Question

Consider the following statements:
1. Only the surface flow constitutes the flood hydrograph due to an isolated storm.
2. For a given storm, the flood peak is dependent on the drainage density.
3. Fan shaped catchments give narrow hydrograph with low peak.
Which of these statements is/are correct?

• A. 1, 2 and 3
• B. 1 and 3
• C. 2 only
• D. 3 only

Answer 1

The correct option is C 2 only

The flood hydrograph consists of flow in all the three phases of runoff, viz.surface runoff, interflow and base flow.
The factors affecting flood hydrograph are shape, size, slope and drainage density. A large drainage density creates situation conducive for quick disposal of runoff down the channels. This fast response is reflected in a pronounced peak discharge.
Fan shaped i.e. nearly semicircular shaped catchments give high peak and narrow hydrograph while elongated catchments give broad and low-peaked hydrograph.