Empirical runoff formula identification: The relation where Q is yearly runoff (cm), P is yearly rainfall (cm), H is the relief (difference in R.L. of highest and lowest points), and A is catchment area (m^2) is referred to as which named formula?

Introduction / Context:
Numerous empirical relations estimate annual runoff where gauged records are scarce. These formulas combine climatic input (P), basin geometry (A), and relief/topography (H) to approximate long-term runoff Q for planning-level assessments.

Given Data / Assumptions:

• Q in centimetres depth over the basin or converted as required.
• P in centimetres per year.
• H characterizes terrain relief (highest minus lowest R.L.).
• A is the plan area of the catchment.

Concept / Approach:

Among classical Indian runoff estimators, the form explicitly involving rainfall P, catchment area A, and relief H has been associated with Khosla’s approach to annual runoff estimation, which recognizes the hydrologic influence of topographic relief in addition to rainfall amount and basin size.

Step-by-Step Solution:

Verification / Alternative check:

Standard competitive-exam references list Khosla’s formula as the relation incorporating rainfall, area, and relief for annual runoff estimation, distinguishing it from English/Justin/Vermeule variants.

Why Other Options Are Wrong:

• English / Justin / Vermule: These forms either omit explicit relief or are applied differently.
• Inglis: Primarily regional for Maharashtra/Western India with other parameterizations.

Common Pitfalls:

• Confusing regional flood-peak formulas (e.g., Dickens, Ryves) with annual runoff relations.
• Ignoring units when converting Q from depth to volume by area scaling.

Final Answer:

Khosla's formula.