Which historical relation is commonly associated with selecting or relating roughness values (that can be translated to Manning's n ≈ 0.012 for smooth pipes) for use in open-channel flow computations?

Introduction / Context:
Several hydraulic formulae predate today's widespread use of Manning's equation. Designers historically used relations that provided coefficients convertible to present-day roughness terms. The question points to the tradition of choosing smooth-conduit values that correspond roughly to Manning's n ≈ 0.012.

Given Data / Assumptions:

• Smooth pipe or finished surface representative of low roughness.
• Open-channel or full-flow conditions requiring empirical coefficients.

Concept / Approach:
Kutter's formula was widely used to obtain Chezy's C as a function of hydraulic radius and a roughness parameter. From Chezy's C, equivalence to Manning's n can be established since Manning's and Chezy's forms are interrelated. Values that imply n around 0.012 are typical for very smooth pipes (e.g., glazed or drawn tubing), offering a historical pathway to today's roughness selection.

Step-by-Step Solution:
Recognize that Kutter provided a formula to determine Chezy's C based on roughness.Use the C–n relationship: C = (1/n) * R^(1/6) to convert between systems.Note that a smooth-pipe selection can map to n ≈ 0.012, a commonly cited low roughness value.

Verification / Alternative check:
Hydraulic texts list tables showing equivalences among Chezy C, Manning n, and Kutter/Bazin parameters; Kutter is most frequently cited for historic selection of C leading to modern n-values.

Why Other Options Are Wrong:

• Bazin: Another relation for Chezy C, but the common exam linkage for the n ≈ 0.012 reference is typically associated with Kutter.
• Williams–Hazen: Pressurized water distribution loss formula; not an open-channel roughness selection path.
• Crimp and Burge/Scobey: Less standard in this specific context for municipal sewers.

Common Pitfalls:
Confusing the role of formulas that produce Chezy C versus Manning n directly; forgetting that conversions depend on hydraulic radius assumptions.

Final Answer:
Kutter