Question

Which of the following is not a common use of unit hydrographs?

• A. Extending flood flow records based on rainfall
• B. Flood forecasting and warning systems
• C. Estimation of time of concentration
• D. Design of hydraulic structures

Hint:

Unit hydrographs are powerful tools in hydrology for modeling watershed response to rainfall. They are based on the principle of linearity and time-invariance. While UHs are used for predicting runoff and designing hydraulic structures, the time of concentration is generally an input or a characteristic derived from the watershed's physical properties, not an output from applying a UH.

Answer 1

The Correct Option is C

The role of unit hydrographs in hydrology and water resource management:

A unit hydrograph is a hydrologic tool used to model the response of a watershed to a unit of rainfall excess over a specified duration. Here is an explanation of the different options provided:

1. Extending flood flow records based on rainfall: Unit hydrographs help estimate the streamflow response to rainfall events, thereby extending flood flow records.
2. Flood forecasting and warning systems: By predicting how rainfall will translate into runoff, unit hydrographs assist in flood forecasting and provide critical information for warning systems.
3. Estimation of time of concentration: This is not a common use of unit hydrographs. Time of concentration refers to the time it takes for water to travel from the most distant point in the watershed to the outlet, and is typically estimated using empirical formulas or travel time methods, not unit hydrographs.
4. Design of hydraulic structures: Hydraulic structures benefit from the flow information provided by unit hydrographs as they aid in understanding peak flows and storm response.

The correct answer is: Estimation of time of concentration, as it is not a common use of unit hydrographs.