How do you calculate time of concentration?
When the drainage area consists of several different types of surfaces, time of concentration is calculated by adding the time for each type of flow along the flow path from the watershed divide to the watershed outlet. Time of concentration is generally applied only to surface runoff.
What is time of concentration in rational method?
This command calculates the time of concentration (Tc) by the Rational method. The Tc is the time required for water to flow from the most distant point in the watershed to the measurement point.
What do you mean by time of concentration and how it is determined?
Time of concentration is a concept used in hydrology to measure the response of a watershed to a rain event. It is defined as the time needed for water to flow from the most remote point in a watershed to the watershed outlet.
What are the factors affecting time of concentration?
It is one of the most important parameters for determining timing of direct runoff response of a watershed to precipitation. The time of concentration is correlated to different watershed parameters such as watershed area, main channel length, basin slope, soil type, and vegetation (roughness) [McCuen 1989].
What is the minimum time of concentration?
5 minutes
Minimum Time of Concentration Use a minimum tc value of 5 minutes for urbanized areas and a minimum tc value of 10 minutes for areas that are not considered urban. Use minimum values even when calculations result in a lesser time of concentration.
How does time of concentration affect peak flow?
Urbanization usually decreases time of concentration, thereby increasing the peak discharge. However, time of concentration can be increased as a result of ponding behind small or inadequate drainage systems (including inlets and road culverts) or by reduction of land slope through grading.
What is meant by time of concentration?
Time of concentration (Tc) is the time required for runoff to travel from the hydraulically most distant point in the watershed to the outlet.
What is the minimum time of concentration for rational method?
Minimum Time of Concentration Use a minimum tc value of 5 minutes for urbanized areas and a minimum tc value of 10 minutes for areas that are not considered urban. Use minimum values even when calculations result in a lesser time of concentration.
How does watershed shape affect time of concentration?
Shape. For equal sized watersheds, runoff decreases as overland flow length increases. This results from the increased time of concentration. Longer duration storms, needed to produce runoff from all points in watershed, have lower average intensities.