Hydraulic Structures: Fourth Edition

collective importance is such, however, that Fig. 1.7 and Table 1.7 are pro-
vided in illustration. Selection of type of dam is discussed, with examples,
in Fell, MacGregor and Stapledon (1992), USBR (1987), Thomas (1976)
and Walters (1974).
The situation of a wide valley floored with deep deposits of fine-
grained soils, e.g. glacial tills etc., is illustrated in Fig. 1.7(a). Considera-
tions of foundation deformation and the depth of excavation required
favour an earthfill embankment, given the ready availability of suitable fill,
as at Kielder dam (Fig. 2.10 and Coats and Rocke, 1983). The availability
of competent rock at shallow depth, however, as shown in Fig. 1.7(b),
favours either a rockfill embankment or, alternatively, a concrete gravity
or buttress dam. Availability of rockfill, and thus relative cost, would
dictate the final choice. A narrow and steep-sided valley in sound rock, as
illustrated in Fig. 1.7(c), may be suited to an arch or cupola dam given
competent abutments. Economic considerations may, however, suggest
the rockfill embankment as a viable alternative.

SITE ASSESSMENT AND SELECTION OF TYPE OF DAM 33

(a) Wide valley with deep overburden:

fine-grained deposits, e.g. Fine glacial soils, tills etc., over 5m deep favour earthfill

embankment dam

(b) Valley with little overburden:

suitable for embankment,

gravity, or buttress dam

(c) Narrow valley, steep sides,

little overburden:

suitable for arch, cupola, or

rockfill embankment dam

(d) Valley with irregular depth of overburden:

possible composite solution as shown; spillway on concrete dam

SOUND ROCK

Fig. 1.7 Illustrative examples of dam type in relation to valley profile