Hydraulic Structures: Fourth Edition

flow depth0.25 m. Adopt a minimum depth of 0.5 m. The upstream
curtain wall depth is one-third of the FSL flow depth0.32 m. Adopt a
minimum depth of 0.5 m.

DOWNSTREAM BED PROTECTION

Length of protectionofftake flow depthworking head1.10 m. Pro-
vide a gravel apron, about 1 m long and 150 mm thick, downstream of the
cistern. The upstream approach length of the crest

{[5H (crest level bed level)](crest level bed level)}1/2

0.64 m.

The radius joining the crest 2 H1.728 m. The details of the layout are
shown in plan and section in Fig. 9.31.

INTAKES 407

Fig. 9.31 Intake structure for a minor canal (outflow0.5 m^3 s^1 ; propor-
tional setting, H/D0.9); all dimensions in metres