Chapter 7
Dam safety:
instrumentation and
surveillance
7.1 Introduction
7.1.1 A perspective on dam safetyReservoirs constitute a potential hazard to downstream life and property.
The floodplain at risk in the event of catastrophic breaching may be exten-
sive, densely populated and of considerable economic importance. In such
instances dam failure can result in unacceptable fatalities and economic
damage.
Catastrophic failures involving large modern dams are rare, but
major disasters at Malpasset (France 1959), Vaiont (Italy 1963), Teton
(USA 1976) and Macchu II (India 1979) in particular had a seminal influ-
ence on all matters relating to dam safety. The four named disasters are
briefly put into perspective in Table 7.1. Collectively with the numerous
lesser failures of old or smaller dams occurring during the same period,
those four disasters focused international attention on dam safety and sur-
veillance to significant effect.
Surveys and statistical analyses of failures and other serious incidents
have been published by the International Commission on Large Dams
(ICOLD, 1995). Jansen (1980) provides a more detailed review of a
number of major dam disasters.
Catastrophic failure of a dam, other than as the direct result of an
extreme flood event, is invariably preceded by a period of progressively
increasing ‘structural’ distress within the dam and/or its foundation. Dam
surveillance programmes and instrumentation are intended to detect
symptoms of distress and, where possible, to relate those symptoms to spe-
cific problems at the earliest possible stage.
Instruments strategically placed within or on a dam are not of them-
selves a guarantee against serious incident or failure. Their prime function