stage to data-handling procedures (Sections 7.2.6 and 7.3). It is advisable
to consider instrumentation programmes in terms of the overall ‘system’
required, i.e. instruments, installation, commissioning, monitoring, and
data management and interpretation.
An illustrative instrumentation profile for the major section of a new
earthfill embankment is illustrated in Fig. 7.6. Comprehensive instrumen-
tation programmes of this type are described in Millmore and McNicol
(1983) and in Evans and Wilson (1992). A valuable review of embankment
instrumentation experience in the UK is given by Penman and Kennard
(1981); the rôle of instrumentation is discussed in Penman (1989), in
Charles, Tedd and Watts (1992) and in Charles et al.(1996).
For new-construction dams presenting little danger to life in the
event of breaching a modest level of instrumentation is generally ade-
quate. As a minimum, provision should be made for monitoring seepage
flow through the internal drainage system and, in the case of embankment
dams, secure levelling stations should be established at intervals of 20 m or
25 m along the crest for monitoring settlement. Instrumentation at this
level may also be appropriate on lesser dams, including small farm or
amenity dams, if their location suggests a possible hazard to life in the
event of breaching.
The retrospective instrumentation of existing embankment dams, in
particular those considered to represent a significant potential hazard, is
now common practice. The limitations on the type of instrument which
can be installed retrospectively are self-evident, and the datum values
against which subsequent change may be assessed now become those
302 DAM SAFETY: INSTRUMENTATION AND SURVEILLANCE
Fig. 7.6 Schematic instrument layout: major section of new embankment
dam
