Question

To derive the total flood hydrograph at a catchment outlet from an isolated storm, the order in which the following methods are applied, from the first method to the last method, is

• A. PRSQ
• B. PQRS
• C. RPSQ
• D. PSQR

Hint:

When deriving a flood hydrograph, always follow the correct sequence of steps to ensure accurate results, starting with rainfall data and ending with the baseflow addition.

Answer 1

The Correct Option is A

To derive the total flood hydrograph at a catchment outlet from an isolated storm, the following sequence of methods is used:

1. P - Obtaining the hyetograph: This is the first step where the rainfall data (hyetograph) is collected.
2. R - Estimation of initial and infiltration losses: This step involves estimating the losses due to initial abstraction and infiltration during the storm.
3. S - Application of unit hydrograph: Using the unit hydrograph method, the runoff is derived from the storm's rainfall.
4. Q - Addition of baseflow: Finally, the baseflow is added to the hydrograph to get the total flood hydrograph.

Thus, the correct order is PRSQ, which corresponds to option (A).

This sequence ensures that all aspects of the storm’s effect on the catchment are considered in the right order, starting with the rainfall data and ending with the addition of the baseflow.