SOME TERMS IN MOST COMMON USE IN REGARD TO RUN-OFF
- 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.