Question

An unlined canal of a trapezoidal shape having side slope 1.5 H : 1 V carries a discharge of Q MLD. The bed material is composed of soil having slit factor f. As per Lacey theory, the velocity of flow is given by $V=\frac{[Q{f}^2{]}^{1/6}}{k}$, the value of k (correct upto two decimal places) is _______.

• A. 4.79

Answer 1

The correct option is A 4.79
As per Lacey theory,

$V={\left[\frac{Q{f}^2}{140}\right]}^{1/6}$

where Q = discharge in cumecs

f = silt factor

$1\text{MLD}=0.011574m^3/sec$

$\therefore V={\left[\frac{0.011574Q{f}^2}{140}\right]}^{1/6}$

$=\frac{(Q{f}^2{)}^{1/6}}{4.79}$

Hence k = 4.79