Step 1: Establish relationships.
- (A) Mean velocity in Lacey regime channel is proportional to $S^{1/2}$, corresponding to I.
- (B) Mean velocity in a lined channel is proportional to $S^{1/3}$, corresponding to II.
- (C) Normal scour depth in an alluvial channel is proportional to $Q^{1/2}$, corresponding to III.
- (D) Wetted perimeter in Lacey's regime is proportional to $Q^{2/3}$, corresponding to IV.
Step 2: Correlate the items.
\[ A \to I, B \to II, C \to III, D \to IV \]
Step 3: Finalize the answer.
Therefore, the correct pairing is option (1).
A hydraulic jump occurs in an open channel when the slope of the channel changes from ___________.
Consider flow in a long and very wide rectangular open channel. Width of the channel can be considered as infinity compared to the depth of flow. Uniform flow depth is 1.0 m. The bed slope of the channel is 0.0001. The Manning roughness coefficient value is 0.02. Acceleration due to gravity, \( g \), can be taken as 9.81 m/s\(^2\).
The critical depth (in m) corresponding to the flow rate resulting from the above conditions is ________ (round off to one decimal place).