

the left abutment was later remedied by installation of 

drains. Minor leakage at the left abutment of Upper 

Wheeler Dam also has been controlled by installation 

of drains. 

•

Earth and Debris Slides

Twenty-four of the 254 dams tabulated in this study have 

earth- or debris-slide material in the foundation or abutments. 

With two important exceptions, these were embankment dams. 

The exceptions are two concrete dams: Grand Coulee Dam, 

United States, and Vodo Dam, Italy. Some examples of the 24 

dams in Appendix table A are described below.

Grand Coulee Dam—Grand Coulee Dam (fig. 21) is a 

168-m-high concrete-gravity structure on the Columbia 

River in Washington State, United States. This dam, at 

one time the largest (in volume) concrete dam in the 

world (its volume recently has been exceeded by that 

of China’s Three Gorges Dam), was completed in 1942 

to provide irrigation water, hydroelectric power, and 

flood control for the U.S. Pacific Northwest. Granite is 

the main foundation material for Grand Coulee Dam, 

but the right abutment included unstable glacial varved 

clays. Preparation of the right abutment reactivated 

movement of these clays (Irwin, 1938). The clays were 

stabilized by flattening the abutment slope, construction of a timber-crib retaining wall, and freezing the 

soil upslope from the wall by installation of a system 

of pipes that carried brine at below-freezing temperatures (Gordon, 1937). The slide area was then buttressed by the right end of the dam. This abutment 

•

Figure 21. Grand Coulee Dam, eastern Washington 

State, United States. In 1969, the original landslideprone glacial-soil right abutment was removed to 

make room for the second powerplant at the right 

end of the dam (left edge of photo). Photograph 

taken in 1999.

was subsequently removed in 1967–81 when the dam 

was lengthened to accommodate the third powerplant. 

Thus, the dam no longer abuts a landslide and is performing well.

Vodo Dam—Vodo Dam on the Boite River in the 

northern Italian Province of Veneto is a 42-m-high 

•

Selected Case Histories of Dams on Landslides (by Landslide Type) 15
16  Interaction of Dams and Landslides—Case Studies and Mitigation

concrete domed-arch dam that was built in 1960 to 

provide hydroelectric power. Its left abutment has been 

described as consisting of “morainic materials and 

alluvial landslides” (ANIDEL, 1961, v. 1, p. 320). To 

prevent movement of these materials during construction, a diaphragm, consisting of overlapping piles 

in reinforced concrete, was placed in the abutment 

through a bentonitic-slurry trench, and there have been 

no problems since.

Lake Sherburne Dam—Two examples of earthfill dams 

that have been built on earth slides are located in the 

State of Montana, United States; both were built on 

unstable glacial deposits. The better-known of these 

is Lake Sherburne Dam, a 33-m-high earthfill dam on 

Swiftcurrent Creek at the northeastern edge of Glacier 

National Park. This dam was completed in 1921 to provide irrigation water for eastern Montana. Apparently, 

it was known at the time that both valley walls consisted of massive landslides derived mainly from glacial deposits (Carrara, 1990; Whipple, 1992). Although 

the right abutment appears to be relatively stable, the 

left abutment is surrounded by a large unstable slide. 

The original foundation preparation included installation of three continuous cutoff trenches into stable till 

across the valley floor (Lowe, 1988). Prior to 1960, 

movement of the left abutment destroyed the original 

spillway, which was then moved to the right end of the 

dam. The left abutment remains unstable; its movement is being monitored regularly.

•

Hyalite Dam—Hyalite Dam in southwestern Montana 

is a 38-m-high earthfill dam that was completed in 

1951 to provide water for irrigation and water supply. The left abutment of this dam consists of mixed 

landslide and glacial deposits made up of clay, silt, 

sand, poorly sorted gravel, rock fragments, conglomerate, and boulders. There have been no problems with 

stability; however, seepage through this abutment 

material has been a continuing problem. Thus, during 

the 1990s, a compacted earth liner was placed at the 

left end of the dam to reduce the seepage. The dam is 

now performing well.

Rock and Debris Avalanches

Only three of the 254 dams in Appendix table A have 

been in contact with rock or debris avalanches. These three are 

Parangana, Cheakamus, and Smith and Morehouse Dams.

Parangana Dam—Parangana Dam is a 53-m-high 

rockfill structure on the Mersey River on the island of 

Tasmania, southeastern Australia. The dam was completed in 1968 to produce electric power for the island. 

Debris-avalanche deposits more than 50 m thick form 

part of the dam’s foundation, and its left abutment is in 

talus (fig. 22) (Paterson, 1971; Thomas, 1976, p. 156; 

Fell and others, 1992, p. 140–141). Apparently, there 

have been no difficulties with the debris-avalanche 

foundation or the talus abutment.

•

•

300

350

400

ELEVATION IN METERS

EXCAVATION LINE

DOMINANTLY QUARTZITE DOMINANTLY QUARTZITE

DIVERSION CONDUIT

EXCAVATION

LINE

SPILLWAY

BOULDER

LEFT ABUTMENT DAM CREST

GLACIAL DRIFT

DEBRIS AVALANCHE

TALUS

Figure 22. Cross section through the Parangana Dam site, Victoria, Australia, showing debris-avalanche 

deposits in the foundation and left abutment of the dam and talus deposits in the left abutment. All deposits 

above the excavation line were removed during construction. Modified from Paterson (1971).
might enter the reservoir at high velocity, and could 

possibly cause overtopping of the dam.

Smith and Morehouse Dam—In the United States, 

the only dam known to have been built on a pre-existing debris-avalanche deposit is the 25-m-high Smith 

and Morehouse Dam, an earthfill structure that was 

completed in 1988 to provide irrigation water to northcentral Utah. The entire dam foundation is a large 

avalanche (age ~4,000 yr B.P.) of sedimentary rock and 

glacial debris that filled Smith and Morehouse canyon 

to a depth of about 60 m. Although the dam was built 

on this debris avalanche, a cutoff key placed through 

the debris increased the strength and imperviousness of 

the foundation.

Debris, Mud, and Earth Flows

Debris, mud, and earth flows, including flows of volcanic origin, make up the foundations and/or abutments of 24 

of the 254 dams listed in Appendix table A. Of these, 17 are 

conventional debris, mud, or earth flows, and seven are flows 

of volcanic origin, also known by the Indonesian term lahars. 

Flow deposits usually are stable, but can be pervious enough 

to allow seepage through a dam’s foundation or abutments. 

This can pose possible problems for traditional dams. However, a few of the cases noted in this study are debris-retention 

or sediment-retention structures (also known as check dams 

or by the Japanese term, sabo dams); for these cases, permeability of the foundation is not a negative factor because these 

dams are intended to intercept only the solid fractions of the 

debris flows, not the water. Some examples of the 24 dams are 

described below.

Several dams in the Pacific Northwest of Canada and 

the United States have been built on flows, both regular and 

volcanic. These include Seymour Falls, Mud Mountain, and 

Swift Dams and the North Fork Toutle River sediment-retention structure.

Seymour Falls Dam—Seymour Falls Dam on the 

northern outskirts of Vancouver, British Columbia, 

Canada, is a 30-m-high earthfill/concrete water-supply 

dam that was completed in 1961. The right abutment 

of this dam is a debris-flow cone from a tributary 

stream (Ripley and Campbell, 1963). The cost of an 

impervious cutoff through the debris cone to bedrock 

was considered to be prohibitive. Instead, an extensive 

impervious upstream blanket was installed to minimize 

seepage through the debris-cone abutment and the 

foundation (Heidstra and others, 1995).

Mud Mountain Dam—Several major dams have been 

built on debris flows or mud flows (lahars) that originated from volcanoes in the Cascade Range of southwest Washington State, United States. Mud Mountain 

Dam is a 130-m-high earthfill flood-control dam that 

•

•

•

Figure 23. Oblique aerial view of Cheakamus Dam, British 

Columbia, southwestern Canada. The foundation of the dam 

is mainly Rubble Creek Wash, a debris avalanche–debris flow 

deposit (see fig. 24). Photograph taken in 1999 by BC Hydro, 

Burnaby, British Columbia.

.

..

..

.

. .

.

.

.

.

. ..

.

.

. .

.

HORIZONTAL 0 100 METERS

VERTICAL 0 50 METERS

Left abutment

Basalt

Granite

Elevation

353 meters

Elevation

378 meters

Elevation

293 meters

Contact zone

(buried forest)

Cheakamus 

River

Midpoint of 

dam

Basalt 

talus

Rubble Creek Wash

Alluvium

Figure 24. Cross section through the site of Cheakamus Dam, 

British Columbia, southwestern Canada, showing the location 

of the Rubble Creek Wash, the remains of an 1855–56 debris 

avalanche–debris flow deposit, on which the dam was built. 

Modified from Terzaghi (1960b).

Cheakamus Dam—Professor Karl Terzaghi served as 

the geotechnical consultant for Cheakamus Dam, a 28-

m-high earthfill/rockfill hydropower dam, which was 

built in 1957 in southwestern British Columbia, Canada (fig. 23). The Cheakamus River valley at the site is 

partially filled with materials known as “Rubble Creek 

Wash” (fig. 24), the deposits of a large debris avalanche–debris flow that occurred in 1855–56 (Terzaghi, 

1960a,b; Moore and Matthews, 1978). The permeability and stability of these deposits were approved before 

construction. The only hazard facing Cheakamus Dam 

and Reservoir seems to be the possibility of another 

debris avalanche coming from The Barrier, a volcanic 

mass at high elevation upstream. Such an avalanche 

•

Selected Case Histories of Dams on Landslides (by Landslide Type) 17
18  Interaction of Dams and Landslides—Case Studies and Mitigation

0 100 METERS

400

350

300

250

ELEVATION, METERS

Vashon outwash

EXPLANATION

Hayden Creek gravels

Hayden Creek lakebeds

Hayden Creek Till

Mud Mountain 

 complex

Top of bedrock

Top of Dam Spillway

Figure 26. Cross section through the site of Mud Mountain 

Dam, Washington State, United States, showing the Mud 

Mountain complex (Pleistocene mud-flow deposits) in both 

abutments. Modified from Galster (1989b).

Figure 27. Aerial view of Swift Dam, Lewis River, western 

Washington State, United States, showing forested debris-flow 

deposits that form the right abutment of the dam (see fig. 28). 

Photograph by Lynn Topinka, U.S. Geological Survey.

Figure 25. Aerial-oblique view of Mud Mountain Dam, western 

Washington State, United States. At both banks of the White 

River, the dam abuts into a Pleistocene mud-flow (lahar) deposit 

from Mount Rainier volcano. Photograph taken in 1979 by U.S. 

Army Corps of Engineers.

Swift Dam—Farther south in the Cascade Range of 

Washington State, two hydropower dams have been 

built on prehistoric lahars in the valley of the Lewis 

River, a glacial stream from the southeastern slopes of 

the cone of Mount St. Helens. The upstream structure 

is Swift Dam (fig. 27), a 126-m-high earthfill dam that 

was completed in 1958. Swift Dam’s right abutment 

and foundation are a thick, well-consolidated volcanic debris flow from a prehistoric eruption of Mount 

St. Helens (fig. 28) (Jensen, 1981; Tilford and Sullivan, 1981; Bliton, 1989). In the channel, an open-cut 

excavation for an impervious cutoff was made through 

this debris-flow material to a depth of about 30 m. 

Sheet piling was then driven to bedrock from the bottom of the trench (~25 m). A positive seal was formed 

by a grout curtain ranging in depth from 6–30 m and 

reaching into volcanic bedrock (Lowe, 1988). The right 

end of the dam was built on the lahar abutment with a 

drainage gallery to intercept any seepage. The system 

is operating successfully.

Yale and Yale Saddle Dams—Yale Dam, a 98-m-high 

earthfill structure, also on the Lewis River, approximately 20 km downstream from Swift Dam, was completed in 1953. As is the case for Swift Dam, the Lewis 

River valley at the Yale Dam site was partly filled by 

prehistoric lahars from Mount St. Helens. A geologic 

map by Tilford and Sullivan (1981) shows the distribution of these lahar deposits at and near the damsite 

(fig. 29). The lahar deposit was excavated from under 

the impervious core of the dam; however, the papers 

cited do not make it clear whether it remains under the 

outer shell. Three kilometers north of Yale Dam is Yale 

Saddle Dam, a 12-m-high earthfill structure that helps 

to impound Yale Reservoir; this saddle dam is founded 

entirely on lahar deposits. Neither dam has shown dis-

•

•

was completed in 1948 on the White River, a glacial 

stream from Mount Rainier (fig. 25). At both banks of 

the river, the dam abuts Pleistocene mud-flow deposits (Mud Mountain complex) (fig. 26) from Mount 

Rainier, which at the time of construction were thought 

to be glacial debris (Galster, 1989b; Eckerlin, 1992, 

1993). Fortunately, these deposits are nearly impervious and are generally stable, particularly because they 

are buttressed by the dam. The only difficulties at this 

site have involved slides along the reservoir shore, 

which have not directly affected performance of the 

dam.
Figure 28. Geologic map of the area around Swift Dam, Washington State, United States, showing the distribution of 

Holocene debris flow (lahar) deposits that form the right abutment of the dam. Modified from Tilford and Sullivan (1981). 

0 1 2 3 4 5 6 7 KILOMETERS

EXPLANATION

Intrusives

Volcanics of Mount St. Helens

Lava flows

Basalt

Holocene debris flows (lahars)

Alluvium

Yale Lake

Swift Reservoir

122 ̊10’

122 ̊10’

46 ̊ 46 ̊

McClellon Mtn.

Diamond

Creek

Marble Creek Marble Mtn.

Mt. Mitchell

Range Cre

ek

Swift Creek

Cinnamon Peak

Dry Creek

Cougar Creek

Cougar

Beaver Bay

Lewis River

Lost Creek

Panamaker Creek

Ole Creek

Rain Cr

Swift 

Dam

Pine Creek

Selected Case Histories of Dams on Landslides (by Landslide Type) 19
20 Interaction of Dams and Landslides—Case Studies and Mitigation

LAKE MERWIN

YALE LAKE

Speelyai Creek

Lewis River

YALE SADDLE

DAM

YALE

DAM

Speelyai Bay

YALE

GREEN MOUTAIN

DUNEGAN

MOUNTAIN

Brush Creek

John Creek

Buncombe Hollow Creek

Woodland Park 

Indian George Creek

Rock Creek

0 5 KILOMETERS

EXPLANATION

Volcanics of Mount St. Helens Holocene debris flows (lahars) Glacial drift

46°

122° 20 ́

West Fork

Brooks Creek

Figure 29. Geologic map of the area around Yale Dam and Yale Saddle Dam, Washington State, 

United States, showing the distribution of Holocene debris-flow (lahar) deposits that form the dams’ 

foundations and abutments. Modified from Tilford and Sullivan (1981).

tress due to the debris-flow materials in the foundation 

or abutments, and they continue to perform well.

North Fork Toutle River sediment-retention structure—

Another dam on Mount St. Helens debris-flow deposits 

is the sediment-retention structure (SRS) built in 1988 

on the North Fork Toutle River to retain debris-flow 

material that is washed from the surface of the 1980 

debris avalanche, as well as any future debris flows 

that might come down the valley (Schuster, 1989). 

This 73-m-high earthfill dam (fig. 30) was constructed 

on at least 30 m of debris-flow material from the 1980 

eruption and previous eruptions of Mount St. Helens. 

The dam is stable, and thus far is performing well 

(Bernton, 2000). The debris-retention function of this 

dam was augmented by the 1984–85 construction of 

an outlet tunnel from debris-avalanche-dammed Spirit 

Lake, the source of the North Fork Toutle River (Sager 

and Budai, 1989). This 2.6-km-long bedrock tunnel 

was built to prevent overtopping and failure of the 

debris-avalanche dam, which could have resulted in a 

catastrophic outburst debris flow, the volume and force 

•

of which might have overwhelmed the planned debrisretention structure.

Medeo Dam on the Malaya Alma-Atinka River and an 

unnamed dam on the Bolshaya Alma-Atinka River upstream 

from the city of Almaty in Kazakhstan are two other very successful debris-retention dams that have been founded on preexisting debris flows. Both were built to protect Almaty from 

the catastrophic debris flows that had entered the city from the 

Tien Shan Range every few years. 

Medeo Dam—The original 110-m-high Medeo Dam 

(fig. 31) on the Malaya Alma-Atinka River was built 

in 1968–69 by setting off explosive charges in the 

valley walls to form a man-made “landslide” dam that 

is founded on valley-bottom debris-flow deposits (Yesenov and Degovets, 1979, 1982). In July 1973, Medeo 

Dam retained a debris flow with a volume of about 5.5 

million m3 and maximum discharge of 10,000 m3/sec 

that came from the outburst of a moraine-dammed lake 

on the upper Malaya Alma-Atinka River (Yesenov 

and Degovets, 1982; Popov, 1999). As a result, the 

retention basin of the Medeo Dam was nearly filled. 

•
Figure 30. Sketch of the earthfill sediment-retention dam (SRS 

Dam) on the North Fork Toutle River, southwestern Washington 

State, United States. This dam, which was constructed in 1988 

to intercept sediment and debris washed downstream from the 

debris avalanche triggered by the 1980 eruption of Mount St. 

Helens, is founded on debris-flow deposits (Schuster, 1989). 

Sketch by U.S. Army Corps of Engineers.

Figure 31. Medeo Dam, a debris-flow retention structure on 

the Malaya Alma-Atinka River in Kazakhstan, which is founded 

on debris-flow deposits. Photograph taken in 2001.

Figure 32. Photograph of construction of a cellular 

reinforced-concrete debris-retention dam on the Bolshaya 

Alma-Atinka River of Kazakhstan. This 40-m-high dam, which 

was built in 1981–82 to protect the city of Almaty from the 

many debris flows from the Tien Shan Range, is founded on 

debris-flow deposits. Photograph taken in 1981 by D.J. Varnes, 

U.S. Geological Survey.

To contain future flows, the original earthfill dam was 

raised to a height of 150 m by traditional construction methods, providing a new retention basin with a 

volume of 12.6 million m3.

Unnamed debris-retention dam on the Bolshaya AlmaAtinka River—In 1982, a 40-m-high cellular reinforced-concrete dam (fig. 32) was built on debris-flow 

deposits in the valley of the Bolshaya Alma-Atinka 

River north of Almaty for the same debris-retention 

purpose as Medeo Dam. The retention-basin volume of 

•

the Bolshaya Alma-Atinka Dam is about 14.5 million 

m3 of debris-flow material (Yesenov and Degovets, 

1982).

There are many debris-flow retention dams (sabo dams) 

in China, Indonesia, and Japan. Most of these are small check 

dams and most have been built on bedrock. The following are 

two examples of debris-flow-retention dams that have been 

built on landslides.

Hunshui Gully debris-retention dam #4—An example 

from Yunnan Province, China, which qualifies as a 

“large dam” that was built on pre-existing debris-flow 

deposits is the 16-m-high Hunshui Gully debrisretention dam #4, a stone and concrete structure that 

was completed in about 1979–81 (Li and Luo, 1981; 

Zhang and others, 1985). This dam is one of a series of 

debris-retention structures built from 1978 to 1981 to 

intercept nonvolcanic debris flows on tributaries of the 

Xiao River (itself a tributary of the Yangtze River).

Jinnosuke #5 sabo dam—An example from Ishikawa 

Prefecture, Japan, is 17-m-high Jinnosuke #5 sabo 

dam, which is the largest of more than 50 sabo dams 

built on a pre-existing slide in altered sandstone, shale, 

and rhyolite in the valley of the Tedori River (Fukuoka 

and Taniguchi, 1961; Ohta and others, 1996; Wang and 

others, 2003; Okuno and others, 2004). The original 

Jinnosuke #5 Dam has moved about 5 m since it was 

built in 1925, and was recently rebuilt as a new Jinnosuke #5. There are several other dams in the valley 

•

•

Selected Case Histories of Dams on Landslides (by Landslide Type)  21
22  Interaction of Dams and Landslides—Case Studies and Mitigation

that are 10-m high or higher; even though these dams 

are slowly moving, all are successfully fulfilling their 

debris-retention function.

Of the many other debris-retention structures in these 

countries, a few undoubtedly are large dams that have been 

built on debris-flow foundations. However, I don’t have sufficient information on these dams to include them here or in 

Appendix table A. 

Cambering and Valley Bulging

Cambering and valley bulging have been noted in 

England as valleyward toppling of blocks of periglacial soils 

(Hutchinson, 1988). According to Cruden and Varnes (1996), 

a camber in rock may be described as a “relict, complex rock 

spread-rock topple.” When occurring in periglacial soils, it 

would be known as a relict, complex soil spread-soil topple.

Empingham Dam—During construction in 1975 of 

Empingham Dam, a 40-m-high earthfill water-supply 

dam in northern England, cambering and valley bulging in “boulder clay” (glacial till) were encountered 

in the foundation excavation (Horswill and Horton, 

1976). The cambering and resulting valley bulging 

had no negative effects on dam construction or 

performance.

Problems Encountered Due to 

Interaction Between Dams and 

Landslides

Landslides in dam foundations or abutments may lead to 

instability of the dam or seepage within these units. Example 

case histories in which these problems have occurred are 

discussed below.

Abutment and Foundation Instability

Of the total of 254 dams in Appendix table A, 78 encountered abutment-slope or foundation movement either during 

construction (43 cases) or after completion of the dam (35 

cases). For most construction-triggered failures, all or most of 

the active material was removed. In a few cases, it was left in 

place and stabilized, often by the buttressing effect provided 

by construction of berms or by the dam itself. There are only 

a very few known cases in which postconstruction movement 

affected or threatened the overall stability of the dam; St. 

Francis Dam (discussed earlier) and B.F. Sisk Dam, both in 

California, United States, are outstanding examples.

B.F. Sisk (San Luis) Dam—An excellent example of 

landslide activity in an abutment after construction is 

•

•

B.F. Sisk (San Luis) Dam in central California. This 

116-m-high earthfill dam, which was built for irrigation, hydroelectric power, and recreation, was completed in 1967. During drawdown in September 1981, 

a slide originated in “hard clay” slopewash of the left 

abutment and passed through the upstream face of the 

dam (Von Thun, 1985) (fig. 33). The slide moved about 

20 m. The main mass of the dam remained stable, and 

the reservoir was not threatened. Remedial measures 

consisted of construction of a buttressing berm at the 

upstream toe of the dam and reconstruction of the 

upstream face.

In addition, three cases of failure at an abutment that 

included a pre-existing landslide have happened under flood 

conditions; a basic underlying cause of failure for each was 

probably the presence of a relatively easily erodible landslide. 

The three cases are (1) Cheurfas Dam, Algeria, which failed 

in 1885, (2) Euclides da Cunha Dam, Brazil, which failed in 

1977, and (3) Star Mountain Dam, Oregon, United States, 

which failed in 1983.

Cheurfas Dam—The right abutment of the original 37-

m-high, masonry Cheurfas Dam in Algeria was in talus 

and alluvium (fig. 34) (Gignoux and Barbier, 1955). In 

1885, a flood removed the right one-half of the dam, 

which was later rebuilt (see below). Cheurfas Dam has 

not been included in Appendix table A because I was 

unsuccessful in obtaining sufficient data on the original 

dam.

Euclides da Cunha Dam—Euclides da Cunha Dam is 

a 92-m-high earthfill structure in southeastern Brazil. 

The original dam was completed in 1960 to provide 

hydroelectric power. “Ancient landslides,” consisting 

of clayey talus, covered both abutments (Vargas, 1971; 

Brazilian Committee on Large Dams, 1982). Torrential 

rains in January 1977 generated a flood that quickly 

overtopped the dam, causing severe erosion of the right 

abutment and resulting failure of the dam. Almost all 

of the talus on the right abutment was removed by the 

force of the flood. Thus, when the dam was subsequently rebuilt, seepage was better controlled at that 

end of the dam than it was before the failure.

Star Mountain Dam—The 1983 failure of 21-m-high 

Star Mountain Dam, an earthfill dam built in 1961 to 

provide local irrigation water to southeastern Oregon, 

is a similar case to that of the failure of Euclides da 

Cunha Dam. The entire right bank of Granite Creek at 

the damsite is the toe of a large pre-historic landslide. 

In late March 1983, a flood eroded out the original 

spillway, which was at the contact between the dam 

and the landslide abutment, causing damaging downstream flooding (Holton, 1983). The landslide character of the abutment probably was a factor in the failure 

of the spillway. When the dam was reconstructed, the 

•

•

•
Figure 34. Cheurfas Dam, a masonry dam in Algeria. This 

dam was originally built in 1880–82, at a time when only very 

superficial geologic studies were made. As a result, the right 

abutment consisted of talus and alluvial debris. After the dam 

failed at its right end in 1885 due to a flood, it was rebuilt to a 

bedrock abutment slightly upstream, leaving a “dogleg” in the 

dam (Gignoux and Barbier, 1955, p. 208–209). Note: “Eb” is éboulis,

which translates as “debris,” or, in this case, talus and alluvium; 

“T” is limestone. Photograph by M. Gignoux, courtesy of Dunod/

Masson Sciences, Paris. 

100

250 200 150 100 50 0

150

200

4:1

4:1

3:1

Zone 1

Failure surface Zones 4 & 5

Sandstone and shale

Zone 3

Slope wash

Toe berm

ELEVATION IN METERS

IN METERS

Figure 33. Cross section through B.F. Sisk (San Luis) Dam, California, United States, showing the location of the postconstruction slide surface and the toe berm installed to stop further movement. The slide surface passed through slope 

wash and zones 1 and 3 of the dam. Modified from Von Thun (1985).

Problems Encountered Due to Interaction Between Dams and Landslides  23
24  Interaction of Dams and Landslides—Case Studies and Mitigation

Kunzer, 1998). Right-abutment seepage occurred 

during the first filling of the reservoir. Upstream 

right-abutment treatment in 1921 reduced this seepage 

from an estimated 100,000 m3/day to 70,000 m3/day. 

In 1950, additional modifications at the right end of 

the dam further reduced the seepage to approximately 

25,000 m3/day. Complete reconstruction of the right 

end of the dam and its immediate abutment during the 

1990s has reduced seepage to acceptable levels.

Howard Hanson Dam—Another Western U.S. example 

of seepage problems due to landslide material in an 

abutment is Howard Hanson Dam, a 72-m-high rockfill 

and earthfill flood-control dam that was built in 1962 

in the Cascade Range of southwestern Washington. 

The right abutment for this dam is the toe of a large 

landslide in Tertiary andesite flows, andesitic tuffs, and 

breccias (fig. 37). The slide debris consists of a heterogeneous assemblage of rock blocks as large as 6 m in 

diameter in a matrix of finer debris (Galster, 1989a). 

After the first filling of the reservoir in 1965, a spring 

abruptly issued from the landslide materials about 

100 m downstream from the right abutment. The spring 

originally flowed at about 450–550 m3/day. Flow has 

since been controlled by a gravel blanket supported by 

a crib wall. A drainage adit was added in 1968. This 

system seems to adequately control abutment leakage 

through the slide debris.

•

Figure 35. Star Mountain Dam, a 21-m-high irrigation dam in 

southeast Oregon, United States. The right abutment of this dam 

is the toe of a large landslide. After the dam failed in 1983 due 

to flood erosion of the unlined spillway at the landslide right 

abutment, a circular concrete-lined spillway was installed within 

the embankment. Photograph taken in 1998.

original surface spillway was replaced by a circular-concrete spillway embedded in the embankment 

(fig. 35).

Abutment and Foundation Seepage

Of the 254 dams in Appendix table A, 59 have had 

unanticipated seepage problems, most commonly through an 

abutment. Of these 59 cases, 51 are in the Western United 

States, a result of the large number of irrigation dams that 

were built in this area in the early part of the 20th century 

without adequate geologic exploration or foundation/abutment 

design. Another reason for the tabulation of so many Western 

U.S. dams that have reported seepage problems may be the 

readily available technical information on U.S. dams from 

State dam-safety agencies. Furthermore, it also is possible that 

seepage from non-U.S. dams has been underreported in the 

technical publications from which the data in Appendix table 

A were obtained.

Ochoco Dam—Probably the most outstanding example 

of seepage through a landslide abutment of a Western 

United States irrigation dam is provided by Ochoco 

Dam, a 38-m-high hydraulic-fill dam built in 1920 in 

central Oregon. The right abutment and the foundation 

of the right end of this dam is a massive late Pleistocene rock slide–lateral spread (fig. 36) that probably 

resulted from plastic flow of bentonitic zones in dacitic 

tuff and tuffaceous claystone that underlay welded 

rhyolitic tuff of the slide mass (Carter, 1998a,b; 

•

Figure 36. Oblique-aerial view of Ochoco Dam, central Oregon, 

United States, and the huge rock slide–lateral spread that serves 

as its right abutment. Note the long head scarp (marked by 

arrows) of the slide along the upper part of the ridge. Photograph 

taken in 1999 by U.S. Bureau of Reclamation.
Mitigative Measures

Procedures used to prevent or alleviate problems encountered because of the existence of landslides at potential or 

actual damsites can be broadly subdivided into two main 

categories:

Planning measures—These include those measures that 

avoid or alleviate the problems as part of the planning 

process (passive measures). Common measures are 

avoidance, dam-type selection, control of reservoir 

level, and/or relocation of the spillway.

Physical prevention or remediation measures (active

measures)—These commonly include removal of all 

or part of the landslide; flattening of the slope; construction of berms that serve as buttresses; and installation of impervious membranes or cutoffs, retaining 

walls, surface or underground drains, and rock-anchor 

systems. These physical prevention and remediation 

measures have been used in the abutments or foundations of 154 of the dams in Appendix table A. Seventy-seven of the 101 non-U.S. dams utilized active 

measures, as was the case for 77 of the 153 U.S. dams. 

As presented in Appendix table A, of the 154 dams 

that were subject to active prevention and remedial 

measures, the use of individual types of prevention 

and remediation are as follows (note, however, that 

multiple types have been used on many dams): partial 

removal of landslide deposits (46 dams), cutoff walls 

(43 dams), berms/buttresses (43 dams), grouting (36 

dams), drainage (36 dams), impervious membranes/

blankets (20 dams), flattening of abutment slopes 

(15 dams), rock anchors (12 dams), piles/piers (8 

dams), guniting/dental work (six dams), retaining walls 

(5 dams), and other measures (6 dams). Another, 

•

•

sometimes overlooked, physical measure is the buttressing effect of the dam itself, which has proven to 

be a very important factor in the retention of many 

abutment landslides.

Planning Measures

Avoidance of Landslides

A very basic passive preventive measure if a landslide has 

been recognized in a planned foundation or abutment area during the siting process is avoidance, that is, relocation to a more 

favorable site nearby, or, in extreme cases, complete abandonment of the site. 

Relocation of Site

Several cases have been noted in which a damsite was 

relocated because the original site included a hazardous landslide in the foundation or an abutment. Most of these dams 

have not been included in Appendix table A because as constructed they do not interact with landslides. Notable examples 

include the following:

Orlik Dam—The most often cited example of relocation of a major dam because of a pre-existing landslide 

has been that of Orlik Dam on the Vltava River in 

the southwestern part of the Czech Republic (Záruba, 

1965; Záruba and Mencl, 1976; Legget and Karrow, 

1983; Legget and Hatheway, 1988). Preliminary studies for the siting of Orlik Dam indicated that a narrow 

stretch of the valley and the existence of Proterozic 

metamorphic rocks in the abutments would provide 

an ideal site for construction of a concrete-gravity 

dam. However, further study found that the narrowing of the valley at the site was actually caused by a 

massive Pleistocene rock slide. The original site was 

abandoned and a new site selected 200 m upstream, 

where the 91-m-high dam was successfully completed 

in 1963. For the same reason, several other potential 

damsites on the Vltava River have had to be relocated 

or abandoned.

Salagou Dam—In the case of Salagou Dam on the 

Salagou River in south-central France, the site was 

relocated only a short distance away (Comité Français 

des Grandes Barrages, 1982). In addition to removing 

87,600 m3 of landslide material from the right abutment of the site and 38,450 m3

 from the left abutment, 

the 63-m-high earthfill dam was moved upstream—the 

right end a distance of 40 m and the left end 80 m—to 

avoid building on landslide materials. Construction 

was completed successfully in 1971.

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. . . 0 100 METERS

300

350

400

ELEVATION, METERS

Older slide debris

Lacustrine deposits (sand, 

 silt, clay)

Fluvial deposits (sand 

 and gravel)

Bedrock surface

EXPLANATION

Spillway

Slide debris

Geology after Corps of Engineers 

unpublished data

Embankment

dam

Figure 37. Cross section through the site of Howard Hanson 

Dam in western Washington State, United States, showing the 

huge landslide that serves as the right abutment of the dam. 

Modified from Galster (1989a).

Mitigative Measures  25
26  Interaction of Dams and Landslides—Case Studies and Mitigation

Kotmale Dam—Kotmale Dam, an 87-m-high rockfill 

dam on the Kotmale Oya (river) in Sri Lanka, was 

completed in 1985 to produce hydroelectric power. 

As construction began, a landslide was noted in the 

left abutment, necessitating relocation of the dam site 

200 m downstream where it avoids any landslides 

(Kumara and Kulasinghe, 1987).

Talbingo Dam—The original site for Talbingo Dam, a 

161-m-high rockfill hydroelectric dam in the Snowy 

Mountains of southeastern Australia, included the 

toe of a large landslide of weathered basalt in the left 

abutment (Fell and others, 1992, p. 58). An alternative 

landslide-free site, more than 100 m upstream, was 

selected. The dam was completed in 1971, incorporating 2.3 million m3

 of the basaltic landslide deposit for 

its impervious core.

North Fork Dam—An example of landslide avoidance 

during the original exploration stage of site selection 

is that of North Fork Dam, a hydroelectric dam on the 

Clackamas River in northern Oregon, United States. 

During site exploration for this 63-m-high concretearch dam, a 25–30 m thick deposit of slide and talus 

debris was noted in the left-abutment area (O’Reilly, 

1958). As a result of this preliminary exploration, the 

dam was relocated upstream utilizing an abutment of 

stable basalt and was completed in 1958.

Casitas and Castaic Dams—As indicated in Appendix 

table A, the axes of Casitas and Castaic Dams, California, United States, were realigned in the planning 

stage to minimize the effects of pre-existing landslides 

(Hanegan, 1973). In both cases, final alignment placed 

only a small part of the dam in contact with a landslide. 

San Dimas Dam—San Dimas Dam, California, was 

redesigned to reduce the area of contact of the dam 

with a pre-existing landslide.

There also have been a few cases in which one end of a 

pre-existing or partially built dam has been diverted to avoid 

a landslide, thus forming a “dogleg” in the dam. Three cases 

(not included in Appendix table A) where the axes of dams 

have been diverted midstream in order to avoid landslides 

are Cheurfas Dam (Algeria), Scott Dam (California, United 

States), and Gogoşu Dam (Romania).

Cheurfas Dams—As briefly mentioned earlier, the 

original Cheurfas Dam (Cheurfas I) was a masonry 

dam built from 1880–82 at a time when only very 

superficial geologic studies were made of the damsite 

(Gignoux and Barbier, 1955, p. 63); for this reason 

the right end of the dam abutted against alluvium and 

talus deposits (“partially strengthened scree”). In 1885, 

a severe flood carried away the right one-half of the 

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•

Figure 38. Scott Dam on the Eel River, northern California, 

United States. During construction in 1921, the left end of this 

dam was diverted downstream to miss the landslide on the left 

bank of the river, resulting in a “dogleg” in the dam. Photograph 

taken in 1997 by J.C. Gamble, Pacific Gas and Electric Company, 

San Francisco.

structure. By 1892, the dam had been rebuilt, leaving in 

place the left-end remnant that had survived the 1885 

flood, but putting a “dogleg” in the dam to allow its 

right end to abut a stable limestone outcrop upstream 

from the unstable talus that formed the original right 

abutment (fig. 34) (Gignoux and Barbier, 1955; p. 63, 

208; Walters, 1971, p. 313–320). During the early 

1980s, it was decided to replace the 1892 dam because 

of siltation in the reservoir and the general instability of the site (Ajabi and others, 1991). The new dam 

(Cheurfas II) was built upstream at a more stable site.

Scott Dam—Scott Dam (also known as Pillsbury 

Dam), a 42-m-high concrete-gravity structure on the 

Eel River in northwestern California, was built in 1921 

to produce hydroelectric power. Construction began at 

the right end of the dam. When the dam was two thirds 

of the way across the river, it was realized that the 

planned left abutment was actually a “floater” of serpentinite in a slide of softened, weathered serpentinite 

and serpentine clay. The engineers in charge decided 

to divert the remainder of the dam downstream to miss 

the landslide, forming a “dog leg” (fig. 38) similar to 

that for Cheurfas Dam, which was described above 

(Kiersch and James, 1991; Goodman, 1993). 

Gogoşu Dam—Gogoşu Dam on the Danube River 

in Romania is a 24-m-high zoned earthfill dam that 

provides hydroelectric power to the nation. During 

construction, a slide occurred in the stiff, marly clays 

that formed the left abutment. In addition to partially 

removing the slide material, the left end of the dam 

axis was “upstream curved” to miss the slide area 

(Corda, 1988).

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Site Abandonment

An option that can be considered in extreme cases is to 

abandon the damsite because the landslide problem at the 

chosen site is without a solution that is economically feasible, 

and because no suitable alternate site is available nearby. The 

literature search noted only two cases in which the original site 

was deemed completely unsuitable and was abandoned. These 

two cases are a site on the Romanche River in France and the 

Ok Ma tailings dam site in Papua New Guinea. Abandoned 

dam sites are not included in Appendix table A.

Romanche River site—An apparently morphologically suitable site for a dam was located on the upper 

Romanche River in the French Alps (Gignoux and 

Barbier, 1955, p. 88; Záruba and Mencl, 1982, p. 238; 

Bowen, 1984, p. 311–312). The left abutment at 

this site was composed of stable granite and Triassic sandstones and limestones. The more moderately 

sloping right abutment also appeared to be stable. 

However, geologic investigation of the slope found that 

the entire right side of the valley at the site consisted 

of a landslide in Lias (Lower Jurassic) shales, which 

had constricted the valley, and overlay alluvial sandy 

gravels on the original valley floor (fig. 39). The site 

was abandoned.

Ok Ma tailings dam site—The proposed Ok Ma (“ok” 

translates as “river”) tailings dam was intended to 

provide a retention reservoir for tailings from the 

Ok Tedi gold/copper mine in the Star Mountains of 

western Papua New Guinea. However, in December 

1983, during construction of this conventional zoned 

earthfill/rockfill dam, a major, deep-seated landslide 

occurred in the weak mudstones and siltstones of the 

•

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middle Miocene Pnyang Formation at its proposed left 

abutment (Fookes and others, 1991; Fookes and Dale, 

1992; Fookes and others, 2000). Because no technically or economically feasible option was available for 

mitigation of the landslide or for shifting the axis of the 

tailings dam to a position off the landslide, the tailings 

dam site was abandoned.

Redesign of Dams Because of Landslide 

Problems

A few dams have been redesigned when a landslide 

was discovered in the foundation or an abutment. Excellent 

examples are Selevir Dam in western Turkey and Sweasey 

Dam, California, United States.

Selevir Dam—Selevir Dam is a 31-m-high earthfill, 

irrigation dam in western Turkey. During construction, 

movement occurred in schist that forms the right abutment. As a result, (1) the outlet tunnel was redesigned 

and rerouted, (2) the outlet portal excavation, which 

had caused the slide, was refilled with recompacted 

material (that is, the fill became a buttress berm), (3) 

the intake structure was moved 455 m upstream, and 

(4) the original cutoff trench was replaced by a concrete cutoff wall with piles extending to schist bedrock 

(Sezginer and Karacaoğlu, 1961).

Sweasey Dam—Sweasey Dam, on the Mad River in 

northern California, was originally designed to be a 

40–45 m high concrete arch municipal water-supply 

dam. During construction, however, a slide occurred 

in Franciscan Complex sandstones and clayey shales 

of the left abutment (Kiersch and James, 1991). As a 

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0 50 METERS

1575

1600

1625

1650

1675

ELEVATION IN METERS

Granite

Sandstone

Limestone

Shale slide

Sandy gravel

Romanche

River

Potential dam crest

Figure 39. Cross section through a narrowed section of the Romanche River valley, France, showing the shale landslide 

that constricted the valley. Plans to construct a dam at this site were abandoned because of the landslide. Modified from 

Gignoux and Barbier (1955, p. 88).

Mitigative Measures  27
28  Interaction of Dams and Landslides—Case Studies and Mitigation

result, the dam was redesigned from a full concrete 

arch to a composite section employing an arch dam 

across the channel section, which abutted a massive 

concrete thrust block at the left end. An earthfill section then connected the thrust block with the excavated 

left abutment. Design height was also reduced by 20 

m to an as-constructed 23-m height. During the 1970s, 

the dam was purposely breached because of excessive sedimentation in the reservoir (no relation to the 

landslide).

As noted earlier, embankment dams are more flexible 

than concrete structures, and thus can be built on pre-existing 

landslides with less risk of stability problems than is the case 

for concrete, and particularly concrete-arch, structures. Three 

dams in Appendix table A that were changed from concrete 

to rockfill during the preliminary design process because of 

pre-existing landslides in their footprints are Iril-Emda Dam 

(Algeria), Kangaroo Creek (Australia), and Pandoh Dam 

(India).

Lowering Reservoir Level or Reducing Rate of 

Filling

Although use of these procedures tends to impair the 

function of the dam, they constitute an effective means of 

increasing abutment stability by reducing abutment pore pressures and reducing seepage through the abutment by lowering 

the head or reducing its rate of increase. Five cases of reservoir 

lowering or reduction of rate of filling have been noted in this 

study: 

Casanuova Dam (central Italy)—Filling of the reservoir was temporarily suspended pending installation 

of additional remedial measures (Catalano and others, 

2000).

Rossella Dam (Island of Sicily, Italy)—Reservoir level 

was lowered to counter reactivation of a left-abutment 

earthflow (Catalano and others, 2000).

Los Naranjos Dam (Mexico)—Release from the 

reservoir was controlled as one of several mitigative 

measures to slow reactivation of a 2-million-m3 slide in 

the right abutment (Ramirez Reynaga, 1998).

Rio Grande Dam (Colorado, United States)—For several years in the 1990s, Rio Grande Dam (fig. 1) operated at lowered reservoir level mandated by the State 

of Colorado because of left-abutment seepage through 

the toe of a pre-existing rock slide. The problem was 

solved by installation of the following remedial measures at the left abutment: (1) retaining wall, (2) french 

drains, and (3) horizontal drains. After completion of 

the remedial measures, reservoir level was allowed to 

be raised.

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•

Sam’s Valley Dam (Oregon, United States)—Operation at a temporarily lowered reservoir level has been 

mandated by the State of Oregon because of excessive 

seepage through the landslide right abutment.

Physical Measures for Foundation and 

Abutment Stabilization

Da Costa Nunes and others (1982) have noted several 

physical mitigative measures for stabilization of abutments 

that are threatened by landslides. These stabilization methods 

include removal of landslide deposits; flattening the abutment 

slope; construction of earthfill or rockfill berms that serve as 

buttresses; construction of cutoffs or keys, retaining walls, 

piles or caissons, and anchors; moving or reinforcing the spillway; guniting; and “dental work.” 

Removal of Landslide Deposits

For cases in which a decision has been made to proceed 

with construction of a dam at the site of an old landslide, 

removal of all or part of the landslide material has often been 

accomplished as a successful preventive measure. There are 

47 cases in Appendix table A in which part of the landslide 

deposit has been removed, but the remainder is included in the 

foundation or as part of an abutment in contact with the dam. 

Some examples of dams from which all or part of the landslide 

deposit has been removed are briefly mentioned below. The 

dams for which the landslide deposit has been totally removed 

have not been included in Appendix table A. 

Total Removal of Landslide

Examples of total removal of landslide material that 

would have interacted with a dam or its appurtenant structures include the following dams (not included in Appendix 

table A): Little Para (Australia) (Beal, 1975), Ouchi (Japan) 

(Mikuni, 1980; Watanabe, 1985), Bell Canyon (California, 

United States) (Connell and others, 1985), Los Vaqueros 

(California) (Simpson and Schmoll, 2001), Dillon (Colorado, 

United States) (Wahlstrom and Nichols, 1969), Kinzua (Pennsylvania, United States) (Philbrick, 1976), and Tioga (Pennsylvania, United States) (Wilshusen and Wilson, 1981). In most 

such cases, all or part of the removed material was used to 

construct a berm, which served as a buttress.

Partial Removal of Landslide

Removal of part of the landslide took place in 47 of the 

dams listed in Appendix table A; well-documented examples 

include Kangaroo Creek (Australia), Thomson (Australia), 

•
Gardiner (Canada), Slezka Harta (Czech Republic), Bort 

(France), Evinos (Greece), Kassa (Japan), Ouchi (Japan), 

d’Aït Youb (Morocco), Arenós (Spain), Cortes de Pallás 

(Spain), Broomhead (United Kingdom), Austrian (California, 

United States), Castaic (California), Hernandez (California), 

San Dimas (California), Black Lake No. 1 (Colorado, United 

States), and Silver Jack (Colorado).

Partial Removal of Talus Cover 

Removal of part of talus cover from an abutment commonly consists of placing a wide cutoff trench through the 

talus into bedrock, but may involve stripping of a larger area 

to bedrock. There are 14 such cases in Appendix table A: 

Parangana (Australia) (fig. 22), Eberlaste (Austria), Gepatsch 

(Austria), Euclides de Cunha (Brazil), Serre-Ponçon (France), 

Ancipa (Italy), Ozola (Italy), Francisco Zarco (Mexico), 

Vicente Guerrero (Mexico), Wemmershoek (South Africa), 

Marmorera (Switzerland), Taylor Park (Colorado, United 

States) (fig. 4), Anderson Ranch (Idaho, United States), and 

Joes Valley (Utah, United States).

Partial Removal of Landslide Deposit Following 

Construction or Postconstruction Slope Failure

Partial removal of landslide materials during construction 

or postconstruction slope failure took place at 65 of the dams 

in Appendix table A; examples of these include Quebrada 

de Ullum (Argentina), Gardiner (Canada), Slezska Harta 

(Czech Republic), Daniel Palacios (Ecuador), Chaudanne 

(France), Los Naranjos (Mexico), Tresna (Poland), Arenós 

(Spain), Broomhead (United Kingdom), Castaic (California, 

United States), Trinity (California), Ridgway (Colorado, 

United States), Silver Jack (Colorado), Lovewell (Kansas, 

United States), Agate (Oregon, United States), Lookout Point 

(Oregon), Oahe (South Dakota, United States), Joes Valley 

(Utah, United States), and Grand Coulee (Washington, United 

States).

Flattening Abutment Slopes

Flattening of abutment slopes (unloading the upper part 

of the landslide) has been used as a preventive/remedial measure on 15 of the dams listed in Appendix table A. These are 

Quebrada de Ullum (Argentina), Gardiner (Canada), Dalešice 

(Czech Republic), Nechranice (Czech Republic), Slezska 

Harta (Czech Republic), Ranaptrap Sagar (India), Los Naranjos (Mexico), Cortes de Pallás (Spain), Devil’s Dingle (United 

Kingdom), Castaic (California, United States), San Dimas 

(California, United States), Silver Jack (Colorado, United 

States), Agate (Oregon, United States), Oahe (South Dakota, 

United States), and Grand Coulee (Washington, United 

States).

Earthfill or Rockfill Berms Serving as Buttresses

Earthfill and rockfill berms often have been used as buttresses to increase the stability of abutment slopes. If these 

berms include fine-grained materials, they may also reduce 

seepage at the toe of the dam. In many cases, the material 

for construction of berms is obtained directly from landslide 

deposits excavated from upslope areas along or near the 

abutment. Thirty-nine examples of construction of berms as 

abutment-slope buttresses are presented in Appendix table A. 

Some of the more interesting examples and the types of berms 

installed include the following: 

Thomson Dam (Australia)—2.6-million-m3 rockfill 

berm 

Eberlaste Dam (Austria)—50-m-wide stabilizing fill 

that served as berm 

Dalešice Dam (Czech Republic) (fig. 10)—150,000-m3

rockfill berm

Mornos Dam (Greece)—8-million-m3 toe berm placed 

along the reservoir shore immediately upstream from 

dam 

Tablachaca Dam (Peru)—467,000-m3 toe berm placed 

in the reservoir immediately upstream from dam 10 

years after original construction 

Liptovaská Mara Dam (Slovakia)—700,000-m3 sand/

gravel berm 

Cortes de Pallás Dam (Spain)—800,000 m3 excavated 

from upper part of slide and moved to lower part to 

form toe berm 

•

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•

Figure 40. Oblique view of the left end of Mojave River 

Dam, an earthfill flood-control structure in southern 

California, United States, showing the two earth berms 

that were added to the left abutment to buttress a small 

abutment slide (marked by arrow) that occurred during 

construction. Photograph taken in 1998.

Physical Measures for Foundation and Abutment Stabilization  29
30 Interaction of Dams and Landslides—Case Studies and Mitigation

B.F. Sisk (San Luis) Dam (California, United States)—

Addition of an upstream toe berm (fig. 32) was necessitated by a postconstruction slide in left abutment

Mojave River Dam (California, United States)—Two 

earthfill berms serve as buttresses (fig. 40) 

Terminal Dam (California, United States)—6.5-m-high 

upstream and downstream berms 

Silver Jack Dam (Colorado, United States)—87,000-m3

toe berm obtained from slope above abutment 

Lake Harriet Dam (Oregon, United States)—Berm with 

an impervious bentonitic membrane was placed against 

upstream face of the concrete-arch dam, mainly to 

reduce seepage (fig. 14) 

Oahe Dam (South Dakota, United States)—3.5-million-m3

 construction-caused slide in left abutment 

was excavated and material was placed as a berm that 

serves as toe buttress

Dam Serving as Buttress

Often, potential abutment slides have been successfully 

buttressed by the mass of the dam itself. In this manner, the 

abutment slopes may be more stable than before the dam was 

built. However, the existence of the dam will have little effect 

on seepage through the abutment. All dams have a buttressing effect; some examples from Appendix table A, where this 

effect has been specifically noted, include Iril-Emda (Algeria), 

Mornos (Greece), Pandoh (India), Clyde (New Zealand), Trinity (California, United States), Gross (Colorado, United States) 

(figs. 5 and 6), Ridgway (Colorado), Lovewell (Kansas, 

United States), Conchas (New Mexico, United States), Oahe 

(South Dakota, United States), Calder (Utah, United States), 

Jordanelle (Utah), Red Creek (Utah), and Yale (Washington, 

United States).

Cutoffs or Keys

An impervious cutoff (usually concrete) is often placed in 

a trench that is excavated beneath the location of the dam core. 

The main function of a cutoff usually is to reduce seepage 

through the foundation or abutment. However, these cutoffs 

also “key” the dam into the foundation or abutment, and thus 

increase stability in addition to reducing permeability. Some 

examples of dams with cutoffs are given in the following section on reducing seepage.

An instance of the reinforcement of a landslide abutment 

using a concrete mass is San Jacinto Dam (Bolivia), where the 

left abutment was strengthened by filling adits with concrete 

(Riemer, 1995).

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Retaining Walls

Conventional retaining structures occasionally have been 

used to increase abutment stability during construction. These 

walls commonly are left in place and become part of the dam. 

Dams in Appendix table A in which retaining walls were 

used to increase abutment stability include Zardezas (Algeria), Ichari (India), Jaldhaka Stage I (India), Ranaptrap Sagar 

(India), Tresna (Poland), Brooktrails No. 3 North (California, 

United States), Rio Grande (Colorado, United States) (fig. 

1), Conchas (New Mexico, United States), and Grand Coulee 

(Washington, United States) (fig. 21).

Piles and Caissons

Dams from Appendix table A in which piles or caissons 

have been used to increase lateral stability include Wuping 

(China, vertical rock piles), Pong (India, concrete caissons), 

Bass Lake (Montana, United States, sheet piling), Madison 

(Montana, steel piling), Swift (Washington, United States, 

sheetpiling), and McElroy’s Run (West Virginia, United States, 

augercast grout columns).

Anchors

Anchors (usually prestressed steel) are often used to 

increase the stability of rock abutments, particularly during 

construction. Included in Appendix table A are the following 

dams that have successfully utilized anchors in abutments: 

Meishan (China), Dalešice (Czech Republic) (fig. 10), Daniel 

Palacios (Ecuador), Chaudanne (France), Ranaptrap (India), 

Kawamata (Japan), Santa Rosa (Mexico), Tablachaca (Peru), 

Tresna (Poland), Pacoima (California, United States), and San 

Dimas (California).

Moving or Reinforcing Spillway

In a few cases, either the main or the emergency spillway has been known to leak water into or cause erosion of a 

landslide abutment. In these cases, the spillway has either been 

moved to the other end of the dam or has been sealed or reinforced to prevent leakage or erosion. Examples of such cases 

in Appendix table A include the following:

Trinità Dam (Island of Sicily, Italy)—The spillway, 

which was located on a pre-existing earth flow–earth 

slide, was founded on a system of piles to protect it 

from movement (Catalano and others, 2000). 

Austrian Dam (California, United States)—The spillway was relocated (partially to protect the spillway and 

partially to help stabilize the landslide abutment).

•

•
Star Mountain Dam (Oregon, United States)—A 

circular concrete-lined emergency spillway replaced 

an earlier unlined spillway that had failed due to flood 

erosion, thus causing failure of the landslide abutment, 

and then failure of the dam (fig. 35).

Guniting

Although guniting provides almost no direct structural 

strength, it is occasionally used to increase the stability of a 

very steep slope by inhibiting surface erosion. The only dams 

in Appendix table A with abutment slopes that are protected 

by gunite are Santa Rosa (Mexico) and Pacoima (California, 

United States).

“Dental Work”

“Dental work” is the filling of joints and other voids 

with cement grout or concrete to increase local stability and 

possibly to reduce permeability. It is often used on rock abutments during construction. The only Appendix table A dams 

for which dental work has been carried out on a rock abutment 

to reduce the landslide hazard during excavation are Tooma 

(Australia), Daule Peripa, (Ecuador), Los Naranjos (Mexico), 

and Jordanelle (Utah, United States).

Physical Measures for Reducing 

Abutment and Foundation Seepage

Impervious Cutoffs

Probably the most common seepage-reduction measures are impervious cutoffs that are constructed through the 

landslide materials to solid rock. Usually, these cutoffs are 

made of Portland-cement concrete and serve as vertical “keys” 

in zone 1 of the dams to increase stability of the structure in 

addition to reducing seepage; however, some are impervioussoil or bentonitic-slurry cutoffs, which do little or nothing to 

increase stability. Cutoffs are commonly installed during the 

construction process. Dams in which concrete cutoffs have 

been installed during construction to prevent seepage include 

O’Shannassay (Australia), Eberlaste (Austria, asphaltic 

concrete), Freibach (Austria), Ichari (India), Pandoh (India), 

Salal (India), Ancipa (Italy), Ozola (Italy), Pian Palù (Italy), 

Vodo (Italy), Rules (Spain), Marmorera (Switzerland), Selevir 

(Turkey), and Woodhead No. 2 (United Kingdom). Flexible 

slurry-trench or clay cutoffs were installed at Eberlaste Dam 

(Austria, slurry trench), Euclides da Cunha (Brazil, “impervious soil”), Nechranice (Czech Republic, “clay-cement”), 

Francisco Zarco Dam (Mexico, slurry trench), and Vicente 

Guerrero (Mexico, impervious clay). Cases in which a cutoff 

• was added when seepage problems were encountered during 

operation include Site 19 (New York, United States), Long 

Park (Utah, United States), and Mud Mountain (Washington, 

United States).

Impervious Curtains, Membranes, and Blankets

Seepage can also be intercepted and diverted by impervious curtains, membranes, or blankets that have little inherent 

structural strength, for example, cement or chemical grout 

curtains, plastic or geosynthetic membranes, and clay blankets. Thirty-seven dams from Appendix table A include grout 

curtains in their foundations and/or abutments. Fourteen of 

the dams in Appendix table A include impervious membranes or clay blankets. These measures are not intended to 

act as strengthening “keys” through the landslide material to 

bedrock, but may increase stability as well as reduce seepage 

by locally lowering pore pressures in the foundation and abutments. Dams in which these measures have been used include 

the following:

Grouting (during construction)—Quebrada de Ullum 

(Argentina), Parangana (Australia), Tooma (Australia), 

Durlassboden (Austria), Euclides da Cunha (Brazil), 

Polemidhia (Cyprus), Terlicko (Czechoslovakia), 

Chaudanne (France), Ranaptrap Sagar (India), Salal 

(India), Beauregard (Italy), Kassa (Japan), Terayama 

(Japan), Francisco Zarco (Mexico), Marmorera 

(Switzerland), Castaic (California, United States), 

San Dimas (California), Black Lake No. 1 (Colorado, 

United States), El Vado (New Mexico, United States), 

and Moon Lake (Utah, United States) 

Grouting (after seepage or movement developed)—

Freibach (Austria), Yeso (Chile), Meishan (China), 

Los Naranjos (Mexico), Nakhla (Morocco), Arnensee 

(Switzerland), Broomhead (United Kingdom), Austrian 

(California, United States), Pacoima (California), Clear 

Lake (Colorado, United States), Scholl (Colorado), 

Young’s Creek Nos. 1 and 2 (Colorado), Bull Run No. 

2 (Oregon, United States), and Waterbury (Vermont, 

United States)

Impervious membranes or clay blankets (during construction)—Seymour Falls (Canada), Ranaptrap Sagar 

(India), Salal (India), Terayama (Japan), and South 

Creek (Utah, United States)

Impervious membranes or clay blankets (after seepage 

or movement had occurred)—Meishan (China), Beaver 

(Colorado, United States), Cedar Mesa (Colorado), 

Matheson (Colorado), Scholl (Colorado), Young’s 

Creek Nos. 1 and 2 (Colorado), Black Lake (Montana, 

United States), Hyalite (Montana), and Stemilt Main 

(Washington, USA)

•

•

•

•

Physical Measures for Reducing Abutment and Foundation Seepage  31
32  Interaction of Dams and Landslides—Case Studies and Mitigation

Note the relatively large number of dams in the Western 

United States that have been repaired by installation of grout 

curtains or impervious membranes after the occurrence of 

seepage. This is indicative of the seriousness of seepage problems faced by dams that have been built on landslides.

Drainage Systems

Drainage systems are commonly used to intercept water 

before it enters the landslide deposit or to remove water from 

the landslide material. Drainage helps to stabilize abutment 

landslide materials, to control seepage through the abutment or 

foundation, and to reduce the possibility of piping. Thirty-four 

dams in Appendix table A have been improved by installation 

of drainage systems. These systems commonly consist of one 

or more of the following: surface drainage, interceptor trench 

drains (vertical trenches backfilled with pervious materials, 

such as sand and gravel), “horizontal” drains, adits and galleries, filter blankets, and pumping wells. Toe drains and relief 

wells also are used to allow water to exit without building up 

pore pressures within the abutment or foundation materials. 

Any of these measures may be installed during dam construction as preventive measures, or may be added later as remedial 

measures.

Examples of dams in Appendix table A for which drainage systems were added either during or after construction 

include the 

following:

Surface drains—Slezska Harta (Czech Republic), Polyphyton (Greece), Wemmershoek (South Africa), Currier #2 (Colorado, United States), Silver Jack (Colorado), and Nevada Creek (Montana, United States)

Trench drains—Broomhead (United Kingdom), Brooktrails No. 3 North (California, United States), Kiser 

Slough (Colorado, United States), Rio Grande (Colorado), and Bumping Lake (Washington, United States)

Horizontal drains—Pandoh (India), Tablachaca (Peru), 

Rio Grande (Colorado, United States), Silver Jack 

(Colorado), South Creek (Utah, United States), and 

Howard Hanson (Washington, United States)

Adits, tunnels, and galleries—Polyphyton (Greece), 

Nakhla (Morocco), Tablachaca (Peru), City of Portland 

No. 3 (Oregon, United States), and Howard Hanson 

(Washington, United States)

Filter blankets—Wungong (Australia) and Howard 

Hansen (Washington, United States)

Pumping wells—Evinos (Greece)

•

•

•

•

•

•

Toe drains and relief wells—Quebrada de Ullum 

(Argentina), Engenheiro Avidos (Brazil), saddle dam 

for F. Mohamed B.A. el Khattabi (Morocco), Jones #2 

(Colorado, United States), Overland #1 (Colorado), 

and Howard Hanson (Washington, United States)

Multiple Mitigation Methods

All of the above preventive and remedial measures have 

been known to increase stability and/or reduce seepage, and, 

in some cases, they have been completely successful. However, in most successful cases more than one method has been 

utilized.

•

Figure 41. The remains of Mystic Lake Dam, a small 

water-supply dam in southwestern Montana, United 

States, which was constructed in 1903–04 on the site 

of a landslide dam. The earthfill dam was purposely 

breached in 1984 because of the hazard it posed to the 

downstream city of Bozeman. Photograph taken in 1997.

Breaching as a “Remedy”

The only dams that I know of that have been purposely 

breached because of the downstream hazard that they posed 

due to a landslide are Mystic Lake Dam, a 13-m-high, earthfill 

water-supply dam for the city of Bozeman, Montana, United 

States, and Site 19 Dam, a 20-m-high flood-control dam in 

New York State, United States. 

Mystic Lake Dam—Mystic Lake Dam (fig. 41), which 

was constructed in 1903–04 on the site of a “recent” 

(about 100 yr old) landslide dam, leaked excessively 

throughout its lifetime, and was in possible danger of 

failure due to piping. Thus, it was purposely breached 

in 1984 in response to the U.S. Dam Safety Program 

(High Country Independent Press, 1985). 

•
Site 19 Dam—Site 19 Dam, which was constructed 

in 1971, was breached in 1980 because of excessive 

leakage in the left abutment due to a pre-existing 

ancient slump (Kirkaldie and Thomas, 1984; Kiersch 

and James, 1991). The dam was redesigned and rebuilt 

with remedial measures consisting of (1) a cutoff 

trench to bedrock and into the embankment and (2) an 

enlarged foundation drainage system.

Summary and Conclusions

Geologists sometimes feel that it is impossible to safely 

construct a dam on a pre-existing landslide. Conversely, some 

engineers have been known to assume that today’s advanced 

construction and prevention techniques can overcome any 

landslide problem. This study of 254 dams that either have 

been built on pre-existing landslides or were subjected to landslides during or after construction shows that reality is somewhere in between these extremes. Some dams have been built 

on landslides with no ensuing difficulties, even in cases where 

preventive measures were not used; others have encountered 

serious seepage or stability problems, most of which have 

been at least partly alleviated by installation of remedial measures, such as berms, cutoff walls, drainage systems, grouting, 

or impervious membranes. However, avoidance of sites where 

landslides may result in exorbitant costs during construction or 

remediation should always be considered as a serious option.

This study has noted many cases in which dams built 

on landslides have operated for many years without major 

stability or seepage problems. In only four cases, Cheurfas 

Dam (Algeria) [not included in Appendix table A], Euclides 

da Cunha Dam (Brazil), St. Francis Dam (California, United 

States), and Star Mountain Dam (Oregon, United States), can 

failure (that is, natural breaching) of a dam be considered to 

have been related to problems caused by pre-existing landslides. Only in the case of the failure of St. Francis Dam was 

the failure catastrophic in terms of loss of life. Mystic Lake 

Dam (fig. 39) and Site 19 Dam were the only cases found in 

which a dam was intentionally breached because of concerns 

that major landslide-related failure was probable.

This survey indicates that seepage through an abutment 

has been the most common negative result of building a dam 

on a landslide. Seepage occurs through open joints and failure 

surfaces in rock and earth landslides, and through voids in 

more pervious landslide masses, such as rock falls and debris 

flows. When carried to the extreme, seepage could possibly 

lead to piping (particularly in loose granular materials) and 

possible dam failure; however, we found no case in which this 

has occurred as a result of a dam having been constructed on 

a landslide. More commonly, seepage has resulted in loss of 

water intended for irrigation or power production, thus resulting in project inefficiency and economic loss.

• There seems to be no clear indication as to which landslide types perform best or worst when used as an abutment or 

a foundation. In most cases, all landslide types have proven to 

be fairly stable, although slides in shales appear to perform the 

poorest. In contrast, all landslide types seem to be subject to 

possible seepage problems unless proper preventive or remedial measures are taken. In general, rock-fall deposits (such as 

talus) are pervious, and thus provide ready paths for seepage; 

however, some talus deposits include enough fine material to 

be relatively impervious. Thus, in regard to both stability and 

seepage, the physical characteristics of the individual landslides and the physical properties of the landslide materials 

should be carefully considered in the siting process for any 

dam in which a landslide will be part of an abutment or the 

foundation. Of particular importance in regard to seepage is 

the permeability of the landslide mass.

Acknowledgments

I would like to thank my many professional colleagues 

around the world who helped me by providing ideas and case 

histories for this study.

In the United States, special thanks go to the various 

State dam-safety agencies and Federal dam-building and damregulating agencies, who allowed ready access to their files on 

dams that have been built on landslides. The same degree of 

cooperation was extended by companies, irrigation districts, 

city water departments, and private parties, who own the dams.

Thanks also go to CAMBIOR (Canada) and Geotecnica 

Consultores (Chile), who provided funding for the early stages 

of the study, an expenditure that ensured its success.

I would also like to note the day-to-day help I received 

from colleagues in the U.S. Geological Survey, the U.S. 

Bureau of Reclamation, and the U.S. Army Corps of Engineers, as well as the services of the excellent technical libraries of these agencies.

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Published in the Central Region, Denver, Colorado

Manuscript approved for publication February 24, 2006

Page layout and cover design by Sharon M. Powers

References Cited  49
Appendix

Appendix  51
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

Algeria/ none/ 36.48N, 5.27E Iril-Emda/ Agrioun River Rockfill/ Hydroelec- tric 1954/ Govern- ment power company 76/575 160 Slide in schist Left abutment Rockfill dam substituted for concrete dam because of slide. “Dam built on a sliding section and in this case the dam “supports” landslide and drainage facilities are provided to raise up the stability.” (Tolmachev, 1994) Algeria/ Skikda/ 36.59N, 6.90E Zardezas/ Saf-Saf River Concrete gravity/ Irrigation 1948/ Federal government 64/242 31 Slide in sandstone Left abutment During construction, 100,000-m3 slide occurred in sandstone left abutment. Left end of dam was moved downstream to stable limestone body. Cylindrical wall was built in slide mass to allow construction of left part of dam. In 1970, dam height was raised from 40 m to 64 m. Part of the new dam rests on this cylindrical wall, and thus was built over the landslide. Stability of the new dam ensured by 500-ton anchor cables. Argentina/ San Juan/31.5S, 8.7W Quebrada de Ullum/San Juan River Earthfill/ Irrigation, hydro- electric, flood control 1981/ Provincial government 60/300 440 Rock slide Right abutment Bedding-plane slips at contacts between sandstone and claystone were probably caused by tectonic folding. However, during construction a 260,000-m3 rock slide occurred adjacent to the right abutment causing partial obstruction of the diversion channel. Remedial mea- sures: (1) buttress at toe of slide, (2) debris removed 

from river bottom, (3) excavation slope flattened, (4) grout curtain, (5) two rows of drains installed in right bank downstream of the dam.

Australia/South Australia/34.87S, 138.78E

Kangaroo Creek/ TorrensRiver

Rockfill/Water supply, flood control

1969/Government

64/131 19 Slides, 

boulders, loose slabs

Both abutment areas

In dam-site area, there are scars of two slides on left bank and one on right. Slides are “block-slide” type. Also, some scree and boulders. Because of slides, dam design changed from arch to rockfill. Most of slide material probably removed during construction, but some remains.

Australia/Victoria/37.70S, 145.82E

O’Shannassy/O’Shannassay River

Earthfill with reinforced concrete core wall/ Water supply

1928/ Municipal government

34/226 4.2 Debris 

slide

Right abutment

Right end of dam abuts extensive area of landslide debris (colluvium). Shears and slickensided surfaces were found in undisturbed samples of landslide debris. Concrete corewall was taken to bedrock.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state or 

province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative 

to dam Comments

Australia/Tasmania/41.66S, 146.22E

Parangana/Mersey River

Rockfill/Hydroelectric

1968/Hydroelectric commission

53/189 15 Thick

debrisavalanchedeposits in valley, talus on slopes

Foundation and both abutments

Thick (>50 m) debris-avalanche deposits associated with glacial advance form part of foundation. Talus forms part of surface of both abutments. Talus removed under dam core on both abutments. Talus fairly impermeable; however, extensive cement-grout fan through talus was included in design of both abutments.

Australia/Victoria/39.68.S, 145.29E

Sugarloaf/Sugarloaf Creek

Concretefaced rockfill/Water supply

1980/Rural water commission

85/1,050

100 “Old landslide” Right abutment Suspected old landslide on downstream right abutment confirmed by trenching. Minor down-dip movements a

left abutment due to past undercutting by erosion.

Australia/Victoria/37.85S, 146.40E

Thomson/ Thomson River

Rockfill/Water supply, irrigation

1983/Rural water commission

166/1,170

1,122 Dip-slope 

slides

Both abutments, right most serious

Most of slides in sedimentary rocks were removed during construction. Remaining disturbed rock stabilized by 2.6-million-m3 rockfill buttress. 

Australia/Victoria/36.06S, 148.27E

Tooma/Tooma River

Earthfillrockfill/Hydroelectric

1961/Hydroelectric authority

67/305 28 Sliding on 

joints in granite

Both abutments, right the most serious

Because past slope movements were not recognized before construction, there was extra cost for (1) rockfilbuttresses, (2) dental work on open joints, (3) addition of downstream grout curtain, and (4) rezoning of embankment.

Australia/Western Australia/ 32.20S, 116.06E

Wungong/Wungong Brook

Earthfill–rockfill/Water supply

1979/City water corporation

65/460 60 Landslide Right 

abutment

During construction, landslide was reactivated. Stabilized by addition of rockfill buttress. Filter blanket placed over slide materials that were left in place under the rockfill.

Austria/Tyrol/47.23N, 12.10E

Durlassboden/Gerlosbach

Earthfill/Hydroelectric

1966/Electric power company

83/470 53.5 Rock slide 

overlying talus

Rightabutment

Right abutment consists of a large block of graphitic schist and quartzite that had slid down valley wall into valley deposits of glaciofluvial sands and gravels and lacustrine silts. Foundation and abutment sealed by double-row grout curtain extended 50 m into valley sediment.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments Austria/ Tyrol/47.12N, 11.87E Eberlaste (Stillup)/ Zemm River tributary Earthfill/ Hydro- electric 1968/ Electric power company 28/480 8.2 Rock fall (talus) Sides of foundation Foundation is talus interfingered with alluvium. Asphalic-concrete impervious core continuous with slurry-trench cutoff into talus/alluvium to depth of 52 m. In addition, ~50-m-wide stabilizing fill was buil

as a buttress at downstream toe of dam. 

Austria/ Carinthia/ 46.52N, 14.47E Freibach/ Drau River tributary Rockfill/ Hydro- electric 1958/Electric power company 41/150 5.5 Rock slide inlimestone Left abutment Concrete diaphragm constructed through slide. During reservoir filling, diaphragm leaked. Grout curtain added, but leaked. Second grout curtain successfully added, supplemented by sealing with chemical materials. Austria/ Tyrol/46.95N, 10.75E Gepatsch/ Faggenbach River Rockfill/ Hydro- electric 1965/Electric power company 153/600 140 Rock fall (talus) Left abutment “On the left slope the rock is covered with a layer of talus and redeposited boulder clay up to 25 m thick” (Lauffer and Schober, 1964). “Mass movement was seen to occur on the left valley slope already during first partial filling. Thorough investigation and model studies proved this to be the reactivation of an old rock 

slide” (Simmler, 1977, p. 120). Apparently, the only material removed was in the upstream zone of the dam foundation/left abutment.

Bolivia/Tarija/21.7S, 64.8W

San Jacinto/Tolomosa River

Concrete arch/Irrigation, hydroelectric, recreation

Under construction(1998)/Electricpowerconsortium

49/100 54.3 Wedge

failure,topple

Leftabutment

Landslide in slate, sandstone, and overlying lacustrine sediments is one of several along left valley wall. Reactivated during construction. Left abutment rebuilt by filling adits with concrete.

Brazil/Paraíba/6.89S, 38.39W

Engenheiro Avidos (Piranhas)/Piranhas River

Zoned rockfill/Irrigation, water supply, flood control

1936/Federalgovernment

47/359 255 Block

slump,talus

Bothabutments

Right abutment is weathered-gneiss block slump; left abutment is talus. Both are fairly impervious; howevertoe-drain system was installed on each abutment.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state or 

province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

Brazil/Sao Paolo/21.60S, 46.95W

Euclides da Cunha/Pardo River

Earthfill/Hydroelectric

1960 (rebuilt 1977)/Electric power company

92/312 13.4 “Ancient 

landslides”

Both abutments

“Ancient landslides” in form of clayey “residual talus” found at both abutments. Cutoff trenches filled with impervious soil were placed through talus, followed by grocurtains placed through the trenches. Dam failed at right end in 1977 due to flood ovetopping. Slide material at right abutment mhave been factor.

Bulgaria/Plovdiv/42.04N, 24.47E

Krichim/Vacha River

Concrete buttressgravity/Hydroelectric

1972/ Government 105/269 18 Rock slide Right abutment “Ancient” rock slide (80 m thick; total vol

ume: 10.5 million m3) in gneiss and marbl

extends along the valley wall from 500 m above dam to river bottom.

Canada/

British Columbia/49.98N, 123.15W

Cheakamus/Cheakamus River

Earthfillrockfill/Hydroelectric

1957/ Electric power company

28/683 52.4 Debris 

avalanche–debris flow

Most of foundation

Foundation is “Rubble Creek Wash,” a debavalanche–debris flow that occurred in 18556. Permeability and stability of this materwere studied before construction. Dam has functioned well. Greatest hazard may be slight possibility of another avalanche–flow occurrence, sending wave over top of dam

Canada/ Saskatchewan/

51.27N, 106.88W

Gardiner/SouthSaskatchewanRiver

Earthfill/Irrigation,water supply,hydroelectric

1968/Provincialgovernment 

69/5090 9,867 Massive 

slump in shale

Leftabutment area

Large-scale prehistoric slide in shale of lefabutment. Local failure during constructioled to removal of much of unstable shale under central zone of dam. Extensive bermadded and abutment slopes flattened.

Canada/Quebec/

50.9N, 66.9W

Sainte Marguerite3/Sainte Marguerite River

Earthfillrockfill/Hydroelectric

1998/Electric power company

171/378 Not 

known

Rock fall (talus) and rock slide

Left abutment, left foundation, right abutment 

Core of dam is in excavation to gneiss bedrock. Under left dam shell, talus was consiered to be acceptable as foundation and wanot removed. Large right-abutment slide mmostly left in place during construction; msettled <15 cm under weight of >40 m of f
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

Canada/British Columbia/ 49.44N, 122.97W Seymour Falls/ Sey- mour River Earthfill- concrete/ Water supply 1961/City water district 30/457 25.3 Debris- flow cone Right abutment Debris-flow cone from tributary stream for

right abutment of embankment dam. Impervious upstream blanket prevents seepage through debris cone. 

Chile/VII Region/ 36.17S, 71.25W Bullileo/ Bul- lileo River Earthfill/ Irrigation 1949/ Irrigation association 70/260 60 “Great slide” Left abutment Very large slide in moraine deposits forms 

abutment. Dam has had piping problems in moraine of right abutment (1982), but no dficulty with left abutment. 

Chile/V Región (Valparaíso)/ 32.97S, 70.25W Los Leones/ Los Leones Stream Earthfill/ Mine tailings disposal 1998 (final stage)/ Mining company 160/500 Not known Debris slide, earth slide Right abutment Slide not recognized originally; however, it has had no effect on dam performance. Thu

no remedial measures installed. 

Chile/Santiago Metropolitan Region/33.65S, 70.08W

Yeso/Yeso River

Earthfill/Water supply

1967/Local 

government

61/350 250 Debris 

flow androck fall

Both abutments (?)

Unacceptable seepage through both abutments. Extensive cement grouting in 1979–Debris-flow materials probably also presenfoundation.

China/Yunnan/26.25N, 103.15E

Hunshui Gully debrisretention dam #4/Hunshui Stream

Stone and concrete/Debris retention 

1978–81(?)/District government

16/Not known

Not 

known

Debris flow

Entire foundation

Debris-retention dam #4 is one of a series bfrom 1978 to about 1981 to retain debris-fldeposits in Hunshui Gully. Present status nknown.

China/Anhui/31.66N, 115.88E

Meishan/Shihe River

Concrete multiple arch/Flood control, irrigation,hydroelectric

1956/Government

88/443 2,275 Rock 

slide along joints in granite

Right abutment

In 1962, movement occurred along joints in right abutment. Apparently, these joints had shown some movement before constructionRemedial measures: (1) grout curtain, (2) impervious membrane upstream of right abment, (3) anchors, and (4) buttresses.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

China/Yunnan/near Sichuan border

Wuping/Papa River

Rockfill/Hydroelectric

Under construction/Government

49/215 49.9 Earth slide Right 

end of foundation

Slide deposit (volume: 1.2 million m3) is in right end of foundation. Remedial measure(1) 14-m-high rockfill platform constructeon slide as preload, (2) vertical rock piles inserted through slide deposit.

Cyprus/Limassol/34.72N, 32.99E

Polemidhia/Garyllis River

Earthfill/Irrigation

1965/Government

45/196 3.9 Rock 

slide, rock fall

Left abutment

Left abutment consists of limestone and chrock slide–rock fall blocks. Permeability olandslide material led to installation of grocurtain.

Czech Republic/South Moravia/49.12N, 16.16E

Dalešice/Jihlava River

Rockfill/Hydroelectric,water supply, irrigation

1979/Government

100/330 127.3 Rock slide Right abutment Construction caused 150,000-m3 reactivati

of rock slide in amphibolite zone of right abutment. Slide stabilized by (1) rockfill btress at toe of slope, (2) unloading of uppepart of slide, and (3) use of rock anchors.

Czech Republic/North Bohemia/50.36N 13.42N 

Nechranice/Ohre River

Earthfill/Flood control, hydroelectric, irrigation,recreation, water supply 

1968/Government

52/3,280

287.6 Slides in 

claystone

Right abutment Pleistocene bank erosion had caused slides 

depth of 15 m in claystone of right abutmeAngle of slope immediately upstream of riabutment flattened to increase stability. Imvious clay-cement cutoff installed though right abutment to reduce seepage. 

Czech Republic/North Moravia/49.90N, 17.57E

Slezska Harta/MoraviceRiver

Rockfill/Water supply,flood control

1997/Government

65/540 217.5 “Ancient” 

slides in shale and basalt

Both abutments During construction, movement occurred i

shale slide of left abutment and creep in bablocks of right abutment. Remediation: (1) excavation of upper left slope, (2) buttress toe of left slope, and (3) surface/subsurface drainage. 
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

Czech Republic/ North Moravia/ 49.77N, 18.52E Terlicko/ Stonávka River Earthfill/ Water supply, flood control 1962/ Government 28/617 24.4 Slide in clay shale Right abutment Right abutment is in toe of huge clay-shale sl

Chemical and cement grout curtains placed. Sity increased by construction of buttress on riside. Movement continues (as of 1996). 

Czech Republic/ North Moravia/ 49.73N, 18.45E Zermanice/ Lucina River Concrete gravity/Water supply, flood control 1958/ Government 37/617 27.2 Slide in flysch Right abutment Slide of entire hillside of clay shales with lay

sandstone and weathered teschenite. Reactivaduring construction. Right abutment continueslowly deform by bulging. 

Ecuador/Azuay/ 2.68S, 78.63W Daniel Palacios 

(Amaluza)/Paute River

Concrete archgravity/Hydroelectric

1983/Federalgovernment

167/420 120 Rock slide Left 

abutment

Reactivation during construction; probably patoe of large prehistoric slide in decomposed gdiorite. Remedial measures: (1) active part reand (2) concrete beams with prestressed anchplaced at the abutment. 

Ecuador/Guayas/1.0S, 79.8W

Daule Peripa/Daule River

Earthfill/Irrigation, flood control, water supply, hydroelectric 

Uncertain (under construction in 1988)/Government

78/246 6,000 Small 

shale slide due to stress relief

Right abutment

Reactivation of slide during construction. Bloof tuffaceous sediments slid on sheared shale Cracks were filled with concrete and additionfilters were placed. 

France/Corrèze/45.41N, 2.49E

Bort/ Dordogne River

Concrete gravity arch/Hydroelectric

1951/Hydroelectric company

131/390 477 Bedding 

plane slips in gneiss and schist

Both abutments

Bedding-surface slips formed weak clay layebetween gneiss and underlying schist beds. Dconstruction, a slide of several thousand cubimeters occurred in left abutment; slide area wbridged by concrete arch. Right abutment: zocrushed material removed and replaced by reiforced concrete.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

France/Basse Alps/43.85N, 6.54E

Chaudanne/Verdon River

Concrete thin arch/Hydroelectric

1952/Federal government hydroelectric company

71/95 16 Rock slide

on joints

Right abutment

During construction, a limestone block (vol. ~1,200 m3) broke off along steeply-dipping, pre-existing fault, and was removed. Another 4,000 m3 was stabilized by rock anchors, concrete buttress, and cement grout.

France/Hautes Alpes/44.46N, 6.24E

Serre-Ponçon/ Durance River

Earthfill/Hydroelectric, irrigation

1960/ Electricité de France

129/600 1.2 Talus 

(scree)

Both abutments and foundation

Large deposit of talus interbedded with alluvium was left in place in foundation of righend of dam. Seepage prevented by injection oimpervious cutoff to bedrock. 500,000 m3 of scree removed from left abutment.

Greece/Sterea Hellas/ 38.66N, 21.87E

Evinos/ Evinos River

Earthfill/Water supply

1998/Government

124/640 113 Slide in 

colluvium and weatheredflysch

Just above left abutment

Abutment excavation reactivated part of large slide in left abutment immediately upstream from spillway entrance, barely in contact witdam. Remedial measures: (1) pumping wells(2) replacing part of sliding surface with freedraining material, and (3) removing part of upper slide.

Greece/Fokis/38.53N, 22.12E

Mornos/Mornos River

Earthfill/Water supply

1979/Government

126/815 780 Rock slide Right 

abutment

Pleistocene rock slide (vol. ~25 million m3) iat right end of dam. Dam acts as buttress, and toe buttress (8 million m3) was installed alonreservoir shore.

Greece/West Macedonia/40.30N, 22.10E

Polyphyton/Aliakmon River

Rockfill/Hydroelectric

1974/Government

112/640 1,939 Slide in 

colluvium and gneiss

Both abutments

Several slides in area. Left-bank downstream slide barely contacts toe of dam. Alexis slide (20 million m3) lies directly above right abutment but is not in contact with dam because design was adjusted to remove vital structurefrom slide area. Surface drains and drainage adit added. 
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

Greece/East Macedonia/ 41.3N, 24.3E Thissavros/ Nestos River Rockfill/ Hydroelectric 1986/ Government 170/480 705 Slide in gneiss Not known During excavation, slide reactivation occur

Part of dam sits on slide mass in gneiss. Exremediation installed. Currently, no indicatmovement. 

India/ Uttar Pradesh/ 30.6N, 77.8E Ichari/ Tons River Concrete gravity/ Hydroelectric 1975/State government 59/155 14.3 Slide in slates and quartzites Left abutment Depth of slide debris in left abutment was 3

m. To stabilize left abutment: (1) reinforced concrete cutoff wall tied to sound quartzite and (2) 45-m-long concrete diaphragm ties sound rock. 

India/West Bengal/ 27.1N, 88.9E Jaldhaka Stage I/ Jaldhaka River Diversion wier/ Hydroelectric 1967/State government 18/98 Not known Rock and debris slides in schist and gneiss Right abutment “Huge rock-cum-debris slides occurred fro

right abutment during the 1964–66 monsoocovering the partly constructed intake struc(Roy, 1975). Remedial measures: (1) abutmwas “dressed” and benched at suitable inter(2) retaining and “breast” walls were constto prevent further slides, and (3) slide area grouted.

India/Himachal Pradesh/31.80N, 76.95E

Pandoh/ Beas River

Earthfill-rockfill/ Irrigation, hydroelectric 

1977/Federal government

76/411 41 Slump 

mass and shear zone in phyllite 

Both abutments

Proposed concrete dam changed to rockfill of slump mass (right abutment) and shear zabutment). Shear zone excavated to 3-m detrench backfilled with impervious materialaxis of dam moved upstream to prevent faiinto reservoir. Prevention measures: (1) 15-concrete cutoff through slump, (2) horizontsystem, and (3) buttressing by dam.

India/Himachal Pradesh/31.98N, 75.94E

Pong/ Beas River

Earthfill/ Irrigation, hydroelectric

1974/State government

133/1,950

8,570 Block 

glide in clay shale

Left abutment

Large, inactive slide in left abutment in victunnel intakes. Many open cracks (“glide cRemedial measures: (1) shallow unsound rmoved from core foundation, (2) concrete cinstalled as “keys,” and (3) toe buttresses inat river level.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

India/Rajasthan/24.93N, 75.56E

Ranaptrap Sagar/ Chambal River

Masonry/ Irrigation, hydroelectric

1967/State government

58/1,143

290 Slumps in 

shale

Left abutment

Deep-seated slumping in shale and cracking sandstone. Remedial measures: (1) flattening slopes, (2) clay blankets with filters, (3) area grouting, (4) anchors, (5) retaining wall, and drainage. 

India/Jammu and Kashmir/~32.8N, 74.8W (near Dyangarh)

Salal/ Chinab River

Rockfill/ Hydroelectric

1986/State government

118/630 1.5 Deepseated 

rock slump in dolomite

Right abutment

“...the right abutment...has a deep seated huge slump of rock overlain by thick cover ooverburden” (Sen and others, 1987). Treatmeof abutment: (1) removal of slump mass in cocontact area, (2) areal and curtain grouting, (concrete cutoff, and (4) “wrap around” of cormaterial covering the slump zone.

Iran/Khuzestan/32.3N, 48.9E

Upper Gotvand/ Karun River

Rockfill/ Hydroelectric

Under construction (2004)/ Government power company

170/760 4,500 Right 

abutment: rock topple; left abutment: rock slide 

Both abutments

Both abutments include dislocated rock massin Bakhtyari Fm. (conglomerate). Right abutment mass apparently is a rock topple; dislocated left-abutment mass is a rock slide.

Italy/Sicily37.83N, 14.58E

Ancipa/ Troina River

Cellular concrete gravity/Irrigation, hydroelectric 

1953/Government 105/253 30.4 Thick talus Foundation and right 

abutment

“...bottom and right shoulder are covered witalus.” Concrete diaphragm 4 m thick sunk through talus to bedrock at right abutment.

Italy/Val D’Aosta/45.63N, 7.06E

Beauregard/ Dora di Valgrisenche

Concrete arch-gravity/ Hydroelectric

1960/Government 132/394 74 Slide in schist Left abutment Large slide in mica schist moved onto alluviu

During first filling of reservoir the landslide accelerated, attaining a displacement rate of 20 mm/month producing cracks in lower thirof the dam. Glaciofluvial sediments from deep pocket under slide had to be replaced by concrete. Also, water-tight membrane placed cement injection.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

Italy/Umbria/ 43.16N, 12.60E Casanuova/ Chiascio River Earthfill/ Irrigation, water supply 1994/Irriga- tion district 88/444 224 Trans- lational slide Right abutment Slide is 70–80 m thick. Water level increase i

reservoir during construction (1991) caused 2lion-m3 slide reactivation. Remedial measure

reduced rate of reservoir filling and (2) instalphysical remediation. 

Italy/Reggio Emilia/ 44.29N, 10.37E Ozola/Ozola River Concrete mul- tiple arch/ Hydroelectric 1929/Govern- ment 25/96 0.061 Slide in thick talus Left abutment Concrete cutoff at left abutment was sunk thr

39.5 m of talus by means of superimposed tu

Italy/Trentino A. Adige/ 46.30N, 10.68E Pian Palù/ Noce Torrent Concrete blocks/Hydro- electric 1959/Govern- ment 52/180 16.1 Deep- seated slump Left abutment Deep-seated rotational slump (sackung?) in m

schist. To avoid consequences of possible moment of abutment, dam type was chosen consof concrete blocks separated by sand. Concreoff wall placed to depth of 30 m in landslide of left abutment during construction. 

Italy/Reggio Emilia/43.88N, 12.09E

Quarto sul Savio/Savio River

Concrete gravity/Hydroelectric

1925/Government 21/59 6.67 Landslide in flysch Left abutment Dam was built partially on 1812 natural land

dam derived from clayey sandstone. A few yeafter construction, problems occurred in opergates of the dam.

Italy/Modena/44.27N, 10.73E

Riolunato/ Scoltenna River

Concrete multiple arch/ Hydroelectric

1920/Government 27/90 0.06 “Mass- flow” Right abutment Monitoring from 1979–93 indicated total cre

right abutment of 17 cm toward the dam. Theis no failure surface; therefore, authors classimovement as “flow.” Probably continuation odam movement.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

Italy/Sicily/37.96N, 13.37E

Rossella/ Rossella River

Earthfill/ Water supply, irrigation

1965/Irrigation district 27/336 17.2 Earthflow in clay 

shale

Left abutment

Pre-existing earthflow in flysch of the left abument was reactivated during construction in 1In 1997–98, sudden reactivation again occurrcausing cracks in cutoff wall at dam toe and displacements on dam crest. Remedial measulowering reservoir level. Monitoring programinclinometers, piezometers, and topographic monuments.

Italy/Tuscany/44.08N, 10.77E

Sperando (Tistino)/ Lima River

Concrete gravity/Hydroelectric

1929/Government 34/112 0.4 Landslide Left abutment Lower half of left abutment consists of landsl

deposits. Probably part of the 1818 Lizzano lslide. Apparently stable at present. 

Italy/Sicily/37.70N, 12.76E

Trinità/Delia River

Earthfill/Irrigation, water supply

Irrigation district/Not known

30/322 18 Earth 

flow–earthslide

Left abutment

Existence of earth flow–earth slide was knowduring construction. Thus, spillway was built piles. In 1965 and 1981, landslide reactivateddamaging caretaker’s house, but not dam or atenant structures. Landslide still active. Instrutation is being added.

Italy/Veneto/46.41N, 12.25E

Vodo/Boite River

Concrete domed-arch/ Hydroelectric

1960/Government 42/74 1.39 “Alluvial landslides” Left abutment Diaphragm, consisting of overlapped piles in 

forced concrete, contacts left abutment, whicis described as “morainic materials and alluvlandslides.” Bentonitic slurry aided excavatiodiaphragm.

Japan/Saitama/36 N, 139E

Futase/Ara River

Concrete arch/Multipurpose, irrigation, hydroelectric

1962/Federal government

95/289 26.9 Slide Left 

abutment

Slide in phyllite, sericite, and schist of the lefabutment occurred during construction (mid-ruary 1958). Remedial measures: (1) piling, (underground drainage, and (3) a buttress. Dam eventually completed.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

Japan/Ishikawa/ 36.02N, 136.76E Jinnosuke #5 sabo dam (new dam)/ Tedori River Concrete grav- ity/Debris- flow retention 1925 (original dam)/ Government 22.5/ ~50 Not known Deep- seated slide Entire foundation Largest of more than 50 sabo dams built on p

existing slide (Jinnosuke-dani) in altered sanshale, and rhyolite (entire gully is moving). Toriginal Jinnosuke #5 dam (height:17 m) has about 5 m since 1925 and was recently rebuiNew Jinnosuke #5. There are several other din the valley that are 10 m high or higher (noJinnosuke #3,~18 m, and Jinnosuke #6,~13 mthough these dams are slowly moving, all are cessfully performing their debris-retention fu

Japan/Niigata/ 37.5N, 138.9E Kassa/ Kassa River Rockfill/ Hydroelectric 1978/Electric power com- pany 90/487 13.5 Volcanic mudflow Left abutment Most of left abutment consists of “low-ceme

volcanic mud-flow deposit.” Entire foundatiosubjected to shallow grouting (~1,500 m3 of After grouting, top 2–3 m of mud flow was r

Japan/Tochigi/36.7N, 139.5E

Kawamata/Kinu River

Concrete arch/ Flood control,hydroelectric,irrigation

1966/Federal government

117/137 87.6 Rock 

fractures and shear zones

Abutment “....rock strata were permeated by fractures 

failure zones, and could not be relied upon to the stresses transmitted by the dam unless spmeasures were adopted” (Hobst and Zajíc, 1392–394). Prestressed anchors were used to load-distribution wall to the rock face.

Japan/Fukushima/ 37.5N, 140.0E

Ouchi/Ono River

Earthfill/Hydroelectric

1988/Electric power company

102/340 18.5 Mud flow Left 

abutment and left end of foundation

Pre-existing mud-flow deposit, derived from canic tuffs upstream, was removed at cutoff tand partially moved upstream (replaced by roHowever, deposit was left in place beneath thdownstream part of the dam.

Japan/Tochigi/36.8N, 139.9E

Terayama/Miya River

Rockfill/Flood control, irrigation

1984/ Prefecture government 62/260 1.2 Rock fall (talus) Right abutment Surface of right abutment covered by talus. A

dial measure, talus layer was covered by an “blanket.” Curtain grouting performed througend of blanket.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state or 

province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

Kazakhstan/None/43.16N, 76.90E

Debris-flowretention dam/Bolshaya AlmaAtinka River

Cellular reinforced concrete/Debris-flowretention

~1982/Government

40/422 14.5 Debris 

flows

Foundation This debris-flow-retention structure was built 

on pre-existing debris flows with no loss of function. It is meant to control debris flows thoften occur on the Bolshaya Alma-Atinka Rivupstream from Almaty.

Kazakhstan/None/43.20N, 76.99E

Medeo/Malaya Alma-Atinka River 

Earthfill/Debris-flowretention

First dam: 1969; additional higher dam: ~1975–80/ Government

150/530 Useful 

retention 

capacity

12.6

Debris flows

Foundation Original 110-m-high dam was built on debrisflow base as an explosives-charged “landslide

dam. “Reservoir” was nearly filled by 1973 debris flow. Additional height added after 197as a conventional earthfill dam. Dam serves function well; bedrock foundation is not need

Mexico/Durango/36.02N, 136.76W

Francisco Zarco (Las Tórtolas)/Nazas River 

Earthfill/Irrigation, flood control

1969/Government

40/480 438 Talus with 

landslide blocks

Both abutments

Talus deposits, as well as limestone blocks, arfound on both abutments. Impervious slurry trench 3 m wide and 20 m deep constructed through these materials. A 3-line grout curtain was placed from bottom of trench.

Mexico/Durango/24.61N, 103.31W

Los Naranjos/Santa Clara River

Earthfill/Irrigation, flood control

1985/Government

48/542 26 Landslide 

in pyroclastic rocks

Right abutment

Original site exploration inadequate to detect pre-existing slide. Reactivation of 2-million-mslide began in 1987. Immediate remediation: (controlled release of reservoir, (2) cement-bentonite grouting of cracks, (3) unloading of uppslide, and (4) permanent monitoring.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

Mexico/Jalisco/ 20.91N, 103.70W Santa Rosa/ Santiago River Concrete arch/ Hydroelectric, irrigation(?) 1963/ Government 114/150 400 “Buried” landslide Both abutments Old slide in right abutment underlies volcanic mud flow (lahar). Highly jointed rhyolite of left abutment was covered by “large rock falls” (removed?) (Castilla and Colina, 1985). Durin

1970s, minor progressive rock-wedge move- ments occurred, triggering additional rock fallIn 1981, rate of movement increased. Remediameasures: (1) rock anchors, (2) drains, and (3) gunniting. 

Mexico/ Tamaulipas/ 23.96N, 98.66W Vicente Guerrero/ Soto la Marina River Rockfill/ Irrigation, water supply, flood control 1971/ Government 63/423 3,900 Talus Right abutment Talus on abutment had 6-m maximum thicknes

Impervious clay core and sand/gravel transitiozones were founded on limestone bedrock abument after talus was removed from under these zones. Apparently, dam shell (about one half odam width) was placed on talus and weathered rock. No significant seepage has been noted.

Morocco/Fez/33.93N, 4.67W

Aït Youb/Sebou River

Earthfill/Hydroelectric

1990/Government

66/Not known

Not 

known

Ancient landslide dam

Entire foundation and both abutments

Entire valley filled with landslide. Upstream andownstream cofferdams (on landslide) served as buttresses. Other remedial measures: (1) removed part of landslide, (2) added rock buttresand (3) added downstream drainage.

Morocco/Tetouan/35.44N, 5.40W

Nakhla/Nakhla River

Rockfillearthfill/Water supply

1961/Government

46/240 5.7 Large 

landslide in flysch

Left abutment

Large sandstone/shale slide overlying permeaballuvium was overlooked in pre-construction geologic investigation. Remedial measures to reduce seepage: (1) grout curtain, (2) buttresse(3) impervious diaphragm along dam axis, and (4) drainage gallery. Methods were successful, but extra cost was large.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam

Comments

Morocco/Not known/34.97N, 3.81W

Saddle Dam F, Mohamed B. A. el Khattabi/ Neckor River

Earthfill/Irrigation, water supply

1981/Government

~16/Not known

33.6 Landslide Foundation Upon attempted filling of reservoir in 1981

springs occurred downstream. Series of dowstream relief wells were installed.

New Zealand/Otago/45.19S, 169.35E

Clyde/Clutha River

Concrete gravity/Hydroelectric,irrigation

1989/Power company

75/490 320 Dip-slope 

rock slide in schist

Right abutment

Ancient rock slide in schist (vol. ~60 milliom3) encroaches on right abutment. Lower slsuccessfully stabilized by buttressing action dam and by berm placed along right reservoshore beginning at dam face.

New Zealand/East Coast/37.34S, 175.79E

Golden Cross tailings dam/Tributary Waitekauri River

Earthfillrockfill/Mine tailings storage

1997/Gold mining company

40/~400 5 Dip-slope 

slide in soft volcanics

Entire foundation and both abutments

Tailings dam was constructed on pre-existin90-million-m3 slide in weak volcanic rocksa result of filling tailings pond and removal part of toe of landslide, slide was reactivateRemedial measures considered: (1) drainagand (2) massive toe buttress. Golden Cross currently closed because of low value of go

New Zealand/East Coast/37.34S, 175.79E

Union Silt tailings dam/Tributary Waitekauri River

Earthfill/Silt control in mine area

1997/Gold mining company

13/~350 0.06 Dip-slope 

slide in soft volcanics

Entire foundation

Silt-retention dam was constructed on pre-eing 90-million-m3 slide in weak volcanic ro(same slide as Golden Cross tailings dam). Remedial measures considered: (1) drainagmassive toe buttress. Golden Cross mine curently closed because of low value of gold.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

Papua New Guinea/Eastern Highlands/ 6.25S, 145.98E Yonki/ Ramu River Earthfill/ Hydroelectric 1991/ Government 60/680 332 Slump in stiff, fissured clay Left abutment During construction in 1987, a significant s

occurred in downstream left abutment of davestigation showed that slide was a reactivaDesign of dam modified to include upstream downstream berms that act as abutments. 

Peru/ Huancavelica/ 12.7S, 74.5W Tablachaca/ Mantaro River Concrete grav- ity/ Hydroelectric 1972/ Government 80/180 16 Slump in phyllite and col- luvium Right abutment Part of deep-seated slump (‘Derrumbe no. 5”) at right abutment reactivated by reservo

Active part is only 30–50 m from right end dam. Movement very slow. From 1982–84, following costly remedial measures were sucessfully added: (1) 467,000-m3 toe buttresrock anchors, and (3) radial, horizontal, and drains. In 2003, abutment area began showinew distress. 

Poland/Bielsko Biala/49.65N, 19.21E

Tresna/Sola River

Earthfill/Flood control,water supply, hydroelectric,recreation

1967/Government

37/312 102.7 Rock slide 

in sandstone and shale

Left abutment

Large sliding wedge (~100,000 m3) moved slickensided surface during construction. Mof wedge remains in place. Remedial meas(1) concrete retaining block and wall, (2) totress, (3) prestressed anchors, and (4) drainupper part of slide. 

Poland/Bielsko Biala/49.6N 18.8E

Wisla-Czarne/Vistula River

Earthfill/Flood control, water supply

1974/Not known

37/271 4.5 Rock slide 

in shale and sandstone

Right abutment

“At the right side abutment, the huge, presently not active landslide is supported by thbody of the dam” (Dluzewski and others, 2Inclinometers and piezometers installed in abutment to monitor possible activity.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

Slovakia/None/ 48.63N, 17.71E

Čerenec/ Holeska River

Earthfill/Multipurpose

1964/Not known

10/280 1.7 “Ancient” 

landslide in clay and sandstone

Right abutment

After construction, seepage occurred through pervious materials in the foundation (not relato landslide). Remedial measures added to dto increase stability and reduce seepage: (1) earth berm on downstream side of dam and (drainage wells.

Slovakia/Central Slovakia/49.10N, 19.45E

Liptovská Mara/Váh River

Earthfill/Hydroelectric, flood control, water supply

1976/Government

53/1,250

360 Numerous earth 

flows and slides

Right abutment

Dam designed so that abutment lies between two slides/flows. Largest, only 150 m upstrefrom dam axis (but immediately adjacent to edge of dam), stabilized by 700,000-m3 sandgravel buttress. Smaller slide separated from downstream edge of dam by fill. Dam system stable.

South Africa/Western Cape/33.81S, 19.08E

Wemmershoek/Wemmers River

Rockfill/Water supply

1957/City government

53/488 58.8 Talus Both 

abutments

Layers of talus were encountered along loweslopes of both abutments. During excavation core trench, talus became unstable due to wanecessitating drainage ditches. Talus removefor core trench.

Spain/Castellón/40.2N, 0.6 W

Arenós/Mijares River

Rockfill with clay core/Irrigation

1978/Government

107/428 137.7 Rock fall 

and slides

Both abutments

Slides and rock-fall blocks were removed fosupport of clay core and upstream filters. In 1982 and 1987, large slides occurred near lefabutment. Slides were stabilized and anchoreConstant surveillance since.

Spain/Valencia/39.25N, 0.95W

Cortes de Pallás/Júcar River

Concrete archgravity/Hydroelectric

1989/Hydroelectric power company

112/312 116 Rock 

slide in limestone and marl

Left abutment

Large rock slide (vol. ~5 million m3) barely makes contact with left end of dam. Remedition: 800,000 m3 excavated from upper part olandslide and moved to lower part to form beApparently successful.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

Spain/Cordoba/ 37.27N, 4.40W Iznajar/ Genil River Concrete gravity/ Irrigation, hydroelectric, water supply 1969/State government 122/407 980 Rock- block slide in limestone Foundation “The geology of the dam site....is compose

slided [sic] limestone blocks....” (Bravo, 19“Special drainage” measures were installed insure stability. 

Spain/Granada/ 36.87N, 3.47W Rules/ Guadalfeo River Concrete arch-gravity/ Irrigation, water supply, hydroelectric` Under con- struction (1996)/ Federal gov- ernment 130/610 117 Surficial and deep- seated slides Mainly left abutment Surficial slides reactivated by road cuts, etc

seated slide in phyllite of left abutment is dbut could be reactivated. Impervious concrecutoffs installed in lower parts of both abut

Spain/Navarra/ 42.61N, 1.17W Yesa/ Aragón River Concrete gravity/ Irrigation, 

hydroelectric, water supply, 

1960/Government

77/398 471 Slide Right 

abutment

“Its right abutment leans on a slide zone, wcaused very important delays and extra exp

Switzerland/Berne/46.4N, 7.3E

Arnensee(d’Arnon)/TscherzisbachRiver

Earthfill/Hydroelectric

1942–56/Power company

17/140 10.5 Rock slide Entire 

dam

Small dam on tributary of the Sarine River founded on a natural rock-slide dam. Becauseepage through the foundation, in 1968–64-m-wide cement-clay grout curtain was ininto foundation to a depth of 5 m. 

Switzerland/Graubünden/46.51N, 9.63E

Marmorera (Castilleto)/Julia River

Earthfill/Hydroelectric

1954/Local power company

91/400 62.6 Talus 

deposit

Left abutment

Left side of dam rests on large pervious tal(mainly serpentine detritus, 70 m thick) unby alluvium and moraine. Three different trments: (1) concrete diaphragm into alluviuraine, (2) grout curtain (colloidal clay and cin talus, and (3) grout curtain in upper bedr
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river

 or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

Switzerland/Glarus/46.7N, 9.8E

Rhodannenberg (Klöntal Reservoir)/Löntsch River

Earthfill/Hydroelectric

1910/Local government

27/217 56.4 Rock slide Entire 

dam

Small dam constructed on natural rock-slide dam to gain additional power head. Consideseepage through rock-slide foundation. Jet ging was considered but rejected because of hcost. Monitoring: (1) seepage measuring sysand (2) piezometers.

Turkey/38.52N, 30.71E

Selevir/ Kaliçay River

Earthfill/ Irrigation

Not known/ Federal government

31/470 62.8 Slide in 

decomposed schist and clay

Right abutment

Slide occurred in right abutment during contion. Outlet tunnel was moved away from abment and slide. Original outlet tunnel (affecby slide) serves as a drainage outlet. Fill plaat downstream portal as a buttress. Cutoff trwas changed to a concrete cutoff to increase stability.

United Kingdom/South Yorkshire/ 53.47N, 1.60W

Broomhead/Ewden Beck

Earthfill/Water supply

1934 (repair of 1929 failure)/County water authority

31/302 5.2 “Slip” in 

“grits and shales”

Left abutment

Beginning in 1924, hillside slip (caused by reservoir?) damaged valve tower and within a few years threatened overflow weir. Remedial measures: (1) surface-drain trench filled with free-draining rubble, and (2) removal o~300,000 m3 of material from the slide masIn 1930, 6 million kg of cement was injectereduce leakage. 

United Kingdom/Shropshire/52.64N, 2.53W

Devil’s Dingle/Tributary Severn River

Earthfill/Fly-ash disposal

Continuing construction/Electric power company

64/570 1.68 “Landslipping” in 

mudstone

Foundation Information obtained from foundation boreh

showed wider extent of pre-existing slip surthan previously thought. Thus, design of dowstream slope was flattened to increase stabilShallow slips in valley sides stabilized by trdrains.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United Kingdom/ Leicester/ 52.66N, 0.59W Empingham/ Gwash River Earthfill/ Water supply 1975/ Government water-supply authority 40/ 1,200 4.7 Camber- ing and valley bulging Foundation Construction showed pre-existing camberi

valley bulging in the “boulder-clay” (i.e., gtill) foundation. Cruden and Varnes (1996infer that a camber in periglacial soils may described as a “relict, complex soil spreadtopple.” No negative effects on dam found

United Kingdom/ Cheshire/ 53.2N, 2.1W Trentabank/ Bollin River Earthfill/ Water supply 1929/Local water-supply authority 23/245 0.59 Slide in sandstone and shale Both abutments and foundation Before construction, “grits” (soft sandston

shales had slid toward the valley. Slopes owere designed to be very flat to prevent fudisturbance. 

United Kingdom/ Derbyshire/ 53.50N, 1.84W Woodhead No.1/ Etherow River Apparently earthfill/Water supply Failed 1850/ Local water- supply authority Not known/ Not known Not known “Land- slips” Abutment in “steep-sided valley” “A dam was actually completed in landslip

material, but the leakage was so serious thwas abandoned ***”(Bromehead, 1936). 

United Kingdom/Derbyshire/53.50N, 1.84W

Woodhead No. 2/Etherow River

Earthfill/Water supply

1877/Local water-supply authority

29/140 5.4 “Landslips” Abutment Ancient slides in shale and sandstone expo

trench for concrete cutoff. “***a fresh site at hand [close to site of Woodhead No.1] wchosen,***, a good bottom in impervious was found. One end was again in a landsli(Bromehead, 1936). Problem partly overcotaking new heading into hillside.

United States/Alaska/55.43N, 131.67W

Lake Connell/Ward Creek

Concrete gravity/Water supply for pulp mill

1953/Private company

29/183 13.6 Rock slide 

in phyllite leaving overhang

Left abutment 

During construction, a rock slide occurred steep slope of left abutment, leaving an unoverhang. To remove overhang would havcaused a setback in construction schedule. overhang was underpinned with prestresseshoring, and volume of rock lost in slide wplaced with concrete, which became part o
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ Arizona/35.09N, 108.79W

Black Rock (Zuni)/Zuni River tributary

Earthfill-rockfill/Irrigation, recreation

1908/Federal government

36/238 3.22 Rock fall 

(collapse of basalt abutment), talus

Both abutments

Left abutment: continuing fall of basalt blocdue to piping of underlying alluvium. Right abutment: talus cover. Considerable seepage through both abutments. Remedial measurebeing considered: (1) covering basalt with impervious material, (2) grouting the basalt beds, (3) horizontal impervious blanket, and vertical cutoff trench.

United States/ California/37.13N, 121.93W

Austrian/Los Gatos Creek

Earthfill/Water supply

1950/Watersupply public utility

56/213 9.4 Slides in 

sandstone and siltstone

Right and possibly upper-left abutments

Right abutment consists of debris from largQuaternary slide. M7.1 Loma Prieta quake (1989) reactivated part of slide causing majdamage to spillway, which was rebuilt at lefof dam. Spillway relocation required removof large quantity of rocky landslide material from left abutment. Grouting in 1993 in botabutments.

United States/ California/37.06N, 121.08W

B.F. Sisk (San Luis)/San Luis Creek

Earthfill/Irrigation, hydroelectric, recreation

1967/Federal and State governments

116/5,669

2,540 Slide 

in clay slopewash and dam materials

Left abutment

During drawdown in 1981, slide occurred in “hard” clay slopewash of left abutment and passed through the upstream face of the damSlide moved about 20 m. Reservoir was not threatened. Remedial measures: (1) construof a “keyed” berm at upstream toe of dam a(2) reconstruction of face of dam.

United States/ California/34.29N, 118.18W

Big Tujunga No.1/Big Tujunga Creek

Concrete arch/Water supply, flood control

1931/County government

63/154 87 Massive 

granite blockslide

Right abutment

Controversy as to whether or not toe of largrock-block slide upslope from right abutmeis at the contact with end of the dam. Mortoand Streitz (1969) think it is; county geologsay it isn’t. Discussion is academic in that rabutment seems completely stable because large size of slide mass. Has been absolutelmovement. 
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ California/ 39.45N, 123.39W Brooktrails No. 3 North/ Willits Creek Earthfill/ Water supply, recreation, irrigation, flood control 1970/Private 14/117 0.6 Earth slide Left abutment There are several slides in vicinity of the da

In 1971, slide activity (reactivation?) damaretaining wall at spillway. Slope was rebuilRemedial measures: (1) slope reshaped and network of deep intersecting drains added. 

United States/ California/ 37.49N, 121.82W Calaveras/ Calaveras Creek Earthfill/ Water supply 1925/City government 75/366 163 Major slide in shale and sandstone Right abutment Disagreement as to existence of large slide 

right abutment. Nilsen (1972) mapped largslide. Kintzer (1980) stated slide was small was removed during construction. Field recnaissance by author from distance noted larslide still exists; however, slide is so large tposes no stability problem. 

United States/ California/34.37N, 119.33W

Casitas/Coyote Creek

Earthfill/Irrigation, water supply, recreation

1959/Federal government

102/607 354 Slide in 

sedimentary rocks

Lower right abutment

Landslide in shale, siltstone, and sandstone largely avoided by modifying axis alignmefinal design, only a small amount of landslitoe underlies downstream edge of embankmNo problems.

United States/ California/34.52N, 118.60W

Castaic/Castaic Creek

Earthfill/Water supply, recreation, irrigation, hydroelectric

1973/State government

125/1,585

450 Block 

glides in shale

Mainly in left abutment

Old slides, as much as 35 m thick, led to shdesign of dam axis to minimize effects. Hoever, considerable slide activity occurred dconstruction. Remedial measures: (1) partiremoval of slide material, (2) resloping of c(3) large toe buttresses, and (4) grouting. Sof unstable areas in left abutment conductelate as 1995.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/California/37.40N, 121.76W

Cherry Flat/Penitencia Creek

Earthfill/Water supply

1936/City government

18/70 0.86 Slides in 

sedimentary rocks

Both abutments Both abutments are in “blue clay,” formed 

sheared and decomposed Franciscan Fm. and sandstone. Remedial measure: left abucutoff trench was extended to firm materiaparently, there are no stability problems.

United States/California/37.12N, 121.55W

Coyote/Coyote Creek

Earthfill-rockfill/ Irrigation 1936/County water-supply 

district

43/299 30.2 Shale 

slide

Spillway area at right abutment

“Slide No. 2 appears to be, in part, a reactvated portion of an ancient landslide, moswhich was excavated during construction spillway.” Reactivation of this slide damagspillway. Drainage system was recommenreduce slide potential.

United States/California/37.81N, 122.00W

Danville/Offstream

Earthfill/Water supply

1961/Public utility district

23/233 0.06 Massive 

landslide complex in sedimentary rocks

Entire dam and reservoir

City water-supply dam and reservoir built Quaternary landslide complex (dimensionkm x 1 km). Thickness of slide under rese~30 m. No evidence of slide movement in sands of years, nor of lack of stability of d

United States/California/36.40N, 120.84W

Hernandez/San Benito River

Earthfill/Recreation, irrigation

1962/County government

38/290 39.2 Slide in 

shale and serpentinite

Left abutment Most landslide detritus (mainly serpentini

removed from under left abutment core treDental work where necessary. Left abutmeshells were founded on landslide materialloose material was removed. As of 1981 intion, minor slides adjacent to left abutmenactive, but dam was stable.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/lati- tude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ California/ 37.32N, 119.32W Mammoth Pool/ San Joaquin River Earthfill/ Hydroelectric 1959/ Private electric power company 125/250 152 Mainly rock fall Entire foundation Original valley bottom blocked by rock-fal

posits from sheeted granodiorite that impoua lake 2.5 km long. Boulders as large as 5,0m3. Remaining sheets were removed or bolto canyon walls. Cutoff trench constructed m through detritus to bedrock. Blocks at cutrench in valley bottom were broken up or removed, but were left in place under upstrouter shell. Pervious drain and filter zone pvent migration of fine material from embanment into voids in foundation. 

United States/ California/ 37.52N, 121.91W Mayhew Reservoir/ Offstream (downstream 

from Fremont)

Earthfill/Water supply

1962/Public utility district

16/255 0.022 Flow part 

of slumpflow

Entire foundation and reservoir

This rectangular dam/reservoir lies on toe oReservoir landslide, part of the Mission lanslide complex. Reservoir landslide is thougbe dormant. However, in 1994 reservoir-lindistress resulting from active landslide movment was observed on the eastern (upslopeof the dam. Recommended remedial measugravel-filled drainage trenches.

United States/ California/34.34N, 117.23W

Mojave/West Fork Mojave River

Earthfill/Flood control

1971/Federal government

64/670 194 Earth slide Left 

abutment

Small slide occurred in left abutment durinconstruction. Remedial measures: (1) two bto buttress abutment and (2) redesign left endam.

United States/ California/37.05N, 121.29W

North Fork (Pacheco Lake)/Pacheco Creek

Earth fill/Water supply, irrigation

1939/Public utility district

30/323 11.1 Slide in 

sandstone, siltstone, and shale

Left abutment

Entire left abutment area exhibited landslidtopography. Spillway excavation led to reacvation late in 1938. Area was drained and btressed. Movement again in 1966–67. Spillrepaired in 1967; still showed damage in 19Left abutment and spillway wall continue tunstable.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ California/34.34N, 118.40W

Pacoima/Pacoima Creek

Concrete arch/Flood control

1929/County government

111/195 11.4 Rockblock 

slide in banded gneiss

Left abutment

Large rock block, serving as thrust block for lof dam, recognized as possible problem durinand construction of dam. Stabilized by anchorNorthridge earthquake (1994) caused slump omm and horizontal displacement of 250 mm. Nremedial measures: (1) post-tensioned tendon system, (2) foundation/abutment grouting, and gunniting.

United States/ California/34.55N, 118.51W

St. Francis/San Francisquito Creek

Concrete gravity-arch/Water supply, irrigation

1926/City government

62/~400 47 Huge preexisting 

slides in schist

Left abutment

As reservoir approached capacity during first (1928), dam failed causing catastrophic flood drowned about 450 people. Cause of failure othought to be fault in right abutment. Howeverresearch indicated failure occurred as reactivaseries of Pleistocene slides in schist of left abu

United States/ California/34.16N, 117.78W

San Dimas/San Dimas Creek

Concrete gravity-arch/ Flood control, irrigation

1922/Countygovernment

40/104 2.28 Pre-existing rock 

slides

Both abutments

Slides in heavily jointed gneisses of both abutwere recognized before construction. Remediameasures: (1) dam shape modified, (2) foundagrouted, (3) 4,500 m3 of rock removed from uright-abutment slopes, and (4) steel tendons antensioned anchors installed. Now stable.

United States/ California/40.82N, 123.96W

Sweasey/Mad River

Composite concrete arch and earthfill/ Water supply

1936/City government

23/61 1.5 Slide in 

sandstones and shales

Left abutment

During construction, slide occurred in left abuFranciscan Group sandstones and hard, clayey Dam was redesigned from a full masonry arch composite section employing an arch dam acrchannel section, which abutted a massive concthrust block at the left end. An earthfill section connected the thrust block with the excavated abutment. Design height was also reduced abom. Dam was later breached because of siltatioreservoir.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province /latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ California/ 35.17N, 120.53W Terminal/ Tributary Arroyo Grande Creek Earthfill/ Water supply 1969/County public utility 16/168 1.34 Bedding- plane slide in shale Left abutment Preconstruction field studies found “old bu

landslide” in soft shale. Much of the slide wexcavated during construction. Additional provided by addition of 6.5-m-high upstreadownstream berms. 

United States/ California/ 40.80N, 122.76W Trinity/ Trinity River Earthfill/ Irrigation 1962/Federal government 164/792 3,400 Slides in sedimen- tary rocks and meta- volcanics Both abutments Slide at upstream right abutment removed 

construction. Large slide at downstream rigment was partially removed; closely monitremainder is adjacent to corner of dam, ending spillway stilling basin. Toe of third potslump is buttressed by left end of dam, and no threat. 

United States/ California/34.98N, 120.32W

Twitchell/Cuyama River

Earthfill/Irrigation, flood control

1958/Federal government

73/550 491 Slide in 

shale and siltstone

Left abutment

Downstream left margin of dam shell is bacontact with large landslide. No problems. ancient slides present on reservoir shore.

United States/ Colorado/ 39.10N, 107.88W

Atkinson/Atkinson Creek

Earthfill/ Irrigation, hydroelectric

1893/Federal government

11/229 2.5 Massive 

rock glide

Entire dam and reservoir 

Entire dam and reservoir are on Grand Meslide complex (mainly basalt on claystone, by glacial deposits). Seepage from both abhas been a continuing problem.

United States/ Colorado/38.82N, 107.45W

Beaver/Minnesota Creek tributary

Earthfill/Irrigation, fire protection,recreation

1958/Private 34/296 2.3 Shear and 

collapseof sedimentary rocks

Both abutments 

Abutments and foundation are composed ostone, shale, and coal. Coal has burned natureducing support for remaining layers, whifailed locally. Abutment leakage led to 199lation of 60-mil impervious liner at both endam.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position

 relative to 

dam Comments

United States/ Colorado/37.60N, 106.67W

Beaver Park/Beaver Creek

Earthfill/Recreation, fish, irrigation

1912/State government

35/133 7.2 Apparent 

rock slide

Right abutment

Abutment composed of badly fractured latitmapped as “landslide” by Hunter (1918), hastable, but has leaked considerably through years.

United States/ Colorado/39.08N, 108.03W

Big Beaver/ Bull Creek tributary

Earthfill/ Irrigation

1936/Private 11/55 0.25 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir on Grand Mesa lancomplex (mainly basalt on claystone, mantleglacial deposits). Seepage through foundatio1992. Continuing seepage both north and sothe dam.

United States/ Colorado/39.54N, 106.22W

Black Lake No.1/Black Gore Creek

Earthfill/Water supply, recreation

1939 (rebuilt 1995)/Local government

~18 (after raising)/122

 0.4(?) 

(conflicting

data)

Debris flow fromancient landslide

Right abutment

Original dam raised to ~18 m (including cut1995. Much of original landslide removed. Ctrench to sound bedrock. Grout curtain was to competent bedrock in foundation and righabutment.

United States/ Colorado/39.10N, 107.90W

Bonham/Big Creek

Earthfill/ Irrigation, hydroelectric

1900/Federal government

12/457 2.8 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir on Grand Mesa lancomplex (mainly basalt on claystone, mantleglacial deposits). Minor foundation seepage

United States/ Colorado/40.13N, 107.02W

Burnt Mesa/ S. branch of Hunt Creek tributary

Earthfill/ Irrigation

1957/Private 12/83 0.3 Slide in 

shale

Right abutment

Right abutment is in shale slide. In 1987, seoccurred in right abutment area. However, laslide generally has had no negative effect on 
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Colorado/ 39.05N, 107.85W Cedar Mesa/ Surface Creek Earthfill/ Irrigation 1944/Private 14/381 1.7 Massive rock slide Entire dam and reservoir Entire dam and reservoir on Grand Mesa landslide complex (mainly basalt on claysto

mantled by glacial deposits). “Blowout” (19in foundation at left abutment corrected by vnyl membrane; satisfactory performance sin

United States/ Colorado/ 39.67N, 105.70W Clear Lake/ South Clear Creek Rockfill/ Hydro- electric, recreation 1914/Public utility 12/55 0.6 Rock slide Entire dam foundation and both abutments Dam was built on landslide dam formed by r

slides and talus from both valley walls. Seepage and piping occurred through left-abutmetalus, resulting in “sinkholes” (1997). Remegrouting in talus. 

United States/ Colorado/39.27N, 107.72W

Currier #2/ Buzzard Creek

Earthfill/ Irrigation, fire protection, stock

1968/Private 13/112 0.5 Slide in 

shale and sandstone

Left abutment

Left abutment is in “young landslide,” which is in “state of metastable equilibrium” (Soul1988). In 1993–94, slide on left abutment encroached on emergency spillway; problem solved by diverting water from distressed arNo other problems.

United States/ Colorado/40.17N, 107.67W

D.D.&E. Wise (Aldrich Lake)/Hulch Creek diversion ditch

Earthfill/ Irrigation

1946/Private 12/104 1.8 Massive 

slide in shale

Entire dam and reservoir

D.D.&E. Wise Dam and its reservoir, AldricLake, are located on the eastern edge of a massive 13-km2 landslide in Mancos Shale. Landslide material has had no negative effecon dam or reservoir performance.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide

position 

relative to 

dam Comments

United States/ Colorado/39.04N, 107.95W

Eggleston/ Kiser Creek

Earthfill/ Irrigation

1949/Private 12/101 5.0 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir are on Grand Mesa landslide complex (mainly basalt on claystonmantled by glacial deposits). Very minor seeage; no serious problems.

United States/ Colorado/38.83N, 107.96W

Fruitgrowers/Alfalfa Run Creek

Earthfill/Irrigation, recreation

1939/Federal government

17/463 9.3 Apparent 

slide in shale 

Left abutment

Slow movement along gently dipping failure surface began in late 1990s. At present, Bureof Reclamation is trying to define and solve problem.

United States/ Colorado/39.04N, 107.68W

Goodenough #2/Leroux Creek tributary

Earthfill/ Irrigation, water supply

1928/Private 12/232 1.5 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir are on Grand Mesa landslide complex (mainly basalt on claystonmantled by glacial deposits). Minimal foundtion leakage at toe.

United States/ Colorado/39.00N, 108.04W

Granby #12/ Dirty George Creek tributary

Earthfill/Irrigation

1949/Private 10/273 1.3 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir are on Grand Mesa landslide complex (mainly basalt on claystonmantled by glacial deposits). Foundation seeage during 1970s caused small slumps in toe embankment. Minor foundation seepage stiloccurs.

United States/ Colorado/39.95N, 105.36W

Gross/South Boulder Creek

Concrete gravity/ Water supply, hydroelectric, recreation

1955/Public utility

104/332 58.7 Deepseated 

rock slide

Both abutments

Wahlstrom (1974, p. 74) noted deep-seated “gravity-slip surfaces in steep-walled canyon in massive crystalline rock.” No effect on daperformance. Dam forms buttress against anfuture movement.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Colorado/ 40.84N, 106.99W Hahn’s Peak/ Willow Creek Earthfill/ Recreation, fish and wild- life 1978/State government 12/82 1.0 Slide in shale Left abutment Slide in shale of Morrison Formation serve

left abutment. No problems have developed

United States/ Colorado/ 39.00N, 108.11W Hogchute/ Kannah Creek Earthfill/Water supply 1947/City government 17/189 1.1 Rock slide Entire dam and reservoir on landslide Entire dam and reservoir on part of Grand M

landslide complex (mainly basalt on claystomantled by glacial deposits). Right abutmenon basalt talus. No negative effects on dam. 

United States/ Colorado/40.12N, 107.02W

Joe Wright/Joe Wright Creek

Earthfill/Water supply, irrigation, recreation

1979/City government

45/701 11.5 Huge rock 

slide

Right abutment and right end of dam

Entire right valley wall is huge Quaternary landslide mass (volcanics over sedimentary rocks), probably formed upon glacier retreaproblems.

United States/ Colorado/40.06N, 106.45W

Jones #2/ Sheep Creek tributary

Earthfill/ Water supply, irrigation

1887/Private 12/99 0.7 Massive 

block glide

Entire dam and reservoir

Entire dam and reservoir lie on 13-km2 glid

block in Niobrara and Dakota Formations sand sandstones. Abutments are in fractured shales, resulting in seepage from toe drainsReservoir serves as water supply for City oKremmling.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ Colorado/39.06N, 107.84W

Kehmeier/ Surface Creek tributary

Earthfill/ Irrigation

1949/Private 10/172 0.5 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir on Grand Mesa landcomplex (mainly basalt on claystone, mantled by glacial deposits). Minor seepage through babutments.

United States/ Colorado/39.03N, 107.96W

Kennicott Slough/Kiser Creek tributary

Earthfill/ Irrigation

1946/Private 12/380 1.5 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir on Grand Mesa landcomplex (mainly basalt on claystone, mantled by glacial deposits). Minor seepage through leabutment; performance generally good.

United States/ Colorado/39.02N, 107.95W

Kiser Slough/ Kiser Creek

Earthfill/ Irrigation, recreation

1950/Private 12/320 0.9 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir on Grand Mesa landcomplex (mainly basalt on claystone, mantled glacial deposits). Foundation leakage; drainage trenches added as remedial measure have improved situation.

United States/ Colorado/39.04N, 107.88W

Knox/Surface Creek tributary

Earthfill/ Irrigation

1954/Private 12/156 0.5 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir on Grand Mesa landcomplex (mainly basalt on claystone, mantled by glacial deposits). Minor seepage from both abutments.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Colorado/ 40.97N, 107.33W Lower Cogdill/ Government Corral Creek Earthfill/ Water sup- ply, fish and wildlife, fire protection 1956/Private 12/146 0.4 Massive slide in shale and sandstone Entire dam and reservoir Entire dam and reservoir lie in large (18 km2) landslide area overlying Lewis Shale and Mes

Group (sandstone and shale). Landslide deposhad no negative effect on dam/reservoir perfor

United States/ Colorado/ 40.30N, 106.29W Matheson/ Troublesome Creek Earthfill/ Irrigation 1951/Private 18/59 2.2 Massive slide in Tertiary volcanics Left abutment and possibly foundation Dam was built on NE edge of large landslide 

Tertiary volcanics overlying Morrison Fm. sanstones and shales. Seepage in right abutment athrough “shattered lava.” Clay blanket installeprevent seepage, apparently with little success

United States/ Colorado/ 40.14N, 106.47W

McElroy/ Pass Creek

Earthfill/Irrigation

1931/Private 15/76 0.5 Earth flow Right 

abutment

Earth flow from Dakota Fm. shales originally dammed Pass Creek. Serves as right abutment part of foundation. Generally very little seepaminor seepage at right groin in 1975.

United States/ Colorado/ 39.21N, 107.75W

McKelvie #1/ Plateau Creek tributary

Earthfill/ Irrigation

1943/Private 11/137 0.5 “Old 

landslide”

Entire dam Entire dam is in area mapped by Soule (1988) 

landslide.” Minimal foundation seepage (slighboggy downstream; no flowing water). Dam pmance good.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year

 constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ Colorado/39.04N, 107.93W

McKoon/ Young’s Creek

Earthfill/Irrigation

1948/Private 10/84 0.3 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir are on Grand Mesa landslide complex (mainly basalt on claystonemantled by glacial deposits). No negative effeon dam.

United States/ Colorado/ 40.18N, 106.57W

McMahon #2/Red Dirt Creek

Earthfill/Irrigation

1945/Private 15/301 6.5 Slumpearth flow Left abutment Left abutment is slump–earth flow in Morriso

Fm. shale and sandstone. Landslide apparentlhas had no negative effect on dam performanc

United States/ Colorado/40.27N, 106.56W

Milk Creek/Milk Creek

Earthfill/Irrigation

1925/Private 11/43 0.2 Massive 

slide in shale andsandstone

Entire dam and reservoir

Entire dam and reservoir lie in large landslide area in Benton Shale and Dakota Sandstone. Landslide material has had no negative effects dam performance.

United States/ Colorado/38.88N, 107.47W

Monument/Minnesota Creek tributary

Earthfill/Irrigation

1889/Private 23/129 0.8 Rock slide Left 

abutment

Slide mass, which extends vertically 120 m above left end of dam and 450 m laterally, consists mainly of sandstone cobbles and boulderin clay matrix. Instrumented since 1992 to record dam movement; however, there has beeno distress. Apparently no significant remediameasures have yet been needed.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Colorado/ 39.11N, 107.75W Monument #1/Monument Creek Earthfill/ Irrigation 1960/Private 11/152 1.1 Massive rock slide Entire dam and reservoir Entire dam and reservoir on Grand Mesa land

complex (mainly basalt on claystone, mantled glacial deposits). Some seepage from left abutment. 

United States/ Colorado/ 37.39N, 105.39W Mountain Home/ Trinchera Creek Earthfill/ Irrigation, fisheries 1906/Private 47/145 32.0 Rock- block slide Left abutment Slide in basalt underlain by siltstone and sand

stone. No movement since construction. Becaoverflow spillway crosses slide block, possiblstability was conjectured. However, 1993 analindicated no stability problem. 

United States/ Colorado/ 40.55N, 106.02W North Michi- gan Creek/ Michigan River Earthfill/ Recreation, fish and wildlife 1963/State government 23/142 3.6 Earth flow Left (and possibly right) abutment Left abutment (and possibly right abutment) is 

landslide masked by glacial deposits. Except fminor right-abutment seepage, landslide has hno negative effect on dam. 

United States/ Colorado/39.08N, 107.65W

Overland #1/Cow Creek (Muddy Creek tributary)

Earthfill/Irrigation

Originally in early 1900s; rebuilt 1987/ Private

26/975 10.1 Rock slide Entire dam Entire dam and reservoir on huge rock slide. B

fore 1987, toe-buttress stability problems possdue to landslide material. In 1987, toe-buttresdrains installed and material added to toe buttr

United States/ Colorado/39.05N, 107.88W

Park/Surface Creek

Earthfill/Irrigation

1940/Private 14/229 5.6 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir are on Grand Mesa landslide complex (mainly basalt on claystonemantled by glacial deposits). Slide material is fragmental basalt and fairly permeable. Thus, there have been seepage problems (~75–115 l/min) through base of left abutment). Bentoniadded to abutment in 1997 to slow seepage. 
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ Colorado/40.27N, 106.41W

Parsons/ Carter Creek

Earthfill/ Irrigation, stock

1952/Private 12/84 0.2 Slide in 

Pierre Shale

Left abutment and spillway

Left abutment and original spillway in toe opre-existing Pierre Shale slide. There was dficulty with the spillway; so it was moved fthe slide. Some seepage still flows from sli

United States/ Colorado/37.35N, 106.54W

Platoro/Conejos River

Rockfillearthfill/Irrigation

1951/Federal government

50/270 83.6 Massive 

slump block

Left abutment

Left abutment is toe of large (length >1 kmandesite slump block. Abutment is stable. Nseepage problems.

United States/ Colorado/40.13N, 107.26W

Poose Creek/Poose Creek

Earthfill/ Recreation, fish and wildlife

1969/State government

12/133 0.67 Slide in 

volcanics, shale, glacial deposits

Right abutment (possibly entire dam)

Dam was built on mixture of landslide/glacdeposits left behind as glacier retreated from valley. Slide is a mixture of shale/sandstone (Browns Park, Morrison, and Dakota Fms.)overlying Tertiary volcanics, and glacial deits. No negative effects on dam.

United States/ Colorado/38.15N, 107.75W

Ridgway/Uncompahgre River

Earthfill/ Irrigation,water supply, recreation, flood control

1987/Federal government

101/740 101 Slides in 

siltstone, sandstone, and mudstone

Left abutment

Relatively small slide masses uncovered duconstruction; minor sliding occurred. Most debris then removed. Remainder buttressed dam embankment; thus, the abutment is strger than originally.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Colorado/ 37.72N, 107.27W Rio Grande/ Rio Grande River Earthfill/ Irrigation 1916/Private 35/329 64.4 Rock slide Left abutment Huge andesite slide at and above left abutment (Atwood, 1918). Considerable seepage led to r

construction of abutment featuring: (1) retaininwall, (2) french drains, and (3) horizontal drainInstallation of piezometers and inclinometers. 

United States/ Colorado/ 40.14N, 106.20W Scholl/Corral Creek Earthfill/ Irrigation 1964/Private 18/55 0.8 Rock slide Right abutment Right end of dam abuts against slide of basalt boulders up to 2 m in diameter derived from basalt flows in upper valley wall. Serious seep

through this pervious mass. In 1964, right groiwas grouted. In 1965, 1972, 1989–90, impermable membranes were placed in right abutmenbut seepage continued; sinkholes formed on surface. 

United States/ Colorado/40.15N, 107.14W

Sheriff/Trout Creek

Earthfill/Irrigation

1955/Localgovernment

20/192 1.8 Rock slide Right 

abutment

Right valley wall is huge Quaternary landslide mass, probably formed after glacier retreat. No problems.

United States/ Colorado/38.25N, 107.54W

Silver Jack/East Fork Cimarron River

Earthfill/Irrigation

1971/Federal government

53/320 18.9 Huge 

rock slide in valley wall

Right abutment

Excavations for right end of dam were made in toe of slide, causing 375,000-m3 slide reactivation. Remedial measures: (1) resloping slide, (redesigning dam to avoid further cutting at toe slide, (3) horizontal and surface drains, and (487,000-m3 buttress fill. Results were successfu

United States/ Colorado/40.03N, 107.12W

Stillwater No. 1/Bear River

Earthfill/Irrigation

1939/Private 27/457 9.1 Massive 

rock slides

Entire dam and reservoir

Massive Quaternary rock slides filled valley afglacier retreat. Dam built on toes of slides. No problems.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ Colorado/38.81N, 106.60W

Taylor Park/Taylor River

Earthfill/Irrigation, recreation

1937/Federal government

63/188 1.39 Thick 

talus cone

Right abutment

Right abutment covered by thick talus cone fsedimentary rock cliffs. Talus removed beforconstruction except for area ~25 m downstrefrom centerline to downstream toe. 

United States/ Colorado/37.01N, 106.45W

Trujillo Meadows/Los Piños River

Earthfill/Recreation

1956/State government

15/50 1.6 Rock slide 

in tuffs and ash flows

Left abutment and foundation

Dam built on toe of large Quaternary rock slithat had blocked the river. No stability problebut in 1990s seepage through left abutment became unacceptable. Impervious cutoff placthrough left abutment in 1998.

United States/ Colorado/40.04N, 107.07W

Upper Stillwater/Bear River

Earthfill/ Recreation, fish and wildlife

1965/State government

12/84 1.3 Slide in 

volcanic rock, shale, and glacial deposits

Entire dam on landslide and glacial deposits

Valley walls are covered by massive Quaternlandslides (mixtures of sandstone and shale from Browns Park and Morrison Fms.), Tertivolcanics, and glacial deposits. At damsite, landslide and glacial deposits are intermingleNo dam problems related to geology.

United States/ Colorado/39.23N, 107.82W

Vega/Plateau Creek

Rockfill and earthfill/Irrigation

1959/Federal government

49/640 39.3 “Old landslide” Right abutment Much of right abutment area is part of large Quaternary landslide (Soule, 1986). In 1984, 

small part reactivated, slightly damaging spilway. No current activity.

United States/ Colorado/ 39.06N, 107.87W

Vela/Surface Creek tributary

Earthfill/Irrigation

1959/Private 12/191 0.7 Massive 

rock slide

Entire dam and reservoir

Entire dam and reservoir are on Grand Mesa landslide complex (mainly basalt on claystonmantled by glacial deposits). Minor foundatiseepage. Local slide problems at spillway.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Colorado/ 39.01N, 108.00W Ward Creek/ Ward Creek Earthfill/ Irrigation, recreation 1957/Private 14/384 0.7 Massive rock slide Entire dam and reservoir Entire dam and reservoir are on Grand Mesa landslide complex (mainly basalt on clay- stone, mantled by glacial deposits). United States/ Colorado/ 40.33N, 106.52W Whiteley Peak/ Dia- mond Creek Earthfill/ Irrigation, water supply 1952/Private 19/236 1.6 Shale slide Entire dam Slides in Pierre Shale form both abutments and foundation of dam. Reactivation of part of right abutment slide in 1986 slightly dam- aged spillway. No other serious effects. United States/ Colorado/40.55N, 107.05W

Yamcolo/Bear River

Earthfill/Irrigation,water supply

1980/Local government

34/1,214

14.9 Rock slide 

and debris flow

Both abutments

Right end of dam on huge Quaternary rock slide; left end and part of left foundation on Quaternary debris flow. No problems.

United States/ Colorado/39.04N, 107.91W

Young’s Creek Nos. 1 and 2 (one dam)/ Young’s Creek tributary

Earthfill/Irrigation

1952/Private 17/154 1.0 Rock slide Foundation 

and abutments

Entire dam and reservoir are on Grand Mesa landslide complex (mainly basalt on claystone, mantled by glacial deposits). Somseepage at both abutments. Left abutment has been grouted (with little success). Local blanketing with membranes tried without long-term success. Dam is stable.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ Colorado/39.19N, 107.89

YT Ranch/ Grove Creek

Earthfill/ Recreation, irrigation

1911/Private 12/274 0.3 “Old debris flow” Entire dam and reservoir Entire dam and reservoir are on “old debris flow” that originated on Grand Mesa (Soule

1988). Dam is stable, but has considerable seepage through foundation.

United States/ Idaho/43.36N, 115.44W

Anderson Ranch/South Fork Boise River

Earthfill-rockfill/Irrigation, hydroelectric

1971/Federal government

139/411 608 Rockfall 

(talus)

Right abutment

Before construction, right abutment was covered by thick layer of basalt talus, which was removed to granite bedrock under zone 1. Partially removed (“engineered”) under upstream shell; left in place under downstreshell. New landslide has occurred into reserat upstream edge of “engineered” talus slopSeepage on right valley wall downstream frdam apparently passes through talus.

United States/ Idaho/43.33N, 111.21W

Palisades/Snake River

Earthfill/Irrigation, hydroelectric, flood control, recreation, fish and wildlife

1957/Federal government

82/640 1,800 Rock slide Right 

abutment

Large slide at least 10,000 yr old. Maximum thickness ~70 m; width along upstream part right abutment and shore ~1 km. Landslide terial mainly andesite cobbles and boulders matrix of silt, sand, gravel. Closely monitorthus far, no movement. No problems.

United States/ Kansas/39.81N, 99.94W

Lovewell/White Rock Creek

Earthfill/Flood control,irrigation,recreation

1957/Federal government

28/2,590

230 Shale 

slides

Right abutment

Entire abutment slope above right end of daposes threat to dam. In 1955, shale slide occurred during construction; 95,000 m3 of slide material was removed. Abutment now buttressed by dam and two berms. Howeverminor sliding continues in abutment above dam. In 1985, instrumentation and monitoriwere recommended.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Kentucky/ 36.96N, 84.27W Laurel/ Laurel Creek Rockfill/ Flood control, hydroelectric, recreation 1973/Federal government 86/433 537 Bedding- plane shears Both abutments Pre-existing bedding-plane displacement caused 

stress relief in valley. Shear zones and fractures foundation rock at damsite were filled with groupart of grout curtain beneath core of dam. 

United States/ Kentucky/ 38.00N, 85.32W Taylorsville/ Salt River Rockfill and earthfill/Flood control, recreation 1983/Federal government 49/390 360 Small pre- existing slide Left abutment Small pre-existing slide in sedimentary rocks at 

end of dam. Occasional minor movement of rocabutment immediately above end of dam; leads need for minor maintenance. No other problems

United States/ Montana/ 49.59N, 114.28W Bass Lake/ Bass Creek Earthfill/ Irrigation 1952/Private 11/137 4.4 Rock fall (talus) Left abutment Downstream left shell of dam placed on talus sl

Remedial measure: sheetpiling for length of dam

United States/ Montana/ 47.20N, 113.72W Black Lake/ Jocko River Earthfill/ Irrigation 1967/Federal government 26/166 6.4 Rock slide and talus Right abutment Dam founded on ancient landslide dam. Consid

able seepage through rock slide and talus. In 196 ha of 1.5-mm-thick polyethlylene membrane protected by geotextiles was installed in slide/taAbutment continues to leak. Downstream berm being considered. 

United States/ Montana/46.65N, 111.73W

Canyon Ferry Dam/Missouri River

Concrete gravity/Hydroelectric,flood control,irrigation, water supply,recreation

1954/Federal government

69/328 2,529 Beddingplane slip 

in shale

Left abutment

Several left-abutment bedding-plane slips in shawere excavated to competent bedrock. Howeverone prominent slip was only partially removed providing a short path for reservoir water to entfoundation. Remedial measure: two cutoff tunnewere placed parallel to dam axis and filled with concrete; they apparently were successful.

United States/ Montana/45.49N, 110.98W

Hyalite (Middle Creek)/ Hyalite Creek

Earthfill/Irrigation, water supply

1951/State government

38/580 15.8 Slide in 

glacial debris

Left abutment

Geotechnical consultant to State of Montana idefied left abutment as being “founded on mixed landslide and glacial deposits composed of claysilt, sand, poorly sorted gravel, rock fragments, conglomerate, and boulders.” During 1990s, compacted earth liner placed to lower seepage rate. stability problem.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ Montana/48.83N, 113.52W

Lake Sherburne/SwiftcurrentCreek

Earthfill/Irrigation

1921/Federalgovernment

33/366 136.5 Slide in 

glacial deposits

Both abutments

Valley walls: massive landslide debris derived mainly from glacial deposits. Original foundatreatment included three continuous cutoff trereaching into till across valley bottom. Prior t1960, movement of left abutment damaged orspillway; abutment remains unstable. Monitocontinues. 

United States/ Montana/46.56N, 113.31W

Lower Willow Creek/Lower Willow Creek

Earthfill/Irrigation

1962/Local government

29/296 7.7 Rock fall 

(mainly talus)

Left abutment

Considerable seepage through lower left abutHowever, most seepage apparently is through jointed quartzite and argillite, not through the talus/colluvium.

United States/ Montana/45.49N, 111.64W

Madison/Madison River

Concrete gravity/Hydroelectric,flood control,water supply,recreation

1907/Hydroelectric power company

12/78 52 Rock 

slides

Right abutment

Right abutment is in toe of pre-existing slide metamorphic rock. Steel piles and concrete bused to anchor right abutment. 

United States/ Montana/45.54N, 110.92W

Mystic Lake/Bozeman Creek

Earthfill/ Irrigation,water supply

1904/Private 13/119 1.5 Flow in 

volcanic breccia

Left abutment and left end of foundation

Flow of volcanic breccia dammed Bozeman C~200 yr B.P. This landslide formed left abutmand left end of dam foundation. Dam was purbreached in 1982 and 1985 because of leakagrisk to downstream population. 
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Montana/ 46.80N, 112.81W Nevada Creek/ Nevada Creek Earthfill/ Irrigation 1938/State government 32/330 21.3 Rock and earth slide Both abutments; much of foundation Material underlying much of dam and against which dam abuts at both ends is mass of irreg

boulders of basalt in clay. Mass is ancient lanthat moved down valley slopes to stream chanFoundation is stable, but there has been seepaboth abutments and under dam. Remedial me(1) toe berm and (2) seepage collection system relief wells and shallow drains. 

United States/ New Mexico/ 35.40N, 104.19W Conchas/ Canadian River (Conchas River) Concrete gravity- rockfill/ Irrigation, recreation, debris control 1940/Federal government 72/ 5,944 874 Open joints in sandstone and shale Both abutments Valley walls consist of jointed (often slickens

sandstone and shale. As construction scaling progressed to stable rock, new joints opened. prevent this, reinforced columns were used to beams for lateral support. Today, dam acts as buttress. 

United States/ New Mexico/36.88N, 105.28W

Costilla/Costilla River

Earthfill/Irrigation

1920/Private 42/238 37.5 Massive 

landslide

Right abutment

Right end of dam adjacent to toe of deep-seatancient landslide in volcaniclastics, which oriwere identified as glacial debris. In 1985, decwas made to rehabilitate dam because of embment seepage. During reconstruction, reactiva(volume: 8–9 million m3) of landslide occurreBerm added for stability. Slide now stable.

United States/ New Mexico/36.59N, 106.75W

El Vado/Chama River

Earthfill with steel-membrane face/Irrigation,water supply,recreation

1935/Private conservancy district

70/404 258 Beddingplane rock 

slide

Left abutment

Left abutment and canyon wall for about 1 km stream and downstream are large, ancient (~1yr B.P.) slide in sandstone and shale. Major gprogram in left abutment during constructionin 3 years of reservoir filling, steel-plate membuckled, possibly due to abutment deformatioRepaired in 1955; stable since.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state

 or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ New York/42.15N, 79.01W

Site 19/Battle Creek

Earthfill/Flood control

1971/Local government

20/146 0.48 Slump in 

sedimentary rocks

Lower left abutment

Ancient slump in shale/siltstone was not recnized during construction. Because of dangeous seepage, dam was breached in 1980. Furexploration found slump underlain by alluviDam was redesigned and rebuilt in 1981. Remeasures installed: (1) cutoff trench deepenebedrock, (2) cutoff trench into embankment, (3) enlargement of foundation drainage systeFailure to recognize landslide in abutment rein substantial economic loss.

United States/ North Dakota/48.46N, 101.58W

Lake Darling/Souris River

Earthfill/Recreation, fish and wildlife

1936/Federal government

12/1,006

280 Slumps in 

clay till

Both abutments

Slumps in both valley walls (age: ~11,000 yNo movement in past 10,000 yr. Toes of slummoved by post-slide erosion along floor of SRiver valley. Slides cause no problems to da

United States/ Oregon/42.42N, 122.78W

Agate/Dry Creek

Rockfill and earthfill/Irrigation,recreation

1966/Federal government

26/1,158

7.02 Shallow 

slump

Left abutment

Shallow landslide in volcanic rocks occurred abutment during construction; debris was remand slope of excavation flattened. Slump moagain in early 1980s; toe was then excavated rockfill placed as buttress. Dam is now stabl

United States/ Oregon/45.46N, 121.85W

Bull Run Lake/BullRun River

Concrete gravity/Water supply

1965/Citygovernment

17/46 17.9 Massive 

landslide(vol. ~110 million m3)

Entire dam on landslide

Dam constructed on prehistoric landslide daabout 70 m thick. Considerable seepage emefrom landslide dam material downstream of About 60 percent of flow in Bull Run River stream comes from these springs.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Oregon/ 45.50N, 122.10W Bull Run No. 2/Bull Run River Rockfill/ Hydroelectric, water supply 1962/City government 44/275 30.8 Rock slide: andesite and basalt over soft volcanics Both abutments Valley floor in basalt; both abutments are s

tionary slide debris consisting of andesite/brubble in matrix of clay, silt, and sand. Follconstruction, occurrence of springs downstfrom dam resulted in installation of extensicurtain. Some seepage continues. 

United States/ Oregon/ 44.24N, 118.78W Canyon Creek Meadows/ Canyon Creek Earthfill/ Recreation 1963/State government 18/53 0.49 Rock slide Left abutment and part of right abut- ment Left abutment and part of right abutment ar

remnants of large rhyolitic rock slide that fblocked stream channel. Seepage through lment. When visited in 1998, reservoir was and dam was not functioning. 

United States/ Oregon/45.52N, 122.71W

City of Portland Dam No. 3/Bull Run River

Concrete gravity/Water supply

1894/Citygovernment

16/30 0.06 “Ancient” 

landslide in basalt and clay

Foundation and right abutment

Movement in “phenomenal landslide” (volu~2.6 million m3) noted during construction 

1904). From 1895–1903: drainage tunnels stalled; 1904–76: reservoir linings rebuilt. Iflexible membrane liner installed.

United States/ Oregon/42.71N, 122.74W

Elk Creek/ Elk Creek

Rollercompacted concrete (RCC)/Flood control, irrigation

Environmental concerns halted construction in 1986/Federal government

Planned: 76/786

125 Rock slide 

(volcanic rocks)

Right abutment

During construction, three low-angle “sheanoted in right abutment. Excavation caused of movement before concrete-filled key treinstalled to buttress sliding mass. Dam was completed when project was terminated for ronmental reasons (not because of slide pro
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province

/latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ Oregon/42.17N, 122.60W

Emigrant/Emigrant Creek

Earthfill-rockfill, concrete/Irrigation, recreation,flood control

1924/Federal government

62/229 57.6 Rock slide Right 

abutment

Pre-existing slide in sandstone, siltstone, and reactivated during construction; minor movesince. Most of slide is on right shore immedupstream from dam. Mass appears fairly stapresent; dam is in no danger. 

United States/ Oregon/45.09N, 122.05W

Frog Lake/Oak Grove Fork, Clackamas River

Earthfill/Hydroelectric

1955/Private power company

15/738 0.65 Huge ancient rock 

slide (area ~50 km2)

Entire dam and reservoir

Seepage and cracking of reservoir bottom wcontinuing maintenance problem for this dam1991, it was recognized that Frog Lake Dam cated on the reactivated part of a 50-km2 lan(basalt and andesite rubble in tuff breccia). Dwas rebuilt in 1998.

United States/ Oregon/42.13N, 122.47W

Keene Creek/Keene Creek

Rock-faced earthfill/Hydroelectric, irrigation

1959/Federal government

25/170 0.48 Rotational 

earth slump

Right abutment

Slump is chaotic mixture of weathered rock ments, sand, silt, and clay. Slump recognizeto construction, resulting in moving spillway right to left end. Abutment is stable, but prosome seepage.

United States/ Oregon/45.08N, 121.96W

Lake Harriet/Oak Grove Creek

Concrete arch buttressed with rockfill/Hydroelectric

1923/Private power company

21/57 0.49 Edge of 

huge rock slide

Left abutment

Left abutment (basalt) is toe of huge landslidnoted above for Frog Lake Dam. Slide has bmoving toward dam, causing cracking of arcRemedial measures installed in 1985: (1) imous bentonitic membrane placed against upsdam face by means of a tremie pipe and (2) fill buttresses against both dam faces. 
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Oregon/ 43.91N, 122.75W Lookout Point/Middle Fork Willamette River Earthfill/ Flood control, irrigation, navigation, hydroelectric, recreation 1953/Federal government 84/462 589 Slides in volca- nic tuff altered to clay; talus Right abutment Remnants of clay/talus deposit on both sides 

valley. Right end of core trench was excavatethrough pre-existing large slide, resulting in activation upstream of trench. New slide depwas removed, but pre-existing slide material downstream from core trench apparently remin place and is stable. 

United States/ Oregon/ 44.30N, 120.73W Ochoco/ Ochoco Creek Earthfill (hy- draulic fill)/ Irrigation 1920/Private irrigation district 38/411 57.3 Large rock slide– lateral spread Right abutment Late Pleistocene landslide forming right abu

ment probably was caused by plastic flow of bentonitic zones in dacitic tuff and claystonewas probably chosen because of landslide-cavalley constriction. Seepage through right abment has been continuing problem. Modificaduring 1990s: deep interceptor trench with zof impervious material reduces seepage. 

United States/ Oregon/44.72N, 121.25W

Pelton Regulating Dam/ Deschutes River

Concrete gravity/ Hydroelectric,flood control

1950/Private power company

12/325 4.32 Translational/

rotational rock slide in volcanic tuff

Left abutment

“The left abutment of the regulating dam waconstructed on the toe of this extensive ancielandslide” (Benson and Pate, 1998). No problems.

United States/ Oregon/45.95N, 123.92W

Peterson Point/South Fork Necanicum River

Earthfill/Water supply

1954/Local government

14/79 0.21 Slides in 

mudstone

Both abutments

There has been no movement of abutment slsince construction. Dam was raised to 14-m height in 1996. No problems.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative

 to dam Comments

United States/ Oregon/45.53N, 122.99W

Sams Valley/Sams Creek, Zana Creek

Earthfill/Irrigation

1956/Private irrigation district

19/101 1.48 Large 

rotational landslide

Right abutment

Low ridge at right abutment and right shore of reservoir apparently formed by large rotationalandslide in sandstone. Seepage occurs througlandslide mass. Stability and seepage satisfactunder reduced reservoir filling dictated by StaOregon.

United States/ Oregon/45.49N, 123.21W

Scoggins/Scoggins Creek

Earthfill/Irrigation, water supply

1975/Federal government

46/817 77.1 Earth slide Right 

abutment

Quaternary landslide in sandy silt and silty sanforms right abutment. Monitoring program chfor movement every 3 years; there has been no

United States/ Oregon/45.37N, 123.70W

Skookum Lake/Fawcett Creek

Earthfill/ Water supply

1965/Public utility

13/192 1.4 Debris 

slide in soil and rock

Right abutment and right 100 m of foundation

Dam was built on “old” (>500 yr B.P.) landslidam. A deep (~7 m) core trench was excavated through landslide deposit to reduce seepage.

United States/ Oregon/43.53N, 118.08W

Star Mountain/Granite Creek

Earthfill/Irrigation

1961/Private 21/87 1.8 Large 

slide in siltstone (tuff?) and basalt

Right abutment

Entire right bank of Granite Creek in vicinity dam and reservoir is located on toe of huge anlandslide. In 1983, original spillway (at right ament) was eroded out by floodwater. Right endam rebuilt with circular concrete spillway pathrough embankment.

United States/Pennsylvania/40.38N, 79.02W

Sugar Run/Little Sugar Run Creek 

Earthfill/Water supply

1907/Water utility company

18/274 0.58 Rock slide Right 

abutment

Prehistoric rock slide (sandstone, siltstone, anshale) forms right abutment. Dam has long history of foundation/abutment leakage. Flood in 1990s caused minor reactivation of right-abutmlandslide.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province /latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ South Dakota/ 44.45N, 100.39W Oahe/ Missouri River Earthfill/ Flood control, hydroelectric, irrigation, navigation, recreation 1966/Federal government 75/ 2,835 29,000 Rotational slides in shale Remnant of small slide in right abutment; construction slide in left abutment Pre-existing slides in shale originally form

much of right abutment. Slide occurred in abutment during construction; 5.0 million mwas removed (3.5 million m3 used as buttreProbably some remains beneath embankmPart of small slide remains in right abutmeBoth abutments are buttressed by weight odam. No stability problems. 

United States/ Texas/ 97.22N, 31.60W Waco/ Bosque River Earthfill/ Water supply, flood control 1965/Federal government 42/ 5,464 1,021 Basal slide in Pepper Shale Foundation Slide in Pepper Shale foundation occurred 

ing construction (1961); embankment was percent completed. Slide in embankment wslump; translational in foundation shale. Lof slide: 500 m. Remedial measures: (1) embankment slopes extended at flatter slopes original and (2) berm placed at lower toe. 

United States/ Utah/ 40.87N, 111.03W

Boyer Lake/ Chalk Creek

Earthfill/Irrigation

1939/Private 14/396 0.01 Large 

landslide complex

Entire dam Dam and reservoir entirely within large (~5

km2) landslide area. No problems have beereported.

United States/ Utah/40.73N, 109.21W

Calder/Pot Creek

Earthfill/Irrigation

1989/State government

15/114 2.8 Block 

slide in Precambrian sandstone

Left abutment

Small sandstone and shale bedding-plane bslide noted before construction. Cement grcurtain added to successfully prevent seepaSlide buttressed by dam. 

United States/ Utah/40.72N, 109.17W

Crouse/Pot Creek

Earthfill/Recreation, fish and wildlife

1952/State government

11/306 1.34 Small 

block slide in sandstone/shale

Left abutment

“Ancient” rock-block movement of sandstoblocks that form left abutment. Seepage prlems occurred through the slide. Repairs wmade while reservoir was drawn down. Revoir was refilled in 1992.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river

 or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ Utah/39.62N, 110.39W

Grassy Trail/Whitmore Canyon Creek

Earthfill/Water supply

1952/Private 27/183 1.4 Earth-rock 

slumps in Cretaceous shale

Both abutments

Since construction, small slides have occurrin both abutments (but especially in the righunconsolidated materials derived from mudshale, and sandstone. Greatest movement w1957 and 1969; only minor activity at preseMovement and seepage are monitored.

United States/ Utah/39.29N, 111.27W

Joes Valley/Seely Creek

Earthfill/Irrigation, recreation, fish and wildlife, flood control

1966/Federal government

58/229 77 Slide in 

sandstoneshale colluvium and talus

Both abutments

Impervious cutoff to bedrock through aboum of colluvium/talus cover at both abutmenPart of colluvium/talus left in place and shaon downstream parts of both abutments. Sliin talus of right abutment during constructioEarthquake-induced slide occurred in right-ment talus in 1988; cracks remain in abutmarea. Seepage in right-abutment slide area. Seepage collection pipes, collection wells, seepage monitoring points have been instal

United States/ Utah/40.41N, 111.71W

Jordanelle/Provo River

Earthfill/Water supply

1993/Federal government

119/1,164

448 Rockblock 

slide in Tertiary volcanics

Left abutment

Andesite-porphyry rock-block slide (volum~75,000 m3) found in left abutment during construction. Location of slide was centerlito downstream toe. Most was removed. “Dework” assured stability during constructioner, buttressing effect of dam provided stabil

United States/ Utah/40.91N, 109.87W

Long Park/ Sheep Creek

Earthfill/Irrigation

1980/Private irrigation company

35/262 18.0 Beddingplane 

creep in sandstone/shale

Left abutment

Joints in sandstone/shale left abutment open as much as 0.75 m due to bedding-plane creresulting from stress relief. Open joints wergrouted (triple-line grout) during constructihowever, seepage occurred through left abuIn late 1990s, a 20-m-deep concrete cutoff wwas placed through the open-jointed rock to seepage.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Utah/ 37.86N, 109.36W Loyd’s Lake/ South and Pole Creeks Earthfill/ Irrigation 1984/Private 23/457 5.3 Slump in Creta- ceous shale Right abutment Abutment is marginally stable. Berm serves as buttress. Blanket drain underneath. Piezometer

installed. 

United States/ Utah/ 40.49N, 111.10W Mill Hollow/ Mill Hollow Creek Earthfill/ Recreation 1962/State government 13/69 0.50 Earth- flow or compound slump Right abutment Toe of large “earthflow or compound slump” in Tertiary volcanics forms the right abutment. Apparently, this landslide at one time dammed the creek, which has since eroded a small canyo

through the landslide dam. Mill Hollow Dam was built in this canyon. Landslide has caused problems to dam. 

United States/ Utah/ 40.56N, 110.49W Moon Lake/ Lake Fork River Earthfill/ Irrigation 1938/Federal government 46/338 61.0 Block slide in Precam- brian shale Left abutment Left end of dam rests on landslide block. Cutof

trench was dug though block into in-place shaleDisturbed shale heavily grouted. Dam is stable

United States/ Utah/41.90N, 111.98W

Newton/ Clarkston Creek

Earthfill/Irrigation

1946/Federal government

32/1,018

6.9 Deepseated 

earth slide

Left abutment

Abutment is in earth-slide material derived from upslope shale. No serious problems.

United States/ Utah/37.66N, 109.44W

Recapture/Recapture Creek

Earthfill/Irrigation

1984/Private 43/884 19.7 Small 

slump inJurassic shale

Both abutments

Abutments were formed of ancient, opposing landslides that were noted prior to constructionDuring construction of cutoff, left-abutment sliwas reactivated. Cutoff extends to bedrock undcenter core of dam, leaving slide remnants undupstream and downstream parts of dam. 

United States/ Utah/37.87N, 112.68W

Red Creek/Red Creek

Earthfill/Irrigation

1980/Private 23/259 23.4 Large 

earth slide in Tertiary volcanics

Left abutment Left abutment and reservoir shore underlain by large Holocene/late Pleistocene slide (thickness

~60 m), mainly weathered volcanics. Dam buttresses toe of slide. No problems.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/ Utah/40.76N, 111.10W

Smith and Morehouse/ Smith and Morehouse Creek

Earthfill/Irrigation

1987/Private irrigation district

25/670 12.4 Valleywide 

debris avalanche

Foundation, both abutments

Large avalanche (age ~4,000 yr B.P.) in sedmentary rock and glacial debris filled canyoto depth of 60 m. Dam built on debris, but kplaced through the mass both for strength animperviousness. No problems.

United States/ Utah/37.14N, 112.90W

South Creek/South Creek

Earthfill/Irrigation

1988/Private 21/226 2.2 Large 

slump in Triassic shale

Right abutment

Right abutment is slump block of sandstonesiltstone, and shale. Small slide shortly after ervoir filling. Remedial measures: (1) collecdrain system, (2) impervious seepage blankand (3) horizontal drains.

United States/ Utah/37.76N, 112.77W

Yankee Meadows/ Bowery Creek

Earthfill/ Irrigation

1926/Private 10/137 1.27 Large 

slide in Tertiary volcanics

Right abutment

Dam is on toe of very large slide (gravitatioor tectonic) from valley wall. Slide has had negative effect on dam performance.

United States/ Vermont/44.38N, 72.77W

Waterbury/Little River

Earthfill/Flood control, recreation, hydroelectric

1938/State government

57/649 98.4 Rock fall Foundation Part of foundation located in narrow bedroc

gorge. “Detached rock slabs along the right (west) side of the gorge form a roof over a piping tunnel known to have been a piping path in the past, and capable of being a pipipath in the future if injected filter materials destabilized” (Saber and others, 2001). Grouprogram to prevent seepage was completed 1985. Apparently, some seepage continues.

United States/Washington/45.64N, 121.93W

Bonneville/Columbia River

Concrete gravity/Hydroelectric,navigation, recreation

1937/Federal government

60/755 710 Large 

prehistoriclandslide

Right abutment

Right abutment is toe of huge Bonneville laslide (age ~400 yr B.P.). Minor surficial moment currently occurring locally on the slidebut not at abutment location. Toe of slide is and stable. No problems. Note: south end of dam (navigation locks) also is on a pre-existlandslide (smaller than the Bonneville slide)Local problems during construction, but nonpresent.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Washington/ 46.87N, 121.30W Bumping Lake/ Bumping River Earthfill/ Irrigation 1910/Federal government 19/892 46.5 Volcanic debris flow (lahar) Entire foundaion Dam was unknowingly built on a 1–2-m-th

lahar (age ~500 yr B.P.) from Mount RainieConsiderable seepage through foundation. I1990s, drainage trench and stability berm wconstructed at downstream toe of dam. 

United States/ Washington/ 48.00N, 123.62W Glines Canyon/ Elwha River Left wing wall: earthfill/ Hydroelectric 1927/Private Wing- wall height: 10–15 m 49.3 Rock/soil slide Left end of wingwall Field visit confirmed that left end of earthfi

left wingwall (or saddle dam) of this 59-m-concrete arch dam abuts a surficial rock/soislide. No problems. 

United States/ Washington/ 47.96N, 118.98W Grand Cou- lee/ Columbia River Concrete grav- ity/Irrigation, hydroelectric, flood control 1942/Federal government 168/ 1,729 11,780 Soil slide Right abutment Varved clay at right abutment moved during construction. Stabilized by (1) building tim

crib retaining wall, (2) flattening the slope, and (3) freezing the soil above the wall. Thsoil-slide area was removed in 1967–81 whdam was lengthened to accommodate third powerplant. 

United States/Washington/47.27N, 121.79W

Howard A. Hanson/ Green River

Rockfill and earthfill/Flood control

1962/Federalgovernment

72/152 169 Large 

landslide(area: >400 m ×

600 m)

Right abutment

Gorge of Green River was cut into toe of a massive Pleistocene slide. Right end of dam built on landslide deposits consisting of rocblocks up to 6 m in diameter and finer debrConsiderable seepage through right abutmeRemedial measures: (1) gravel drainage blaket, (2) horizontal drains, (3) drainage adit, (4) relief wells.

United States/Washington/47.14N, 121.93W

Mud Mountain/White River

Earthfill/Flood control

1948/Federal government

130/213 131 Volcanic 

debris flow (lahar)

Both abutments

At both banks, dam abuts into Pleistocene l(originally thought to be glacial till). Concrcutoff wall installed in 1989–90 through embankment and into rock foundation to contrseepage.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/Washington/47.94N, 119.02W

North (Banks Lake)/Upper Grand Coulee River

Rockfill and earthfill/ Flood control, navigation, irrigation, hydroelectric

1951/Federal government

44/442 1,572 Rotated 

slide block

Left abutment

Left abutment is a rotated slide-block segmof a basalt flow resting on slide-disturbed sediments. The left two-thirds of the dam on these slide-disturbed sediments. Cutoff was excavated through these materials. No operational problems.

United States/Washington/46.36N, 122.55W

SRS (Sediment retention structure)/North Fork Toutle River

Earthfill/Debris retention

1988/Federal government

73/549 197 Debris 

flow

Entire dam

Dam was built on at least 30 m of debris-fdeposits from prehistoric eruptions of MouHelens. Purpose is to retain sediment derivfrom the 1980 Mount St. Helens debris avlanche. In wet winters of 1996–97, dam re23 million m3 of sediment.

United States/Washington/47.31N, 120.31W

Stemilt Main Dam/Orr Creek–offstream

Earthfill/Irrigation

1962/Private irrigation district

20/305 0.72 Massive 

landslide

Entire dam and reservoir

Entire dam and reservoir built on series of sive landslides (basalt over clay shale) coltively about 17 km long by 5 km wide. Releaked considerably through landslide matuntil impervious geosynthetic membrane wsuccessfully placed in 1986.

United States/Washington/46.08N, 122.21W

Swift/Lewis River

Earthfill/Hydroelectric, flood control, recreation

1958/Private power company

126/640 931 Volcanic 

debris flow

Foundation and right abutment

Right abutment and channel bottom consithick, well-consolidated volcanic debris flfrom prehistoric eruption of Mount St. HeIn the channel, an open-cut excavation for was made to a depth of about 30 m; sheet driven from bottom of trench to bedrock (m). Dam was built on lahar in right abutmDrainage gallery to intercept any seepage. apparent problems.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued. 

Country/ state or province/ latitude, longitude Dam/river or stream Dam type/ purpose Year constructed/ owner Height/ length (m) Storage volume (Mm3) Landslide type Landslide position relative to dam Comments 

United States/ Washington/ 47.28N, 120.36W Upper Wheeler/ Orr Creek Earthfill/ Irrigation, recreation 1922/Private irrigation company 20/274 0.74 Massive landslide Entire dam and reservoir Entire dam and reservoir built on series of ma

sive landslides (basalt over clay shale) collec- tively about 17 km long by 5 km wide. Minor leakage at left abutment has been controlled binstallation of drains. 

United States/ Washington/ 46.81N, 120.67W Wenas/ Wenas Creek Rockfill and earthfill/ Irrigation, recreation 1911/Private irrigation district 27/160 6.78 Ancient large land- slides Both abutments Both abutments are on ancient (probably pre- Pleistocene) landslides. Left abutment: steepl

dipping sediments on basalt (neither in place)Right abutment: lower part of very large landslide mass. Both masses are so large that they inherently stable. No problems. 

United States/ Washington/ 45.98N, 122.35W Yale/ Lewis River Earthfill/ Hydro- electric, 

flood control,recreation, fish and wildlife

1953/Private power company

98/457 496 Volcanic 

debris flow (lahar)

Both abutments and possibly the foundation

Right abutment: during construction, large bablock moved. Partially removed by blasting; now stabilized by dam. Left abutment: slump in clayey tuff was removed; joints and “faultsthen developed in overlying basalt. Stabilized dam. Tilford and Sullivan (1981) showed lahachannel at damsite; apparently, it was removeunder the impervious part of the dam foundatNot clear if lahar remains under outer shell. Nproblems.

United States/Washington/45.98N, 122.35W

Yale Saddle Dam/Lewis River

Earthfill/ Hydroelectric,flood control,recreation, fish and wildlife

1953/Private power company

12/488 496 Volcanic 

debris flow (lahar)

Entire dam

Entire saddle dam is founded on volcanic debflow (lahar). No problems.
Appendix table A. Dam characteristics, relation to landslides, mitigative measures, and cited references—Continued.

Country/

state 

or province/

latitude,

longitude

Dam/river 

or stream

Dam type/ 

purpose

Year 

constructed/

owner

Height/

length 

(m)

Storage 

volume

(Mm3)

Landslide 

type

Landslide 

position 

relative to 

dam Comments

United States/West Virginia/39.37N, 81.27W

McElroy’s Run/McElroy’s Run Creek

Fly-ash embankment/Fly-ash storage

1978/Public utility

74/655 24.53 Slide in 

colluvium

Left abutment

Before placing fly-ash embankment on downstream edge of tailings dam, slide was noted icolluvium of left abutment. Removal of unstamaterial not feasible. Remediation: grid of aucast grout columns was placed through unstabmaterial.

United States/ Wyoming/41.03N, 110.58W

Meeks Cabin/Black Fork River

Earthfill/Irrigation

1971/Federal government

59/964 47 Rock slide 

in shale

Right abutment

Ancient massive (area ~1 x 0.75 km) shale sliforms right valley wall. Dam constructed with deep cutoff trench. No landslide-related stability or seepage problems. However, seepage haoccurred through glacial outwash materials in left abutment, resulting in 1994 construction ocutoff wall.
Schuster—Interaction of Dams and Landslides—Case Studies and Mitigation—Professional Paper 1723

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