According to FEMA, every area has a risk of flood. Because of this, it is important to know which type of flood zone you live in. More importantly, it's also important to understand what to do when there is a flood warning, particularly a flash flood warning. In fact, in the United States flash floods are the number one weather-related killer. The reason for this is because flash floods can occur rapidly and cause water to rise 30 feet high or more.