The Burge formula for estimating discharge (in cumecs) is primarily based on which catchment characteristic(s)?

Introduction:
Regional flood formulas provide quick discharge estimates from simple catchment descriptors. The Burge formula (empirical) is one such relation historically used where detailed hydromet data are sparse.

Given Data / Assumptions:

• Context: Burge formula gives discharge in cumecs.
• Options vary: area-only vs area plus other factors.

Concept / Approach:
Empirical regional formulas often scale peak discharge to drainage area using a power-law, Q = C * A^n, with constants tuned from historical peaks. Burge’s form relies primarily on the drainage area A, implicitly absorbing other influences into the empirical constants.

Step-by-Step Solution:
Step 1: Identify the class of formula: area–discharge scaling.Step 2: Recognize that no explicit rainfall/runoff term appears; rainfall variability is embedded in the coefficient from regional calibration.Step 3: Conclude the primary variable is drainage area.

Verification / Alternative check:
Comparisons with other regional formulae (e.g., Dickens, Ryve) show similar area-only dependencies with region-specific constants, reinforcing the interpretation for Burge.

Why Other Options Are Wrong:

• Rainfall and drainage area: Burge does not include an explicit rainfall term.
• Runoff and drainage area: runoff is not an independent input; discharge is the output.
• Drainage area and its shape: shape factor is not explicit in the original form.

Common Pitfalls:

• Assuming all empirical formulae include storm rainfall explicitly.
• Confusing embedded calibration effects with explicit variables.

Final Answer:
Drainage area.