Hydraulic Structures: Fourth Edition

in 3 and 1 in 8 are usually recommended. The discharge is given by

the following formula:

Q1.99LH3/2(H/B)1/6. (10.46)

3. Design of cistern is as follows:

length, Lc5(EHdr)1/2; (10.47)

depth, dc

1

4

(EHdr)2/3. (10.48)

4. Minimum length of impervious floor downstream of the crest,

Lbd2(D 1 1.2)Hdr. (10.49)

(c) YMGT-type drop (Japan)

This type of drop is generally used in flumed sections suitable for small
canals, field channels, etc., with discharges up to 1 m^3 s^1 (Fig. 10.19). The
following are the recommended design criteria:

1. sill height, Pvaries from 0.06 m to 0.14 m with the unit discharge q
   between 0.2 and 1.0 m^3 s^1 m^1 ;


2. depth of cistern, dc1/2(EcHdr)1/2; (10.50)


3. length of cistern, Lc2.5Ld, (10.51)

DROP STRUCTURES 453

Fig. 10.19 YMGT-type drop, Japan (Kraatz and Mahajan, 1975)