This tsunami above is from Japan in 2011
Flooding can be caused in a number of ways, but one of the more extreme yet uncommon ways is from tsunamis. A tsunami is a series of waves caused by underwater volcanic explosions and earthquakes. These waves, however, are much bigger and more powerful than regular waves.
The waves tend to be between 10-100 feet tall, and travel between 20-30MPH. These waves often travel far inland, sometimes even more than a mile causing large amounts of damage.
Hawaii is always at great risk for a tsunami – they get about 1 per year and a severe one every 7 years. The biggest tsunami that occurred Hawaii happened in 1946, the coast of Hilo Island was hit with 30 ft waves at 500 mph.Do something.org
Most of the time the flooding will last between 5 minutes to two hours but sometimes the flooding can last for days.