The overflowing of water onto land that is normally dry. Flooding can occur during heavy rains, when ocean waves come on shore, when snow melts rapidly, or when dams or levees break. Flooding can last for days or weeks and is the most common and widespread of all natural disasters.
Floods can be caused by many factors, including:
a lack of vegetation, which slows runoff; human activities such as draining wetlands and building paved surfaces that do not absorb water; and the buildup of materials in or near waterways that obstruct or block their flow. Floods also happen when river channels and coastal areas are too shallow to hold all the water that falls.
In addition to being extremely destructive, flooding is dangerous because of the contaminated waters it brings in. The muddy water may carry disease and parasites, such as malaria and cholera. Floods can also destroy houses and other buildings, and take away essential infrastructure such as roads and bridges. Floods can cause significant economic damage, and it takes years for a community to recover.
Many cultures around the world tell stories about great, earth-drowning floods. The stories often have the same basic plot: a deity warns a virtuous man of impending destruction, and he builds a boat, saving himself, his family, animals, and plants. These floods are usually symbolic of God’s wrath or of man’s inability to control nature. They are sometimes also seen as signs of divine benevolence or as a way to replenish soils that have been depleted by overuse and erosion.