What parameter did Lacey introduce in his theory that was not a factor in Kennedy's approach to canal design?

Explanation:

Lacey's Introduction in Canal Design

In his theory of canal design, Lacey introduced the concept of the silt factor which was not a parameter considered in Kennedy's approach. Kennedy's method focused more on empirical observations and factors like velocity and discharge, but did not specifically account for the characteristics of the silt within the canal. The silt factor introduced by Lacey takes into account the properties of the silt, like its size and cohesion, which significantly affect the stability and design of the canal.

Analyzing the Given Options

1. "Hydraulic radius" (Option 1)

   • Hydraulic radius is the cross-sectional area of flow divided by the wetted perimeter. This is a common hydraulic parameter, but it was already considered in traditional canal design approaches and not unique to Lacey.

2. "Wetted perimeter" (Option 2)

   • The wetted perimeter is the perimeter of the cross-sectional area that is in contact with water. This is another traditional parameter in canal design, not unique to Lacey.

3. "Hydraulic diameter" (Option 3)

   • Hydraulic diameter is a measure used in fluid mechanics, particularly for non-circular conduits. Like hydraulic radius, it is not a unique parameter introduced by Lacey.

4. "Silt factor" (Option 4)

   • The silt factor is a parameter introduced by Lacey that takes into account the properties of silt, such as particle size and cohesion, which directly affect the design and stability of the canal. This was a new concept not considered by Kennedy.