The scour depth D of a river during flood, may be calculated from the Lacey’s equation

A

$$D = 0.47 \left(\frac {Q}{f}\right)^{\frac{1}{2}}$$

B

$$D = 0.47 \left(\frac {Q}{f}\right)$$

C

$$D = 0.47 \left(\frac {Q}{f}\right)^{\frac{1}{4}}$$

D

$$D = 0.47 \left(\frac {Q}{f}\right)^{\frac{1}{3}}$$