ICOLD Bulletin 109

Appendix 1
CLASSIFICATION OF REPORTED FAILURES (excl. China & USSR)

1 .Presentation

Reported failures are cIassified under the following headings :
Dam category : gravit y, arch, buttress and multiple arch, embankment
Cause of failure ; for embankment dams: overtopping during construction, first filling, operation (by overtopping or internaI erosion)
Height (higher/lower than 30 metres)
Dates of failure and construction (pre-/post-1930).
Reservoir capacity, dam length and number of lives lost are also shown where known.

Appendix 1
CLASSIFICATION OF

2. Failures

Most reports of failures were taken from ICOLD Bulletin 99 "Dam Failures ­Statistical Analysis". However, about twenty of the failures mentioned in the Bulletin were not cIassified, through lack of data or because they were not due to the Irerein classified causes, and 15 of the failures in this Appendix do not appear in Bulletin 99 (mark X).

Many failures of dams of moderate height have probably gone unreported ; very few failures of large dams 10-15m high have been reported, although they represent 20 per cent of ail large dams. In addition, there are few reports on the 700 Japanese dams built before 1930 or the thousands of dams in the non-industrialised countries impounding less than 10 hm3. These three groups together represent one-third of aIl large dams and 5 per cent of reported failures, so that 50 to 100 large-dam failures might have gone unreported.

3. Dam Numbers in Tables

Figures for the number of >30m dams built are reliable.
For <30m dams, there is a large margin ofuncertainty on the number built, mainly
in the height range 10-15m, especially embankment types. The figures in the tables (2 000 pre-1930, 7 000 post-1930) are estimates for 15-30m dams and do not allow for 10-15m structures for which failures do not seem to be generally reported.

]

Gravity Dams (Concrete or Masonry)/
Barrages-Poids (Béton ou Maçonnerie)

<30 m

400 built before 1930 : 11 failures
1500 built after 1930 : 1 failure

First filling failures / Ruptures au premier remplissage

>10hm³

Failures in operation / Ruptures en service

>30 m

350 built before 1930 : 11 failures
1500 built after 1930 : 0 failure

First filling failures / Ruptures au premier remplissage

>10hm³|

Failures in operation / Ruptures en service

C=Concrete / Béton
M=Masonry / Maçonnerie
U=Upstream dam failure / Rupture du barrage amont
F=Failure dur to flood / Rupture par crue

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