1. Hydrograph.

  • It is a curve or plot of discharge versus time at any section of a river.
  • It represents the flow characteristic of the river.

2. Period of Surface Run-off.

  • It is the time taken by the surface run off to pass the given section of the river,
  • after the surface run-off makes its first appearance at the section.

3. Period of Rise.

  • It is the time take by the surface run-off to reach its maximum value from the time of its beginning.

4. Time of Concentration.

  • It is the time require by the water to reach the outlet point from the most remote point of the drainage area.
  • When a storm has been in progress for a time equal to the time of concentration.
  • it is assume that all the part of the catchment start contributing to the discharge at the outlet.

5. Time of Over Land Flow.

  • The excess rainfall finds its way over land to the river stream and appears as surface run off, but only after some delay.
  • In other words, there exists a lag between the time when excess rainfall occurs and the time
  • when it appears at run-off at the outlet of the drainage basin.
  • This lag is the time for which water has flown through the basin before entering into a defined drain.
  • This time of overland flow is a variable factor depending upon the slope.
  • the type of surface of the ground, the length of path of flow and so many other factors.