3. Flooding processes

To understand this process, we need to analyze the various factors that contribute to the formation and temporary increase in river flows. To simplify, we distinguish between :

• mobilizable water, made up of water received by the watershed ;

• runoff, corresponding to the proportion of water that has not infiltrated the soil. It depends on the nature of the soil, its surface occupation and the intensity of the rainfall event;

• time of concentration, defined as the time required for a drop of water to reach the watershed outlet from the point furthest away;

• flood wave propagation, a function of the structure of the bed and alluvial valley, in particular the slope and characteristics of the floodplain.