When water levels increase due to natural or unnatural causes, use the word "flood" to describe the situation. Floods are caused when there’s too much rain or a large containment of water breaks.
A large storm caused flooding.
There aren’t too many places in the world that don’t have a flood occur at one time or another. This is what the word looks like when it’s used as a noun:
A large flood wiped out several areas of the city.
Many people were affected by the flood.
A flood forced people from their homes.
Flooding is a problem during and after a storm. ("Flooding" in this sentence is a gerund and it acts as the subject.)
Flooding and high winds are causing power outages.
You can use "flood" as a verb, but sometimes this word has nothing to do with water. Instead, it describes a large, sudden increase of activity:
simple
past
past participle
flood
flooded
flooded
My inbox is flooded with junk mail.
The police department was flooded with phone calls during the emergency.
Football fans flooded onto the field after their team won the game.
Heavy rains flooded the streets of the city.
Our basement was flooded with several inches of water after a week of rain.