A SUGGESTED METHOD FOR LANDSLIDE SUMMARY by eetg eetg

Of the International Association of ENGINEERING GEOLOGY

BULLETIN de I'Association Internationalede GEOLOGIE DE L'INGI~NIEUR

A SUGGESTED

METHOD

PROPOSITION D'UNE

FOR A L A N D S L I D E

METHODE

......

PARIS

1991

SUMMARY

P O U R F I C H E R LES G L I S S E M E N T S

DE TERRAINS

W O R K I N G PARTY ON W O R L D L A N D S L I D E I N V E N T O R Y D.M. CRUDEN, C h a i r m a n *

Abstract A Working Group of members of the International Geotechnical Societies' UNESCO Working Party on World Landslide Inventory, has developed a Suggested Method for a Landslide Summary. The Landslide Record summarizes the information provided by the Landsline Report. The annual compilation of the Landslide Records constitutes the Landslide Summary. National Landslide Summaries can be assembled annually to create a World Landslide Summary. Several differences exist between the Report and the Record. In the Landslide Record descriptive details are omitted, the Country Code and Inventory Number are added, and the damage estimate is based on the per capita GDP for the country for that year. At the National Centre a separate bibliographic database is compiled. Once the landslide information network is established, an invaluable data source will be available at the local, national, and international level.

Rdsume Les Soci6t6s lnternationales G6otechniques ont form6 un Comitd de Travail de l'Unesco pour dresser un lnventaire Mondial des glissements de terrain, et un Groupe de Travail de ce Comit6 a sugg6re et d6velopp6 une mdthode pour dtablir un Fichier des Glissements de terrain. Le R6sumd d'un glissement de terrain condense les informations contenues dans le Compte rendu. La compilation annuelle des r6sumds constitue le Fichier. En assemblant annuellement les fichiers nationaux on peut cr6er un Fichier Mondial. I1 existe des diff6reoces entre le Compte rendu et le Rdsum6. Dans le Rdsum6 on omet la description ddtaill6e, on ajoute le Code du pays et le num6ro de l'tnventaire; l'6valuation des d6g~.ts est bas~e sur le P.N.B. per capita de l'ann6e du pays en question. Au Centre National on compile une base de donndes bibliographique sdparde. Une fois dtabli le rdseau d'informations sur les glissements de terrain, une source de donndes de la plus grande importance au niveau local, national el international sera disponible.

Introduction The International Geotechnical Societies' UNESCO Working Party on the World Inventory has developed a Suggested Method for the compilation of the basic unit of the Inventory, the Landslide Report (Working party on World Landslide Inventory, 1990). The information provided by the Report will become the building block from which Landslide Summaries are constructed. The conceptual information flow for the World Landslide Inventory illustrates the passage of landslide information from notification of occurrence to its place in the World Landslide Inventory (Figure 1). Landslide Summaries may be compiled at both the national and international levels. The Landslide Record, which is a summary of the Landslide Report, is created and compiled at the National Centre. Simultaneously, the cumulative national bibliography is updated. The annual

compilation of the new Landslide Records produces the annual National Landslide Summary. These Summaries will then be forwarded to the Regional or World Centre. Because the bibliographic file cannot be easily transformed into a universal computer processible form, it remains on file at the National Centre. From here, it can be made available upon request. Landslide Summaries from different countries are assembled annually to create a World Landslide Summary. These annual Summaries collectively constitute the World Landslide Inventory. The Landslide Record The Landslide Record (Figure 2) summarizes the information provided by the Landslide Report (Figure 3). The annual compilation of these Records constitutes the landslide Summary. As the information is transferred from the Landslide Report to the Record, several

* Department of Civil Engineering University of Alberta, Edmonton, Alberta Canada, T6G 2G7.

102 KEY

fONL,NE TORAOE(

8ibllograohy,

UNESCO UNDRO

Fig. t : Conceptual information flow for the World Landslide Inventory. changes are made. Some information, the Date of Report, the Landslide Locality, the details about the reporter and the Comments in the Landslide Report is not entered in the Landslide Record. This information as well as information on the volume calculation (the formula applied and the swell factor) can be accessed from the Report, as the need arises. Two fields, the Numeric Code for Country and the National Inventory Number, are additions to the Landslide Report necessary to complete the Landslide Record. The Numeric Code for Country, obtained from the United Nations' List of Country Codes, identifies the country in which the Landslide occurred. The National Inventory Number will identify the landslide in that country's inventory. Combined, the Country Code and the National Inventory Number will represent the landslide in the World Landslide Inventory. The Damage entry in the Landslide Summary differs from that in the Report. When documenting the landslide in the Landslide Report, the damage value should be an estimate of the economic damage caused by the landslide, given in the local currency. For the Landslide Summary, this damage estimate is then converted by division by the per capita GDP into a damage value in 'person-years'. This procedure requires information on the population and GDP for the country for the year during which the landslide occurred. GDP, or Gross Domestic Product, is an economic measure of total expenditures and the total value of goods and services produced in a nation during a specific period, excluding net property income from abroad. The GDP is divided

by the population to produce a value, the person-product, that represents the average contribution per person to the GDP for that year. This value is then divided into the recorded damage estimate to produce a damage value in terms of person-years, or the number of years of production it will take inhabitants of that country to repair the damage caused by the landslide. It is this damage value that is recorded in the Landslide Record. The conversion from the d a m a g e estimate in the local currency to the person-year estimate will provide a culture - and currency-independent measure of the damage for the Landslide Summary. This procedure is further documented in the "Damage" section of this paper. The Date of Occurrence m a y have to be recalculated before it enters the Landslide Record. Many calendars are in existence, but of these, the Gregorian Calendar has been most widely adopted. The International Standards Organization (ISO, 1976) stated that the allnumeric date should be in the following order: year-month-day. Four digits represent the year, while two digits represent the m o n t h and the day. A space separates the year and the month and the month and the day. Some countries m a y have a different National calendar which may be used to record the Date of Occurrence in the Landslide Report. In this case however, the date should be translated to the Gregorian Calendar before it is entered in the Landslide Record. When the Landslide Report Form and, therefore, the Landslide Record is incomplete, some fields in the Record will be left blank. T h e minimum Record requireField r

Field D e s c r i s t i o n

1-3

N u m e r i c code

4-8

National

Field

for c o u n t r y

Inventory

number

Width

9-10 11-12 13-14 15 16-18 19-20 21-22 23 24-26 27-29 30-32

Position,Latitude,degrees minutes seconds hemisphere Longitude, degrees minutes seconds hemisphere Elevation,crown (m a.s.l.) r u p t u r e t o e (m a . s . l . ) t i p (m a . s . l t)

3 4 5 6 7 8 9 i0 ii 12 13

2 2 2 1 3 2 2 1 3 3 3

33-36 37-38 39-40

Date,

year month day

14 15 16

4 2 2

41 42 43 44

Type,

first m o v e m e n t , m a t e r i a l (1-3) t y p e (1-5) second movement,material (1-3) t y p e (1-5)

17 18 19 20

1 ! 1 1

21 22 23 24 25 26 27

4 4 4 3 3 2 2

45-48 49-52 53-56 57-59 60-62 63-64 65-66

Geometry,

Length,

67-69 70

Volume,

in c u b i c m e t r e s x i0 n n, o r d e r of m a g n i t u d e

28 29

3 1

71-75 76-78 79-81

Damage,

v a l u e in p e r s o n injuries deaths

30 31 32

5 3

82-86 87-91 92-96

References,

33 34 35

5 5

Width, Depth,

1 2 3

L r (m) Ld (m) L (m) Wr (m) W d (m) Dr (m) Dd (m)

years

Fig. 2 : The Landslide Record, A line in the Landslide Summary.

103 ments are that the landslide can be located and dated to the nearest year. The Landslide Record is one row long and 35 fields (96 columns) wide. If the software and printer used allow for c o n d e n s e d print, increasing the m a x i m u m number of p e r m i s s i b l e characters from 80, the R e c o r d can be printed on a single line. O b s e r v a t i o n s in the L a n d s l i d e Report are either numeric or descriptive with e x c l u s i v e c a t e g o r i e s that can be classified numerically. A n u m b e r represents each of the possible terms in a field so that information is numerically transcribable to the database. Consequently, with the exception of the h e m i s p h e r e entry, all the information in the Landslide R e c o r d is numeric. References in the Report and d e s c r i p t i v e C o m m e n t s are not transferred to the landslide R e c o r d but remain on file with the Landslide Report. The references are listed in a separate database and are r e p r e s e n t e d by accession numbers in the Record. Using numbers rather than words in the L a n d s l i d e record produces a d a t a b a s e that is l a n g u a g e - i n d e p e n d e n t . A second a d v a n t a g e is that less space is n e e d e d to store the information in the database.

The bibliography As only the accession numbers of the rlevant reports or papers are t r a n s c r i b e d to the L a n d s l i d e Record, a separate b i b l i o g r a p h i e file should be created at the National Centre. R e f e r e n c e s m a y include books, j o u r nals, conference p r o c e e d i n g s , theses, and reports. Here we suggest a w i d e l y a c c e p t e d format (Figure 4) m o d eled after the C h i c a g o Manual of Style (University of Chicago press, 1982). Centres may however, adopt other formats without affecting the L a n d s l i d e Summary. Up to three authors for each article can be stored in the database. W h e r e there are four or m o r e authors for a reference, listing the first three will p r o v i d e enough information to locate the d o c u m e n t . The Title field will usually be filled e x c e p t where the r e f e r e n c e is an entire book. The p u b l i c a t i o n c o n t a i n i n g the article, whether it is a book, c o n f e r e n c e p r o c e e d i n g s , report, thesis, journal or n e w s p a p e r article, will be entered in the Book/Journal field. Both the Title and B o o k / J o u r n a l fields have been allotted two full fields, or 130 characters. Each line is a separate field. Two Editor fields, a Publisher and a Place of P u b l i c a t i o n field have been p r o v i d e d to p e r m i t the i n c l u s i o n o f i n f o r m a t i o n from books. For c o n f e r e n c e p r o c e e d i n g s , the p u b l i s h e r is often the society r e s p o n s i b l e for the c o n f e r e n c e and the Place of P u b l i c a t i o n w o u l d be the city in which that society is based. This i n f o r m a t i o n will make it p o s s i b l e to trace the p r o c e e d i n g s and to procure a copy. The remaining two fields, Volume and Pages, are used for journal references, or to indicate r e l e v a n t pages in a book. With this method o f formatting and by using P C - F I L E , any o f the fifteen fields can be i n d e x e d and retrieved to p r o d u c e a listing in a s c e n d i n g o r d e r o f the field or fields chosen. This format also greatly refines the

search process. For instance, the d a t a b a n k can be searched for all references by a certain author on a certain landslide (providing the name of the landslide is in the title of the references). The b i b l i o g r a p h y can also be sorted by more than one criterion. For instance, it would be possible to p r o d u c e an alphabetical list of authors (using the first author as an index) in order of the date of p u b l i c a t i o n by using y e a r as an index. It is also possible to locate all references of one type. For example, journal references can be located by listing all the references with an e n t r y in the volume field. Structuring the b i b l i o g r a p h y as a d a t a b a s e allows for greater accessibility and m a n i p u l a t i o n of the references.

Software The software and h a r d w a r e used to m a n a g e the landslide database were s e l e c t e d b e c a u s e they are both ine x p e n s i v e and c o m m o n l y a v a i l a b l e . They are e x a m p l e s that work but the W o r k i n g Party is not in a position to specify or r e c o m m e n d them. We expect that many other c o m b i n a t i o n s of software and hardware will also work. We have used P C - F I L E , Version 5.0, as an ine x p e n s i v e e x a m p l e of the s o f t w a r e programs that can manage the landslide d a t a b a s e . It is a general purpose database m a n a g e m e n t p r o g r a m that is powerful and easy to use. Its files are c o m p a t i b l e with P C - F I L E : dB, d B A S E I I I PLUS and o t h e r d B A S E programs. This means that d B A S E files can be read and edited by PCF I L E directly and vice versa, P C - F I L E databases can be processed directly by d B A S E . Because of the popularity of d B A S E as a d a t a b a s e m a n a g e m e n t program, the scope of P C - F I L E is g r e a t l y increased. F o r the exchange of information however, the number of fields and the field lengths o f the two d a t a b a s e s have to be the same. P C - F I L E can also e x c h a n g e data (import and export) with other p r o g r a m s such as WordPerfect, Microsoft Word, Microsoft Excel, Lotus 1-2-3, P C - C a l c + and others. In most cases h o w e v e r , the database that is to be transferred must match the e x i s t i n g file exactly. The database must be d e f i n e d as h a v i n g the same number of fields with m a t c h i n g field lengths, and in the same sequence as the e x i s t i n g d a t a b a s e . In general, P C - F I L E stores, sorts, and r e t r i e v e s data. I n f o r m a t i o n is stored in the given format and can be m o d i f i e d as necessary. Data are organized either a l p h a b e t i c a l l y , by date, or numerically. Also, P C - F I L E prints reports, or lists according to specifications. P C - F I L E can run on the I B M series of personal computers or highly c o m p a t i b l e c o m p u t e r s . P C - F I L E requires a m i n i m u m of 1 m e g a b y t e of a v a i l a b l e disk storage, 512 K a v a i l a b l e R A M , a 80 c o l u m n display, and DOS version 2.0 or later. P C - F I L E has been designed to work with m o s t printers.

Examples At the National and W o r l d Centres, analysis of the landslide data can p r o v i d e v a l u a b l e information on the occurence of landslides. M a p p i n g software can be used

104

LANDffLIDE REPORT Date of Report

Landslide Locality Reporter:

Name

Sore

day Z 7 /

mo. yr. ~ / ~ /

National Inventory Number

~/,a,,t~,e~' 9 j

/&,Q/ J

Affiliation //~J/ff;z/r n / / / ~ I P ~ / ~ 6 / Address

/)e,z~a./'z'z~,/g,r,i/" /ff'~ ~,~/~ev I/~..,:,.~,'I~, n / A/~w//"d 2 d.u.- /.., A i m , , i :

Phone

/ ~ o S ) 9 gz -

degrees Position:

Latitude

minutes *

Longitude

Elevation:

crown

cFy~'

seconds a

rupture surface toe

day

Type:

First movement

hemisphere

a.s.i.

m a.s.l.

mo. yr. ~17/ I

(circle the appropriate n,~mhers and terms)

I. rock

2. debris

3.~~rt~

I. fall

2. topple

Second movement

hemisphere

m a.s.l. m

tip

Date of occurrence:

4. lateral spread

(circle the appropriate numbers and terms)

I. rock

2. debris

I. fall

2. topple

3 ~ . ear~'~ 3. slide

4. lateral spread

Fig. 3 : A Landslide Report - Side 1.

5. flow

105

Geometry:

Rupture

Surface

Displaced

Lr =

Width

Wr =

UI$

wd =

Depth

Dr =

V = ~LdDdWd/6

Damage:

~"./

.Z. <r

r.=

Length

Volume:

Mass

m3 x

Value

S/?'

Swell

V = 10 n

factor

n =

Injuries

Currency

~"',~/~

Deaths

.~/

References :

i(c,#.kZal, c ' x E , A ~ . f

I/f ~,,,1..,~

" -

~,r

z cD .,,,.~,,z

,/,;

~;',~/..s

f- ar~.i~

,I~

9if'u.,/,~Are

..<'so,.,,/..'ro.~:,, ,.+

da~./,_u

,9 ',dro,Z~_

r/,

Fig. 3 : A L a n d s l i d e R e p o r t - Side 2,

_ / ' ~ , . , e -J~o.~ -

106

R~O_M I

F[e!d

Co~ump

Description

Accession

i-3 6-20 22-36 38-52

Author,

54-58

Year

number

2 3

6-70 6-70

Title,

4 5

6-70 6-70

Book/Journal,

6-20 22-36

6-55

Publisher

2-20

P l a c e of

2 3 4

i5 15 15

6 7

65 65

8 9

65 65

i0 ii

15 15

first second third

line line

Editor,

one Two line line

one two

first second

publication

in conjunction with the l a n d s l i d e d a t a b a s e to depict the distribution of landslides. D e p e n d i n g on the scale, the maps can be used to i n d i c a t e local, national, or global patterns of landslide activity.

Field Width

Fiei~

22-31

Volume

33-47

Pages

The data can also be sorted to identify trends 9 For instance, if landslides are s o r t e d a c c o r d i n g to the date of occurrence, temporal trends can be identifed. If the data are sorted by month o f o c c u r r e n c e , seasonal patterns may become apparent ( F i g u r e 5). If the data are sorted by the year of o c c u r r e n c e , l o n g e r term patterns may be identified (Figure 6). As a c o n v e n i e n t small s a m p l e for d e m e n s t r a t i o n purposes,a part of the C a n a d i a n L a n d s l i d e inventory, the historic landslides of A l b e r t a , has been c o m p i l e d in the P C - F I L E database m a n a g e m e n t program. A n u m b e r of tables have been p r o d u c e d from d a t a a c c u m u l a t e d as of April, 1989. Table 1 is an e x a m p l e o f a report pro-

Figl 4 : Tile Bibliographic Database.

6 f

r e

tt e

n c

1 B Jan

Mar Apr

Feb

!~9

Jun J u l

Aus Sep

0c%

Dec

Nov

Fig. 5 : Monthly Occurrence of Landslides in Alberta.

"1 "

. . . .

: -

. . . .

t . . . .

: .....

I . . . .

: .....

: ......

: .....

: . . . . .

: ......

: :

I :

| :

: :

: .

.* :

.= .....

; ......

: .....

;

; .....

: :

q u e 13

.... ==....

:= .

. : ..... .

; .....

: :

at.

: It

.i :

2 I

: .

. = ......

. = ...... .

I :

* 9

. ; .... .

: I

1922

1933

: 1

: ~

: ]

: I

1~r44 1955

Fig. 6 : Historic Landslides of Alberta.

;

..............

: ~

; ......

: I

1966

i :

1977

.....

: I

19B8

107 Table

no 1 2 3 4 5 6 7 8 9 I0 II 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57

I : L a n d s l i d e s of A l b e r t a .

location

year

Sunnyside Hill,Calgary Home Rd.,Calgary Forest Lawn,Calgary Park Hill,Calgary Wildwood,Calgary North East,Calgary Nose Creek,Calgary Lesuer(North S a s k . R. V a l l e y ) Strathcona Park,Edmonton Forest Heights,Edmonton Whitemud Freeway,Edmonton Grierson Hill,Edmonton Laurier Rd., Edmonton Belgravia Rd.,Edmonton Victoria Park Rd.,Edmonton Beverly Bridge,Edmonton 76th Ave. at Mill Ck.,Edmonton Rat Ck.,Edmonton 9804-i12th St.,Edmonton Devon Edgerton West of 3rd Ave. S.,Lethbridge Scout Falls,Medicine Hat Kingsway Ave.,Medicine Hat Power Plant,Medicine Hat Little Sandhill Ck.,Patricia Princess Coulee,Dinosaur Park Princess Coulee,Dinosaur Park Frank, Crowsnest Pass Brazeau Lake,Jasper Nat. Park Judah Hill, Peace River Dunphy, Red Deer River Litchfield, Oldman River Little Smoky River WID Landslide, Calgary Dunvegan Creek, Peace River Whitemud Freeway, Edmonton Northeast Calgary Peace River Highway Bridge SM-C2, North Saskatchewan R. North Sask. R., SW of Edmonton Luscar mine, pit 51-B-2 Nigel Falls, Icefields Pkwy. Bighorn Flow, Highway ii Smoky 2 Bridge, Smoky River Syncrude mine, Fort McMurray Redcliff Pump., Medicine Hat i s t St. S W . , M e d i c i n e Hat A r e a i, N o r t h S a s k . R . , D e v o n A r e a 3, N o r t h S a s k . R . , D e v o n A r e a 4, N o r t h S a s k . R . , D e v o n Athabasca Elementary School Hangingstone R., Fort McMurray Blk.8,Clearwater R.Ft.McMurray Blk. l l , 1 2 , C l e a r w a t e r R . F t . M c M u r Blk. 15,ClearwaterR.,Ft.McMurra Angus Property, Edmonton

duced from portions of the database file. This table is simply constructed. Once the database is established, the 'Report' option is selected from the main menu. For this table, 'row' format was chosen. This format prints one record on each line, and the fields line up in columns. The fields are then ordered, and the report is given a permanent title.

1948 1950 1969 1967 1971 1961 1971 1963 1910 1911 1973 1901 1972 1965 1978 1971 1972 1950 1970 1965 1974 1970 1980 1955 1980 1986 1975 1985 1903 1933 1984 1970 1982 1958 1982 1959 1976 1964 1957 1974 1945 1979 1982 1980 1972 1977 1980 1980 1974 1974 1974 1970 1975 1973 1975 1975 1970

T2 3 4

5 3 3 3 1 3 3 3

3 3

3 3 3 3 1 3 3 1

3 1 3 3 2 2 3

3 3 3 3 3 3 3

I0 09

1 1

3 3

1 2 1 3 1 1 1 1 3 1 1 1 1 1 3 3 1 1 1 1 1 2 1 1 1 1 3 3 3 1 1 3 3

3 3 3 3 3 3 1 3 3 3 3 3 3 3 3 3 3 3 3 3 3 5 3 3 3 3 3 3 3 3 3 3 3

3 1

5 2

3 1

3 3

03 22 07 04 04 07 06 08 08

29 i0 -

05 05 I0

ii Ii 06

I0 05

i0 -

08 i0 08

31 15 07

A variety of graphs such as line and dot graphs, bar charts (vertical and horizontal), pie graphs, regression lines and logarithmic plots can also be produced. Using the information provided by Table 1, three graphs were produced (Figures 5, 6 and 7). The first graph shows the monthly occurrence of landslides in Alberta. To produce this graph a database was created to record the

108

First Movement

First Material

Type

~~ s

mook --

- 86M

Slows

49Z

unmecomaea

sliaes

- -

Type

ae3mls - 7 z ~

eax-th

fmeq~ency

Second Material

Type

iil,,t

ihi: -

88M

35~.

u n ~ e c o ~ e ~

Type

- 88M earth

i ~

f~eq~ency

Second Movement

unrecomaea

un~ecomaea

sliaes

aeb~i~

fmequencM

5~ -

Fig. 7 : Type of Landslides Occurring in Alberta.

number of landslides occurring in each month over the 89 year period. The 'Graph' option is then selected from the main menu. The graph data is summarized using subtotals, the Month field is graphed along the x-axis, and the frequency of occurrence is graphed along the y-axis. The graph is then given a permanent title (and subtitle) and the axes are labeled. Finally, the graph format is chosen. In this case, the vertical bar graph was selected. The resulting graph illustrates the seasonal distribution of landslide activity in Alberta. Although the results are based only on the 38 landslides for which the month of occurrence is known, trends can be identified. Apparently landslides occur in the late spring and summer. Also, it is worth noting that no landslides have occurred in the winter months of December, January, and February, and only one landslide has occurred in March. The second graph (Figure 6), a dot graph, depicts the temporal distribution of Albertan landslides as they have occurred over a ninety year period. To produce this graph, a database was formed to record the number of landslides that occurred each year since 1900. The 'Graph' option is then selected, the data is summarized using subtotals, the Landslide field is the field graphed along the x-axis and the year field is used to trigger the subtotals. The graph format chosen in this case, is the scatter graph. The resulting graph illustrates the temporal distribution of landslide activity in Alberta. Although the historic distribution of landslides is largely dependent on the reliability of the reporting process, there is an apparent increase in slope instability in the early 1970's. The third graph (Figure 7) also uses the information provided by Table 1. The database was formatted with each option of material and movement type as a separate field, With one field being marked for each land-

slide entry. The 'Graph' option is then selected, the data is summarized by using totals, the order of the options is specified, the values of each entry are summed, and the graph is labeled and given a title. In this case, the pie chart format was chosen to display the results. These charts illustrate the type and the material involved in the first and second movements of landslides which have occurred in Alberta between 1900 and 1989. Apparently, most of the cases of slope instability in Alberta are slides in rock. Subsequent analysis of these and other trends might then indicate correlations between the occurrence of landslides and other factors.

Damage As it is not practical to report all landslides, we defined a reportable landslide as one which satisfies at least one of the following criteria (WP/WLI, 1990) : 1) is over 1 million cubic metres in volume 2) causes casualties 3) causes considerable direct or indirect damage. The damage estimate included in the Landslide Report should be in the local currency. The number of deaths and substantial injuries by the direct or indirect effects of the landslide should also be recorded. A substantial injury results in incapacitation for over a year. Direct effects take place on the landslide, indirect effects take place off the landslide (Fleming and Taylor, 1980). At the national level, for the Landslide Summary, we propose the per capita annual Gross Domestic Product (or person-product) as a currency- and culture-independent damage measure. To determine this value, the annual Gross Domestic Product (GDP) of the country is divided by its population. This yields a value, the

109 person-product, that represents the average contribution to the G D P per person, per year, for that country. The dama,,e estimate eiven in the Landslide Report. should then be divided by the person-product. The result, the number of p e r s o n - y e a r s , is an estimate of d a m a g e in terms o f the effort it will take inhabitants of the country to repair the damage.

and (}DP statistics for 1971 (Table 2) allow the total economic damage to be c a l c u l a t e d as :

Population data can be found in D e m o g r a p h i c Yearbooks published by the United Nations. Gross Domestic Products are listed in the Statistical Yearbooks. also published by the United Nationas, and in the World D e v e l o p m e n t Reports published by the World Bank. Local, authoritative sources of statistics can also be used. For instance, the Canada Yearbook, published by Statistics Canada, p r o v i d e s annual estimates of G D P and population.

person-years 9 d'_a_m_ageestimate= $17,000,000 person-product $4,511

Population and G D P data have been tabulated to show the annual per capita G D P for C a n a d a for the fifteen year period, 1970-1985 (Table 2). A similar table for other countries w o u l d provide the n e c e s s a r y information to convert the d a m a g e values given in the Landslide Report to the p r o p o s e d international values. Thus, this culture- and c u r r e n c y - i n d e p e n d e n t method o f assessment, will be the d a m a g e value given in the annual National Landslide Summary. Table 2 : Per Capita GDP tor Canada, 1971")- 1985 (Statistics Canada. 198~).

~_ear

Population in t h o u s a n d s

GDP in $x10 ~

Per

Capita

1970

21,297.0

89,116

4,184

1971

21,568.3

97,290

4,511

1972

21,801.5

I08,629

4,983

1973

22,042.8

127 372

5,778

1974

22,364.0

152

iii

6,802

1975

22,697.1

171

540

7,558

1976

22,992.6

197 924

8,608

1977

23,272.8

217 879

9,362

1978

23,517.0

241604

1979

23,747.3

276 096

11,626

309.891

12,889

24,042.5

1981

24,341.7

355 994

14,625

1982

24,583.1

374442

15,232

1983

24,782.2

405 717

16,371

1984

24,978.2

444735

17,805

1985

25,165.4

478 765

19,025

= $4,511 ( p e r s o n - p r o d u c : )

= 3,769 ( p e r s o n - y e a r s ) 3,769 person-years p r o d u c t i o n are n e e d e d to repair the damage. So, the total economic d a m a g e c a u s e d by the St. Jean Vianney landslide, using this culture- and currency- independent method, is c a l c u l a t e d to be 3,769 personyears. The value of the d a m a g e in 1985 dollars is 3,769 x 19,025 = S72 M.

Discussion The need to establish a World L a n d s l i d e Inventory is apparent. The world d i s t r i b u t i o n of landslides has not yet been mapped. L a n d s l i d e studies are isolated, limited their interpretation to local factors. L o o k i n g at the occurrence of landslides on a much larger scale may reveal broad scale or interactive p r o c e s s e s that contribute to slope movements.

GDP($)

10,274

1980

GDP S97,290 person-product ( 1 9 7 1 ) : . . . . . . . p o p u l a t i o n 21.568,300people

The Landslide S u m m a r y will also have a record of the total n u m b e r of deaths and substantial injuries, as given in the Landslide Report. To illustrate the p r o p o s e d method of d a m a g e assessment, c o n s i d e r the St. Jean Vianney landslide, Quebec, Canada. This landslide occurred on M a y 4. 1971, and involved an area o f about 268,000 m 2. The d a m a g e cost, including relocating the local p o p u l a t i o n , was established at $17 M. F o r t y - t h r e e houses were d e s t r o y e d and 31 lives were lost (Cruden et al., 1989). Population

Once the landslide n o t i f i c a t i o n n e t w o r k is established. the passage of information should readily flow through the system to the World L a n d s l i d e Inventory. The accumulated data at all levels of the n e t w o r k will provide an invaluable resource for the identification of local, national, or world patterns o f landslide distribution. This will lead to a better u n d e r s t a n d i n g o f the causes of landslides and will p r o v i d e more accurate hazard assessments. Thus. the W o r l d L a n d s l i d e Inventory will lead to p r e d i c t i v e models, w h i c h can then be used to alleviate the landslide risk. The structure o f the Inventory and the format o f the S u m m a r y are suggestions which can be m o d i f i e d by d i s c u s s i o n s from both within and outside the Working Party (which is listed in Appendix A of Working Party on W o r l d L a n d s l i d e Inventory (1990)). The C h a i r m a n o f the W o r k i n g party would w e l c o m e carefully d o c u m e n t e d p r o p o s a l s for additions or a m e n d m e n t s to the S u g g e s t e d Method.

Acknowledgements This Suggested M e t h o d was drafted by the Working Group on Landslide S u m m a r i e s , chairman, D.M. Cruden, members. C. B o n n a r d , H.H. Einstein, K. Sassa, M. Hashizume. M. Popescu, and Z-Y. Zhang. It was a p p r o v e d by the W o r k i n g Party at its meeting in A m s t e r d a m in August 1990. Draft revisions were c o m p l e t e d by J.S. de Lugt. Travel of some Working Party m e m b e r s to the A m s t e r d a m m e e t i n g was supported by UNESCO.

110

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