What is a flood ?

A flood corresponds to the presence of water in an area where, usually, there isn't. This flooding can be caused by different phenomena and, in particular, the overflow of a river or a ravine.

There are several types of flooding, including :

• The flood pouring : rapid rise and flow of the water in a river or a ravine, often associated with steep slopes. It is also referred to as "flash flood" or " flash flood ".
• The slow rise of water : rivers, plains or groundwater gorge gradually from the water and outside slowly. This phenomenon is slow is due to the accumulation of water (from rain or submersion marine) and is observable in the areas of plains, or at the mouth of the watercourse.
• The rainfall runoff : intense rains, most often in the city, can result in high volumes of runoff. The waterproofing of the soil increases this phenomenon by preventing the infiltration of water.

Explanatory diagram of the floods

Aggravating factors

The force of the water is even more important during a flood. Thus, materials such as earth, rocks, or branches, are easily transported by the current. These elements accumulated in rivers or ravines, preventing the passage of water, increases the risk of a natural dam. This dam may collapse at any time, resulting in a wave that can do big damage.

On the other hand, plants have a high absorbing power, their reduction may thus increase the risk of flooding.

Finally, facilities, human tarmac waterproof the soil and prevent seepage. Drainage can then be saturated and block the waters to the surface.

Because of climate change, the waters of the oceans heat up and change the habitual rhythm of the rain. The rains will be more rare in the course of the year, but more intense during weather events. The floods associated with hurricanes may be more numerous and important, and this is reinforced by the rise of sea levels.

Source : Booklet teacher-cycle 4 – Project "Pare pa Pare" – French Red Cross – 2024

For more information :

The flood – NEMO – Government of Saint Vincent and the Grenadines. Explanations to understand what are the floods, how to cope and protect themselves before, during, and after the disaster. (English)

The flood – Geohazards – French Government. Resource to understand what are the floods, its risks, the actions necessary to protect and grants available French to deal with. (French)