ABSTRACT
The time of concentration tc of waters in a watershed is defined as the maximum time needed for a drop of water to flow from a particular point in the watershed to the watershed’s outlet.
It is composed of three different terms:
• th - runoff initiation time - the time necessary for the soil to absorb the water before surface runoff begins;
• tr - runoff time - the time corresponding to water flowing over the surface or in the top soil layers into a collection system (natural waterway, collectors or pipes…);
• ta – routing time - the time necessary for the water in the waterway to reach the outlet.
