tailwater level (TWL) is greater than the sequent depth, y 2. The following
are the suggested dimensions of such a structure (Fig. 10.15):
basin length LBLd2.55yc; (10.33)
location of impact block, Ld0.8yc; (10.34)
minimum TW depth, y 2 '2.15yc; (10.35)
impact block height, 0.8yc; (10.36)
width and spacing of impact block, 0.4yc; (10.37)
end sill height, 0.4yc; (10.38)
minimum side wall height, y 2 0.85yc; (10.39)
hereycis the critical depth.
The values of Ldcan be obtained from Fig. 10.16.
450 CROSS-DRAINAGE AND DROP STRUCTURES
Fig. 10.15 Impact block type basin (after Bos, 1976)
Fig. 10.16 Values of Ld/d(after Bos, 1976)
