In surface-water hydrology, who first proposed the widely used 'infiltration capacity' concept for describing the maximum possible rate at which soil can absorb rainfall under given conditions?

Introduction / Context:
The concept of infiltration capacity is fundamental in hydrology and storm-runoff modeling. It represents the upper limit of soil intake rate under prevailing conditions (soil type, moisture, cover, and rainfall intensity). This question checks your recall of the originator of the theory used in many infiltration and excess-rainfall computations.

Given Data / Assumptions:

• The term 'infiltration capacity' refers to a rate (depth per unit time).
• We focus on the origin of the theory, not its formulae or parameter estimation.
• Names listed are historical hydrology figures; only one is directly credited with this theory.

Concept / Approach:
Horton advanced a physically inspired, empirically supported description in which infiltration capacity typically decreases exponentially during a storm toward an asymptotic minimum. His framework underpins Hortons infiltration model and many textbook treatments, making 'Horton' the definitive answer.

Step-by-Step Solution:

Verification / Alternative check:
Standard hydrology texts (storm-runoff analysis, unit hydrograph derivations, infiltration modeling) consistently cite Horton for the infiltration capacity concept and its exponential decay form.

Why Other Options Are Wrong:

• Merrill Bernard / W. W. Horner / LeRoy K. Sherman: Important contributors in hydrology, but not originators of the infiltration capacity theory.
• None of these: Incorrect because the correct name appears in the list.

Common Pitfalls:

• Confusing Horton's infiltration concept with SCS Curve Number abstraction; they are distinct methods.
• Attributing the theory to general 'infiltration tests' or empirical charts rather than the original theoretical framework.

Final Answer:
Robert E. Horton