1.2 Introductory perspectives
1.2.1 Structural philosophy and generic types of dams
The primary purpose of a dam may be defined as to provide for the safe
retention and storage of water. As a corollary to this every dam must rep-
resent a design solution specific to its site circumstances. The design there-
fore also represents an optimum balance of local technical and economic
considerations at the time of construction.
Reservoirs are readily classified in accordance with their primary
purpose, e.g. irrigation, water supply, hydroelectric power generation,
river regulation, flood control, etc. Dams are of numerous types, and type
classification is sometimes less clearly defined. An initial broad classifica-
tion into two generic groups can be made in terms of the principal con-
struction material employed.
- Embankment dams are constructed of earthfill and/or rockfill. Upstream
and downstream face slopes are similar and of moderate angle, giving a
wide section and a high construction volume relative to height.
- Concrete dams are constructed of mass concrete. Face slopes are dis-
similar, generally steep downstream and near vertical upstream, and
dams have relatively slender profiles dependent upon the type.
The second group can be considered to include also older dams of appro-
priate structural type constructed in masonry. The principal types of dams
within the two generic groups are identified in Table 1.1. Essential
characteristics of each group and structural type are detailed further in
Sections 1.3 and 1.4.
Embankment dams are numerically dominant for technical and eco-
nomic reasons, and account for an estimated 85–90% of alldams built.
Older and simpler in structural concept than the early masonry dam, the
4 ELEMENTS OF DAM ENGINEERING
Table 1.1 Large dams: World Register statistics (ICOLD, 1998)
Group Type ICOLD code %
Embankment dams Earthfill TE 82.9
Rockfill ER
Concrete dams
(including masonry Gravity PG 11.3
dams) Arch VA 4.4
Buttress CB 1.0
Multiple arch MV 0.4
Total large dams 41 413
