The origins of floods can be very varied, being able to distinguish, in principle, those of marine or river origin.

When a storm brings more water to the ground than it can absorb, a runoff effect occurs. This can occur because the contribution is torrential, for example in a cold drop, or due to factors that increase the effects of strong storms, for example, deforestation and occupation of the banks of water courses and channels reserved for avenues "Avenida (hydrology)").

Hurricanes are generated as sea storms that reach land and flood coastal areas, although in case of great force they can penetrate several hundred kilometers.

The marine origin can be represented by the effect of storm surge, although there are floods of non-meteorological origin that may be due to earthquakes at sea and the resulting tidal waves.

Tornadoes can be terrestrial or marine and can provide large amounts of water in a very localized manner in space and time.

The sandur of Skeiðarársandur") grew considerably in the floods caused by a volcanic eruption in 1996, which melted a glacier in Iceland.