In California, around 1.4 million people live in high flood risk zones. This figure is alarming and the consequences of climate change are only making the situation worse. Floods can occur at any time, and it's crucial to understand the mechanisms that trigger them to better predict and manage them.
California Floods: A Complex Phenomenon
California floods are often caused by heavy rains, but also by snowmelt in the mountains. The risk of flooding is particularly high in coastal areas and valleys, where waters can rise rapidly. California authorities use flood risk maps to identify the most vulnerable zones, but these maps do not always provide a clear idea of the probability of flooding or its consequences.
The phenomenon of floods is complex because it involves many factors such as the topography of the terrain, the amount of precipitation, the soil's absorption capacity, and drainage infrastructure. When precipitation is abundant, the soil can become saturated with water, which can increase the flow rate of rivers and streams. If drainage infrastructure is not sufficient to handle this flow rate, waters can overflow and cause floods.
Climate change also plays an important role in increasing the risk of flooding in California. The average temperature of the planet is increasing, which can increase evaporation from oceans, lakes, and rivers. This can in turn increase precipitation, which can increase the risk of flooding.